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• Linux configurations that would affect Java memory usage?

  - by wmacura

  Hi, Background: I have a set of java background workers I start as part of my webapp. I develop locally on Ubuntu 10.10 and deploy to an Ubuntu 10.04LTS server (a media temple (ve) instance). They're both running the same JVM: Sun JVM 1.6.0_22-b04. As part of the initialization script each worker is started with explicit Xmx, Xms, and XX:MaxPermGen settings. Yet somehow locally all 10 workers use 250MB, while on the server they use more than 2.7GB. I don't know how to begin to track this down. I thought the Ubuntu (and thus, kernel) version might make a difference, but I tried an old 10.04 VM and it behaves as expected. I've noticed that the machine does not seem to ever use memory for buffer or cache (according to htop), which seems a bit strange, but perhaps normal for a server? (edited) Some info: (server) root@devel:/app/axir/target# uname -a Linux devel 2.6.18-028stab069.5 #1 SMP Tue May 18 17:26:16 MSD 2010 x86_64 GNU/Linux (local) wiktor@beastie:~$ uname -a Linux beastie 2.6.35-25-generic #44-Ubuntu SMP Fri Jan 21 17:40:44 UTC 2011 x86_64 GNU/Linux (edited) Comparing PS output: (ps -eo "ppid,pid,cmd,rss,sz,vsz") PPID PID CMD RSS SZ VSZ (local) 1588 1615 java -cp axir-distribution. 25484 234382 937528 1615 1631 java -cp /home/wiktor/Code/ 83472 163059 652236 1615 1657 java -cp /home/wiktor/Code/ 70624 89135 356540 1615 1658 java -cp /home/wiktor/Code/ 37652 77625 310500 1615 1669 java -cp /home/wiktor/Code/ 38096 77733 310932 1615 1675 java -cp /home/wiktor/Code/ 37420 61395 245580 1615 1684 java -cp /home/wiktor/Code/ 38000 77736 310944 1615 1703 java -cp /home/wiktor/Code/ 39180 78060 312240 1615 1712 java -cp /home/wiktor/Code/ 38488 93882 375528 1615 1719 java -cp /home/wiktor/Code/ 38312 77874 311496 1615 1726 java -cp /home/wiktor/Code/ 38656 77958 311832 1615 1727 java -cp /home/wiktor/Code/ 78016 89429 357716 (server) 22522 23560 java -cp axir-distribution. 24860 285196 1140784 23560 23585 java -cp /app/axir/target/a 100764 161629 646516 23560 23667 java -cp /app/axir/target/a 72408 92682 370728 23560 23670 java -cp /app/axir/target/a 39948 97671 390684 23560 23674 java -cp /app/axir/target/a 40140 81586 326344 23560 23739 java -cp /app/axir/target/a 39688 81542 326168 They look very similar. In fact, the question now is why, if I add up the virtual memory usage on the server (3.2GB) does it more closely reflect 2.4GB of memory used (according to free), yet locally the virtual memory used adds up to a much more substantial 4.7GB but only actually uses ~250MB. It seems that perhaps memory isn't being shared as aggressively. (if that's even possible) Thank you for your help, Wiktor

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• How to compute a unicode string which bidirectional representation is specified?

  - by valdo

  Hello, fellows. I have a rather pervert question. Please forgive me :) There's an official algorithm that describes how bidirectional unicode text should be presented. http://www.unicode.org/reports/tr9/tr9-15.html I receive a string (from some 3rd-party source), which contains latin/hebrew characters, as well as digits, white-spaces, punctuation symbols and etc. The problem is that the string that I receive is already in the representation form. I.e. - the sequence of characters that I receive should just be presented from left to right. Now, my goal is to find the unicode string which representation is exactly the same. Means - I need to pass that string to another entity; it would then render this string according to the official algorithm, and the result should be the same. Assuming the following: The default text direction (of the rendering entity) is RTL. I don't want to inject "special unicode characters" that explicitly override the text direction (such as RLO, RLE, etc.) I suspect there may exist several solutions. If so - I'd like to preserve the RTL-looking of the string as much as possible. The string usually consists of hebrew words mostly. I'd like to preserve the correct order of those words, and characters inside those words. Whereas other character sequences may (and should) be transposed. One naive way to solve this is just to swap the whole string (this takes care of the hebrew words), and then swap inside it sequences of non-hebrew characters. This however doesn't always produce correct results, because actual rules of representation are rather complex. The only comprehensive algorithm that I see so far is brute-force check. The string can be divided into sequences of same-class characters. Those sequences may be joined in random order, plus any of them may be reversed. I can check all those combinations to obtain the correct result. Plus this technique may be optimized. For instance the order of hebrew words is known, so we only have to check different combinations of their "joining" sequences. Any better ideas? If you have an idea, not necessarily the whole solution - it's ok. I'll appreciate any idea. Thanks in advance.

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• Android Camera takePicture function does not call Callback function

  - by Tomáš 'Guns Blazing' Frcek

  I am working on a custom Camera activity for my application. I was following the instruction from the Android Developers site here: http://developer.android.com/guide/topics/media/camera.html Everything seems to works fine, except the Callback function is not called and the picture is not saved. Here is my code: public class CameraActivity extends Activity { private Camera mCamera; private CameraPreview mPreview; private static final String TAG = "CameraActivity"; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.camera); // Create an instance of Camera mCamera = getCameraInstance(); // Create our Preview view and set it as the content of our activity. mPreview = new CameraPreview(this, mCamera); FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview); preview.addView(mPreview); Button captureButton = (Button) findViewById(R.id.button_capture); captureButton.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { Log.v(TAG, "will now take picture"); mCamera.takePicture(null, null, mPicture); Log.v(TAG, "will now release camera"); mCamera.release(); Log.v(TAG, "will now call finish()"); finish(); } }); } private PictureCallback mPicture = new PictureCallback() { @Override public void onPictureTaken(byte[] data, Camera camera) { Log.v(TAG, "Getting output media file"); File pictureFile = getOutputMediaFile(); if (pictureFile == null) { Log.v(TAG, "Error creating output file"); return; } try { FileOutputStream fos = new FileOutputStream(pictureFile); fos.write(data); fos.close(); } catch (FileNotFoundException e) { Log.v(TAG, e.getMessage()); } catch (IOException e) { Log.v(TAG, e.getMessage()); } } }; private static File getOutputMediaFile() { String state = Environment.getExternalStorageState(); if (!state.equals(Environment.MEDIA_MOUNTED)) { return null; } else { File folder_gui = new File(Environment.getExternalStorageDirectory() + File.separator + "GUI"); if (!folder_gui.exists()) { Log.v(TAG, "Creating folder: " + folder_gui.getAbsolutePath()); folder_gui.mkdirs(); } File outFile = new File(folder_gui, "temp.jpg"); Log.v(TAG, "Returnng file: " + outFile.getAbsolutePath()); return outFile; } } After clicking the Button, I get logs: "will now take picture", "will now release camera" and "will now call finish". The activity finishes succesfully, but the Callback function was not called during the mCamera.takePicture(null, null, mPicture); function (There were no logs from the mPicture callback or getMediaOutputFile functions) and there is no file in the location that was specified. Any ideas? :) Much thanks!

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• how to wait multiple function processing to finish

  - by user351412

  I have a problem about multiple function processing , listed as below code, the main function is btnEvalClick, I have try to use alter native 1and 2 to wait the function not move to next record before theprocessed function finish, but it does not work //private function btnEvalClick(event:Event):void { // var i:int; // for(i= 0; i < (dataArr1.length); i++) { // dispatchEvent( new FlexEvent('test') ); // callfunc1('cydatGMX'); //call function 1 // callfun2('cydatGMO'); //call function 1 // editSave(); //save record (HTTP) //## Alternative 1 //if (String(event) == 'SAVEOK') { // RecMov('next'); //move record if save = OK //} //## Alternative 2 //while (waitfc == '') // if waitfc not 'OK' continue looping //{ // z = z + 1; //} // RecMov('next'); //Move to next record to process //} //private function callfunc1(tasal:String):void { // var mySO :SharedObject; // var myDP: Array; // var i:int; // var prm:Array; // try // { // mySO = SharedObject.getLocal(tasal,'/'); // prm = mySO.data.txt.split('?'); // for(i=0; i < (prm.length - 1); i++) { // myDP = prm[i].toString().split('^'); // if ( myDP[0].toString() == String(dataArr1[dg].MatrixCDCol)){ // myDPX = myDP; // break; // } // } // } // catch (err:Error) { // Alert.show('Limit object creation fail (' + tasal + '), please retry ); // } //} //private function editSave():void //{ // var parameters:* = // { // 'CertID': CertIDCol.text, 'AssetID': AssetIDCol.text, 'CertDate': cdt, //'Ccatat': CcatatCol.text, 'CertBy': CertByCol.text, 'StatusID': StatusIDCol.text, //'UpdDate': lele, 'UpdUsr': ApplicationState.instance.luNm }; // doRequest('Update', parameters, saveItemHandler); //} //private function doRequest(method_name:String, parameters:Object, callback:Function):void // { // add the method to the parameters list // parameters['method'] = (method_name + 'ASC'); // gateway.request = parameters; // var call:AsyncToken = gateway.send(); // call.request_params = gateway.request; // call.handler = callback; // } //private function saveItemHandler(e:Object):void // { // if (e.isError) // { // Alert.show('Error: ' + e.data.error); // } // else // { // Alert.show('Record Saved..'); // waitfc = 'OK'; // dispatchEvent( new FlexEvent('SAVEOK') ); // } // }

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• IOC/Autofac problem

  - by Krazzy

  I am currently using Autofac, but am open to commentary regarding other IOC containers as well. I would prefer a solution using Autofac if possible. I am also somewhat new to IOC so I may be grossly misunderstanding what I should be using an IOC container for. Basically, the situation is as follows: I have a topmost IOC container for my app. I have a tree of child containers/scopes where I would like the same "service" (IWhatever) to resolve differently depending on which level in the tree it is resolved. Furthermore if a service is not registered at some level in the tree I would like the tree to be transversed upward until a suitable implementation is found. Furthermore, when constructing a given component, it is quite possible that I will need access to the parent container/scope. In many cases the component that I'm registering will have a dependency on the same or a different service in a parent scope. Is there any way to express this dependency with Autofac? Something like: builder.Register(c=> { var parentComponent = ?.Resolve<ISomeService>(); var childComponent = new ConcreteService(parentComponent, args...); return childComponent; }).As<ISomeService>(); I can't get anything similar to the above pseudocode to work for serveral reasons: A) It seems that all levels in the scope tree share a common set of registrations. I can't seem to find a way to make a given registration confined a certain "scope". B) I can't seem to find a way to get a hold of the parent scope of a given scope. I CAN resolve ILifetimeScope in the container and then case it to a concrete LifetimeScope instance which provides its parent scope, but I'm guessing it is probably note meant to be used this way. Is this safe? C) I'm not sure how to tell Autofac which container owns the resolved object. For many components I would like component to be "owned" by the scope in which it is constructed. Could tagged contexts help me here? Would I have to tag every level of the tree with a unique tag? This would be difficult because the tree depth is determined at runtime. Sorry for the extremely lengthy question. In summary: 1) Is there any way to do what I want to do using Autofac? 2) Is there another container more suited to this kind of dependency structure? 3) Is IOC the wrong tool for this altogether?

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• VB.NET looping through XML to store in singleton

  - by rockinthesixstring

  I'm having a problem with looping through an XML file and storing the value in a singleton My XML looks like this <values> <value></value> <value>$1</value> <value>$5,000</value> <value>$10,000</value> <value>$15,000</value> <value>$25,000</value> <value>$50,000</value> <value>$75,000</value> <value>$100,000</value> <value>$250,000</value> <value>$500,000</value> <value>$750,000</value> <value>$1,000,000</value> <value>$1,250,000</value> <value>$1,500,000</value> <value>$1,750,000</value> <value>$2,000,000</value> <value>$2,500,000</value> <value>$3,000,000</value> <value>$4,000,000</value> <value>$5,000,000</value> <value>$7,500,000</value> <value>$10,000,000</value> <value>$15,000,000</value> <value>$25,000,000</value> <value>$50,000,000</value> <value>$100,000,000</value> <value>$100,000,000+</value> </values> And my function looks like this Public Class LoadValues Private Shared SearchValuesInstance As List(Of SearchValues) = Nothing Public Shared ReadOnly Property LoadSearchValues As List(Of SearchValues) Get Dim sv As New List(Of SearchValues) If SearchValuesInstance Is Nothing Then Dim objDoc As XmlDocument = New XmlDataDocument Dim objRdr As XmlTextReader = New XmlTextReader(HttpContext.Current.Server.MapPath("~/App_Data/Search-Values.xml")) objRdr.Read() objDoc.Load(objRdr) Dim root As XmlElement = objDoc.DocumentElement Dim itemNodes As XmlNodeList = root.SelectNodes("/values") For Each n As XmlNode In itemNodes sv.Add(New SearchValues(n("@value").InnerText, n("@value").InnerText)) Next SearchValuesInstance = sv Else : sv = SearchValuesInstance End If Return sv End Get End Property End Class My problem is that I'm getting an object not set to an instance of an object on the sv.Add(New SearchValues(n("@value").InnerText, n("@value").InnerText)) line.

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• Why are these two sql statements deadlocking? (Deadlock graph + details included).

  - by Pure.Krome

  Hi folks, I've got the following deadlock graph that describes two sql statements that are deadlocking each other. I'm just not sure how to analyse this and then fix up my sql code to prevent this from happening. Main deadlock graph Click here for a bigger image. Left side, details Click here for a bigger image. Right side, details Click here for a bigger image. What is the code doing? I'm reading in a number of files (eg. lets say 3, for this example). Each file contains different data BUT the same type of data. I then insert data into LogEntries table and then (if required) I insert or delete something from the ConnectedClients table. Here's my sql code. using (TransactionScope transactionScope = new TransactionScope()) { _logEntryRepository.InsertOrUpdate(logEntry); // Now, if this log entry was a NewConnection or an LostConnection, then we need to make sure we update the ConnectedClients. if (logEntry.EventType == EventType.NewConnection) { _connectedClientRepository.Insert(new ConnectedClient { LogEntryId = logEntry.LogEntryId }); } // A (PB) BanKick does _NOT_ register a lost connection .. so we need to make sure we handle those scenario's as a LostConnection. if (logEntry.EventType == EventType.LostConnection || logEntry.EventType == EventType.BanKick) { _connectedClientRepository.Delete(logEntry.ClientName, logEntry.ClientIpAndPort); } _unitOfWork.Commit(); transactionScope.Complete(); } Now each file has it's own UnitOfWork instance (which means it has it's own database connection, transaction and repository context). So i'm assuming this means there's 3 different connections to the db all happening at the same time. Finally, this is using Entity Framework as the repository, but please don't let that stop you from having a think about this problem. Using a profiling tool, the Isolation Level is Serializable. I've also tried ReadCommited and ReadUncommited, but they both error :- ReadCommited: same as above. Deadlock. ReadUncommited: different error. EF exception that says it expected some result back, but got nothing. I'm guessing this is the LogEntryId Identity (scope_identity) value that is expected but not retrieve because of the dirty read. Please help! PS. It's Sql Server 2008, btw.

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• SQL Invalid Object Name 'AddressType'

  - by salvationishere

  I am getting the above error in my VS 2008 C# method when I try to invoke the SQL getColumnNames stored procedure from VS. This SP accepts one input parameter, the table name, and works successfully from SSMS. Currently I am selecting the AdventureWorks AddressType table for it to pull the column names from this table. I can see teh AdventureWorks table available in VS from my Server Explorer / Data Connection. And I see both the AddressType table and getColumnNames SP showing in Server Explorer. But I am still getting this error listed above. Here is the C# code snippet I use to execute this: public static DataTable DisplayTableColumns(string tt) { SqlDataReader dr = null; string TableName = tt; string connString = "Data Source=.;AttachDbFilename=\"C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\AdventureWorks_Data.mdf\";Initial Catalog=AdventureWorks;Integrated Security=True;Connect Timeout=30;User Instance=False"; string errorMsg; SqlConnection conn2 = new SqlConnection(connString); SqlCommand cmd = conn2.CreateCommand(); try { cmd.CommandText = "dbo.getColumnNames"; cmd.CommandType = CommandType.StoredProcedure; cmd.Connection = conn2; SqlParameter parm = new SqlParameter("@TableName", SqlDbType.VarChar); parm.Value = TableName; parm.Direction = ParameterDirection.Input; cmd.Parameters.Add(parm); conn2.Open(); dr = cmd.ExecuteReader(); } catch (Exception ex) { errorMsg = ex.Message; } And when I examine the errorMsg it says the following: " at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)\r\n at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)\r\n at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)\r\n at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)\r\n at System.Data.SqlClient.SqlDataReader.ConsumeMetaData()\r\n at System.Data.SqlClient.SqlDataReader.get_MetaData()\r\n at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)\r\n at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)\r\n at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)\r\n at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)\r\n at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)\r\n at System.Data.SqlClient.SqlCommand.ExecuteReader()\r\n at ADONET_namespace.ADONET_methods.DisplayTableColumns(String tt) in C:\Documents and Settings\Admin\My Documents\Visual Studio 2008\Projects\AddFileToSQL\AddFileToSQL\ADONET methods.cs:line 35" Where line 35 is dr = cmd.ExecuteReader();

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• WinForm-style Invoke() in unmanaged C++

  - by Matt Green

  I've been playing with a DataBus-type design for a hobby project, and I ran into an issue. Back-end components need to notify the UI that something has happened. My implementation of the bus delivers the messages synchronously with respect to the sender. In other words, when you call Send(), the method blocks until all the handlers have called. (This allows callers to use stack memory management for event objects.) However, consider the case where an event handler updates the GUI in response to an event. If the handler is called, and the message sender lives on another thread, then the handler cannot update the GUI due to Win32's GUI elements having thread affinity. More dynamic platforms such as .NET allow you to handle this by calling a special Invoke() method to move the method call (and the arguments) to the UI thread. I'm guessing they use the .NET parking window or the like for these sorts of things. A morbid curiosity was born: can we do this in C++, even if we limit the scope of the problem? Can we make it nicer than existing solutions? I know Qt does something similar with the moveToThread() function. By nicer, I'll mention that I'm specifically trying to avoid code of the following form: if(! this->IsUIThread()) { Invoke(MainWindowPresenter::OnTracksAdded, e); return; } being at the top of every UI method. This dance was common in WinForms when dealing with this issue. I think this sort of concern should be isolated from the domain-specific code and a wrapper object made to deal with it. My implementation consists of: DeferredFunction - functor that stores the target method in a FastDelegate, and deep copies the single event argument. This is the object that is sent across thread boundaries. UIEventHandler - responsible for dispatching a single event from the bus. When the Execute() method is called, it checks the thread ID. If it does not match the UI thread ID (set at construction time), a DeferredFunction is allocated on the heap with the instance, method, and event argument. A pointer to it is sent to the UI thread via PostThreadMessage(). Finally, a hook function for the thread's message pump is used to call the DeferredFunction and de-allocate it. Alternatively, I can use a message loop filter, since my UI framework (WTL) supports them. Ultimately, is this a good idea? The whole message hooking thing makes me leery. The intent is certainly noble, but are there are any pitfalls I should know about? Or is there an easier way to do this?

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• How do I make my custom Swing component visible?

  - by Alex

  I have no idea why it won't show. First I create an instance of the component and then add it to a certain element in a two-dimensional JPanel array. Then I loop through that array and add each JPanel to another JPanel container which is to hold all the JPanels. I then add that final container to my JFrame window and set visibility to true, it should be visible? public class View extends JFrame { Board gameBoard; JFrame gameWindow = new JFrame("Chess"); JPanel gamePanel = new JPanel(); JPanel[][] squarePanel = new JPanel[8][8]; JMenuBar gameMenu = new JMenuBar(); JButton restartGame = new JButton("Restart"); JButton pauseGame = new JButton("Pause"); JButton log = new JButton("Log"); View(Board board){ gameWindow.setDefaultCloseOperation(EXIT_ON_CLOSE); gameWindow.setSize(400, 420); gameWindow.getContentPane().add(gamePanel, BorderLayout.CENTER); gameWindow.getContentPane().add(gameMenu, BorderLayout.NORTH); gameMenu.add(restartGame); gameMenu.add(pauseGame); gameMenu.add(log); gameBoard = board; drawBoard(gameBoard); gameWindow.setResizable(false); gameWindow.setVisible(true); } public void drawBoard(Board board){ for(int row = 0; row < 8; row++){ for(int col = 0; col < 8; col++){ Box box = new Box(board.getSquare(col, row).getColour(), col, row); squarePanel[col][row] = new JPanel(); squarePanel[col][row].add(box); } } for(JPanel[] col : squarePanel){ for(JPanel square : col){ gamePanel.add(square); } } } } @SuppressWarnings("serial") class Box extends JComponent{ Color boxColour; int col, row; public Box(Color boxColour, int col, int row){ this.boxColour = boxColour; this.col = col; this.row = row; repaint(); } protected void paintComponent(Graphics drawBox){ drawBox.setColor(boxColour); drawBox.drawRect(50*col, 50*row, 50, 50); drawBox.fillRect(50*col, 50*row, 50, 50); } } A final question as well. Notice how each Box component has a position, what happens to the position when I add the component to a JPanel and add the JPanel to my JFrame? Does it still have the same position in relation to the other Box components?

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• Absolute Xpath to get list of childnodes?

  - by Googler

  Hi this my xml file, <?xml version="1.0"?> <worldpatentdata xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <meta name="elapsed-time" value="329" xmlns="http://ops.epo.org"/> <exchange-documents xmlns="http://www.epo.org/exchange"> <exchange-document country="AT" doc-number="380509" family-id="38826527" kind="T" system="ops.epo.org"> <bibliographic-data> <publication-reference data-format="docdb"> <document-id> <country>AT</country> <doc-number>380509</doc-number> <kind>T</kind> <date>20071215</date> </document-id> </publication-reference> <parties> <applicants> </applicants> <inventors> </inventors> </parties> </bibliographic-data> </exchange-document> </exchange-documents> </worldpatentdata> For the above xml file, i need the xpath to receive the childnodes below it: Output i need is : <exchange-documents xmlns="http://www.epo.org/exchange"> <exchange-document country="AT" doc-number="380509" family-id="38826527" kind="T" system="ops.epo.org"> <bibliographic-data> <publication-reference data-format="docdb"> <document-id> <country>AT</country> <doc-number>380509</doc-number> <kind>T</kind> <date>20071215</date> </document-id> </publication-reference> <parties> <applicants> </applicants> <inventors> </inventors> </parties> </bibliographic-data> </exchange-document> I using Linq-Xml to get the following data: This is my Xpath and code: var list = doc1.XPathSelectElement("exchange-document"); I couldnt retreive the needed output.It returns null for the above code. Can anyone pls help on this by providing the correct xpath to retieve the child nodes. Else is there any other way to retrieve it.

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• Help with listView in Android

  - by jul

  Hi, I'm just starting with Android and can't find how to display a list in my activity. I get some restaurant data from a web service and I'd like to show the results in a list. The activity, the restaurant class and the layout main.xml are shown below. How can I display, for instance, the list of the restaurant names in the ListView 'list' of my layout? thank you Jul public class Atable extends ListActivity { RestaurantList restaurantList; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); //Here I set restaurantList //Now how can I display, for example, the list of the names of the restaurants } main.xml <LinearLayout android:orientation="horizontal" android:layout_width="fill_parent" android:layout_height="wrap_content"> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/search" /> <EditText android:id="@+id/search" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1"/> </LinearLayout> <LinearLayout android:orientation="vertical" android:layout_width="wrap_content" android:layout_height="wrap_content"> <ListView android:id="@+id/android:list" android:layout_width="wrap_content" android:layout_height="wrap_content"/> <TextView android:id="@+id/android:empty" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/noresults"/> </LinearLayout> </LinearLayout> Restaurant list class package org.digitalfarm.atable; import java.util.List; public class RestaurantList { private List<Restaurant> restaurants; public List<Restaurant> getRestaurants() { return restaurants; } public void setRestaurants(List<Restaurant> restaurants) { this.restaurants = restaurants; } } Restaurant class package org.digitalfarm.atable; public class Restaurant { private String name; private float latitude; private float longitude; public String getName() { return name; } public void setName(String name) { this.name = name; } public float getLatitude() { return latitude; } public void setLatitude(float latitude) { this.latitude = latitude; } public float getLongitude() { return longitude; } public void setLongitude(float longitude) { this.longitude = longitude; } }

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• vector related memory allocation question

  - by memC

  hi all, I am encountering the following bug. I have a class Foo . Instances of this class are stored in a std::vector vec of class B. in class Foo, I am creating an instance of class A by allocating memory using new and deleting that object in ~Foo(). the code compiles, but I get a crash at the runtime. If I disable delete my_a from desstructor of class Foo. The code runs fine (but there is going to be a memory leak). Could someone please explain what is going wrong here and suggest a fix? thank you! class A{ public: A(int val); ~A(){}; int val_a; }; A::A(int val){ val_a = val; }; class Foo { public: Foo(); ~Foo(); void createA(); A* my_a; }; Foo::Foo(){ createA(); }; void Foo::createA(){ my_a = new A(20); }; Foo::~Foo(){ delete my_a; }; class B { public: vector<Foo> vec; void createFoo(); B(){}; ~B(){}; }; void B::createFoo(){ vec.push_back(Foo()); }; int main(){ B b; int i =0; for (i = 0; i < 5; i ++){ std::cout<<"\n creating Foo"; b.createFoo(); std::cout<<"\n Foo created"; } std::cout<<"\nDone with Foo creation"; std::cout << "\nPress RETURN to continue..."; std::cin.get(); return 0; }

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• Dynamically find other hosts in a LAN in Java

  - by Federico Cristina

  A while ago I developed a little LAN chat app. in Java which allows chatting with other hosts, send images, etc. Although it was created just for fun, now it's being used where I work. Currently, there is no "chat server" on the app. where each client registers, updates it's status, etc. (I liked the idea of symmetric design and not depending on a server running on some other machine). Instead, each host is a client/server which has a hosts.properties file with the hostname of the other hosts, and - for instance - broadcasts to each one of them when sending a massive message/image/whatever. In the beginning there were just a couple of hosts, so this hosts.properties file wasn't an issue. But as the amount of users increased, the need of updating that file was a bit daunting. So now I've decided to get rid of it, and each time the app. starts, dynammically find the other active hosts. However, I cannot find the correct way of implement this. I've tried starting different threads, each one of them searching for other hosts in a known range of IP addresses. Something like this (simplified for the sake of readability): /** HostsLocator */ public static void searchForHosts(boolean waitToEnd) { for (int i=0; i < MAX_IP; i+= MAX_IP / threads) { HostsLocator detector = new HostsLocator(i, i+(MAX_IP / threads - 1)); // range: from - to new Thread(detector).start(); } } public void run() { for (int i=from; i<=to; i++) findHosts( maskAddress + Integer.toString(i) ); } public static boolean findHosts(String IP) { InetAddress address = InetAddress.getByName(IP); if ( address.isReachable(CONNECTION_TIME_OUT) ) // host found! } However: With a single thread and a low value in CONNECTION_TIME_OUT (500ms) I get wrong Host Not Found status for for hosts actually active. With a high value in CONNECTION_TIME_OUT (5000ms) and only one single thread takes forever to end With several threads I've also found problems similar like the first one, due to collisions. So... I guess there's a better way of solving this problem but I couldn't find it. Any advice? Thanks!

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• CultureManager issue

  - by Serge

  I have a bug I don't understand. While the following works fine: Resources.Classes.AFieldFormula.DirectFieldFormula this one throws an exception: new ResourceManager(typeof(Resources.Classes.AFieldFormula)).GetString("DirectFieldFormula"); Could not find any resources appropriate for the specified culture or the neutral culture. Make sure \"Resources.Classes.AFieldFormula.resources\" was correctly embedded or linked into assembly \"MygLogWeb\" at compile time, or that all the satellite assemblies required are loadable and fully signed. How comes? Resource designer.cs file: //------------------------------------------------------------------------------ // <auto-generated> // This code was generated by a tool. // Runtime Version:4.0.30319.18408 // // Changes to this file may cause incorrect behavior and will be lost if // the code is regenerated. // </auto-generated> //------------------------------------------------------------------------------ namespace Resources.Classes { using System; /// <summary> /// A strongly-typed resource class, for looking up localized strings, etc. /// </summary> // This class was auto-generated by the StronglyTypedResourceBuilder // class via a tool like ResGen or Visual Studio. // To add or remove a member, edit your .ResX file then rerun ResGen // with the /str option, or rebuild your VS project. [global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Resources.Tools.StronglyTypedResourceBuilder", "4.0.0.0")] [global::System.Diagnostics.DebuggerNonUserCodeAttribute()] [global::System.Runtime.CompilerServices.CompilerGeneratedAttribute()] public class AFieldFormula { private static global::System.Resources.ResourceManager resourceMan; private static global::System.Globalization.CultureInfo resourceCulture; [global::System.Diagnostics.CodeAnalysis.SuppressMessageAttribute("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")] internal AFieldFormula() { } /// <summary> /// Returns the cached ResourceManager instance used by this class. /// </summary> [global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)] public static global::System.Resources.ResourceManager ResourceManager { get { if (object.ReferenceEquals(resourceMan, null)) { global::System.Resources.ResourceManager temp = new global::System.Resources.ResourceManager("MygLogWeb.Classes.AFieldFormula", typeof(AFieldFormula).Assembly); resourceMan = temp; } return resourceMan; } } /// <summary> /// Overrides the current thread's CurrentUICulture property for all /// resource lookups using this strongly typed resource class. /// </summary> [global::System.ComponentModel.EditorBrowsableAttribute(global::System.ComponentModel.EditorBrowsableState.Advanced)] public static global::System.Globalization.CultureInfo Culture { get { return resourceCulture; } set { resourceCulture = value; } } /// <summary> /// Looks up a localized string similar to Direct field. /// </summary> public static string DirectFieldFormula { get { return ResourceManager.GetString("DirectFieldFormula", resourceCulture); } } } }

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• Is there a way to enforce/preserve order of XML elements in an XML Schema?

  - by MarcoS

  Let's consider the following XML Schema: <?xml version="1.0" encoding="UTF-8"?> <schema targetNamespace="http://www.example.org/library" elementFormDefault="qualified" xmlns="http://www.w3.org/2001/XMLSchema" xmlns:lib="http://www.example.org/library"> <element name="library" type="lib:libraryType"></element> <complexType name="libraryType"> <sequence> <element name="books" type="lib:booksType"></element> </sequence> </complexType> <complexType name="booksType"> <sequence> <element name="book" type="lib:bookType" maxOccurs="unbounded" minOccurs="1"></element> </sequence> </complexType> <complexType name="bookType"> <attribute name="title" type="string"></attribute> </complexType> </schema> and a corresponding XML example: <?xml version="1.0" encoding="UTF-8"?> <lib:library xmlns:lib="http://www.example.org/library" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.example.org/library src/library.xsd "> <lib:books> <lib:book title="t1"/> <lib:book title="t2"/> <lib:book title="t3"/> </lib:books> </lib:library> Is there a way to guarantee that the order of <lib:book .../> elements is preserved? I want to be sure that any parser reading the XML will return books in the specified oder, that is first the book with title="t1", then the book with title="t2", and finally the book with title="t3". As far as I know XML parsers are not required to preserve order. I wonder whether one can enforce this through XML Schema? One quick solution for me would be adding an index attribute to the <lib:book .../> element, and delegate order preservation to the application reading the XML. Comments? Suggestions?

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• XmlSerializer.Deserialize blocks over NetworkStream

  - by Luca

  I'm trying to sends XML serializable objects over a network stream. I've already used this on an UDP broadcast server, where it receive UDP messages from the local network. Here a snippet of the server side: while (mServiceStopFlag == false) { if (mSocket.Available > 0) { IPEndPoint ipEndPoint = new IPEndPoint(IPAddress.Any, DiscoveryPort); byte[] bData; // Receive discovery message bData = mSocket.Receive(ref ipEndPoint); // Handle discovery message HandleDiscoveryMessage(ipEndPoint.Address, bData); ... Instead this is the client side: IPEndPoint ipEndPoint = new IPEndPoint(IPAddress.Broadcast, DiscoveryPort); MemoryStream mStream = new MemoryStream(); byte[] bData; // Create broadcast UDP server mSocket = new UdpClient(); mSocket.EnableBroadcast = true; // Create datagram data foreach (NetService s in ctx.Services) XmlHelper.SerializeClass<NetService>(mStream, s); bData = mStream.GetBuffer(); // Notify the services while (mServiceStopFlag == false) { mSocket.Send(bData, (int)mStream.Length, ipEndPoint); Thread.Sleep(DefaultServiceLatency); } It works very fine. But now i'me trying to get the same result, but on a TcpClient socket, but the using directly an XMLSerializer instance: On server side: TcpClient sSocket = k.Key; ServiceContext sContext = k.Value; Message msg = new Message(); while (sSocket.Connected == true) { if (sSocket.Available > 0) { StreamReader tr = new StreamReader(sSocket.GetStream()); msg = (Message)mXmlSerialize.Deserialize(tr); // Handle message msg = sContext.Handler(msg); // Reply with another message if (msg != null) mXmlSerialize.Serialize(sSocket.GetStream(), msg); } else Thread.Sleep(40); } And on client side: NetworkStream mSocketStream; Message rMessage; // Network stream mSocketStream = mSocket.GetStream(); // Send the message mXmlSerialize.Serialize(mSocketStream, msg); // Receive the answer rMessage = (Message)mXmlSerialize.Deserialize(mSocketStream); return (rMessage); The data is sent (Available property is greater then 0), but the method XmlSerialize.Deserialize (which should deserialize the Message class) blocks. What am I missing?

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• Inserting a string array as a row into an Excel document using the Open XML SDK 2.0

  - by Sam

  The code runs, but corrupts my excel document. Any help would be mucho appreciated! I used this as a reference. public void AddRow(string fileName, string[] values) { using (SpreadsheetDocument doc = SpreadsheetDocument.Open(fileName, true)) { SharedStringTablePart sharedStringPart = GetSharedStringPart(doc); WorksheetPart worksheetPart = doc.WorkbookPart.WorksheetParts.First(); uint rowIdx = AppendRow(worksheetPart); for (int i = 0; i < values.Length; ++i) { int stringIdx = InsertSharedString(values[i], sharedStringPart); Cell cell = InsertCell(i, rowIdx, worksheetPart); cell.CellValue = new CellValue(stringIdx.ToString()); cell.DataType = new EnumValue<CellValues>( CellValues.SharedString); worksheetPart.Worksheet.Save(); } } } private SharedStringTablePart GetSharedStringPart( SpreadsheetDocument doc) { if (doc.WorkbookPart. GetPartsCountOfType<SharedStringTablePart>() > 0) return doc.WorkbookPart. GetPartsOfType<SharedStringTablePart>().First(); else return doc.WorkbookPart. AddNewPart<SharedStringTablePart>(); } private uint AppendRow(WorksheetPart worksheetPart) { SheetData sheetData = worksheetPart.Worksheet. GetFirstChild<SheetData>(); uint rowIndex = (uint)sheetData.Elements<Row>().Count(); Row row = new Row() { RowIndex = rowIndex }; sheetData.Append(row); return rowIndex; } private int InsertSharedString(string s, SharedStringTablePart sharedStringPart) { if (sharedStringPart.SharedStringTable == null) sharedStringPart.SharedStringTable = new SharedStringTable(); int i = 0; foreach (SharedStringItem item in sharedStringPart.SharedStringTable. Elements<SharedStringItem>()) { if (item.InnerText == s) return i; ++i; } sharedStringPart.SharedStringTable.AppendChild( new Text(s)); sharedStringPart.SharedStringTable.Save(); return i; } private Cell InsertCell(int i, uint rowIdx, WorksheetPart worksheetPart) { SheetData sheetData = worksheetPart.Worksheet. GetFirstChild<SheetData>(); string cellReference = AlphabetMap.Instance[i] + rowIdx; Cell cell = new Cell() { CellReference = cellReference }; Row row = sheetData.Elements<Row>().ElementAt((int)rowIdx); row.InsertAt(cell, i); worksheetPart.Worksheet.Save(); return cell; }

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• Creating a binary file from an IntelHex in C#

  - by Allek

  I'm trying to create a binary file from a intelHex file. Iside the intelHex file I have data and address to which I should write the data inside the binary file. IntelHex file looks like that :10010000214601360121470136007EFE09D2190140 :100110002146017EB7C20001FF5F16002148011988 :10012000194E79234623965778239EDA3F01B2CAA7 :100130003F0156702B5E712B722B732146013421C7 :00000001FF So I have 4 lines here with data since the last one tells us thats the end of file. Here is what I'm doing to create the file while (!streamReader.EndOfStream) { string temp = String.Empty; int address = 0; line = streamReader.ReadLine(); // Get address for each data address = Convert.ToInt32(line.Substring(3, 4), 16); // Get data from each line temp = line.Substring(7, 2); if (temp == "01") break; else { temp = line.Substring(9, line.Length - 11); string[] array = new string[(temp.Length / 2)]; int j = 0; for (int i = 0; i < array.Length; ++i) { array[i] = temp[j].ToString() + temp[j + 1].ToString(); j = j + 2; } temp = String.Empty; for (int i = 0; i < array.Length; ++i) { temp = temp + Convert.ToChar(Convert.ToInt32(array[i], 16)); } } binaryWriter.Seek(address, SeekOrigin.Begin); binaryWriter.Write(temp); binaryWriter.Flush(); } Console.WriteLine("Done...\nPress any key to exit..."); The problem here is, that data in binary file in some places is not equal to data from the intelHex file. Looks like there is some random data added to the file and I do not know from where. First time I saw that there is an additional data before the data from the intelHex file. For instance first data line starts with 21, but in binary file I have a number 12 before the 21. I do not know what is wrong here. Hope someone can help me or guide me where I can find some usefull informations about creating binary files in C#

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• Problem persisting inheritance tree

  - by alaiseca

  I have a problem trying to map an inheritance tree. A simplified version of my model is like this: @MappedSuperclass @Embeddable public class BaseEmbedded implements Serializable { @Column(name="BE_FIELD") private String beField; // Getters and setters follow } @MappedSuperclass @Embeddable public class DerivedEmbedded extends BaseEmbedded { @Column(name="DE_FIELD") private String deField; // Getters and setters follow } @MappedSuperclass public abstract class BaseClass implements Serializable { @Embedded protected BaseEmbedded embedded; public BaseClass() { this.embedded = new BaseEmbedded(); } // Getters and setters follow } @Entity @Table(name="MYTABLE") @Inheritance(strategy=InheritanceType.SINGLE_TABLE) @DiscriminatorColumn(name="TYPE", discriminatorType=DiscriminatorType.STRING) public class DerivedClass extends BaseClass { @Id @Column(name="ID", nullable=false) private Long id; @Column(name="TYPE", nullable=false, insertable=false, updatable=false) private String type; public DerivedClass() { this.embedded = new DerivedClass(); } // Getters and setters follow } @Entity @DiscriminatorValue("A") public class DerivedClassA extends DerivedClass { @Embeddable public static NestedClassA extends DerivedEmbedded { @Column(name="FIELD_CLASS_A") private String fieldClassA; } public DerivedClassA() { this.embedded = new NestedClassA(); } // Getters and setters follow } @Entity @DiscriminatorValue("B") public class DerivedClassB extends DerivedClass { @Embeddable public static NestedClassB extends DerivedEmbedded { @Column(name="FIELD_CLASS_B") private String fieldClassB; } public DerivedClassB() { this.embedded = new NestedClassB(); } // Getters and setters follow } At Java level, this model is working fine, and I believe is the appropriate one. My problem comes up when it's time to persist an object. At runtime, I can create an object which could be an instance of DerivedClass, DerivedClassA or DerivedClassB. As you can see, each one of the derived classes introduces a new field which only makes sense for that specific derived class. All the classes share the same physical table in the database. If I persist an object of type DerivedClass, I expect fields BE_FIELD, DE_FIELD, ID and TYPE to be persisted with their values and the remaining fields to be null. If I persist an object of type DerivedClass A, I expect those same fields plus the FIELD_CLASS_A field to be persisted with their values and field FIELD_CLASS_B to be null. Something equivalent for an object of type DerivedClassB. Since the @Embedded annotation is at the BaseClass only, Hibernate is only persisting the fields up to that level in the tree. I don't know how to tell Hibernate that I want to persist up to the appropriate level in the tree, depending on the actual type of the embedded property. I cannot have another @Embedded property in the subclasses since this would duplicate data that is already present in the superclass and would also break the Java model. I cannot declare the embedded property to be of a more specific type either, since it's only at runtime when the actual object is created and I don't have a single branch in the hierarchy. Is it possible to solve my problem? Or should I resignate myself to accept that there is no way to persist the Java model as it is? Any help will be greatly appreciated.

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• Track only iframe history

  - by evanwong

  I have a page which contains an iframe and I want to track the history of the iframe only. I tried to use the history object like this: <!DOCTYPE html> <html> <head> <title></title> <script type="text/javascript"> function checkFrameHistory() { alert(window.frames["test2"].history.length); } function checkThisHistory() { alert(history.length); } </script> </head> <body> <iframe name="test2" src="test2.html"></iframe> <div> <input type="button" onclick="checkFrameHistory()" value="Frame history"/> <input type="button" onclick="checkThisHistory()" value="This history"/> </div> </body> </html> test2.html <!DOCTYPE html> <html> <head> <title></title> <script type="text/javascript"> function checkMyHistory() { alert(history.length); } </script> </head> <body> <div> Test2 </div> <div> <input type="button" onclick="checkMyHistory()" value="My history"/> </div> </body> </html> but it actually gave me the history including the parent window. For instance, I went to another site in the main window and came back to my iframe test site. Both window.frames["test2"].history.length and history.length still gave me the same count by increasing the length by 2. Did I do it wrong? Is there a way to track only the iframe history?

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• What is a good generic sibling control Javascript communication strategy?

  - by James

  I'm building a webpage that is composed of several controls, and trying to come up with an effective somewhat generic client side sibling control communication model. One of the controls is the menu control. Whenever an item is clicked in here I wanted to expose a custom client side event that other controls can subscribe to, so that I can achieve a loosely coupled sibling control communication model. To that end I've created a simple Javascript event collection class (code below) that acts as like a hub for control event registration and event subscription. This code certainly gets the job done, but my question is is there a better more elegant way to do this in terms of best practices or tools, or is this just a fools errand? /// Event collection object - acts as the hub for control communication. function ClientEventCollection() { this.ClientEvents = {}; this.RegisterEvent = _RegisterEvent; this.AttachToEvent = _AttachToEvent; this.FireEvent = _FireEvent; function _RegisterEvent(eventKey) { if (!this.ClientEvents[eventKey]) this.ClientEvents[eventKey] = []; } function _AttachToEvent(eventKey, handlerFunc) { if (this.ClientEvents[eventKey]) this.ClientEvents[eventKey][this.ClientEvents[eventKey].length] = handlerFunc; } function _FireEvent(eventKey, triggerId, contextData ) { if (this.ClientEvents[eventKey]) { for (var i = 0; i < this.ClientEvents[eventKey].length; i++) { var fn = this.ClientEvents[eventKey][i]; if (fn) fn(triggerId, contextData); } } } } // load new collection instance. var myClientEvents = new bsdClientEventCollection(); // register events specific to the control that owns it, this will be emitted by each respective control. myClientEvents.RegisterEvent("menu-item-clicked"); Here is the part where this code above is consumed by source and subscriber controls. // menu control $(document).ready(function() { $(".menu > a").click( function(event) { //event.preventDefault(); myClientEvents.FireEvent("menu-item-clicked", $(this).attr("id"), null); }); }); <div style="float: left;" class="menu"> <a id="1" href="#">Menu Item1</a><br /> <a id="2" href="#">Menu Item2</a><br /> <a id="3" href="#">Menu Item3</a><br /> <a id="4" href="#">Menu Item4</a><br /> </div> // event subscriber control $(document).ready(function() { myClientEvents.AttachToEvent("menu-item-clicked", menuItemChanged); myClientEvents.AttachToEvent("menu-item-clicked", menuItemChanged2); myClientEvents.AttachToEvent("menu-item-clicked", menuItemChanged3); }); function menuItemChanged(id, contextData) { alert('menuItemChanged ' + id); } function menuItemChanged2(id, contextData) { alert('menuItemChanged2 ' + id); } function menuItemChanged3(id, contextData) { alert('menuItemChanged3 ' + id); }

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• Java DriverManager Always Assigns My Driver

  - by JGB146

  I am writing a driver to act as a wrapper around two separate MySQL connections (to distributed databases). Basically, the goal is to enable interaction with my driver for all applications instead of requiring the application to sort out which database holds the desired data. Most of the code for this is in place, but I'm having a problem in that when I attempt to create connections via the MySQL Driver, the DriverManager is returning an instance of my driver instead of the MySQL Driver. I'd appreciate any tips on what could be causing this and what could be done to fix it! Below is a few relevant snippets of code. I can provide more, but there's a lot, so I'd need to know what else you want to see. First, from MyDriver.java: public MyDriver() throws SQLException { DriverManager.registerDriver(this); } public Connection connect(String url, Properties info) throws SQLException { try { return new MyConnection(info); } catch (Exception e) { return null; } } public boolean acceptsURL(String url) throws SQLException { if (url.contains("jdbc:jgb://")) { return true; } return false; } It is my understanding that this acceptsURL function will dictate whether or not the DriverManager deems my driver a suitable fit for a given URL. Hence it should only be passing connections from my driver if the URL contains "jdbc:jgb://" right? Here's code from MyConnection.java: Connection c1 = null; Connection c2 = null; /** *Constructors */ public DDBSConnection (Properties info) throws SQLException, Exception { info.list(System.out); //included for testing Class.forName("com.mysql.jdbc.Driver").newInstance(); String url1 = "jdbc:mysql://server1.com/jgb"; String url2 = "jdbc:mysql://server2.com/jgb"; this.c1 = DriverManager.getConnection( url1, info.getProperty("username"), info.getProperty("password")); this.c2 = DriverManager.getConnection( url2, info.getProperty("username"), info.getProperty("password")); } And this tells me two things. First, the info.list() call confirms that the correct user and password are being sent. Second, because we enter an infinite loop, we see that the DriverManager is providing new instances of my connection as matches for the mysql URLs instead of the desired mysql driver/connection. FWIW, I have separately tested implementations that go straight to the mysql driver using this exact syntax (al beit only one at a time), and was able to successfully interact with each database individually from a test application outside of my driver.

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• Casting to derived type problem in C++

  - by GONeale

  Hey there everyone, I am quite new to C++, but have worked with C# for years, however it is not helping me here! :) My problem: I have an Actor class which Ball and Peg both derive from on an objective-c iphone game I am working on. As I am testing for collision, I wish to set an instance of Ball and Peg appropriately depending on the actual runtime type of actorA or actorB. My code that tests this as follows: // Actors that collided Actor *actorA = (Actor*) bodyA->GetUserData(); Actor *actorB = (Actor*) bodyB->GetUserData(); Ball* ball; Peg* peg; if (static_cast<Ball*> (actorA)) { // true ball = static_cast<Ball*> (actorA); } else if (static_cast<Ball*> (actorB)) { ball = static_cast<Ball*> (actorB); } if (static_cast<Peg*> (actorA)) { // also true?! peg = static_cast<Peg*> (actorA); } else if (static_cast<Peg*> (actorB)) { peg = static_cast<Peg*> (actorB); } if (peg != NULL) { [peg hitByBall]; } Once ball and peg are set, I then proceed to run the hitByBall method (objective c). Where my problem really lies is in the casting procedurel Ball casts fine from actorA; the first if (static_cast<>) statement steps in and sets the ball pointer appropriately. The second step is to assign the appropriate type to peg. I know peg should be a Peg type and I previously know it will be actorB, however at runtime, detecting the types, I was surprised to find actually the third if (static_cast<>) statement stepped in and set this, this if statement was to check if actorA was a Peg, which we already know actorA is a Ball! Why would it have stepped here and not in the fourth if statement? The only thing I can assume is how casting works differently from c# and that is it finds that actorA which is actually of type Ball derives from Actor and then it found when static_cast<Peg*> (actorA) is performed it found Peg derives from Actor too, so this is a valid test? This could all come down to how I have misunderstood the use of static_cast. How can I achieve what I need? :) I'm really uneasy about what feels to me like a long winded brute-casting attempt here with a ton of ridiculous if statements. I'm sure there is a more elegant way to achieve a simple cast to Peg and cast to Ball dependent on actual type held in actorA and actorB. Hope someone out there can help! :) Thanks a lot.

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• Java consistent synchronization

  - by ring0

  We are facing the following problem in a Spring service, in a multi-threaded environment: three lists are freely and independently accessed for Read once in a while (every 5 minutes), they are all updated to new values. There are some dependencies between the lists, making that, for instance, the third one should not be read while the second one is being updated and the first one already has new values ; that would break the three lists consistency. My initial idea is to make a container object having the three lists as properties. Then the synchronization would be first on that object, then one by one on each of the three lists. Some code is worth a thousands words... so here is a draft private class Sync { final List<Something> a = Collections.synchronizedList(new ArrayList<Something>()); final List<Something> b = Collections.synchronizedList(new ArrayList<Something>()); final List<Something> c = Collections.synchronizedList(new ArrayList<Something>()); } private Sync _sync = new Sync(); ... void updateRunOnceEveryFiveMinutes() { final List<Something> newa = new ArrayList<Something>(); final List<Something> newb = new ArrayList<Something>(); final List<Something> newc = new ArrayList<Something>(); ...building newa, newb and newc... synchronized(_sync) { synchronized(_sync.a) { _synch.a.clear(); _synch.a.addAll(newa); } synchronized(_sync.b) { ...same with newb... } synchronized(_sync.c) { ...same with newc... } } // Next is accessed by clients public List<Something> getListA() { return _sync.a; } public List<Something> getListB() { ...same with b... } public List<Something> getListC() { ...same with c... } The question would be, is this draft safe (no deadlock, data consistency)? would you have a better implementation suggestion for that specific problem? update Changed the order of _sync synchronization and newa... building. Thanks

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