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  • For a set of sql-queries, how do you determine which result-set contains a certain row?

    - by ManBugra
    I have a set of sql - queries: List<String> queries = ... queries[0] = "select id from person where ..."; ... queries[8756] = "select id from person where ..."; Each query selects rows from the same table 'person'. The only difference is the where-clause. Table 'person' looks like this: id | name | ... many other columns How can i determine which queries will contain a certain person in their subset? For example: List<Integer> matchingQueries = magicMethod(queries, [23,45]); The list obtained by 'magicMethod' filters all sql queries present in the list 'queries' (defined above) and returns only those that contain either the person with id 23 OR a person with id 45. Why i need it: I am dealing with an application that contains products and categories where the categories are sql queries that define which products belong to them (queries stored in a table also). Now i have a requirement where an admin has to see all categories an item belongs to immediately after the item was created. Btw, over 8.000 categories defined (so far, more to come). language and db: java && postgreSQL Thanks,

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  • Does Hibernate support one-to-one associations as pkeys?

    - by Andrzej Doyle
    Hi all, Can anyone tell me whether Hibernate supports associations as the pkey of an entity? I thought that this would be supported but I am having a lot of trouble getting any kind of mapping that represents this to work. In particular, with the straight mapping below: @Entity public class EntityBar { @Id @OneToOne(optional = false, mappedBy = "bar") EntityFoo foo // other stuff } I get an org.hibernate.MappingException: "Could not determine type for: EntityFoo, at table: ENTITY_BAR, for columns: [org.hibernate.mapping.Column(foo)]" Diving into the code it seems the ID is always considered a Value type; i.e. "anything that is persisted by value, instead of by reference. It is essentially a Hibernate Type, together with zero or more columns." I could make my EntityFoo a value type by declaring it serializable, but I wouldn't expect this would lead to the right outcome either. I would have thought that Hibernate would consider the type of the column to be integer (or whatever the actual type of the parent's ID is), just like it would with a normal one-to-one link, but this doesn't appear to kick in when I also declare it an ID. Am I going beyond what is possible by trying to combine @OneToOne with @Id? And if so, how could one model this relationship sensibly?

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  • Callback function and function pointer trouble in C++ for a BST

    - by Brendon C.
    I have to create a binary search tree which is templated and can deal with any data types, including abstract data types like objects. Since it is unknown what types of data an object might have and which data is going to be compared, the client side must create a comparison function and also a print function (because also not sure which data has to be printed). I have edited some C code which I was directed to and tried to template, but I cannot figure out how to configure the client display function. I suspect variable 'tree_node' of class BinarySearchTree has to be passed in, but I am not sure how to do this. For this program I'm creating an integer binary search tree and reading data from a file. Any help on the code or the problem would be greatly appreciated :) Main.cpp #include "BinarySearchTreeTemplated.h" #include <iostream> #include <fstream> #include <string> using namespace std; /*Comparison function*/ int cmp_fn(void *data1, void *data2) { if (*((int*)data1) > *((int*)data2)) return 1; else if (*((int*)data1) < *((int*)data2)) return -1; else return 0; } static void displayNode() //<--------NEED HELP HERE { if (node) cout << " " << *((int)node->data) } int main() { ifstream infile("rinput.txt"); BinarySearchTree<int> tree; while (true) { int tmp1; infile >> tmp1; if (infile.eof()) break; tree.insertRoot(tmp1); } return 0; } BinarySearchTree.h (a bit too big to format here) http://pastebin.com/4kSVrPhm

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  • Best practices for encrypting continuous/small UDP data

    - by temp
    Hello everyone, I am having an application where I have to send several small data per second through the network using UDP. The application need to send the data in real-time (no waiting). I want to encrypt these data and insure that what I am doing is as secure as possible. Since I am using UDP, there is no way to use SSL/TLS, so I have to encrypt each packet alone since the protocol is connectionless/unreliable/unregulated. Right now, I am using a 128-bit key derived from a passphrase from the user, and AES in CBC mode (PBE using AES-CBC). I decided to use a random salt with the passphrase to derive the 128-bit key (prevent dictionary attack on the passphrase), and of course use IVs (to prevent statistical analysis for packets). However I am concerned about few things: Each packet contains small amount of data (like a couple of integer values per packet) which will make the encrypted packets vulnerable to known-plaintext attacks (which will result in making it easier to crack the key). Also, since the encryption key is derived from a passphrase, this will make the key space way less (I know the salt will help, but I have to send the salt through the network once and anyone can get it). Given these two things, anyone can sniff and store the sent data, and try to crack the key. Although this process might take some time, once the key is cracked all the stored data will be decrypted, which will be a real problem for my application. So my question is, what is the best practices for sending/encrypting continuous small data using a connectionless protocol (UDP)? Is my way the best way to do it? ...flowed? ...Overkill? ... Please note that I am not asking for a 100% secure solution, as there is no such thing. Cheers

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  • Constraint to array dimension in C language

    - by Summer_More_More_Tea
    int KMP( const char *original, int o_len, const char *substring, int s_len ){ if( o_len < s_len ) return -1; int k = 0; int cur = 1; int fail[ s_len ]; fail[ k ] = -1; while( cur < s_len ){ k = cur - 1; do{ if( substring[ cur ] == substring[ k ] ){ fail[ cur ] = k; break; }else{ k = fail[ k ] + 1; } }while( k ); if( !k && ( substring[ cur ] != substring[ 0 ] ) ){ fail[ cur ] = -1; }else if( !k ){ fail[ cur ] = 0; } cur++; } k = 0; cur = 0; while( ( k < s_len ) && ( cur < o_len ) ){ if( original[ cur ] == substring[ k ] ){ cur++; k++; }else{ if( k == 0 ){ cur++; }else{ k = fail[ k - 1 ] + 1; } } } if( k == s_len ) return cur - k; else return -1; } This is a KMP algorithm I once coded. When I reviewed it this morning, I find it strange that an integer array is defined as int fail[ s_len ]. Does the specification requires dimesion of arrays compile-time constant? How can this code pass the compilation? By the way, my gcc version is 4.4.1. Thanks in advance!

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  • How do i access EJB implementing remote interface in separate web application?

    - by Nitesh Panchal
    Hello, I am using Netbeans 6.8 and Glassfish v3.0. I created an ejb module and created entity classes from database and then created stateless session bean with remote interface. Say eg. @Remote public interface customerRemote{ public void add(String name, String address); public Customer find(Integer id); } @Stateless public class customerBean implements customerRemote{ //implementations of methods } Then i created a new web application. But now how do i access remote ejb's in my web application. I could lookup a bean with jndi name but what i want to know is, what type of object it will return? How do i typecast it in customerRemote? I don't have any class named customerRemote in my web application. So, how do i do it? Also, what about the entity class Customer? There is no such class named Customer in my web application also. All ejb's and entity classes are in separate ejb module. Please help me :(

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  • How do i solve A datatable problem in JSF

    - by Nitesh Panchal
    I have a databale on index.xhtml <h:dataTable style="border: solid 2px black;" value="#{IndexBean.bookList}" var="item" binding="#{IndexBean.datatableBooks}"> <h:column> <h:commandButton value="Edit" actionListener="#{IndexBean.editBook}"> <f:param name="index" value="#{IndexBean.datatableBooks.rowIndex}"/> </h:commandButton> </h:column> </h:dataTable> My bean :- @ManagedBean(name="IndexBean") @ViewScoped public class IndexBean implements Serializable { private HtmlDataTable datatableBooks; public HtmlDataTable getDatatableBooks() { return datatableBooks; } public void setDatatableBooks(HtmlDataTable datatableBooks) { this.datatableBooks = datatableBooks; } public void editBook() throws IOException{ int index = Integer.parseInt(FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("index").toString()); System.out.println(index); } } My problem is i always get the same index in server log even though i click the different edit buttons, Imagine that there is one collection which is supplied to the datatable. I have not shown that in bean. If i change scope from ViewScope to RequestScope it works fine. What can be the problem with @ViewScoped? Thanks in advance :)

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  • Entity Framework DateTime update extremely slow

    - by Phyxion
    I have this situation currently with Entity Framework: using (TestEntities dataContext = DataContext) { UserSession session = dataContext.UserSessions.FirstOrDefault(userSession => userSession.Id == SessionId); if (session != null) { session.LastAvailableDate = DateTime.Now; dataContext.SaveChanges(); } } This is all working perfect, except for the fact that it is terribly slow compared to what I expect (14 calls per second, tested with 100 iterations). When I update this record manually through this command: dataContext.Database.ExecuteSqlCommand(String.Format("update UserSession set LastAvailableDate = '{0}' where Id = '{1}'", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fffffff"), SessionId)); I get 55 calls per second, which is more than fast enough. However, when I don't update the session.LastAvailableDate but I update an integer (e.g. session.UserId) or string with Entity Framework, I get 50 calls per second, which is also more than fast enough. Only the datetime field is terrible slow. The difference of a factor 4 is unacceptable and I was wondering how I can improve this as I don't prefer using direct SQL when I can also use the Entity Framework. I'm using Entity Framework 4.3.1 (also tried 4.1).

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  • Php - divide time period into equal intervals

    - by experc
    Hi! I am working on my php course project and for the past few days I have stucked at the point where I have to create php function which gets 5 parameters which represents information about the working time of some department - when the work starts/ends, when the lunchtime (or any other break) starts/ends and integer representing minutes into how small piecies we should divide time period. Besides - it's possible that there are not any breaks in the working time. The function should return all intervals from working time. function split_time_into_intervals($work_starts,$work_ends,$break_starts=null; $break_ends=null,$minutes_per_interval=60){ $intervals=array(); //all of the function code return $intervals; } So if I have the following parameters for the function function split_time_into_intervals("8:30","14:50","11:45"; "12:25"){ .. } I would like to retrieve the following array: $intervals[0]['starts']="8:30"; $intervals[0]['ends']="9:30"; $intervals[1]['starts']="9:30"; $intervals[1]['ends']="10:30"; $intervals[2]['starts']="10:30"; $intervals[2]['ends']="11:30"; $intervals[3]['starts']="11:30"; $intervals[3]['ends']="11:45"; //this interval was smaller than 60 minutes - because of the break (which starts at 11:45) $intervals[4]['starts']="12:25";//starts when the break ends $intervals[4]['ends']="13:25"; // interval is again 60 minutes $intervals[5]['starts']="13:25"; $intervals[5]['ends']="14:25"; $intervals[6]['starts']="14:25"; $intervals[6]['ends']="14:50"; //this period is shorter than 60 minutes - because work ends Any advises? I would apriciate any php (or C#) code regarding to this problem!

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  • Slope requires a real as parameter 2?

    - by Dave Jarvis
    Question How do you pass the correct value to udf_slope's second parameter type? Attempts CAST(Y.YEAR AS FLOAT), but that failed (SQL error). Y.YEAR + 0.0, but that failed, too (see error message). slope(D.AMOUNT, 1.0), failed as well Error Message Using udf_slope fails due to: Can't initialize function 'slope'; slope() requires a real as parameter 2 Code SELECT D.AMOUNT, Y.YEAR, slope(D.AMOUNT, Y.YEAR + 0.0) as SLOPE, intercept(D.AMOUNT, Y.YEAR + 0.0) as INTERCEPT FROM YEAR_REF Y, DAILY D Here, D.AMOUNT is a FLOAT and Y.YEAR is an INTEGER. Create Function The slope function was created as follows: CREATE AGGREGATE FUNCTION slope RETURNS REAL SONAME 'udf_slope.so'; Function Signature From udf_slope.cc: double slope( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char* is_error ) Example Usages Reading the fine manual reveals: UDF intercept() Calculates the intercept of the linear regression of two sets of variables. Function name intercept Input parameter(s) 2 (dependent variable: REAL, independent variable: REAL) Examples SELECT intercept(income,age) FROM customers UDF slope() Calculates the slope of the linear regression of two sets of variables. Function name slope Input parameter(s) 2 (dependent variable: REAL, independent variable: REAL) Examples SELECT slope(income,age) FROM customers Thoughts? Thank you!

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  • Java: ResultSet exception - before start of result set

    - by Rosarch
    I'm having trouble getting data from a ResultSet object. Here is my code: String sql = "SELECT type FROM node WHERE nid = ?"; PreparedStatement prep = conn.prepareStatement(sql); int meetNID = Integer.parseInt(node.get(BoutField.field_meet_nid)); prep.setInt(1, meetNID); ResultSet result = prep.executeQuery(); result.beforeFirst(); String foundType = result.getString(1); if (! foundType.equals("meet")) { throw new IllegalArgumentException(String.format("Node %d must be of type 'meet', but was %s", meetNID, foundType)); } The error trace: Exception in thread "main" java.sql.SQLException: Before start of result set at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1072) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:986) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:981) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926) at com.mysql.jdbc.ResultSetImpl.checkRowPos(ResultSetImpl.java:841) at com.mysql.jdbc.ResultSetImpl.getStringInternal(ResultSetImpl.java:5656) at com.mysql.jdbc.ResultSetImpl.getString(ResultSetImpl.java:5576) at nth.cumf3.nodeImport.Validator.validate(Validator.java:43) at nth.cumf3.nodeImport.Main.main(Main.java:38) What am I doing wrong here?

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  • What's a clean way to have the server return a JavaScript function which would then be invoked?

    - by Khnle
    My application is architected as a host of plug-ins that have not yet been written. There's a long reason for this, but with each new year, the business logic will be different and we don't know what it will be like (Think of TurboTax if that helps). The plug-ins consist of both server and client components. The server components deals with business logic and persisting the data into database tables which will be created at a later time as well. The JavaScript manipulates the DOM for the browsers to render afterward. Each plugin lives in a separate assembly, so that they won't disturb the main application, i.e., we don't want to recompile the main application. Long story short, I am looking for a way to return JavaScript functions to the client from an Ajax get request, and execute these JavaScript functions (which are just returned). Invoking a function in Javascript is easy. The hard part is how to organize or structure so that I won't have to deal with maintenance problem. So concat using StringBuilder to end up with JavaScript code as a result of calling toString() from the string builder object is out of the question. I want to have no difference between writing JavaScript codes normally and writing Javascript codes for this dynamic purpose. An alternative is to manipulate the DOM on the server side, but I doubt that it would be as elegantly as using jQuery on the client side. I am open for a C# library that supports chainable calls like jQuery that also manipulates the DOM too. Do you have any idea or is it too much to ask or are you too confused? Edit1: The point is to avoid recompiling, hence the plug-ins architecture. In some other parts of the program, I already use the concept of dynamically loading Javascript files. That works fine. What I am looking here is somewhere in the middle of the program when an Ajax request is sent to the server. Edit 2: To illustrate my question: Normally, you would see the following code. An Ajax request is sent to the server, a JSON result is returned to the client which then uses jQuery to manipulate the DOM (creating tag and adding to the container in this case). $.ajax({ type: 'get', url: someUrl, data: {'': ''}, success: function(data) { var ul = $('<ul>').appendTo(container); var decoded = $.parseJSON(data); $.each(decoded, function(i, e) { var li = $('<li>').text(e.FIELD1 + ',' + e.FIELD2 + ',' + e.FIELD3); ul.append(li); }); } }); The above is extremely simple. But next year, what the server returns is totally different and how the data to be rendered would also be different. In a way, this is what I want: var container = $('#some-existing-element-on-the-page'); $.ajax({ type: 'get', url: someUrl, data: {'': ''}, success: function(data) { var decoded = $.parseJSON(data); var fx = decoded.fx; var data = decode.data; //fx is the dynamic function that create the DOM from the data and append to the existing container fx(container, data); } }); I don't need to know, at this time what data would be like, but in the future I will, and I can then write fx accordingly.

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  • notify url is not called

    - by Jahangeer Ahmed
    Dim redirecturl As String = "" redirecturl = ConfigurationManager.AppSettings("papalUrl").ToString() & "us/cgi-bin/webscr?cmd=_cart&upload=1&business=" & ConfigurationManager.AppSettings("paypalemail").ToString() Dim j As Integer = 0 Dim dr1 As DataRow If ds.Tables("ReviewOrder").Rows.Count 0 Then Dim requestsFile As String = Server.MapPath("~/App_Data/PaymentRequests.xml") ' ds.Tables("ReviewOrder").WriteXml(requestsFile) For j = 0 To ds.Tables("ReviewOrder").Rows.Count - 1 dr1 = ds.Tables("ReviewOrder").Rows(j) redirecturl += "&item_name_" & j + 1 & "=" & dr1("varTitle") redirecturl += "&amount_" & j + 1 & "=" & dr1("flRate") redirecturl += "&image_url_" & j + 1 & "=" & ConfigurationManager.AppSettings("RSSurl").ToString() & dr1("imgImage") redirecturl += "&quantity_" & j + 1 & "=" & Convert.ToInt64(dr1("flQuantity")) ''redirecturl += "&item_name_2=Sample_testing2&amount_2=9.50" ''redirecturl += "&quantity_2=2" ''redirecturl += "&item_name_3=Sample_testing3" ''redirecturl += "&amount_3=8.50" ''redirecturl += "&quantity_3=3" redirecturl += "&custom_" & j + 1 & "=" & dr1("BasketID") Next End If redirecturl += "&currency=" & ConfigurationManager.AppSettings("CurrencyCode").ToString() redirecturl += "&first_name=" & firstName redirecturl += "&last_name=" & lastName redirecturl += "&city=" & city redirecturl += "&state=" & state redirecturl += "&zip=" & zip redirecturl += "&address1=" & address1 redirecturl += "&address2=" & address2 redirecturl += "&notify_url=" & Server.UrlEncode(ConfigurationManager.AppSettings("NotifyUrl").ToString() & "&rm=2") redirecturl += "&return=" & ConfigurationManager.AppSettings("SuccessURL").ToString() 'Failed return page url redirecturl += "&cancel_return=" & ConfigurationManager.AppSettings("FailedURL").ToString() Page.ClientScript.RegisterClientScriptBlock(Me.GetType(), "Redirect", "window.parent.location='" & redirecturl & "';", True)

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  • sqlalchemy dynamic mapping

    - by adancu
    Hi, I have the following problem: I have the class: class Word(object): def __init__(self): self.id = None self.columns = {} def __str__(self): return "(%s, %s)" % (str(self.id), str(self.columns)) self.columns is a dict which will hold (columnName:columnValue) values. The name of the columns are known at runtime and they are loaded in a wordColumns list, for example wordColumns = ['english', 'korean', 'romanian'] wordTable = Table('word', metadata, Column('id', Integer, primary_key = True) ) for columnName in wordColumns: wordTable.append_column(Column(columnName, String(255), nullable = False)) I even created a explicit mapper properties to "force" the table columns to be mapped on word.columns[columnName], instead of word.columnName, I don't get any error on mapping, but it seems that doesn't work. mapperProperties = {} for column in wordColumns: mapperProperties['columns[\'%']' % column] = wordTable.columns[column] mapper(Word, wordTable, mapperProperties) When I load a word object, SQLAlchemy creates an object which has the word.columns['english'], word.columns['korean'] etc. properties instead of loading them into word.columns dict. So for each column, it creates a new property. Moreover word.columns dictionary doesn't even exists. The same way, when I try to persist a word, SQLAlchemy expects to find the column values in properties named like word.columns['english'] (string type) instead of the dictionary word.columns. I have to say that my experience with Python and SQLAlchemy is quite limited, maybe it isn't possible to do what I'm trying to do. Any help appreciated, Thanks in advance.

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  • How to visually reject user input in a table?

    - by FX
    In the programming of a table-based application module (i.e. the user mostly enters tabular data in an already laid-out table), how would you reject user input for a given cell? The scenario is: the user edits the cell, enters something (text, picture, ...) and you want them to notice when they finish editing (hitting enter, for example) that their entry is not valid for your given "format" (in the wider meaning: it can be that they entered a string instead of a number, that their entry is too long, too short, they include a picture while it's not acceptable, ...). I can see two different things happening: You can rather easily fit their entry into your format, and you do so, but you want them to notice it so they can change if your guess is not good enough (example: they entered "15.47" in a field that needs to be an integer, so your program makes it "15") You cannot guess what to do with their entry, and want to inform them that it's not valid. My question specifically is: what visual display can you offer to inform the user that his input is invalid? Is it preferable to refuse to leave the editing mode, or not? The two things I can imagine are: using colors (red background if invalid, yellow background for my case 1 above) when you reject an input, do something like Apple does for password entry of user accounts: you make the cell "shaking" (i.e. oscillating left and right) for one second, and keep the focus/editing in their so they don't loose what they've typed. Let's hear your suggestions. PS: This question is, at least in my thought process, somehow a continuation and a specialization of my previous question on getting users to read error messages. PPS: Made this community wiki, was that the right thing to do on this kind of question or not?

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  • How can I serve static content with Glassfish embedded?

    - by Andy Fiedler
    I'm trying to setup Glassfish embedded with a WAR project that implements a REST API and then some static Javascript content that calls it. I got the WAR to deploy and the REST API is available with a context root of "/Users". How can I use Glassfish to serve static content with a context root of "/". So for example, if the user requests http://myserver.com/Users/some-REST-call it routes to the WAR application and http://myserver.com/somefile.js serves a static file from some directory? Here's my Main class file so far: public class Main{ public static void main(String[] args) throws Exception { String port = System.getenv("PORT"); port = port != null ? port : "8080"; GlassFishProperties gfProps = new GlassFishProperties(); gfProps.setPort("http-listener", Integer.parseInt(port)); GlassFish glassfish = GlassFishRuntime.bootstrap().newGlassFish(gfProps); glassfish.start(); Deployer deployer = glassfish.getDeployer(); deployer.deploy(new File("target/Users-Rest.war")); } } Thanks a ton for your help!

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  • Open + Save .exe file in notepad makes it corrupted

    - by Jacob Kofoed
    Hi, I just published this simple console application that is supposed to show a textbox with the value of a setting called "userID" with value 1001. This works like a charm. Now what I need is to change this value outside the editor, from notepad etc. When I open the application a lot in there is non-sence (& o! -å Þþþ,o" Ü+) etc. but with a quick (ctrl + F) I found the value 1001, and changed this to some other integer. I ran the application again, and it failed, didn't even give any userful error-message. At a point I tried just opening a newly published non-corrupted version of the application, didn't change anything, then saved from notepad, and it were also corrupted. It seems like notepad can't open some characters or something. Do I need to publish the application in some specific text-unicode language or something? Help much appreciated :) I know it sounds like a stupid application, but it is just a test of concept :) I use vb.net for this

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  • MVC: returning multiple results on stream connection to implement HTML5 SSE

    - by eddo
    I am trying to set up a lightweight HTML5 Server-Sent Event implementation on my MVC 4 Web, without using one of the libraries available to implement sockets and similars. The lightweight approach I am trying is: Client side: EventSource (or jquery.eventsource for IE) Server side: long polling with AsynchController (sorry for dropping here the raw test code but just to give an idea) public class HTML5testAsyncController : AsyncController { private static int curIdx = 0; private static BlockingCollection<string> _data = new BlockingCollection<string>(); static HTML5testAsyncController() { addItems(10); } //adds some test messages static void addItems(int howMany) { _data.Add("started"); for (int i = 0; i < howMany; i++) { _data.Add("HTML5 item" + (curIdx++).ToString()); } _data.Add("ended"); } // here comes the async action, 'Simple' public void SimpleAsync() { AsyncManager.OutstandingOperations.Increment(); Task.Factory.StartNew(() => { var result = string.Empty; var sb = new StringBuilder(); string serializedObject = null; //wait up to 40 secs that a message arrives if (_data.TryTake(out result, TimeSpan.FromMilliseconds(40000))) { JavaScriptSerializer ser = new JavaScriptSerializer(); serializedObject = ser.Serialize(new { item = result, message = "MSG content" }); sb.AppendFormat("data: {0}\n\n", serializedObject); } AsyncManager.Parameters["serializedObject"] = serializedObject; AsyncManager.OutstandingOperations.Decrement(); }); } // callback which returns the results on the stream public ActionResult SimpleCompleted(string serializedObject) { ServerSentEventResult sar = new ServerSentEventResult(); sar.Content = () => { return serializedObject; }; return sar; } //pushes the data on the stream in a format conforming HTML5 SSE public class ServerSentEventResult : ActionResult { public ServerSentEventResult() { } public delegate string GetContent(); public GetContent Content { get; set; } public int Version { get; set; } public override void ExecuteResult(ControllerContext context) { if (context == null) { throw new ArgumentNullException("context"); } if (this.Content != null) { HttpResponseBase response = context.HttpContext.Response; // this is the content type required by chrome 6 for server sent events response.ContentType = "text/event-stream"; response.BufferOutput = false; // this is important because chrome fails with a "failed to load resource" error if the server attempts to put the char set after the content type response.Charset = null; string[] newStrings = context.HttpContext.Request.Headers.GetValues("Last-Event-ID"); if (newStrings == null || newStrings[0] != this.Version.ToString()) { string value = this.Content(); response.Write(string.Format("data:{0}\n\n", value)); //response.Write(string.Format("id:{0}\n", this.Version)); } else { response.Write(""); } } } } } The problem is on the server side as there is still a big gap between the expected result and what's actually going on. Expected result: EventSource opens a stream connection to the server, the server keeps it open for a safe time (say, 2 minutes) so that I am protected from thread leaking from dead clients, as new message events are received by the server (and enqueued to a thread safe collection such as BlockingCollection) they are pushed in the open stream to the client: message 1 received at T+0ms, pushed to the client at T+x message 2 received at T+200ms, pushed to the client at T+x+200ms Actual behaviour: EventSource opens a stream connection to the server, the server keeps it open until a message event arrives (thanks to long polling) once a message is received, MVC pushes the message and closes the connection. EventSource has to reopen the connection and this happens after a couple of seconds. message 1 received at T+0ms, pushed to the client at T+x message 2 received at T+200ms, pushed to the client at T+x+3200ms This is not OK as it defeats the purpose of using SSE as the clients start again reconnecting as in normal polling and message delivery gets delayed. Now, the question: is there a native way to keep the connection open after sending the first message and sending further messages on the same connection?

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  • Help with active record relations

    - by Christian Fazzini
    class CreateActivities < ActiveRecord::Migration def self.up create_table :activities do |t| t.references :user t.references :media t.integer :artist_id t.string :type t.timestamps end end def self.down drop_table :activities end end class Fan < Activity belongs_to :user, :counter_cache => true end class Activity < ActiveRecord::Base belongs_to :user belongs_to :media belongs_to :artist, :class_name => 'User', :foreign_key => 'artist_id' end class User < ActiveRecord::Base has_many :activities has_many :fans end I tried changing my activity model too, without any success: class Activity < ActiveRecord::Base has_many :activities, :class_name => 'User', :foreign_key => 'user_id' has_many :activities, :class_name => 'User', :foreign_key => 'artist_id' end One thing to note. Activity is an STI. Fan inherits from Activity. In console, I do: # Create a fan object. User is a fan of himself fan = Fan.new => #<Fan id: nil, user_id: nil, media_id: nil, artist_id: nil, type: "Fan", comment: nil, created_at: nil, updated_at: nil> # Assign a user object fan.user = User.first => #<User id: 1, genre_id: 1, country_id: 1, .... # Assign an artist object fan.artist_id = User.first.id => 1 # Save the fan object fan.save! => true Activity.last => #<Fan id: 13, user_id: 1, media_id: nil, artist_id: 1, type: "Fan", comment: nil, created_at: "2010-12-30 08:41:25", updated_at: "2010-12-30 08:41:25"> Activity.last.user => #<User id: 1, genre_id: 1, country_id: 1, ..... But... Activity.last.artist => nil Why is Activity.last.artist returning nil?

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  • getSharedPreferences not working for me with concerns to ListPreferences and Integers

    - by ideagent
    I'm stuck at a point where I'm trying to get my project to read a preference value (from a ListPreference listing) and then use that value in a basic mathematical subtraction instance. The problem is that the "seek" preference is not being seen by my Java code, and yet the default value is (I've tried the default value with 3000 and now 0). Am i missing something, is there a bug here, known or unknown? Java code chunk where the issues manifests itself: public static final String PREF_FILE_NAME = "preferences"; seekback.setOnClickListener(new Button.OnClickListener() { @Override public void onClick(View view) { try { SharedPreferences preferences = getSharedPreferences(PREF_FILE_NAME, MODE_PRIVATE); Integer storedPreference = preferences.getInt("seek", 0); (mediaPlayer.getCurrentPosition()-storedPreference); } catch (Exception e) { e.printStackTrace(); } } }); Here are some other code bits for my project: From preferences file: <ListPreference android:entries="@array/seconds" android:entryValues="@array/seconds_values" android:summary="sets the seek interval for the seekback and seekforward buttons" android:title="Seek Interval" android:defaultValue="5000" android:key="@string/seek" From strings file: seek From an array file: Five seconds Fifteen seconds Thirty seconds Sixty seconds 5000 15000 30000 60000 let me know if you need to see more code to figure this one out Thanks in advance for any help that can be offered. I've worked over this issue now for a few hours and I'm burnt, a second pair of eyes on it would be very much appreciated. Arg, not sure how to get the code and plain text to format nicely here, even tried the options, like Code Sample, no luck AndroidCoder

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  • create and write to a text file in vb.net

    - by woolardz
    I'm creating a small vb.net application, and I'm trying trying to write a list of results from a listview to a text file. I've looked online and found the code to open the save file dialog and write the text file. When I click save on the save file dialog, I receive an IOException with the message "The process cannot access the file 'C:\thethe.txt' because it is being used by another process." The text file is created in the correct location, but is empty. The application quits at this line "Dim fs As New FileStream(saveFileDialog1.FileName, FileMode.OpenOrCreate, FileAccess.Write)" Thanks in advance for any help. Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSave.Click Dim myStream As Stream Dim saveFileDialog1 As New SaveFileDialog() saveFileDialog1.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*" saveFileDialog1.FilterIndex = 2 saveFileDialog1.RestoreDirectory = True If saveFileDialog1.ShowDialog() = DialogResult.OK Then myStream = saveFileDialog1.OpenFile() If (myStream IsNot Nothing) Then Dim fs As New FileStream(saveFileDialog1.FileName, FileMode.OpenOrCreate, FileAccess.Write) Dim m_streamWriter As New StreamWriter(fs) m_streamWriter.Flush() 'Write to the file using StreamWriter class m_streamWriter.BaseStream.Seek(0, SeekOrigin.Begin) 'write each row of the ListView out to a tab-delimited line in a file For i As Integer = 0 To Me.ListView1.Items.Count - 1 m_streamWriter.WriteLine(((ListView1.Items(i).Text & vbTab) + ListView1.Items(i).SubItems(0).ToString() & vbTab) + ListView1.Items(i).SubItems(1).ToString()) Next myStream.Close() End If End If End Sub

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  • can a python script know that another instance of the same script is running... and then talk to it?

    - by Justin Grant
    I'd like to prevent multiple instances of the same long-running python command-line script from running at the same time, and I'd like the new instance to be able to send data to the original insance before the new instance commits suicide. How can I do this in a cross-platform way? Specifically, I'd like to enable the following behavior: "foo.py" is launched from the command line, and it will stay running for a long time-- days or weeks until the machine is rebooted or the parent process kills it. every few minutes the same script is launched again, but with different command-line parameters when launched, the script should see if any other instances are running. if other instances are running, then instance #2 should send its command-line parameters to instance #1, and then instance #2 should exit. instance #1, if it receives command-line parameters from another script, should spin up a new thread and (using the command-line parameters sent in the step above) start performing the work that instance #2 was going to perform. So I'm looking for two things: how can a python program know another instance of itself is running, and then how can one python command-line program communicate with another? Making this more complicated, the same script needs to run on both Windows and Linux, so ideally the solution would use only the Python standard library and not any OS-specific calls. Although if I need to have a Windows codepath and an *nix codepath (and a big if statement in my code to choose one or the other), that's OK if a "same code" solution isn't possible. I realize I could probably work out a file-based approach (e.g. instance #1 watches a directory for changes and each instance drops a file into that directory when it wants to do work) but I'm a little concerned about cleaning up those files after a non-graceful machine shutdown. I'd ideally be able to use an in-memory solution. But again I'm flexible, if a persistent-file-based approach is the only way to do it, I'm open to that option. More details: I'm trying to do this because our servers are using a monitoring tool which supports running python scripts to collect monitoring data (e.g. results of a database query or web service call) which the monitoring tool then indexes for later use. Some of these scripts are very expensive to start up but cheap to run after startup (e.g. making a DB connection vs. running a query). So we've chosen to keep them running in an infinite loop until the parent process kills them. This works great, but on larger servers 100 instances of the same script may be running, even if they're only gathering data every 20 minutes each. This wreaks havoc with RAM, DB connection limits, etc. We want to switch from 100 processes with 1 thread to one process with 100 threads, each executing the work that, previously, one script was doing. But changing how the scripts are invoked by the monitoring tool is not possible. We need to keep invocation the same (launch a process with different command-line parameters) but but change the scripts to recognize that another one is active, and have the "new" script send its work instructions (from the command line params) over to the "old" script.

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  • Error in bisection method code in Matlab

    - by Amanda Collins
    I need to write a proper implementation of the bisection method, which means I must address all possible user input errors. Here is my code: function [x_sol, f_at_x_sol, N_iterations] = bisection(f, xn, xp, eps_f, eps_x) % solving f(x)=0 with bisection method % f is the function handle to the desired function, % xn and xp are borders of search, % f(xn)<0 and f(xp)>0 required, % eps_f defines how close f(x) should be to zero, % eps_x defines uncertainty of solution x if(f(xp) < 0) error('xp must be positive') end; if(f(xn)>0) error('xn must be negative') end; if (xn >= xp) error ('xn must be less than xp') end; xg=(xp+xn)/2; %initial guess fg=f(xg); % initial function evaluation N_iterations=1; while ( (abs(fg) > eps_f) & (abs(xg-xp) > eps_x) ) if (fg>0) xp=xg; else xn=xg; end xg=(xp+xn)/2; %update guess fg=f(xg); %update function evaluation N_iterations=N_iterations+1; end x_sol=xg; %solution is ready f_at_x_sol=fg; if (f_at_x_sol > eps_f) error('No convergence') end and here is the error message I receive when I try to test this in Matlab: >> bisection(x.^2, 2, -1, 1e-8, 1e-10) Attempted to access f(-1); index must be a positive integer or logical. Error in bisection (line 9) if(f(xp)<0) I was attempting to see if my error codes worked, but it doesn't look like they do. I get the same error when I try to test it on a function that should work.

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  • How to deal with a flaw in System.Data.DataTableExtensions.CopyToDataTable()

    - by andy
    Hey guys, so I've come across something which is perhaps a flaw in the Extension method .CopyToDataTable. This method is used by Importing (in VB.NET) System.Data.DataTableExtensions and then calling the method against an IEnumerable. You would do this if you want to filter a Datatable using LINQ, and then restore the DataTable at the end. i.e: Imports System.Data.DataRowExtensions Imports System.Data.DataTableExtensions Public Class SomeClass Private Shared Function GetData() As DataTable Dim Data As DataTable Data = LegacyADO.NETDBCall Data = Data.AsEnumerable.Where(Function(dr) dr.Field(Of Integer)("SomeField") = 5).CopyToDataTable() Return Data End Function End Class In the example above, the "WHERE" filtering might return no results. If this happens CopyToDataTable throws an exception because there are no DataRows. Why? The correct behavior should be to return a DataTable with Rows.Count = 0. Can anyone think of a clean workaround to this, in such a way that whoever calls CopyToDataTable doesn't have to be aware of this issue? System.Data.DataTableExtensions is a Static Class so I can't override the behavior....any ideas? Have I missed something? cheers UPDATE: I have submitted this as an issue to Connect. I would still like some suggestions, but if you agree with me, you could vote up the issue at Connect via the link above cheers

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  • Will this class cause memory leaks, and does anything need disposing of? (asp.net vb)

    - by Phil
    Here is the class to export a gridview to an excel sheet: Imports System Imports System.Data Imports System.Configuration Imports System.IO Imports System.Web Imports System.Web.Security Imports System.Web.UI Imports System.Web.UI.WebControls Imports System.Web.UI.WebControls.WebParts Imports System.Web.UI.HtmlControls Namespace ExcelExport Public NotInheritable Class GVExportUtil Private Sub New() End Sub Public Shared Sub Export(ByVal fileName As String, ByVal gv As GridView) HttpContext.Current.Response.Clear() HttpContext.Current.Response.AddHeader("content-disposition", String.Format("attachment; filename={0}", fileName)) HttpContext.Current.Response.ContentType = "application/ms-excel" Dim sw As StringWriter = New StringWriter Dim htw As HtmlTextWriter = New HtmlTextWriter(sw) Dim table As Table = New Table table.GridLines = GridLines.Vertical If (Not (gv.HeaderRow) Is Nothing) Then GVExportUtil.PrepareControlForExport(gv.HeaderRow) table.Rows.Add(gv.HeaderRow) End If For Each row As GridViewRow In gv.Rows GVExportUtil.PrepareControlForExport(row) table.Rows.Add(row) Next If (Not (gv.FooterRow) Is Nothing) Then GVExportUtil.PrepareControlForExport(gv.FooterRow) table.Rows.Add(gv.FooterRow) End If table.RenderControl(htw) HttpContext.Current.Response.Write(sw.ToString) HttpContext.Current.Response.End() End Sub Private Shared Sub PrepareControlForExport(ByVal control As Control) Dim i As Integer = 0 Do While (i < control.Controls.Count) Dim current As Control = control.Controls(i) If (TypeOf current Is LinkButton) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, LinkButton).Text)) ElseIf (TypeOf current Is ImageButton) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, ImageButton).AlternateText)) ElseIf (TypeOf current Is HyperLink) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, HyperLink).Text)) ElseIf (TypeOf current Is DropDownList) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, DropDownList).SelectedItem.Text)) ElseIf (TypeOf current Is CheckBox) Then control.Controls.Remove(current) control.Controls.AddAt(i, New LiteralControl(CType(current, CheckBox).Checked)) End If If current.HasControls Then GVExportUtil.PrepareControlForExport(current) End If i = (i + 1) Loop End Sub End Class End Namespace Will this class cause memory leaks? And does anything here need to be disposed of? The code is working but I am getting the app pool falling over frequently when it is in use. Thanks.

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