static block - Page 147

SQL ADO.NET shortcut extensions (old school!)

- by Jeff

As much as I love me some ORM's (I've used LINQ to SQL quite a bit, and for the MSDN/TechNet Profile and Forums we're using NHibernate more and more), there are times when it's appropriate, and in some ways more simple, to just throw up so old school ADO.NET connections, commands, readers and such. It still feels like a pain though to new up all the stuff, make sure it's closed, blah blah blah. It's pretty much the least favorite task of writing data access code. To minimize the pain, I have a set of extension methods that I like to use that drastically reduce the code you have to write. Here they are... public static void Using(this SqlConnection connection, Action<SqlConnection> action) { connection.Open(); action(connection); connection.Close(); } public static SqlCommand Command(this SqlConnection connection, string sql){ var command = new SqlCommand(sql, connection); return command;}public static SqlCommand AddParameter(this SqlCommand command, string parameterName, object value){ command.Parameters.AddWithValue(parameterName, value); return command;}public static object ExecuteAndReturnIdentity(this SqlCommand command){ if (command.Connection == null) throw new Exception("SqlCommand has no connection."); command.ExecuteNonQuery(); command.Parameters.Clear(); command.CommandText = "SELECT @@IDENTITY"; var result = command.ExecuteScalar(); return result;}public static SqlDataReader ReadOne(this SqlDataReader reader, Action<SqlDataReader> action){ if (reader.Read()) action(reader); reader.Close(); return reader;}public static SqlDataReader ReadAll(this SqlDataReader reader, Action<SqlDataReader> action){ while (reader.Read()) action(reader); reader.Close(); return reader;} It has been awhile since I've really revisited these, so you will likely find opportunity for further optimization. The bottom line here is that you can chain together a bunch of these methods to make a much more concise database call, in terms of the code on your screen, anyway. Here are some examples: public Dictionary<string, string> Get(){ var dictionary = new Dictionary<string, string>(); _sqlHelper.GetConnection().Using(connection => connection.Command("SELECT Setting, [Value] FROM Settings") .ExecuteReader() .ReadAll(r => dictionary.Add(r.GetString(0), r.GetString(1)))); return dictionary;} or... public void ChangeName(User user, string newName){ _sqlHelper.GetConnection().Using(connection => connection.Command("UPDATE Users SET Name = @Name WHERE UserID = @UserID") .AddParameter("@Name", newName) .AddParameter("@UserID", user.UserID) .ExecuteNonQuery());} The _sqlHelper.GetConnection() is just some other code that gets a connection object for you. You might have an even cleaner way to take that step out entirely. This looks more fluent, and the real magic sauce for me is the reader bits where you can put any kind of arbitrary method in there to iterate over the results.

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Solving 2D Collision Detection Issues with Relative Velocities

- by Jengerer

Imagine you have a situation where two objects are moving parallel to one-another and are both within range to collide with a static wall, like this: A common method used in dynamic collision detection is to loop through all objects in arbitrary order, solve for pair-wise collision detection using relative velocities, and then move the object to the nearest collision, if any. However, in this case, if the red object is checked first against the blue one, it would see that the relative velocity to the blue object is -20 m/s (and would thereby not collide this time frame). Then it would see that the red object would collide with the static wall, and the solution would be: And the red object passes through the blue one. So it appears to be a matter of choosing the right order in which you check collisions; but how can you determine which order is correct? How can this passing through of objects be avoided? Is ignoring relative velocity and considering every object as static during pair-wise checks a better idea for this reason?

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creating a pre-menu level select screen

- by Ephiras

Hi I am working on creating a tower Defence java applet game and have come to a road block about implementing a title screen that i can select the level and difficulty of the rest of the game. my title screen class is called Menu. from this menu class i need to pass in many different variables into my Main class. i have used different classes before and know how to run them and such. but if both classes extend applet and each has its individual graphics method how can i run things from Main even though it was created in Menu. what i essentially want to do is run the Menu class withits action listeners and graphics until a Difficulty button has been selected, run the main class (which 100% works without having to have the Menu class) and pretty much terminate Menu so that i cannot go back to it, do not see its buttons or graphics menus. can i run one applet annd when i choose a button close that one and launch the other one? IF you would like to download the full project you can find it here, i had to comment out all the code that wasn't working my Menu class import java.awt.*; import java.awt.event.*; import java.applet.*; public class Menu extends Applet implements ActionListener{ Button bEasy,bMed,bHard; Main m; public void init(){ bEasy= new Button("Easy"); bEasy.setBounds(140,200,100,50); add(bEasy); bMed = new Button("Medium");bMed.setBounds(280,200,100,50); add(bMed); bHard= new Button("Hard");bHard.setBounds(420,200,100,50); add(bHard); setLayout(null); } public void actionPerformed(ActionEvent e){ Main m = new Main(20,10,3000,mapMed);//break; switch (e.getSource()){ case bEasy: Main m = new Main(6000,20,"levels/levelEasy.png");break;//enimies tower money world case bMed: Main m = new Main(4000,15,"levels/levelMed.png");break; case bHard: Main m = new Main(2000,10,"levels/levelEasy.png");break; default: break; } } public void paint(){ //m.draw(g) } } and here is my main class initialising code. import java.awt.*; import java.awt.event.*; import java.applet.*; import java.io.IOException; public class Main extends Applet implements Runnable, MouseListener, MouseMotionListener, ActionListener{ Button startButton, UpgRange, UpgDamage; //set up the buttons Color roadCol,startCol,finCol,selGrass,selRoad; //set up the colors Enemy e[][]; Tower t[]; Image towerpic,backpic,roadpic,levelPic; private Image i; private Graphics doubleG; //here is the world 0=grass 1=road 2=start 3=end int world[][],eStartX,eStartY; boolean drawMouse,gameEnd; static boolean start=false; static int gridLength=15; static int round=0; int Mx,My,timer=1500; static int sqrSize=31; int towers=0,towerSelected=-10; static int castleHealth=2000; String levelPath; //choose the level Easy Med or Hard int maxEnemy[] = {5,7,12,20,30,15,50,30,40,60};//number of enimies per round int maxTowers=15;//maximum number of towers allowed static int money =2000,damPrice=600,ranPrice=350,towerPrice=700; //money = the intial ammount of money you start of with //damPrice is the price to increase the damage of a tower //ranPrice is the price to increase the range of a tower public void main(int cH,int mT,int mo,int dP,int rP,int tP,String path,int[] mE)//constructor 1 castleHealth=cH; maxTowers=mT; money=mo; damPrice=dP; ranPrice=rP; towerPrice=tP; String levelPath=path; maxEnemy = mE; buildLevel(); } public void main(int cH,int mT,String path)//basic constructor castleHealth=cH; maxTowers=mT; String levelPath=path; maxEnemy = mE; buildLevel(); } public void init(){ setSize(sqrSize*15+200,sqrSize*15);//set the size of the screen roadCol = new Color(255,216,0);//set the colors for the different objects startCol = new Color(0,38,255); finCol = new Color(255,0,0); selRoad = new Color(242,204,155);//selColor is the color of something when your mouse hovers over it selGrass = new Color(0,190,0); roadpic = getImage(getDocumentBase(),"images/road.jpg"); towerpic = getImage(getDocumentBase(),"images/tower.png"); backpic = getImage(getDocumentBase(),"images/grass.jpg"); levelPic = getImage(getDocumentBase(),"images/level.jpg"); e= new Enemy[maxEnemy.length][];//activates all of the enimies for (int r=0;r<e.length;r++) e[r] = new Enemy[maxEnemy[r]]; t= new Tower[maxTowers]; for (int i=0;i<t.length;i++) t[i]= new Tower();//activates all the towers for (int i=0;i<e.length; i++)//sets all of the enimies starting co ordinates for (int j=0;j<e[i].length;j++) e[i][j] = new Enemy(eStartX,eStartY,world); initButtons();//initialise all the buttons addMouseMotionListener(this); addMouseListener(this); }

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IsNullOrEmpty generic method for Array to avoid Re-Sharper warning

- by Michael Freidgeim

I’ve used the following extension method in many places. public static bool IsNullOrEmpty(this Object[] myArr) { return (myArr == null || myArr.Length == 0); }Recently I’ve noticed that Resharper shows warning covariant array conversion to object[] may cause an exception for the following codeObjectsOfMyClass.IsNullOrEmpty()I’ve resolved the issue by creating generic extension method public static bool IsNullOrEmpty<T>(this T[] myArr) { return (myArr == null || myArr.Length == 0); }Related linkshttp://connect.microsoft.com/VisualStudio/feedback/details/94089/add-isnullorempty-to-array-class public static bool IsNullOrEmpty(this System.Collections.IEnumerable source) { if (source == null) return true; else { return !source.GetEnumerator().MoveNext(); } }http://stackoverflow.com/questions/8560106/isnullorempty-equivalent-for-array-c-sharp

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Useful Extension Method for ICloneable

- by DesigningCode

In the past, I’ve had to put a type specific clone in each cloneable class, but with extension methods you can write a generic T specific clone class Program { static void Main(string[] args) { var b = new Blah() {X = 1, Y = 2}; var bb = b.Clone(); Console.WriteLine(string.Format("{0} {1}", bb.X, bb.Y)); } } public class Blah : ICloneable { public int X; public int Y; object ICloneable.Clone() { return MemberwiseClone(); } } public static class CloneExtension { public static T Clone<T>(this T o) where T : ICloneable { return (T)o.Clone(); } }

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A Basic Thread

- by Joe Mayo

Most of the programs written are single-threaded, meaning that they run on the main execution thread. For various reasons such as performance, scalability, and/or responsiveness additional threads can be useful. .NET has extensive threading support, from the basic threads introduced in v1.0 to the Task Parallel Library (TPL) introduced in v4.0. To get started with threads, it's helpful to begin with the basics; starting a Thread. Why Do I Care? The scenario I'll use for needing to use a thread is writing to a file. Sometimes, writing to a file takes a while and you don't want your user interface to lock up until the file write is done. In other words, you want the application to be responsive to the user. How Would I Go About It? The solution is to launch a new thread that performs the file write, allowing the main thread to return to the user right away. Whenever the file writing thread completes, it will let the user know. In the meantime, the user is free to interact with the program for other tasks. The following examples demonstrate how to do this. Show Me the Code? The code we'll use to work with threads is in the System.Threading namespace, so you'll need the following using directive at the top of the file: using System.Threading; When you run code on a thread, the code is specified via a method. Here's the code that will execute on the thread: private static void WriteFile() { Thread.Sleep(1000); Console.WriteLine("File Written."); } The call to Thread.Sleep(1000) delays thread execution. The parameter is specified in milliseconds, and 1000 means that this will cause the program to sleep for approximately 1 second. This method happens to be static, but that's just part of this example, which you'll see is launched from the static Main method. A thread could be instance or static. Notice that the method does not have parameters and does not have a return type. As you know, the way to refer to a method is via a delegate. There is a delegate named ThreadStart in System.Threading that refers to a method without parameters or return type, shown below: ThreadStart fileWriterHandlerDelegate = new ThreadStart(WriteFile); I'll show you the whole program below, but the ThreadStart instance above goes in the Main method. The thread uses the ThreadStart instance, fileWriterHandlerDelegate, to specify the method to execute on the thread: Thread fileWriter = new Thread(fileWriterHandlerDelegate); As shown above, the argument type for the Thread constructor is the ThreadStart delegate type. The fileWriterHandlerDelegate argument is an instance of the ThreadStart delegate type. This creates an instance of a thread and what code will execute, but the new thread instance, fileWriter, isn't running yet. You have to explicitly start it, like this: fileWriter.Start(); Now, the code in the WriteFile method is executing on a separate thread. Meanwhile, the main thread that started the fileWriter thread continues on it's own. You have two threads running at the same time. Okay, I'm Starting to Get Glassy Eyed. How Does it All Fit Together? The example below is the whole program, pulling all the previous bits together. It's followed by its output and an explanation. using System; using System.Threading; namespace BasicThread { class Program { static void Main() { ThreadStart fileWriterHandlerDelegate = new ThreadStart(WriteFile); Thread fileWriter = new Thread(fileWriterHandlerDelegate); Console.WriteLine("Starting FileWriter"); fileWriter.Start(); Console.WriteLine("Called FileWriter"); Console.ReadKey(); } private static void WriteFile() { Thread.Sleep(1000); Console.WriteLine("File Written"); } } } And here's the output: Starting FileWriter Called FileWriter File Written So, Why are the Printouts Backwards? The output above corresponds to Console.Writeline statements in the program, with the second and third seemingly reversed. In a single-threaded program, "File Written" would print before "Called FileWriter". However, this is a multi-threaded (2 or more threads) program. In multi-threading, you can't make any assumptions about when a given thread will run. In this case, I added the Sleep statement to the WriteFile method to greatly increase the chances that the message from the main thread will print first. Without the Thread.Sleep, you could run this on a system with multiple cores and/or multiple processors and potentially get different results each time. Interesting Tangent but What Should I Get Out of All This? Going back to the main point, launching the WriteFile method on a separate thread made the program more responsive. The file writing logic ran for a while, but the main thread returned to the user, as demonstrated by the print out of "Called FileWriter". When the file write finished, it let the user know via another print statement. This was a very efficient use of CPU resources that made for a more pleasant user experience. Joe

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Trouble with AABB collision response and physics

- by WCM

I have been racking my brain trying to figure out a problem I am having with physics and basic AABB collision response. I am fairly close as the physics are mostly right. Gravity feels good and movement is solid. The issue I am running into is that when I land on the test block in my project, I can jump off of it most of the time. If I repeatedly jump in place, I will eventually get stuck one or two pixels below the surface of the test block. If I try to jump, I can become free of the other block, but it will happen again a few jumps later. I feel like I am missing something really obvious with this. I have two functions that support the detection and function to return a vector for the overlap of the two rectangle bounding boxes. I have a single update method that is processing the physics and collision for the entity. I feel like I am missing something very simple, like an ordering of the physics vs. collision response handling. Any thoughts or help can be appreciated. I apologize for the format of the code, tis prototype code mostly. The collision detection function: public static bool Collides(Rectangle source, Rectangle target) { if (source.Right < target.Left || source.Bottom < target.Top || source.Left > target.Right || source.Top > target.Bottom) { return false; } return true; } The overlap function: public static Vector2 GetMinimumTranslation(Rectangle source, Rectangle target) { Vector2 mtd = new Vector2(); Vector2 amin = source.Min(); Vector2 amax = source.Max(); Vector2 bmin = target.Min(); Vector2 bmax = target.Max(); float left = (bmin.X - amax.X); float right = (bmax.X - amin.X); float top = (bmin.Y - amax.Y); float bottom = (bmax.Y - amin.Y); if (left > 0 || right < 0) return Vector2.Zero; if (top > 0 || bottom < 0) return Vector2.Zero; if (Math.Abs(left) < right) mtd.X = left; else mtd.X = right; if (Math.Abs(top) < bottom) mtd.Y = top; else mtd.Y = bottom; // 0 the axis with the largest mtd value. if (Math.Abs(mtd.X) < Math.Abs(mtd.Y)) mtd.Y = 0; else mtd.X = 0; return mtd; } The update routine (gravity = 0.001f, jumpHeight = 0.35f, moveAmount = 0.15f): public void Update(GameTime gameTime) { Acceleration.Y = gravity; Position += new Vector2((float)(movement * moveAmount * gameTime.ElapsedGameTime.TotalMilliseconds), (float)(Velocity.Y * gameTime.ElapsedGameTime.TotalMilliseconds)); Velocity.Y += Acceleration.Y; Vector2 previousPosition = new Vector2((int)Position.X, (int)Position.Y); KeyboardState keyboard = Keyboard.GetState(); movement = 0; if (keyboard.IsKeyDown(Keys.Left)) { movement -= 1; } if (keyboard.IsKeyDown(Keys.Right)) { movement += 1; } if (Position.Y + 16 > GameClass.Instance.GraphicsDevice.Viewport.Height) { Velocity.Y = 0; Position = new Vector2(Position.X, GameClass.Instance.GraphicsDevice.Viewport.Height - 16); IsOnSurface = true; } if (Collision.Collides(BoundingBox, GameClass.Instance.block.BoundingBox)) { Vector2 mtd = Collision.GetMinimumTranslation(BoundingBox, GameClass.Instance.block.BoundingBox); Position += mtd; Velocity.Y = 0; IsOnSurface = true; } if (keyboard.IsKeyDown(Keys.Space) && !previousKeyboard.IsKeyDown(Keys.Space)) { if (IsOnSurface) { Velocity.Y = -jumpHeight; IsOnSurface = false; } } previousKeyboard = keyboard; } This is also a full download to the project. https://www.box.com/s/3rkdtbso3xgfgc2asawy P.S. I know that I could do this with the XNA Platformer Starter Kit algo, but it has some deep flaws that I am going to try to live without. I'd rather go the route of collision response via an overlay function. Thanks for any and all insight!

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/etc/network/interfaces doesn't always take affect

- by user1221444

For some reason my eth0 does not have internet on reboot sometimes. I am using a static ip. I can ping my gateway, but I am unable to ping dns servers, or anything out of my network. It seems that when my internet does work(Usually but just restarting enough times), my /etc/resolv.conf has a nameserver in it. It is empty when I have no internet access. I believe something is overwriting my interfaces settings sometimes on boot. Any help would be appreciated. I am running Ubuntu Server 12.04 64bit /etc/network/interfaces: auto lo iface lo inet loopback auto eth0 iface eth0 inet static address 173.213.192.234 netmask 255.255.255.248 network 173.213.192.232 broadcast 173.213.192.239 gateway 173.213.192.233 dns-nameservers 8.8.8.8 auto eth1 iface eth1 inet static address 10.0.0.106 netmask 255.255.255.0 gateway 10.0.0.1

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Hosting a website from a dynamic IP

- by nick

I recently upgraded my internet to the point that it is much faster and more reliable than my current webhost. I would like to move my current domain to be hosted at home, but my IP address is dynamic. As far as I know, I only get a new IP when I restart my modem and or router (which is almost never) or when cable one (my ISP) pushes out a firmware update (rarely). There are a few ways I can see doing this 1) convince my ISP to give me a static IP 2) assign my router my current IP to force a static IP (which might work?) 3) set my dns record to my current IP address and update it on the rare occasions that it changes. Obviously I'm hoping that the first one works, but I don't want to pay a lot of extra money (if that's what it takes) to get a static IP address. Has anyone had any luck with something like that?

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Passing class names or objects?

- by nischayn22

I have a switch statement switch ( $id ) { case 'abc': return 'Animal'; case 'xyz': return 'Human'; //many more } I am returning class names,and use them to call some of their static functions using call_user_func(). Instead I can also create a object of that class, return that and then call the static function from that object as $object::method($param) switch ( $id ) { case 'abc': return new Animal; case 'xyz': return new Human; //many more } Which way is efficient? To make this question broader : I have classes that have mostly all static methods right now, putting them into classes is kind of a grouping idea here (for example the DB table structure of Animal is given by class Animal and so for Human class). I need to access many functions from these classes so the switch needs to give me access to the class

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Exadata?????????INSERT?UPDATE

- by Liu Maclean(???)

Hybrid Columnar Compression??????Exadata?????????????,??????????(advanced compression)??,Hybrid columnar compression (HCC) ???Exadata????????HCC???????????CU(compression unit?????),??CU??????????,?????????????????????????,???CU????block??????????????? ???????INSERT/UPDATE??,??????????????,????UPDATE/INSERT???HCC?????????????????? hybrid columnar compression???????????????(bulk initial load)??,??????(direct load)??ALTER TABLE MOVE, IMPDP???????(append INSERT),??HCC??????????????????????? ???????????????????,?????????CU????????? ??????????????HCC?????????????for OLTP?????? ????????: SQL*Plus: Release 11.2.0.2.0 Production on Wed Sep 12 06:14:53 2012 Copyright (c) 1982, 2010, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - Production With the Partitioning, Automatic Storage Management, OLAP, Data Mining and Real Application Testing options SQL> grant dba to scott; Grant succeeded. SQL> conn scott/oracle Connected. SQL> SQL> create table hcc_maclean tablespace users compress for query high as select * from dba_objects; Table created. 1* select rowid,owner,object_name,dbms_rowid.rowid_block_number(rowid) from hcc_maclean where owner='MACLEAN' SQL> / ROWID OWNER OBJECT_NAME DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID) ------------------------------ ------------------------------ -------------------- ------------------------------------ AAAThuAAEAAAHTJAOI MACLEAN SALES 29897 AAAThuAAEAAAHTJAOJ MACLEAN MYCUSTOMERS 29897 AAAThuAAEAAAHTJAOK MACLEAN MYCUST_ARCHIVE 29897 AAAThuAAEAAAHTJAOL MACLEAN MYCUST_QUERY 29897 AAAThuAAEAAAHTJAOh MACLEAN COMPRESS_QUERY 29897 AAAThuAAEAAAHTJAOi MACLEAN UNCOMPRESS 29897 AAAThuAAEAAAHTJAOj MACLEAN CHAINED_ROWS 29897 AAAThuAAEAAAHTJAOk MACLEAN COMPRESS_QUERY1 29897 8 rows selected. select dbms_rowid.rowid_block_number(rowid),dbms_rowid.rowid_relative_fno(rowid) from hcc_maclean where owner='MACLEAN'; session A: update hcc_maclean set OBJECT_NAME=OBJECT_NAME||'DBM' where rowid='AAAThuAAEAAAHTJAOI'; session B: update hcc_maclean set OBJECT_NAME=OBJECT_NAME||'DBM' where rowid='AAAThuAAEAAAHTJAOJ'; SQL> select sid,wait_event_text,BLOCKER_SID from v$wait_chains; SID WAIT_EVENT_TEXT BLOCKER_SID ---------- ---------------------------------------------------------------- ----------- 13 enq: TX - row lock contention 136 136 SQL*Net message from client ????session A block B,????HCC???update row??CU?????CU?????? SQL> alter system checkpoint; System altered. SQL> / System altered. SQL> alter system dump datafile 4 block 29897 2 ; Block header dump: 0x010074c9 Object id on Block? Y seg/obj: 0x1386e csc: 0x00.1cad7e itc: 3 flg: E typ: 1 - DATA brn: 0 bdba: 0x10074c8 ver: 0x01 opc: 0 inc: 0 exflg: 0 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0xffff.000.00000000 0x00000000.0000.00 C--- 0 scn 0x0000.001cabfa 0x02 0x000a.00a.00000430 0x00c051a7.0169.17 ---- 1 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 avsp=0x14 tosp=0x14 r0_9ir2=0x0 mec_kdbh9ir2=0x0 76543210 shcf_kdbh9ir2=---------- 76543210 flag_9ir2=--R----- Archive compression: Y fcls_9ir2[0]={ } 0x16:pti[0] nrow=1 offs=0 0x1a:pri[0] offs=0x30 block_row_dump: tab 0, row 0, @0x30 tl: 8016 fb: --H-F--N lb: 0x2 cc: 1 ==>??CU??ITL 0x02 nrid: 0x010074ca.0 col 0: [8004] Compression level: 02 (Query High) Length of CU row: 8004 kdzhrh: ------PC CBLK: 1 Start Slot: 00 NUMP: 01 PNUM: 00 POFF: 7984 PRID: 0x010074ca.0 CU header: CU version: 0 CU magic number: 0x4b445a30 CU checksum: 0xf8faf86e CU total length: 8694 CU flags: NC-U-CRD-OP ncols: 15 nrows: 995 algo: 0 CU decomp length: 8487 len/value length: 100111 row pieces per row: 1 num deleted rows: 1 deleted rows: 904, START_CU: ????????????row?????: SQL> select DBMS_COMPRESSION.GET_COMPRESSION_TYPE('SCOTT','HCC_MACLEAN','AAAThuAAEAAAHTJAOk') from dual; DBMS_COMPRESSION.GET_COMPRESSION_TYPE('SCOTT','HCC_MACLEAN','AAATHUAAEAAAHTJAOK' -------------------------------------------------------------------------------- 4 COMP_NOCOMPRESS CONSTANT NUMBER := 1;COMP_FOR_OLTP CONSTANT NUMBER := 2;COMP_FOR_QUERY_HIGH CONSTANT NUMBER := 4;COMP_FOR_QUERY_LOW CONSTANT NUMBER := 8;COMP_FOR_ARCHIVE_HIGH CONSTANT NUMBER := 16;COMP_FOR_ARCHIVE_LOW CONSTANT NUMBER := 32; COMP_RATIO_MINROWS CONSTANT NUMBER := 1000000;COMP_RATIO_ALLROWS CONSTANT NUMBER := -1; ?????????????,??COMP_FOR_QUERY_HIGH?4,COMP_FOR_QUERY_LOW ?8 ?????????GET_COMPRESSION_TYPE??rowid????????4?????COMP_FOR_QUERY_HIGH????: SQL> update hcc_maclean set OBJECT_NAME=OBJECT_NAME||'DBM' where owner='MACLEAN'; 8 rows updated. SQL> commit; Commit complete. SQL> select DBMS_COMPRESSION.GET_COMPRESSION_TYPE('SCOTT','HCC_MACLEAN',rowid) from HCC_MACLEAN where owner='MACLEAN'; DBMS_COMPRESSION.GET_COMPRESSION_TYPE('SCOTT','HCC_MACLEAN',ROWID) ------------------------------------------------------------------ 1 1 1 1 1 1 1 1 8 rows selected. ??????????????COMPRESSION_TYPE?COMP_FOR_QUERY_HIGH???COMP_NOCOMPRESS,????????compress for query high????????????????? ?11g????????????????????HCC??????????? ALTER TABLE MOVE???????????????????HCC??? SQL> ALTER TABLE hcc_MACLEAN move COMPRESS FOR ARCHIVE HIGH; Table altered. SQL> select DBMS_COMPRESSION.GET_COMPRESSION_TYPE('SCOTT','HCC_MACLEAN',rowid) from HCC_MACLEAN where owner='MACLEAN'; DBMS_COMPRESSION.GET_COMPRESSION_TYPE('SCOTT','HCC_MACLEAN',ROWID) ------------------------------------------------------------------ 16 16 16 16 16 16 16 16 8 rows selected.

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Euler Problem 20

- by MarkPearl

This was probably one of the easiest ones to complete – a quick bash got me the following… The Problem n! means n (n 1) ... 3 2 1 For example, 10! = 10 9 ... 3 2 1 = 3628800, and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27. Find the sum of the digits in the number 100! The Solution private static BigInteger Factorial(int num) { if (num > 1) return (BigInteger)num * Factorial(num - 1); else return 1; } private static BigInteger SumDigits(string digits) { BigInteger result = 0; foreach (char number in digits) { result += Convert.ToInt32(number)-48; } return result; } static void Main(string[] args) { Console.WriteLine(SumDigits(Factorial(100).ToString())); Console.ReadLine(); }

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Use Extension Methods to find first and last day of the month

- by Tim Hibbard

A lot of reports work on data from last month. It is a nice touch to have these dates pre-populated for your users. Using extension methods, the code can look cleaner too. Extension Methods: public static class DateHelper { public static DateTime FirstOfTheMonth(this DateTime dt) { return new DateTime(dt.Year, dt.Month, 1); } public static DateTime LastOfTheMonth(this DateTime dt) { return dt.FirstOfTheMonth().AddMonths(1).AddDays(-1); } } Consuming Code: void Prepopulate() { startDateBox.CurrentlySelectedDate = DateTime.Now.AddMonths(-1).FirstOfTheMonth(); endDateBox.CurrentlySelectedDate = DateTime.Now.AddMonths(-1).LastOfTheMonth(); }

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Please help me to improve Re-Sharper

- by TATWORTH

Re-Sharper is an excellent aid to producing good code in either C# or VB.NET. Recently through using Resharper and StyleCop, I have found three area where ReSharper needs to be improved. Please log into the YouTrack at http://youtrack.jetbrains.net and vote for the following: RSRP-268868 Improvement to removal of redundant else and invert if optimisations for enhanced stylecop compliance. When Resharper removes a redundant else, there needs to be a blank line added. Currently there is no provision to specify this. Please vote for this! RSRP-272286 Resharper Feature Request to move initialisation to static constructor Currently ReSharper offers moving initialisation of of non-static variable to a constructor. Why not offer the same for a static constructor? Please vote for this! RSRP-272285 Expansion of Switch Statement by Resharper Currently ReSharper will fill an empty switch statement based upon an enumeration but will not add missing enumeration values to such a switch statement. Can't code withoutCoding assistance, smart code editing and code completion for C# and VB.NET

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Where should I put a method that returns a list of active entries of a table?

- by darga33

I have a class named GuestbookEntry that maps to the properties that are in the database table named "guestbook". Very simple! Originally, I had a static method named getActiveEntries() that retrieved an array of all GuestbookEntry objects. Each row in the guestbook table was an object that was added to that array. Then while learning how to properly design PHP classes, I learned some things: Static methods are not desirable. Separation of Concerns Single Responsibility Principle If the GuestbookEntry class should only be responsible for managing single guestbook entries then where should this getActiveEntries() method most properly go? Update: I am looking for an answer that complies with the SOLID acronym principles and allows for test-ability. That's why I want to stay away from static calls/standard functions. DAO, repository, ...? Please explain as though your explanation will be part of "Where to Locate FOR DUMMIES"... :-)

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Naming convention: field starting with "m" or "s"

- by Noya

Hope this question hasn't posted yet... I saw lot of code (for example some Android source code) where fields name start with a "m" while static fields start with "s" Example (taken from Android View class source): private SparseArray<Object> mKeyedTags; private static int sNextAccessibilityViewId; I was wondering what "m" and "s" stand for... maybe is "m" mutable and "s" static? Since it seems that is a largely adopted pattern do you know if there some literature about this kind of naming convention?

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Where would a senior PHP developer locate the method getActiveEntries()?

- by darga33

I have a class named GuestbookEntry that maps to the properties that are in the database table named "guestbook". Very simple! Originally, I had a static method named getActiveEntries() that retrieved an array of all GuestbookEntry objects. Each row in the guestbook table was an object that was added to that array. Then while learning how to properly design PHP classes, I learned some things: Static methods are not desirable. Separation of Concerns Single Responsibility Principle If the GuestbookEntry class should only be responsible for managing single guestbook entries then where should this getActiveEntries() method most properly go? Update: I am looking for an answer that complies with the SOLID acronym principles and allows for test-ability. That's why I want to stay away from static calls/standard functions. DAO, repository, ...? Please explain as though your explanation will be part of "Where to Locate FOR DUMMIES"... :-)

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MAC filtering after DHCP

- by user1655161

How to manage filtering by MAC in Ubuntu? Scenario: Ubuntu DHCP is configured and working (network 192.168.1.0) a) Laptop 1 is set in configuration on Ubuntu as static IP Laptop 1 is configured for automatic IP and when is connected to server everything works. I'm taking laptop 2 which is configured as static IP 192.168.1.10 and his configuration is not set in Ubuntu dhcpd.conf After laptop 2 is connected internet working. It is possible to do MAC filtering which disallow to connect PCs with address IP set as static but MAC address is not configured in Ubuntu (something like: intruder in network)?

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System.getProperty("user.dir") cannot get my project root path ,but the path which my eclipse is located

- by facebook-100005613813158

As the title goes , I have class named GetException.java,inside it ,I read a xml file in a static code block like(Because this document is shared): static{ ... document = db.parse(new File(System.getProperty("user.dir")+"/src/exception/ExceptionCode.xml")); ... } To test if the file path is correct, I write a main function just inside GetException.java, it proves that the path is correct ,xml file can be read successfully. My project root dir is "/home/wuchang/workspace/MongodbI". But When this Class is loaded from other class,such as I called one of its static functions , it reports the error message: /home/mrs/??/eclipse/src/exception/ExceptionCode.xml (No such file or directory) /home/mrs/??/eclipse/ is actually my eclipse installation directory.So , I wander how System.getProperty("user.dir") returned the eclipse installation directory to me ,instead of my project root directory?

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Question about main(String[] args) [migrated]

- by Andrew0085

I'm new to programming, and I'm using java. Here's a program I wrote: class HelloApp { static String hi; public static void main(String[] args) { int length = args.length; if (length > 0) { hi = args[0]; sayHi(); } } static void sayHi() { if (hi == "hello") { System.out.println("Hello!"); } } } My question is: Why doesn't inputting "java HelloApp hello" make "Hello!" appear on the next line?

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Failure connecting to Dell MD3200i from XenServer 6.2 pool

- by Tom Sparrow

This question also asked at Citrix Forums http://forums.citrix.com/thread.jspa?threadID=332289 I have a MD3200i that is currently working fine with my Xen5.6 pool, but I cannot get a connection to the new 6.2 pool to work. I previously had a problem with a 6.0 upgrade (which is why the old pool is still on 5.6), but rolled back rather than fix it as it wasn't urgent at the time. This install is on new machines - I tried 6.1 first (which had the same problems) then 6.2 was released the second day after installation so I switched to that. I've not installed anything from the Dell resource DVD at this point - I can't find anything saying I should, and everything I have read suggests it shouldn't be necessary. I can ping all 8 ip addresses from both servers in the pool, iscsiadm -m discovery works fine, I can login to the nodes and iscsiadm reports the sessions active correctly. I've added the required sections to multipath.conf, but multipath -ll reports DM multipath kernel driver not loaded immediately after boot. The following is a log of a test session immediately after boot. root@xen3 ~]# iscsiadm -m node --loginall=all Logging in to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.130.101,3260] Logging in to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.131.101,3260] Logging in to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.131.104,3260] Logging in to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.131.102,3260] Logging in to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.130.103,3260] Logging in to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.130.104,3260] Logging in to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.130.102,3260] Logging in to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.131.103,3260] Login to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.130.101,3260]: successful Login to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.131.101,3260]: successful Login to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.131.104,3260]: successful Login to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.131.102,3260]: successful Login to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.130.103,3260]: successful Login to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.130.104,3260]: successful Login to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.130.102,3260]: successful Login to [iface: default, target: iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91, portal: 192.168.131.103,3260]: successful [root@xen3 ~]# iscsiadm -m session tcp: [1] 192.168.130.101:3260,1 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [2] 192.168.131.101:3260,1 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [3] 192.168.131.104:3260,2 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [4] 192.168.131.102:3260,2 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [5] 192.168.130.103:3260,1 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [6] 192.168.130.104:3260,2 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [7] 192.168.130.102:3260,2 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [8] 192.168.131.103:3260,1 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 [root@xen3 ~]# service multipathd restart ok Stopping multipathd daemon: [ OK ] Starting multipathd daemon: [ OK ] [root@xen3 ~]# multipath Jul 04 09:58:47 | DM multipath kernel driver not loaded Jul 04 09:58:47 | DM multipath kernel driver not loaded [root@xen3 ~]# multipath -ll Jul 04 09:59:03 | DM multipath kernel driver not loaded Jul 04 09:59:03 | DM multipath kernel driver not loaded [ root@xen3 ~]# modprobe dm_multipath [root@xen3 ~]# multipath Jul 04 10:19:50 | 36b8ca3a0e7024800194a0bd11891cd14: ignoring map create: 1Dell_Internal_Dual_SD_0123456789AB undef Dell,Internal Dual SD size=1.9G features='0' hwhandler='0' wp=undef `-+- policy='round-robin 0' prio=1 status=undef `- 7:0:0:0 sdb 8:16 undef ready running [root@xen3 ~]# multipath -ll 1Dell_Internal_Dual_SD_0123456789AB dm-1 Dell,Internal Dual SD size=1.9G features='0' hwhandler='0' wp=rw `-+- policy='round-robin 0' prio=1 status=enabled `- 7:0:0:0 sdb 8:16 active ready running [root@xen3 ~]# iscsiadm -m session tcp: [1] 192.168.130.101:3260,1 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [2] 192.168.131.101:3260,1 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [3] 192.168.131.104:3260,2 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [4] 192.168.131.102:3260,2 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [5] 192.168.130.103:3260,1 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [6] 192.168.130.104:3260,2 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [7] 192.168.130.102:3260,2 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 tcp: [8] 192.168.131.103:3260,1 iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 [root@xen3 ~]# dmesg | tail -n 50 [ 1161.881010] sd 8:0:0:0: [sdf] Unhandled error code [ 1161.881013] sd 8:0:0:0: [sdf] Result: hostbyte=DID_TRANSPORT_DISRUPTED driverbyte=DRIVER_OK [ 1161.881017] sd 8:0:0:0: [sdf] CDB: Read(10): 28 00 00 00 00 00 00 00 08 00 [ 1161.881024] end_request: I/O error, dev sdf, sector 0 [ 1161.881031] Buffer I/O error on device sdf, logical block 0 [ 1161.881045] sd 15:0:0:0: [sdi] Unhandled error code [ 1161.881048] sd 15:0:0:0: [sdi] Result: hostbyte=DID_TRANSPORT_DISRUPTED driverbyte=DRIVER_OK [ 1161.881052] sd 15:0:0:0: [sdi] CDB: Read(10): 28 00 00 00 00 00 00 00 08 00 [ 1161.881058] end_request: I/O error, dev sdi, sector 0 [ 1161.881065] Buffer I/O error on device sdi, logical block 0 [ 1161.881122] sd 9:0:0:0: [sdg] Unhandled error code [ 1161.881124] sd 9:0:0:0: [sdg] Result: hostbyte=DID_TRANSPORT_DISRUPTED driverbyte=DRIVER_OK [ 1161.881126] sd 9:0:0:0: [sdg] CDB: Read(10): 28 00 00 00 00 00 00 00 08 00 [ 1161.881132] end_request: I/O error, dev sdg, sector 0 [ 1161.881140] Buffer I/O error on device sdg, logical block 0 [ 1168.220951] connection6:0: ping timeout of 15 secs expired, recv timeout 10, last rx 84060, last ping 85060, now 86560 [ 1168.220957] connection7:0: ping timeout of 15 secs expired, recv timeout 10, last rx 84060, last ping 85060, now 86560 [ 1168.220967] connection7:0: detected conn error (1011) [ 1168.220969] connection4:0: ping timeout of 15 secs expired, recv timeout 10, last rx 84060, last ping 85060, now 86560 [ 1168.220973] connection4:0: detected conn error (1011) [ 1168.220975] connection3:0: ping timeout of 15 secs expired, recv timeout 10, last rx 84060, last ping 85060, now 86560 [ 1168.220978] connection3:0: detected conn error (1011) [ 1168.220985] connection6:0: detected conn error (1011) [ 1168.480994] sd 14:0:0:0: [sde] Unhandled error code [ 1168.480998] sd 14:0:0:0: [sde] Result: hostbyte=DID_TRANSPORT_DISRUPTED driverbyte=DRIVER_OK [ 1168.481001] sd 14:0:0:0: [sde] CDB: Read(10): 28 00 00 00 00 00 00 00 08 00 [ 1168.481009] end_request: I/O error, dev sde, sector 0 [ 1168.481015] Buffer I/O error on device sde, logical block 0 [ 1168.481076] sd 11:0:0:0: [sdc] Unhandled error code [ 1168.481078] sd 11:0:0:0: [sdc] Result: hostbyte=DID_TRANSPORT_DISRUPTED driverbyte=DRIVER_OK [ 1168.481080] sd 11:0:0:0: [sdc] CDB: Read(10): 28 00 00 00 00 00 00 00 08 00 [ 1168.481087] end_request: I/O error, dev sdc, sector 0 [ 1168.481092] Buffer I/O error on device sdc, logical block 0 [ 1168.481144] sd 10:0:0:0: [sdd] Unhandled error code [ 1168.481147] sd 10:0:0:0: [sdd] Result: hostbyte=DID_TRANSPORT_DISRUPTED driverbyte=DRIVER_OK [ 1168.481150] sd 10:0:0:0: [sdd] CDB: Read(10): 28 00 00 00 00 00 00 00 08 00 [ 1168.481156] end_request: I/O error, dev sdd, sector 0 [ 1168.481163] Buffer I/O error on device sdd, logical block 0 [ 1168.481168] sd 13:0:0:0: [sdj] Unhandled error code [ 1168.481170] sd 13:0:0:0: [sdj] Result: hostbyte=DID_TRANSPORT_DISRUPTED driverbyte=DRIVER_OK [ 1168.481172] sd 13:0:0:0: [sdj] CDB: Read(10): 28 00 00 00 00 00 00 00 08 00 [ 1168.481178] end_request: I/O error, dev sdj, sector 0 [ 1168.481184] Buffer I/O error on device sdj, logical block 0 [ 1457.105996] device-mapper: multipath round-robin: version 1.0.0 loaded [ 1457.106155] device-mapper: multipath: Cannot access device path 8:0: -16 [ 1457.106164] device-mapper: table: 252:1: multipath: error getting device [ 1457.106172] device-mapper: ioctl: error adding target to table [ 1457.171292] device-mapper: multipath: Cannot access device path 8:0: -16 [ 1457.171299] device-mapper: table: 252:1: multipath: error getting device [ 1457.171304] device-mapper: ioctl: error adding target to table [root@xen3 ~]# fdisk -l Disk /dev/sda: 299.4 GB, 299439751168 bytes 255 heads, 63 sectors/track, 36404 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sda1 1 5 40131 de Dell Utility /dev/sda2 * 6 528 4194304 83 Linux Partition 2 does not end on cylinder boundary. /dev/sda3 528 1050 4194304 83 Linux /dev/sda4 1050 36404 283986359+ 8e Linux LVM Disk /dev/sdb: 2040 MB, 2040528896 bytes 255 heads, 63 sectors/track, 248 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 1 248 1992028+ 83 Linux Disk /dev/dm-1: 2040 MB, 2040528896 bytes 255 heads, 63 sectors/track, 248 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/dm-1p1 1 248 1992028+ 83 Linux [root@xen3 ~]# xe sr-probe type=lvmoiscsi device-config:target=192.168.130.101 device-config:targetIQN=iqn.1984-05.com.dell:powervault.md3200i.6782bcb0006bd850000000004ed88b91 Error code: SR_BACKEND_FAILURE_107 Error parameters: , The SCSIid parameter is missing or incorrect, <?xml version="1.0" ?> <iscsi-target/> Note: the xml ends there correctly on the last line - it doesn't ever return a list of LUNs (and there is one in the group on the SAN for those servers.

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Know More About Oracle Row Lock

- by Liu Maclean(???)

??????Oracle??????????row lock,??ORACLE????????????????????,row lock???????????????????????????????,??Server Process?pin????block buffer????????? ????????,?process A ??update???????? Z?????????, ???????rollback???commit;??Process B??????DML??, ???????rowid???? Z???, ???????????process A????????ITL???,????????cleanout??,????????row???????????commit, ???????Process B????”enq: TX – row lock contention”??????? ????Process B????????????? ?????????Process A???????row,??Process B???????”enq: TX – row lock contention”???? ???????? ????????: SESSION A: SQL> select * from v$version; BANNER ---------------------------------------------------------------- Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bi PL/SQL Release 10.2.0.5.0 - Production CORE 10.2.0.5.0 Production TNS for Linux: Version 10.2.0.5.0 - Production NLSRTL Version 10.2.0.5.0 - Production SQL> select * from global_name; GLOBAL_NAME -------------------------------------------------------------------------------- www.oracledatabase12g.com SQL> create table maclean_lock(t1 int); Table created. SQL> insert into maclean_lock values (1); 1 row created. SQL> commit; Commit complete. SQL> select dbms_rowid.rowid_block_number(rowid),dbms_rowid.rowid_relative_fno(rowid) from maclean_lock; DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID) DBMS_ROWID.ROWID_RELATIVE_FNO(ROWID) ------------------------------------ ------------------------------------ 67642 1 SQL> select distinct sid from v$mystat; SID ---------- 142 SQL> select pid,spid from v$process where addr = ( select paddr from v$session where sid=(select distinct sid from v$mystat)); PID SPID ---------- ------------ 17 15636 ??SESSION A ????savepoint ,?update ????????? SQL> savepoint NONLOCK; Savepoint created. SQL> select * From v$Lock where sid=142; no rows selected SQL> set linesize 140 pagesize 1400 SQL> update maclean_lock set t1=t1+2; 1 row updated. SQL> select * From v$Lock where sid=142; ADDR KADDR SID TY ID1 ID2 LMODE REQUEST CTIME BLOCK ---------------- ---------------- ---------- -- ---------- ---------- ---------- ---------- ---------- ---------- 0000000091FC69F0 0000000091FC6A18 142 TM 55829 0 3 0 6 0 00000000914B4008 00000000914B4040 142 TX 393232 609 6 0 6 0 SQL> select dump(3,16) from dual; DUMP(3,16) -------------------------------------------------------------------------------- Typ=2 Len=2: c1,4 ALTER SYSTEM DUMP DATAFILE 1 BLOCK 67642; Object id on Block? Y seg/obj: 0xda16 csc: 0x00.234718 itc: 2 flg: O typ: 1 - DATA fsl: 0 fnx: 0x0 ver: 0x01 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.00f.000001e0 0x00800075.02a6.29 C--- 0 scn 0x0000.00234711 0x02 0x0007.018.000001fe 0x0080065c.017a.02 ---- 1 fsc 0x0000.00000000 data_block_dump,data header at 0x81d185c =============== tsiz: 0x1fa0 hsiz: 0x14 pbl: 0x081d185c bdba: 0x0041083a 76543210 flag=-------- ntab=1 nrow=1 frre=-1 fsbo=0x14 fseo=0x1f9a avsp=0x1f83 tosp=0x1f83 0xe:pti[0] nrow=1 offs=0 0x12:pri[0] offs=0x1f9a block_row_dump: tab 0, row 0, @0x1f9a tl: 6 fb: --H-FL-- lb: 0x2 cc: 1 col 0: [ 2] c1 04 end_of_block_dump ?? BLOCK DUMP ???? ??????XID=0x0007.018.000001fe ?transaction?? lb:0x1 ??SESSION B ,?????UPDATE?? ???enq: TX - row lock contention ?? SQL> select distinct sid from v$mystat; SID ---------- 140 SQL> select pid,spid from v$process where addr = ( select paddr from v$session where sid=(select distinct sid from v$mystat)); PID SPID ---------- ------------ 24 15652 SQL> alter system set "_trace_events"='10000-10999:255:24'; System altered. SQL> update maclean_lock set t1=t1+2; select * From v$Lock where sid=142 or sid=140 order by sid; SESSION C: SQL> select * From v$Lock where sid=142 or sid=140 order by sid; ADDR KADDR SID TY ID1 ID2 LMODE REQUEST CTIME BLOCK ---------------- ---------------- ---------- -- ---------- ---------- ---------- ---------- ---------- ---------- 0000000091FC6B10 0000000091FC6B38 140 TM 55829 0 3 0 84 0 00000000924F4A58 00000000924F4A78 140 TX 458776 510 0 6 84 0 00000000914B51E8 00000000914B5220 142 TX 458776 510 6 0 312 1 0000000091FC69F0 0000000091FC6A18 142 TM 55829 0 3 0 312 0 ???? SESSION B SID=140 ?SESSION A ?TX ENQUEUE ?X mode?REQUEST SQL> oradebug dump systemstate 266; Statement processed. SESSION B waiter's enqueue lock SO: 0x924f4a58, type: 5, owner: 0x92bb8dc8, flag: INIT/-/-/0x00 (enqueue) TX-00070018-000001FE DID: 0001-0018-00000022 lv: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 res_flag: 0x6 req: X, lock_flag: 0x0, lock: 0x924f4a78, res: 0x925617c0 own: 0x92b76be0, sess: 0x92b76be0, proc: 0x92a737a0, prv: 0x925617e0 TX-00070018-000001FE=> TX 458776 510 SESSION A owner's enqueue lock SO: 0x914b51e8, type: 40, owner: 0x92b796d0, flag: INIT/-/-/0x00 (trans) flg = 0x1e03, flg2 = 0xc0000, prx = 0x0, ros = 2147483647 bsn = 0xed5 bndsn = 0xee7 spn = 0xef7 efd = 3 file:xct.c lineno:1179 DID: 0001-0011-000000C2 parent xid: 0x0000.000.00000000 env: (scn: 0x0000.00234718 xid: 0x0007.018.000001fe uba: 0x0080065c.017a.02 statement num=0 parent xid: xid: 0x0000.000.00000000 scn: 0x00 00.00234718 0sch: scn: 0x0000.00000000) cev: (spc = 7818 arsp = 914e8310 ubk tsn: 1 rdba: 0x0080065c useg tsn: 1 rdba: 0x00800069 hwm uba: 0x0080065c.017a.02 col uba: 0x00000000.0000.00 num bl: 1 bk list: 0x91435070) cr opc: 0x0 spc: 7818 uba: 0x0080065c.017a.02 (enqueue) TX-00070018-000001FE DID: 0001-0011-000000C2 lv: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 res_flag: 0x6 mode: X, lock_flag: 0x0, lock: 0x914b5220, res: 0x925617c0 own: 0x92b796d0, sess: 0x92b796d0, proc: 0x92a6ffd8, prv: 0x925617d0 xga: 0x8b7c6d40, heap: UGA Trans IMU st: 2 Pool index 65535, Redo pool 0x914b58d0, Undo pool 0x914b59b8 Redo pool range [0x86de640 0x86de640 0x86e0e40] Undo pool range [0x86dbe40 0x86dbe40 0x86de640] ---------------------------------------- SO: 0x91435070, type: 39, owner: 0x914b51e8, flag: -/-/-/0x00 (List of Blocks) next index = 1 index itli buffer hint rdba savepoint ----------------------------------------------------------- 0 2 0x647f1fc8 0x41083a 0xee7 ?SESSION A? ROLLBACK ?savepoint: SQL> rollback to NONLOCK; Rollback complete. ????savepoint ??update??????? ??UPDATE???????? ROLLBACK: SQL> select * From v$Lock where sid=142 or sid=140; ADDR KADDR SID TY ID1 ID2 LMODE REQUEST CTIME BLOCK ---------------- ---------------- ---------- -- ---------- ---------- ---------- ---------- ---------- ---------- 00000000924F4A58 00000000924F4A78 140 TX 458776 510 0 6 822 0 0000000091FC6B10 0000000091FC6B38 140 TM 55829 0 3 0 822 0 00000000914B51E8 00000000914B5220 142 TX 458776 510 6 0 1050 1 ???? SESSION A 142 ???SAVEPOINT ???????TM LOCK ????? ROLLBACK TO SAVEPOINT?????SESSION???TX LOCK!!!! ??????SESSION 142???TX ID1=458776 ID2=510, ????ROLLBACK TO SAVEPOINT?????????ABORT TRANSACTION ?? SESSION B SID=140?? SESSION A ?? , ?????????SESSION B? update???HANG?? ?????????CACHE?????: Object id on Block? Y seg/obj: 0xda16 csc: 0x00.2347b7 itc: 2 flg: O typ: 1 - DATA fsl: 0 fnx: 0x0 ver: 0x01 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.00f.000001e0 0x00800075.02a6.29 C--- 0 scn 0x0000.00234711 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 data_block_dump,data header at 0x745d85c =============== tsiz: 0x1fa0 hsiz: 0x14 pbl: 0x0745d85c bdba: 0x0041083a 76543210 flag=-------- ntab=1 nrow=1 frre=-1 fsbo=0x14 fseo=0x1f9a avsp=0x1f83 tosp=0x1f83 0xe:pti[0] nrow=1 offs=0 0x12:pri[0] offs=0x1f9a block_row_dump: tab 0, row 0, @0x1f9a tl: 6 fb: --H-FL-- lb: 0x0 cc: 1 col 0: [ 2] c1 02 end_of_block_dump ???? ITL=0x02? ?????????,col 0: [ 2] c1 02 ????????? ?????????SESSION D ,??????row lock?? ?UPDATE???????? SESSION D: SQL> update maclean_lock set t1=t1+2; 1 row updated. SQL> rollback; Rollback complete. ??SESSION B ??????????? ?????ORACLE????????, ??????????? TX lock?? row lock , ????????2??? row lock?????????, ?TX lock????????ENQUEUE LOCK???? ?????????PROCESS K?DML???????????????????????,??????????TX LOCK, ????PROCESS Z?????????????????????????ROW LOCK????????, ???????OLTP?????????????????????? ??ROW LOCK?Release ??????TX?ENQUEUE LOCK,?????????Process J ????????????, Process K??????????? ,Process K?????????,???row piece?lb??0x0 ,?????ITL, Process Z???ITL???????Process J????XID,?????Process J?????TX lock, PROCESS K ???TX resource?Enqueue Waiter Linked List?????X mode(exclusive)?enqueue lock? ???Process J??TX lock?,Process J?????TX resource?Enqueue Waiter Linked List ???Process K??????,??POST?????Process K? TX lock??????, ???????row lock???????,????????? ?????????? ?????: SESSION A ???PID =17 ?????????????????? SESSION B ???PID =24 ??????? "_trace_events"='10000-10999:255:24'; KST trace ??????? Server Process??? SESSION A PID=17 ?? acqure?SX mode???TM Lock ,?? ????Transaction?????UNDO SEGMENT 7,???XID 7.24.510, ?acquire ?X mode? TX-00070018-000001fe ? ?????? 00070018-000001fe ???? 7- 24 - 510? XID ? 781F4B8A:007A569C 17 142 10704 83 ksqgtl: acquire TM-0000da15-00000000 mode=SX flags=GLOBAL|XACT why="contention" 781F4B92:007A569D 17 142 10704 19 ksqgtl: SUCCESS 781F4BB3:007A569E 17 142 10812 2 0x000000000041083A 0x0000000000000000 0x0000000000234717 781F4BBA:007A569F 17 142 10812 3 0x0000000000000000 0x0000000000000000 0x0000000000000000 781F4BC0:007A56A0 17 142 10812 4 0x0000000000000000 0x0000000000000000 0x0000000000000000 781F4BD3:007A56A1 17 142 10812 5 0x000000000041083A 0x0000000000000000 0x0000000000000000 781F4BFE:007A56A2 17 142 10811 1 0x000000000041083A 0x0000000000000000 0x0000000000234711 0x0000000000000002 781F4C06:007A56A3 17 142 10811 2 0x000000000041083A 0x0000000000000000 0x0000000000234718 0x00007FA074EDA560 781F4C26:007A56A4 17 142 10813 1 ktubnd: Bind usn 7 nax 1 nbx 0 lng 0 par 0 781F4C43:007A56A5 17 142 10813 2 ktubnd: Txn Bound xid: 7.24.510 781F4C4A:007A56A6 17 142 10704 83 ksqgtl: acquire TX-00070018-000001fe mode=X flags=GLOBAL|XACT why="contention" 781F4C51:007A56A7 17 142 10704 19 ksqgtl: SUCCESS ?????????? ???????? 781F4CBF:007A56A8 17 142 10005 1 KSL WAIT BEG [SQL*Net message to client] 1650815232/0x62657100 1/0x1 0/0x0 781F4CCC:007A56A9 17 142 10005 2 KSL WAIT END [SQL*Net message to client] 1650815232/0x62657100 1/0x1 0/0x0 time=13 781F4CDE:007A56AA 17 142 10005 1 KSL WAIT BEG [SQL*Net message from client] 1650815232/0x62657100 1/0x1 0/0x0 786BD85D:007A57E0 17 142 10005 2 KSL WAIT END [SQL*Net message from client] 1650815232/0x62657100 1/0x1 0/0x0 time=5016447 786BD966:007A57E1 17 142 10005 1 KSL WAIT BEG [SQL*Net message to client] 1650815232/0x62657100 1/0x1 0/0x0 786BD96E:007A57E2 17 142 10005 2 KSL WAIT END [SQL*Net message to client] 1650815232/0x62657100 1/0x1 0/0x0 time=8 SESSION B ???PID =24 ,??????? SX mode? TM lock,??row lock? acquire X mode?TX-00070018-000001fe ksqgtl: acquire TM-0000da15-00000000 mode=SX flags=GLOBAL|XACT why="contention" ksqgtl: SUCCESS 0x000000000041083A 0x0000000000000000 0x00000000002354F8 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x000000000041083A 0x0000000000000000 0x00000000002354F8 0x0000000000000001 0x000000000041083A 0x0000000000000000 0x00000000002354F8 0x0000000008A63780 0x0000000000000001 0x0000000000800861 0x0000000000000241 0x0000000000000001 0x000000000041083A 0x0000000000000001 0x0000000000000001 0x000000000041083A 0x0000000000000000 0x00000000002354F9 0x0000000000000002 ksqgtl: acquire TX-00070018-000001fe mode=X flags=GLOBAL|LONG why="row lock contention" C4048EBD:007F52B6 24 140 10005 2 KSL WAIT END [enq: TX - row lock contention] 1415053318/0x54580006 458776/0x70018 510/0x1fe time=2929879 C4048ED4:007F52B7 24 140 10005 1 KSL WAIT BEG [enq: TX - row lock contention] 1415053318/0x54580006 458776/0x70018 510/0x1fe C43146CA:007F535E 24 140 10005 2 KSL WAIT END [enq: TX - row lock contention] 1415053318/0x54580006 458776/0x70018 510/0x1fe time=2930676 ????????? ,PID=24 ??????ksqcmi???????? deadlock C43146D9:007F535F 24 140 10704 134 ksqcmi: performing local deadlock detection on TX-00070018-000001fe C43146F8:007F5360 24 140 10704 150 ksqcmi: deadlock not detected on TX-00070018-000001fe ?? ??? PID 17 ??ROLLBACK ???? ,????????: PID 17 ROLLBACK; D7A495BB:007F9D3E 17 142 10005 4 KSL POST SENT postee=24 loc='ksqrcl' id1=0 id2=0 name= type=0 D7A495D8:007F9D3F 17 142 10444 12 ABORT TRANSACTION - xid: 0x0007.018.000001fe ?? PID 17 ??? TX resource?Enqueue Waiter linked List ???PID 24???,????KSL POST SENT ?? PID 24, ???ksqrcl???ENQUEUE LOCK ?PID 24??????KSL POST (KSL POST RCVD poster=17), ?ksqgtl???? TX-00070018-000001fe ?? ksqrcl??, ??PID 24???????? TX lock?USN ,??????? USN 3 XID 3.11.582 ,???acquire TX-0003000b-00000246 D7A49616:007F9D41 24 140 10005 3 KSL POST RCVD poster=17 loc='ksqrcl' id1=0 id2=0 name= type=0 fac#=0 facpost=1 D7A4961C:007F9D42 24 140 10704 19 ksqgtl: SUCCESS D7A4967D:007F9D43 24 140 10704 117 ksqrcl: release TX-00070018-000001fe mode=X D7A496A5:007F9D44 24 140 10813 1 ktubnd: Bind usn 3 nax 1 nbx 0 lng 0 par 0 D7A496C2:007F9D45 24 140 10813 2 ktubnd: Txn Bound xid: 3.11.582 D7A496C7:007F9D46 24 140 10704 83 ksqgtl: acquire TX-0003000b-00000246 mode=X flags=GLOBAL|XACT why="contention" D7A496E4:007F9D47 24 140 10704 19 ksqgtl: SUCCESS ROW LOCK?Release ??????TX?ENQUEUE LOCK,?????????Process J ????????????, Process K??????????? ,Process K?????????,???row piece?lb??0×0 ,?????ITL,Process Z???ITL???????Process J????XID,?????Process J?????TX lock,PROCESS K ???TX resource?Enqueue Waiter Linked List?????X mode(exclusive)?enqueue lock? ???Process J??TX lock?,Process J?????TX resource?Enqueue Waiter Linked List ???Process K??????,??POST?????Process K? TX lock??????,???????row lock???????,?????????

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Abstracting the adding of click events to elements selected by class using jQuery

- by baroquedub

I'm slowly getting up to speed with jQuery and am starting to want to abstract my code. I'm running into problems trying to define click events at page load. In the code below, I'm trying to run through each div with the 'block' class and add events to some of its child elements by selecting them by class: <script language="javascript" type="text/javascript"> $(document).ready(function (){ $('HTML').addClass('JS'); // if JS enabled, hide answers $(".block").each(function() { problem = $(this).children('.problem'); button = $(this).children('.showButton'); problem.data('currentState', 'off'); button.click(function() { if ((problem.data('currentState')) == 'off'){ button.children('.btn').html('Hide'); problem.data('currentState', 'on'); problem.fadeIn('slow'); } else if ((problem.data('currentState')) == 'on'){ button.children('.btn').html('Solve'); problem.data('currentState', 'off'); problem.fadeOut('fast'); } return false; }); }); }); </script> <style media="all" type="text/css"> .JS div.problem{display:none;} </style> <div class="block"> <div class="showButton"> <a href="#" title="Show solution" class="btn">Solve</a> </div> <div class="problem"> <p>Answer 1</p> </div> </div> <div class="block"> <div class="showButton"> <a href="#" title="Show solution" class="btn">Solve</a> </div> <div class="problem"> <p>Answer 2</p> </div> </div> Unfortunately using this, only the last of the divs' button actually works. The event is not 'localised' (if that's the right word for it?) i.e. the event is only applied to the last $(".block") in the each method. So I have to laboriously add ids for each element and define my click events one by one. Surely there's a better way! Can anyone tell me what I'm doing wrong? And how I can get rid of the need for those IDs (I want this to work on dynamically generated pages where I might not know how many 'blocks' there are...) <script language="javascript" type="text/javascript"> $(document).ready(function (){ $('HTML').addClass('JS'); // if JS enabled, hide answers // Preferred version DOESN'T' WORK // So have to add ids to each element and laboriously set-up each one in turn... $('#problem1').data('currentState', 'off'); $('#showButton1').click(function() { if (($('#problem1').data('currentState')) == 'off'){ $('#showButton1 > a').html('Hide'); $('#problem1').data('currentState', 'on'); $('#problem1').fadeIn('slow'); } else if (($('#problem1').data('currentState')) == 'on'){ $('#showButton1 > a').html('Solve'); $('#problem1').data('currentState', 'off'); $('#problem1').fadeOut('fast'); } return false; }); $('#problem2').data('currentState', 'off'); $('#showButton2').click(function() { if (($('#problem2').data('currentState')) == 'off'){ $('#showButton2 > a').html('Hide'); $('#problem2').data('currentState', 'on'); $('#problem2').fadeIn('slow'); } else if (($('#problem2').data('currentState')) == 'on'){ $('#showButton2 > a').html('Solve'); $('#problem2').data('currentState', 'off'); $('#problem2').fadeOut('fast'); } return false; }); }); </script> <style media="all" type="text/css"> .JS div.problem{display:none;} </style> <div class="block"> <div class="showButton" id="showButton1"> <a href="#" title="Show solution" class="btn">Solve</a> </div> <div class="problem" id="problem1"> <p>Answer 1</p> </div> </div> <div class="block"> <div class="showButton" id="showButton2"> <a href="#" title="Show solution" class="btn">Solve</a> </div> <div class="problem" id="problem2"> <p>Answer 2</p> </div> </div>

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Handling file upload in a non-blocking manner

- by Kaliyug Antagonist

The background thread is here Just to make objective clear - the user will upload a large file and must be redirected immediately to another page for proceeding different operations. But the file being large, will take time to be read from the controller's InputStream. So I unwillingly decided to fork a new Thread to handle this I/O. The code is as follows : The controller servlet /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse * response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub System.out.println("In Controller.doPost(...)"); TempModel tempModel = new TempModel(); tempModel.uploadSegYFile(request, response); System.out.println("Forwarding to Accepted.jsp"); /*try { Thread.sleep(1000 * 60); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }*/ request.getRequestDispatcher("/jsp/Accepted.jsp").forward(request, response); } The model class package com.model; import java.io.IOException; import java.util.concurrent.ExecutionException; import java.util.concurrent.Future; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.utils.ProcessUtils; public class TempModel { public void uploadSegYFile(HttpServletRequest request, HttpServletResponse response) { // TODO Auto-generated method stub System.out.println("In TempModel.uploadSegYFile(...)"); /* * Trigger the upload/processing code in a thread, return immediately * and notify when the thread completes */ try { FileUploaderRunnable fileUploadRunnable = new FileUploaderRunnable( request.getInputStream()); /* * Future<FileUploaderRunnable> future = ProcessUtils.submitTask( * fileUploadRunnable, fileUploadRunnable); * * FileUploaderRunnable processed = future.get(); * * System.out.println("Is file uploaded : " + * processed.isFileUploaded()); */ Thread uploadThread = new Thread(fileUploadRunnable); uploadThread.start(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } /* * catch (InterruptedException e) { // TODO Auto-generated catch block * e.printStackTrace(); } catch (ExecutionException e) { // TODO * Auto-generated catch block e.printStackTrace(); } */ System.out.println("Returning from TempModel.uploadSegYFile(...)"); } } The Runnable package com.model; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.nio.ByteBuffer; import java.nio.channels.Channels; import java.nio.channels.ReadableByteChannel; public class FileUploaderRunnable implements Runnable { private boolean isFileUploaded = false; private InputStream inputStream = null; public FileUploaderRunnable(InputStream inputStream) { // TODO Auto-generated constructor stub this.inputStream = inputStream; } public void run() { // TODO Auto-generated method stub /* Read from InputStream. If success, set isFileUploaded = true */ System.out.println("Starting upload in a thread"); File outputFile = new File("D:/06c01_output.seg");/* * This will be changed * later */ FileOutputStream fos; ReadableByteChannel readable = Channels.newChannel(inputStream); ByteBuffer buffer = ByteBuffer.allocate(1000000); try { fos = new FileOutputStream(outputFile); while (readable.read(buffer) != -1) { fos.write(buffer.array()); buffer.clear(); } fos.flush(); fos.close(); readable.close(); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println("File upload thread completed"); } public boolean isFileUploaded() { return isFileUploaded; } } My queries/doubts : Spawning threads manually from the Servlet makes sense to me logically but scares me coding wise - the container isn't aware of these threads after all(I think so!) The current code is giving an Exception which is quite obvious - the stream is inaccessible as the doPost(...) method returns before the run() method completes : In Controller.doPost(...) In TempModel.uploadSegYFile(...) Returning from TempModel.uploadSegYFile(...) Forwarding to Accepted.jsp Starting upload in a thread Exception in thread "Thread-4" java.lang.NullPointerException at org.apache.coyote.http11.InternalInputBuffer.fill(InternalInputBuffer.java:512) at org.apache.coyote.http11.InternalInputBuffer.fill(InternalInputBuffer.java:497) at org.apache.coyote.http11.InternalInputBuffer$InputStreamInputBuffer.doRead(InternalInputBuffer.java:559) at org.apache.coyote.http11.AbstractInputBuffer.doRead(AbstractInputBuffer.java:324) at org.apache.coyote.Request.doRead(Request.java:422) at org.apache.catalina.connector.InputBuffer.realReadBytes(InputBuffer.java:287) at org.apache.tomcat.util.buf.ByteChunk.substract(ByteChunk.java:407) at org.apache.catalina.connector.InputBuffer.read(InputBuffer.java:310) at org.apache.catalina.connector.CoyoteInputStream.read(CoyoteInputStream.java:202) at java.nio.channels.Channels$ReadableByteChannelImpl.read(Unknown Source) at com.model.FileUploaderRunnable.run(FileUploaderRunnable.java:39) at java.lang.Thread.run(Unknown Source) Keeping in mind the point 1., does the use of Executor framework help me in anyway ? package com.utils; import java.util.concurrent.Future; import java.util.concurrent.ScheduledThreadPoolExecutor; public final class ProcessUtils { /* Ensure that no more than 2 uploads,processing req. are allowed */ private static final ScheduledThreadPoolExecutor threadPoolExec = new ScheduledThreadPoolExecutor( 2); public static <T> Future<T> submitTask(Runnable task, T result) { return threadPoolExec.submit(task, result); } } So how should I ensure that the user doesn't block and the stream remains accessible so that the (uploaded)file can be read from it?

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Use IIS Application Initialization for keeping ASP.NET Apps alive

- by Rick Strahl

I've been working quite a bit with Windows Services in the recent months, and well, it turns out that Windows Services are quite a bear to debug, deploy, update and maintain. The process of getting services set up, debugged and updated is a major chore that has to be extensively documented and or automated specifically. On most projects when a service is built, people end up scrambling for the right 'process' to use for administration. Web app deployment and maintenance on the other hand are common and well understood today, as we are constantly dealing with Web apps. There's plenty of infrastructure and tooling built into Web Tools like Visual Studio to facilitate the process. By comparison Windows Services or anything self-hosted for that matter seems convoluted.In fact, in a recent blog post I mentioned that on a recent project I'd been using self-hosting for SignalR inside of a Windows service, because the application is in fact a 'service' that also needs to send out lots of messages via SignalR. But the reality is that it could just as well be an IIS application with a service component that runs in the background. Either way you look at it, it's either a Windows Service with a built in Web Server, or an IIS application running a Service application, neither of which follows the standard Service or Web App template.Personally I much prefer Web applications. Running inside of IIS I get all the benefits of the IIS platform including service lifetime management (crash and restart), controlled shutdowns, the whole security infrastructure including easy certificate support, hot-swapping of code and the the ability to publish directly to IIS from within Visual Studio with ease.Because of these benefits we set out to move from the self hosted service into an ASP.NET Web app instead.The Missing Link for ASP.NET as a Service: Auto-LoadingI've had moments in the past where I wanted to run a 'service like' application in ASP.NET because when you think about it, it's so much easier to control a Web application remotely. Services are locked into start/stop operations, but if you host inside of a Web app you can write your own ticket and control it from anywhere. In fact nearly 10 years ago I built a background scheduling application that ran inside of ASP.NET and it worked great and it's still running doing its job today.The tricky part for running an app as a service inside of IIS then and now, is how to get IIS and ASP.NET launched so your 'service' stays alive even after an Application Pool reset. 7 years ago I faked it by using a web monitor (my own West Wind Web Monitor app) I was running anyway to monitor my various web sites for uptime, and having the monitor ping my 'service' every 20 seconds to effectively keep ASP.NET alive or fire it back up after a reload. I used a simple scheduler class that also includes some logic for 'self-reloading'. Hacky for sure, but it worked reliably.Luckily today it's much easier and more integrated to get IIS to launch ASP.NET as soon as an Application Pool is started by using the Application Initialization Module. The Application Initialization Module basically allows you to turn on Preloading on the Application Pool and the Site/IIS App, which essentially fires a request through the IIS pipeline as soon as the Application Pool has been launched. This means that effectively your ASP.NET app becomes active immediately, Application_Start is fired making sure your app stays up and running at all times. All the other features like Application Pool recycling and auto-shutdown after idle time still work, but IIS will then always immediately re-launch the application.Getting started with Application InitializationAs of IIS 8 Application Initialization is part of the IIS feature set. For IIS 7 and 7.5 there's a separate download available via Web Platform Installer. Using IIS 8 Application Initialization is an optional install component in Windows or the Windows Server Role Manager: This is an optional component so make sure you explicitly select it.IIS Configuration for Application InitializationInitialization needs to be applied on the Application Pool as well as the IIS Application level. As of IIS 8 these settings can be made through the IIS Administration console.Start with the Application Pool:Here you need to set both the Start Automatically which is always set, and the StartMode which should be set to AlwaysRunning. Both have to be set - the Start Automatically flag is set true by default and controls the starting of the application pool itself while Always Running flag is required in order to launch the application. Without the latter flag set the site settings have no effect.Now on the Site/Application level you can specify whether the site should pre load: Set the Preload Enabled flag to true.At this point ASP.NET apps should auto-load. This is all that's needed to pre-load the site if all you want is to get your site launched automatically.If you want a little more control over the load process you can add a few more settings to your web.config file that allow you to show a static page while the App is starting up. This can be useful if startup is really slow, so rather than displaying blank screen while the user is fiddling their thumbs you can display a static HTML page instead: <system.webServer> <applicationInitialization remapManagedRequestsTo="Startup.htm" skipManagedModules="true"> <add initializationPage="ping.ashx" /> </applicationInitialization> </system.webServer>This allows you to specify a page to execute in a dry run. IIS basically fakes request and pushes it directly into the IIS pipeline without hitting the network. You specify a page and IIS will fake a request to that page in this case ping.ashx which just returns a simple OK string - ie. a fast pipeline request. This request is run immediately after Application Pool restart, and while this request is running and your app is warming up, IIS can display an alternate static page - Startup.htm above. So instead of showing users an empty loading page when clicking a link on your site you can optionally show some sort of static status page that says, "we'll be right back". I'm not sure if that's such a brilliant idea since this can be pretty disruptive in some cases. Personally I think I prefer letting people wait, but at least get the response they were supposed to get back rather than a random page. But it's there if you need it.Note that the web.config stuff is optional. If you don't provide it IIS hits the default site link (/) and even if there's no matching request at the end of that request it'll still fire the request through the IIS pipeline. Ideally though you want to make sure that an ASP.NET endpoint is hit either with your default page, or by specify the initializationPage to ensure ASP.NET actually gets hit since it's possible for IIS fire unmanaged requests only for static pages (depending how your pipeline is configured).What about AppDomain Restarts?In addition to full Worker Process recycles at the IIS level, ASP.NET also has to deal with AppDomain shutdowns which can occur for a variety of reasons:Files are updated in the BIN folderWeb Deploy to your siteweb.config is changedHard application crashThese operations don't cause the worker process to restart, but they do cause ASP.NET to unload the current AppDomain and start up a new one. Because the features above only apply to Application Pool restarts, AppDomain restarts could also cause your 'ASP.NET service' to stop processing in the background.In order to keep the app running on AppDomain recycles, you can resort to a simple ping in the Application_End event:protected void Application_End() { var client = new WebClient(); var url = App.AdminConfiguration.MonitorHostUrl + "ping.aspx"; client.DownloadString(url); Trace.WriteLine("Application Shut Down Ping: " + url); }which fires any ASP.NET url to the current site at the very end of the pipeline shutdown which in turn ensures that the site immediately starts back up.Manual Configuration in ApplicationHost.configThe above UI corresponds to the following ApplicationHost.config settings. If you're using IIS 7, there's no UI for these flags so you'll have to manually edit them.When you install the Application Initialization component into IIS it should auto-configure the module into ApplicationHost.config. Unfortunately for me, with Mr. Murphy in his best form for me, the module registration did not occur and I had to manually add it.<globalModules> <add name="ApplicationInitializationModule" image="%windir%\System32\inetsrv\warmup.dll" /> </globalModules>Most likely you won't need ever need to add this, but if things are not working it's worth to check if the module is actually registered.Next you need to configure the ApplicationPool and the Web site. The following are the two relevant entries in ApplicationHost.config.<system.applicationHost> <applicationPools> <add name="West Wind West Wind Web Connection" autoStart="true" startMode="AlwaysRunning" managedRuntimeVersion="v4.0" managedPipelineMode="Integrated"> <processModel identityType="LocalSystem" setProfileEnvironment="true" /> </add> </applicationPools> <sites> <site name="Default Web Site" id="1"> <application path="/MPress.Workflow.WebQueueMessageManager" applicationPool="West Wind West Wind Web Connection" preloadEnabled="true"> <virtualDirectory path="/" physicalPath="C:\Clients\…" /> </application> </site> </sites> </system.applicationHost>On the Application Pool make sure to set the autoStart and startMode flags to true and AlwaysRunning respectively. On the site make sure to set the preloadEnabled flag to true.And that's all you should need. You can still set the web.config settings described above as well.ASP.NET as a Service?In the particular application I'm working on currently, we have a queue manager that runs as standalone service that polls a database queue and picks out jobs and processes them on several threads. The service can spin up any number of threads and keep these threads alive in the background while IIS is running doing its own thing. These threads are newly created threads, so they sit completely outside of the IIS thread pool. In order for this service to work all it needs is a long running reference that keeps it alive for the life time of the application.In this particular app there are two components that run in the background on their own threads: A scheduler that runs various scheduled tasks and handles things like picking up emails to send out outside of IIS's scope and the QueueManager. Here's what this looks like in global.asax:public class Global : System.Web.HttpApplication { private static ApplicationScheduler scheduler; private static ServiceLauncher launcher; protected void Application_Start(object sender, EventArgs e) { // Pings the service and ensures it stays alive scheduler = new ApplicationScheduler() { CheckFrequency = 600000 }; scheduler.Start(); launcher = new ServiceLauncher(); launcher.Start(); // register so shutdown is controlled HostingEnvironment.RegisterObject(launcher); }}By keeping these objects around as static instances that are set only once on startup, they survive the lifetime of the application. The code in these classes is essentially unchanged from the Windows Service code except that I could remove the various overrides required for the Windows Service interface (OnStart,OnStop,OnResume etc.). Otherwise the behavior and operation is very similar.In this application ASP.NET serves two purposes: It acts as the host for SignalR and provides the administration interface which allows remote management of the 'service'. I can start and stop the service remotely by shutting down the ApplicationScheduler very easily. I can also very easily feed stats from the queue out directly via a couple of Web requests or (as we do now) through the SignalR service.Registering a Background Object with ASP.NETNotice also the use of the HostingEnvironment.RegisterObject(). This function registers an object with ASP.NET to let it know that it's a background task that should be notified if the AppDomain shuts down. RegisterObject() requires an interface with a Stop() method that's fired and allows your code to respond to a shutdown request. Here's what the IRegisteredObject::Stop() method looks like on the launcher:public void Stop(bool immediate = false) { LogManager.Current.LogInfo("QueueManager Controller Stopped."); Controller.StopProcessing(); Controller.Dispose(); Thread.Sleep(1500); // give background threads some time HostingEnvironment.UnregisterObject(this); }Implementing IRegisterObject should help with reliability on AppDomain shutdowns. Thanks to Justin Van Patten for pointing this out to me on Twitter.RegisterObject() is not required but I would highly recommend implementing it on whatever object controls your background processing to all clean shutdowns when the AppDomain shuts down.Testing it outI'm still in the testing phase with this particular service to see if there are any side effects. But so far it doesn't look like it. With about 50 lines of code I was able to replace the Windows service startup to Web start up - everything else just worked as is. An honorable mention goes to SignalR 2.0's oWin hosting, because with the new oWin based hosting no code changes at all were required, merely a couple of configuration file settings and an assembly directive needed, to point at the SignalR startup class. Sweet!It also seems like SignalR is noticeably faster running inside of IIS compared to self-host. Startup feels faster because of the preload.Starting and Stopping the 'Service'Because the application is running as a Web Server, it's easy to have a Web interface for starting and stopping the services running inside of the service. For our queue manager the SignalR service and front monitoring app has a play and stop button for toggling the queue.If you want more administrative control and have it work more like a Windows Service you can also stop the application pool explicitly from the command line which would be equivalent to stopping and restarting a service.To start and stop from the command line you can use the IIS appCmd tool. To stop:> %windir%\system32\inetsrv\appcmd stop apppool /apppool.name:"Weblog"and to start> %windir%\system32\inetsrv\appcmd start apppool /apppool.name:"Weblog"Note that when you explicitly force the AppPool to stop running either in the UI (on the ApplicationPools page use Start/Stop) or via command line tools, the application pool will not auto-restart immediately. You have to manually start it back up.What's not to like?There are certainly a lot of benefits to running a background service in IIS, but… ASP.NET applications do have more overhead in terms of memory footprint and startup time is a little slower, but generally for server applications this is not a big deal. If the application is stable the service should fire up and stay running indefinitely. A lot of times this kind of service interface can simply be attached to an existing Web application, or if scalability requires be offloaded to its own Web server.Easier to work withBut the ultimate benefit here is that it's much easier to work with a Web app as opposed to a service. While developing I can simply turn off the auto-launch features and launch the service on demand through IIS simply by hitting a page on the site. If I want to shut down an IISRESET -stop will shut down the service easily enough. I can then attach a debugger anywhere I want and this works like any other ASP.NET application. Yes you end up on a background thread for debugging but Visual Studio handles that just fine and if you stay on a single thread this is no different than debugging any other code.SummaryUsing ASP.NET to run background service operations is probably not a super common scenario, but it probably should be something that is considered carefully when building services. Many applications have service like features and with the auto-start functionality of the Application Initialization module, it's easy to build this functionality into ASP.NET. Especially when combined with the notification features of SignalR it becomes very, very easy to create rich services that can also communicate their status easily to the outside world.Whether it's existing applications that need some background processing for scheduling related tasks, or whether you just create a separate site altogether just to host your service it's easy to do and you can leverage the same tool chain you're already using for other Web projects. If you have lots of service projects it's worth considering… give it some thought…© Rick Strahl, West Wind Technologies, 2005-2013Posted in ASP.NET SignalR IIS Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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