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  • DOM + need to remove element from XML bt VB script

    - by yael
    I have the following VB script , I want to remove the "NET ID" element from name list but after running the VB script the "NET ID" element still exist in the XML doc? Something wrong in the VB? Yael Set objXMLDoc = CreateObject("Microsoft.XMLDOM") objXMLDoc.async = False objXMLDoc.load("\dir\d.xml") Set objRoot = objXMLDoc.documentElement Set objExNode = objRoot.removeChild(objRoot.childNodes.item(0)) objRoot.appendChild(objExNode) the XML file:

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  • select rows with column that is not null?

    - by fayer
    by default i have one column in mysql table to be NULL. i want to select some rows but only if the field value in that column is not NULL. what is the correct way of typing it? $query = "SELECT * FROM names WHERE id = '$id' AND name != NULL"; is this correct?

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  • SQL Select * from multiple tables

    - by zaf
    Using PHP/PDO is it possible to use a wildcard for the columns when a select is done on multiple tables and the returned array keys are fully qualified to avoid column name clash? example: SELECT * from table1, table2; gives: Array keys are 'table1.id', 'table2.id', 'table1.name' etc. I tried "SELECT table1.*,table2.* ..." but the returned array keys were not fully qualified so columns with the same name clashed and were overwritten.

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  • mysql query for getting all messages that belong to user's contacts

    - by aharon
    So I have a database that is setup sort of like this (simplified, and in terms of the tables, all are InnoDBs): Users: contains based user authentication information (uid, username, encrypted password, et cetera) Contacts: contains two rows per relationship that exists between users as (uid1, uid2), (uid2, uid1) to allow for a good 1:1 relationship (must be mutual) between users Messages: has messages that consist of a blob, owner-id, message-id (auto_increment) So my question is, what's the best MySQL query to get all messages that belong to all the contacts of a specific user? Is there an efficient way to do this?

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  • Two Questions about the WebBrowser Control

    - by Rudi
    How can I get an HtmlElement if the source code doesn't have the "id=''", but only has the "name=''". Document.GetElementById() doesn't work, and Document.All[""] doesn't work (obviously, because there is no ID. How can I simulate a form post? Question 1 is more important because I found it harder to search. Question 2 I think i can get with more searching.

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  • Sort Hash Tables Glibc - qsort

    - by Mike
    I'm trying to sort a GLibc hash table by id that looks something like: key - id { "Red", 2, "BLue", 4, "Yellow", 5, "Orange", 8 } I'm just not sure how to approach this because GLibc does not have a sort method. I was thinking to use qsort or GCompareFunc Any ideas will be appreciate it!

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  • mvc fill dropdownlist

    - by user276640
    i use this code to fill dropdownlist ViewData["projectType"] = new SelectList(_dataManager.Project.ProjectTypeList(), "Id", "Name"); but what i must do if i want to use not one table column but two or more columns? for example ViewData["projectType"] = new SelectList(_dataManager.Project.ProjectTypeList(), "Id", "Name1"+"Name2");

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  • Mysql: Perform of NOT EXISTS. Is it possible to improve permofance?

    - by petRUShka
    I have two tables posts and comments. Table comments have post_id attribute. I need to get all posts with type "open", for which there are no comments with type "good" and created date MAY 1. Is it optimal to use such SQL-query: SELECT posts.* FROM posts WHERE NOT EXISTS ( SELECT comments.id FROM comments WHERE comments.post_id = posts.id AND comments.comment_type = 'good' AND comments.created_at BETWEEN '2010-05-01 00:00:00' AND '2010-05-01 23:59:59') I'm not sure that NOT EXISTS is perfect construction in this situation.

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  • derby + hibernate ConstraintViolationException using manytomany relationships

    - by user364470
    Hi, I'm new to Hibernate+Derby... I've seen this issue mentioned throughout the google, but have not seen a proper resolution. This following code works fine with mysql, but when I try this on derby i get exceptions: ( each Tag has two sets of files and vise-versa - manytomany) Tags.java @Entity @Table(name="TAGS") public class Tags implements Serializable { @Id @GeneratedValue(strategy=GenerationType.AUTO) public long getId() { return id; } @ManyToMany(targetEntity=Files.class ) @ForeignKey(name="USER_TAGS_FILES",inverseName="USER_FILES_TAGS") @JoinTable(name="USERTAGS_FILES", joinColumns=@JoinColumn(name="TAGS_ID"), inverseJoinColumns=@JoinColumn(name="FILES_ID")) public Set<data.Files> getUserFiles() { return userFiles; } @ManyToMany(mappedBy="autoTags", targetEntity=data.Files.class) public Set<data.Files> getAutoFiles() { return autoFiles; } Files.java @Entity @Table(name="FILES") public class Files implements Serializable { @Id @GeneratedValue(strategy=GenerationType.AUTO) public long getId() { return id; } @ManyToMany(mappedBy="userFiles", targetEntity=data.Tags.class) public Set getUserTags() { return userTags; } @ManyToMany(targetEntity=Tags.class ) @ForeignKey(name="AUTO_FILES_TAGS",inverseName="AUTO_TAGS_FILES") @JoinTable(name="AUTOTAGS_FILES", joinColumns=@JoinColumn(name="FILES_ID"), inverseJoinColumns=@JoinColumn(name="TAGS_ID")) public Set getAutoTags() { return autoTags; } I add some data to the DB, but when running over Derby these exception turn up (the don't using mysql) Exceptions SEVERE: DELETE on table 'FILES' caused a violation of foreign key constraint 'USER_FILES_TAGS' for key (3). The statement has been rolled back. Jun 10, 2010 9:49:52 AM org.hibernate.event.def.AbstractFlushingEventListener performExecutions SEVERE: Could not synchronize database state with session org.hibernate.exception.ConstraintViolationException: could not delete: [data.Files#3] at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96) at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66) at org.hibernate.persister.entity.AbstractEntityPersister.delete(AbstractEntityPersister.java:2712) at org.hibernate.persister.entity.AbstractEntityPersister.delete(AbstractEntityPersister.java:2895) at org.hibernate.action.EntityDeleteAction.execute(EntityDeleteAction.java:97) at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:268) at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:260) at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:184) at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321) at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51) at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1206) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:613) at org.hibernate.context.ThreadLocalSessionContext$TransactionProtectionWrapper.invoke(ThreadLocalSessionContext.java:344) at $Proxy13.flush(Unknown Source) at data.HibernateORM.removeFile(HibernateORM.java:285) at data.DataImp.removeFile(DataImp.java:195) at booting.DemoBootForTestUntilTestClassesExist.main(DemoBootForTestUntilTestClassesExist.java:62) I have never used derby before so maybe there is something crutal that i'm missing 1) what am I doing wrong? 2) is there any way of cascading properly when I have 2 many-to-many relationships between two classes? Thanks!

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  • Objective C IBOutlets

    - by Alan
    In cases where multiple buttons call an IBOutlet, can the IBOutlet determine which button was pressed? edit: All fixed and wired up. key point: Object ID is not sender tag! Tag is a standalone value on the first page of the attributes. - (IBAction)buttonPressed:(id)sender { switch ( [sender tag] ) { case 109: NSLog(@"Button 1"); break; case 108: NSLog(@"Button 2"); break; } }

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  • Backbone.js Adding Model to Collection Issue

    - by jtmgdevelopment
    I am building a test application in Backbone.js (my first app using Backbone). The app goes like this: Load Data from server "Plans" Build list of plans and show to screen There is a button to add a new plan Once new plan is added, add to collection ( do not save to server as of now ) redirect to index page and show the new collection ( includes the plan you just added) My issue is with item 5. When I save a plan, I add the model to the collection then redirect to the initial view. At this point, I fetch data from the server. When I fetch data from the server, this overwrites my collection and my added model is gone. How can I prevent this from happening? I have found a way to do this but it is definitely not the correct way at all. Below you will find my code examples for this. Thanks for the help. PlansListView View: var PlansListView = Backbone.View.extend({ tagName : 'ul', initialize : function() { _.bindAll( this, 'render', 'close' ); //reset the view if the collection is reset this.collection.bind( 'reset', this.render , this ); }, render : function() { _.each( this.collection.models, function( plan ){ $( this.el ).append( new PlansListItemView({ model: plan }).render().el ); }, this ); return this; }, close : function() { $( this.el ).unbind(); $( this.el ).remove(); } });//end NewPlanView Save Method var NewPlanView = Backbone.View.extend({ tagName : 'section', template : _.template( $( '#plan-form-template' ).html() ), events : { 'click button.save' : 'savePlan', 'click button.cancel' : 'cancel' }, intialize: function() { _.bindAll( this, 'render', 'save', 'cancel' ); }, render : function() { $( '#container' ).append( $( this.el ).html(this.template( this.model.toJSON() )) ); return this; }, savePlan : function( event ) { this.model.set({ name : 'bad plan', date : 'friday', desc : 'blah', id : Math.floor(Math.random()*11), total_stops : '2' }); this.collection.add( this.model ); app.navigate('', true ); event.preventDefault(); }, cancel : function(){} }); Router (default method): index : function() { this.container.empty(); var self = this; //This is a hack to get this to work //on default page load fetch all plans from the server //if the page has loaded ( this.plans is defined) set the updated plans collection to the view //There has to be a better way!! if( ! this.plans ) { this.plans = new Plans(); this.plans.fetch({ success: function() { self.plansListView = new PlansListView({ collection : self.plans }); $( '#container' ).append( self.plansListView.render().el ); if( self.requestedID ) self.planDetails( self.requestedID ); } }); } else { this.plansListView = new PlansListView({ collection : this.plans }); $( '#container' ).append( self.plansListView.render().el ); if( this.requestedID ) self.planDetails( this.requestedID ); } }, New Plan Route: newPlan : function() { var plan = new Plan({name: 'Cool Plan', date: 'Monday', desc: 'This is a great app'}); this.newPlan = new NewPlanView({ model : plan, collection: this.plans }); this.newPlan.render(); } FULL CODE ( function( $ ){ var Plan = Backbone.Model.extend({ defaults: { name : '', date : '', desc : '' } }); var Plans = Backbone.Collection.extend({ model : Plan, url : '/data/' }); $( document ).ready(function( e ){ var PlansListView = Backbone.View.extend({ tagName : 'ul', initialize : function() { _.bindAll( this, 'render', 'close' ); //reset the view if the collection is reset this.collection.bind( 'reset', this.render , this ); }, render : function() { _.each( this.collection.models, function( plan ){ $( this.el ).append( new PlansListItemView({ model: plan }).render().el ); }, this ); return this; }, close : function() { $( this.el ).unbind(); $( this.el ).remove(); } });//end var PlansListItemView = Backbone.View.extend({ tagName : 'li', template : _.template( $( '#list-item-template' ).html() ), events :{ 'click a' : 'listInfo' }, render : function() { $( this.el ).html( this.template( this.model.toJSON() ) ); return this; }, listInfo : function( event ) { } });//end var PlanView = Backbone.View.extend({ tagName : 'section', events : { 'click button.add-plan' : 'newPlan' }, template: _.template( $( '#plan-template' ).html() ), initialize: function() { _.bindAll( this, 'render', 'close', 'newPlan' ); }, render : function() { $( '#container' ).append( $( this.el ).html( this.template( this.model.toJSON() ) ) ); return this; }, newPlan : function( event ) { app.navigate( 'newplan', true ); }, close : function() { $( this.el ).unbind(); $( this.el ).remove(); } });//end var NewPlanView = Backbone.View.extend({ tagName : 'section', template : _.template( $( '#plan-form-template' ).html() ), events : { 'click button.save' : 'savePlan', 'click button.cancel' : 'cancel' }, intialize: function() { _.bindAll( this, 'render', 'save', 'cancel' ); }, render : function() { $( '#container' ).append( $( this.el ).html(this.template( this.model.toJSON() )) ); return this; }, savePlan : function( event ) { this.model.set({ name : 'bad plan', date : 'friday', desc : 'blah', id : Math.floor(Math.random()*11), total_stops : '2' }); this.collection.add( this.model ); app.navigate('', true ); event.preventDefault(); }, cancel : function(){} }); var AppRouter = Backbone.Router.extend({ container : $( '#container' ), routes : { '' : 'index', 'viewplan/:id' : 'planDetails', 'newplan' : 'newPlan' }, initialize: function(){ }, index : function() { this.container.empty(); var self = this; //This is a hack to get this to work //on default page load fetch all plans from the server //if the page has loaded ( this.plans is defined) set the updated plans collection to the view //There has to be a better way!! if( ! this.plans ) { this.plans = new Plans(); this.plans.fetch({ success: function() { self.plansListView = new PlansListView({ collection : self.plans }); $( '#container' ).append( self.plansListView.render().el ); if( self.requestedID ) self.planDetails( self.requestedID ); } }); } else { this.plansListView = new PlansListView({ collection : this.plans }); $( '#container' ).append( self.plansListView.render().el ); if( this.requestedID ) self.planDetails( this.requestedID ); } }, planDetails : function( id ) { if( this.plans ) { this.plansListView.close(); this.plan = this.plans.get( id ); if( this.planView ) this.planView.close(); this.planView = new PlanView({ model : this.plan }); this.planView.render(); } else{ this.requestedID = id; this.index(); } if( ! this.plans ) this.index(); }, newPlan : function() { var plan = new Plan({name: 'Cool Plan', date: 'Monday', desc: 'This is a great app'}); this.newPlan = new NewPlanView({ model : plan, collection: this.plans }); this.newPlan.render(); } }); var app = new AppRouter(); Backbone.history.start(); }); })( jQuery );

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  • How do I assign custom classes to YUI3 plugin/widget objects

    - by Akshar Prabhu Desai
    Consider the following code. var overlay = new Y.Overlay({ id:'tooltip-tag', bodyContent:"Loading.....", xy:[e.target.getX(),e.target.getY()+30] }); The overlay gets the id as given in attributes. But what if I want to add a class ? IS there something like: var overlay = new Y.Overlay({ **class:'tooltip-tag'**, bodyContent:"Loading.....", xy:[e.target.getX(),e.target.getY()+30] });

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  • android: how to specify multipe listivews

    - by Yang
    It seems that android has enforced that a listview must have the name android:id="@android:id/list", is there anyway to create multiple listview then? I have two activities which are both listview but have to control different format of Lists, one with image+text the other is just text.

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  • ASP MVC - Getting Controller Level error handling

    - by RP
    How to get Controller-Level error handling: This is my map-route: routes.MapRoute( "Default", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = "" } // Parameter defaults ); And I have 2 controllers - HomeController and AwayController I want both both controllers to handle their own errors For example, a call to /Home/InvalidAction would be handled by one method and /Away/InvalidAction would be handled by another method Where InvalidAction currently results in a 404 as there's no Action method with that name

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  • Modify xml element name in SQL Server

    - by sesame
    I want to change element name with following statement: SET @myDoc.modify('replace value of (/CustomerInfo)[1] with "Customer"') from <CustomerInfo>     <ID1</ID> </CustomerInfo> to <Customer>     <ID1</ID> </Customer> But failed. So how can i change it just in sql ?

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  • LockMode With Subclasses

    - by Lester
    I'm using Fluent Nhibernate with the following query on DerivedClass which extends BaseClass: var query = Session.CreateCriteria<DerivedClass>().SetLockMode(LockMode.Upgrade) What I want is the lock hints (updlock, rowlock) to be applied to both DerivedClass and BaseClass, but the generated SQL only applies the lock hints to DerivedClass: SELECT * FROM DerivedClass this_ with (updlock, rowlock) inner join [BaseClass] this_1_ on this_.Id=this_1_.Id WHERE ... This is the same situation described in http://opensource.atlassian.com/projects/hibernate/browse/HHH-2392 If anyone could point me in the right direction it would be much appreciated.

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  • JQuery fadeIn after src changed but fadeIn on the previous src anyway !

    - by Anna
    Hello ! I have a jquery bug and I've been looking for hours now, I can't figure out what's wrong... I have this code : $(document).ready(function(){ $('#ulPhotos a').click(function() { var newSrc= $(this).find('img').attr('src').split("/"); bigPictureName = 'big'+newSrc[2]; $('#pho').hide(); $('#imageBig').attr("src", "images/photos/"+bigPictureName); $('#pho').fadeIn('slow'); var alt = $(this).find('img').attr('alt'); $('#legend').html(alt); }); }); and this in html : <ul id="ulPhotos"> <li><a href="#centre"><img src="images/photos/09.jpg" title="La Reine de la Nuit au Comedia" alt="<em>La Reine de la Nuit</em> au Comedia"/></a> <a href="#centre"><img src="images/photos/03.jpg" title="Manuelita, La Périchole à l&rsquo;Opéra Comique" alt="Manuelita, <em>La Périchole</em> à l&#8217;Opéra Comique" /></a></li> <li><a href="#centre" ><img src="images/photos/12.png" title="" alt="Marion Baglan Carnac Ré" /></a> and this in for bigImage : </div> <div id="pho" a name="centre"> <p id="legend"> La Reine de la Nuit</p> <img src="images/photos/big09.jpg" alt="Marion Baglan" id="imageBig"/> </div> It simply changes the source of my img in a div named pho... but sometimes when the new image is too heavy, the fadeIn executes on the previous src !! so we see the fadeIn first on the previous image, and then, the right picture appears without fadeIn.... am I missing something? ps : the page is here http://www.marion-baglan.net/photos.htm#centre if you click fast you can see it... and when I try to put some bigger photos, it's very obvious...

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  • java.sql.SQLWarning: [Microsoft][SQLServer 2000 Driver for JDBC]Database changed to X

    - by adisembiring
    Hi all, I'm using Hibernate 3.2.1 and database SQLServer2000 while I'm try to insert some data using my dao, some warning occurred like this: java.sql.SQLWarning: [Microsoft][SQLServer 2000 Driver for JDBC]Database changed to BTN_SPP_DB at com.microsoft.jdbc.base.BaseWarnings.createSQLWarning(Unknown Source) at com.microsoft.jdbc.base.BaseWarnings.get(Unknown Source) at com.microsoft.jdbc.base.BaseConnection.getWarnings(Unknown Source) at org.hibernate.util.JDBCExceptionReporter.logAndClearWarnings(JDBCExceptionReporter.java:22) at org.hibernate.jdbc.ConnectionManager.closeConnection(ConnectionManager.java:443) at org.hibernate.jdbc.ConnectionManager.aggressiveRelease(ConnectionManager.java:400) at org.hibernate.jdbc.ConnectionManager.afterTransaction(ConnectionManager.java:287) at org.hibernate.jdbc.JDBCContext.afterTransactionCompletion(JDBCContext.java:221) at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:119) at co.id.hanoman.btnmw.spp.dao.TagihanDao.save(TagihanDao.java:43) at co.id.hanoman.btnmw.spp.dao.TagihanDao.save(TagihanDao.java:1) at co.id.hanoman.btnmw.spp.dao.test.TagihanDaoTest.testSave(TagihanDaoTest.java:81) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.junit.internal.runners.TestMethodRunner.executeMethodBody(TestMethodRunner.java:99) at org.junit.internal.runners.TestMethodRunner.runUnprotected(TestMethodRunner.java:81) at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34) at org.junit.internal.runners.TestMethodRunner.runMethod(TestMethodRunner.java:75) at org.junit.internal.runners.TestMethodRunner.run(TestMethodRunner.java:45) at org.junit.internal.runners.TestClassMethodsRunner.invokeTestMethod(TestClassMethodsRunner.java:66) at org.junit.internal.runners.TestClassMethodsRunner.run(TestClassMethodsRunner.java:35) at org.junit.internal.runners.TestClassRunner$1.runUnprotected(TestClassRunner.java:42) at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34) at org.junit.internal.runners.TestClassRunner.run(TestClassRunner.java:52) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:45) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196) my hibernate initialization log is: 2010-04-26 22:54:05,203 INFO [Version] Hibernate Annotations 3.3.0.GA 2010-04-26 22:54:05,234 INFO [Environment] Hibernate 3.2.1 2010-04-26 22:54:05,234 INFO [Environment] hibernate.properties not found 2010-04-26 22:54:05,234 INFO [Environment] Bytecode provider name : cglib 2010-04-26 22:54:05,234 INFO [Environment] using JDK 1.4 java.sql.Timestamp handling 2010-04-26 22:54:05,343 INFO [Configuration] configuring from resource: /hibernate.cfg.xml 2010-04-26 22:54:05,343 INFO [Configuration] Configuration resource: /hibernate.cfg.xml 2010-04-26 22:54:05,406 DEBUG [DTDEntityResolver] trying to resolve system-id [http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd] 2010-04-26 22:54:05,406 DEBUG [DTDEntityResolver] recognized hibernate namespace; attempting to resolve on classpath under org/hibernate/ 2010-04-26 22:54:05,406 DEBUG [DTDEntityResolver] located [http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd] in classpath 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.dialect=org.hibernate.dialect.SQLServerDialect 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.connection.driver_class=com.microsoft.jdbc.sqlserver.SQLServerDriver 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.connection.url=jdbc:microsoft:sqlserver://12.56.11.65:1433;databaseName=BTN_SPP_DB 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.connection.username=spp 2010-04-26 22:54:05,453 DEBUG [Configuration] hibernate.connection.password=spp

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  • Problems with asp:Button OnClick event...

    - by Matt
    Hi, Here is my button <asp:Button ID="myButton" Text="Click Me" OnClick="doSomething(10)" runat="server" /> Here is the server function public void doSomething(int num) { int someOtherNum = 10 + num; } When I try to compile the code I get the error "Method Name Expected" for the line: <asp:Button ID="myButton" Text="Click Me" OnClick="doSomething(10)" runat="server" /> What am I doing wrong? Am I not allowed to pass values to the server from an OnClick event?

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  • Mysql Left Join Null Result

    - by Ozzy
    I have this query SELECT articles.*, users.username AS `user` FROM `articles` LEFT JOIN `users` ON articles.user_id = users.id ORDER BY articles.timestamp Basically it returns the list of articles and the username that the article is associated to. Now if there is no entry in the users table for a particular user id, the users var is NULL. Is there anyway to make it that if its null it returns something like "User Not Found"? or would i have to do this using php?

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  • .Net 3.5 Asynchronous Socket Server Performance Problem

    - by iBrAaAa
    I'm developing an Asynchronous Game Server using .Net Socket Asynchronous Model( BeginAccept/EndAccept...etc.) The problem I'm facing is described like that: When I have only one client connected, the server response time is very fast but once a second client connects, the server response time increases too much. I've measured the time from a client sends a message to the server until it gets the reply in both cases. I found that the average time in case of one client is about 17ms and in case of 2 clients about 280ms!!! What I really see is that: When 2 clients are connected and only one of them is moving(i.e. requesting service from the server) it is equivalently equal to the case when only one client is connected(i.e. fast response). However, when the 2 clients move at the same time(i.e. requests service from the server at the same time) their motion becomes very slow (as if the server replies each one of them in order i.e. not simultaneously). Basically, what I am doing is that: When a client requests a permission for motion from the server and the server grants him the request, the server then broadcasts the new position of the client to all the players. So if two clients are moving in the same time, the server is eventually trying to broadcast to both clients the new position of each of them at the same time. EX: Client1 asks to go to position (2,2) Client2 asks to go to position (5,5) Server sends to each of Client1 & Client2 the same two messages: message1: "Client1 at (2,2)" message2: "Client2 at (5,5)" I believe that the problem comes from the fact that Socket class is thread safe according MSDN documentation http://msdn.microsoft.com/en-us/library/system.net.sockets.socket.aspx. (NOT SURE THAT IT IS THE PROBLEM) Below is the code for the server: /// /// This class is responsible for handling packet receiving and sending /// public class NetworkManager { /// /// An integer to hold the server port number to be used for the connections. Its default value is 5000. /// private readonly int port = 5000; /// /// hashtable contain all the clients connected to the server. /// key: player Id /// value: socket /// private readonly Hashtable connectedClients = new Hashtable(); /// /// An event to hold the thread to wait for a new client /// private readonly ManualResetEvent resetEvent = new ManualResetEvent(false); /// /// keeps track of the number of the connected clients /// private int clientCount; /// /// The socket of the server at which the clients connect /// private readonly Socket mainSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); /// /// The socket exception that informs that a client is disconnected /// private const int ClientDisconnectedErrorCode = 10054; /// /// The only instance of this class. /// private static readonly NetworkManager networkManagerInstance = new NetworkManager(); /// /// A delegate for the new client connected event. /// /// the sender object /// the event args public delegate void NewClientConnected(Object sender, SystemEventArgs e); /// /// A delegate for the position update message reception. /// /// the sender object /// the event args public delegate void PositionUpdateMessageRecieved(Object sender, PositionUpdateEventArgs e); /// /// The event which fires when a client sends a position message /// public PositionUpdateMessageRecieved PositionUpdateMessageEvent { get; set; } /// /// keeps track of the number of the connected clients /// public int ClientCount { get { return clientCount; } } /// /// A getter for this class instance. /// /// only instance. public static NetworkManager NetworkManagerInstance { get { return networkManagerInstance; } } private NetworkManager() {} /// Starts the game server and holds this thread alive /// public void StartServer() { //Bind the mainSocket to the server IP address and port mainSocket.Bind(new IPEndPoint(IPAddress.Any, port)); //The server starts to listen on the binded socket with max connection queue //1024 mainSocket.Listen(1024); //Start accepting clients asynchronously mainSocket.BeginAccept(OnClientConnected, null); //Wait until there is a client wants to connect resetEvent.WaitOne(); } /// /// Receives connections of new clients and fire the NewClientConnected event /// private void OnClientConnected(IAsyncResult asyncResult) { Interlocked.Increment(ref clientCount); ClientInfo newClient = new ClientInfo { WorkerSocket = mainSocket.EndAccept(asyncResult), PlayerId = clientCount }; //Add the new client to the hashtable and increment the number of clients connectedClients.Add(newClient.PlayerId, newClient); //fire the new client event informing that a new client is connected to the server if (NewClientEvent != null) { NewClientEvent(this, System.EventArgs.Empty); } newClient.WorkerSocket.BeginReceive(newClient.Buffer, 0, BasePacket.GetMaxPacketSize(), SocketFlags.None, new AsyncCallback(WaitForData), newClient); //Start accepting clients asynchronously again mainSocket.BeginAccept(OnClientConnected, null); } /// Waits for the upcoming messages from different clients and fires the proper event according to the packet type. /// /// private void WaitForData(IAsyncResult asyncResult) { ClientInfo sendingClient = null; try { //Take the client information from the asynchronous result resulting from the BeginReceive sendingClient = asyncResult.AsyncState as ClientInfo; // If client is disconnected, then throw a socket exception // with the correct error code. if (!IsConnected(sendingClient.WorkerSocket)) { throw new SocketException(ClientDisconnectedErrorCode); } //End the pending receive request sendingClient.WorkerSocket.EndReceive(asyncResult); //Fire the appropriate event FireMessageTypeEvent(sendingClient.ConvertBytesToPacket() as BasePacket); // Begin receiving data from this client sendingClient.WorkerSocket.BeginReceive(sendingClient.Buffer, 0, BasePacket.GetMaxPacketSize(), SocketFlags.None, new AsyncCallback(WaitForData), sendingClient); } catch (SocketException e) { if (e.ErrorCode == ClientDisconnectedErrorCode) { // Close the socket. if (sendingClient.WorkerSocket != null) { sendingClient.WorkerSocket.Close(); sendingClient.WorkerSocket = null; } // Remove it from the hash table. connectedClients.Remove(sendingClient.PlayerId); if (ClientDisconnectedEvent != null) { ClientDisconnectedEvent(this, new ClientDisconnectedEventArgs(sendingClient.PlayerId)); } } } catch (Exception e) { // Begin receiving data from this client sendingClient.WorkerSocket.BeginReceive(sendingClient.Buffer, 0, BasePacket.GetMaxPacketSize(), SocketFlags.None, new AsyncCallback(WaitForData), sendingClient); } } /// /// Broadcasts the input message to all the connected clients /// /// public void BroadcastMessage(BasePacket message) { byte[] bytes = message.ConvertToBytes(); foreach (ClientInfo client in connectedClients.Values) { client.WorkerSocket.BeginSend(bytes, 0, bytes.Length, SocketFlags.None, SendAsync, client); } } /// /// Sends the input message to the client specified by his ID. /// /// /// The message to be sent. /// The id of the client to receive the message. public void SendToClient(BasePacket message, int id) { byte[] bytes = message.ConvertToBytes(); (connectedClients[id] as ClientInfo).WorkerSocket.BeginSend(bytes, 0, bytes.Length, SocketFlags.None, SendAsync, connectedClients[id]); } private void SendAsync(IAsyncResult asyncResult) { ClientInfo currentClient = (ClientInfo)asyncResult.AsyncState; currentClient.WorkerSocket.EndSend(asyncResult); } /// Fires the event depending on the type of received packet /// /// The received packet. void FireMessageTypeEvent(BasePacket packet) { switch (packet.MessageType) { case MessageType.PositionUpdateMessage: if (PositionUpdateMessageEvent != null) { PositionUpdateMessageEvent(this, new PositionUpdateEventArgs(packet as PositionUpdatePacket)); } break; } } } The events fired are handled in a different class, here are the event handling code for the PositionUpdateMessage (Other handlers are irrelevant): private readonly Hashtable onlinePlayers = new Hashtable(); /// /// Constructor that creates a new instance of the GameController class. /// private GameController() { //Start the server server = new Thread(networkManager.StartServer); server.Start(); //Create an event handler for the NewClientEvent of networkManager networkManager.PositionUpdateMessageEvent += OnPositionUpdateMessageReceived; } /// /// this event handler is called when a client asks for movement. /// private void OnPositionUpdateMessageReceived(object sender, PositionUpdateEventArgs e) { Point currentLocation = ((PlayerData)onlinePlayers[e.PositionUpdatePacket.PlayerId]).Position; Point locationRequested = e.PositionUpdatePacket.Position; ((PlayerData)onlinePlayers[e.PositionUpdatePacket.PlayerId]).Position = locationRequested; // Broadcast the new position networkManager.BroadcastMessage(new PositionUpdatePacket { Position = locationRequested, PlayerId = e.PositionUpdatePacket.PlayerId }); }

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  • B-trees, databases, sequential inputs, and speed.

    - by IanC
    I know from experience that b-trees have awful performance when data is added to them sequentially (regardless of the direction). However, when data is added randomly, best performance is obtained. This is easy to demonstrate with the likes of an RB-Tree. Sequential writes cause a maximum number of tree balances to be performed. I know very few databases use binary trees, but rather used n-order balanced trees. I logically assume they suffer a similar fate to binary trees when it comes to sequential inputs. This sparked my curiosity. If this is so, then one could deduce that writing sequential IDs (such as in IDENTITY(1,1)) would cause multiple re-balances of the tree to occur. I have seen many posts argue against GUIDs as "these will cause random writes". I never use GUIDs, but it struck me that this "bad" point was in fact a good point. So I decided to test it. Here is my code: SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[T1]( [ID] [int] NOT NULL CONSTRAINT [T1_1] PRIMARY KEY CLUSTERED ([ID] ASC) ) GO CREATE TABLE [dbo].[T2]( [ID] [uniqueidentifier] NOT NULL CONSTRAINT [T2_1] PRIMARY KEY CLUSTERED ([ID] ASC) ) GO declare @i int, @t1 datetime, @t2 datetime, @t3 datetime, @c char(300) set @t1 = GETDATE() set @i = 1 while @i < 2000 begin insert into T2 values (NEWID(), @c) set @i = @i + 1 end set @t2 = GETDATE() WAITFOR delay '0:0:10' set @t3 = GETDATE() set @i = 1 while @i < 2000 begin insert into T1 values (@i, @c) set @i = @i + 1 end select DATEDIFF(ms, @t1, @t2) AS [Int], DATEDIFF(ms, @t3, getdate()) AS [GUID] drop table T1 drop table T2 Note that I am not subtracting any time for the creation of the GUID nor for the considerably extra size of the row. The results on my machine were as follows: Int: 17,340 ms GUID: 6,746 ms This means that in this test, random inserts of 16 bytes was almost 3 times faster than sequential inserts of 4 bytes. Would anyone like to comment on this? Ps. I get that this isn't a question. It's an invite to discussion, and that is relevant to learning optimum programming.

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