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  • Updating entity fields in app engine development server

    - by Joey
    I recently tried updating a field in one of my entities on the app engine local dev server via the sdk console. It appeared to have updated just fine (a simple float). However, when I followed up with a query on the entity, I received an exception: "Items in the mSomeList list must all be Key instances". mSomeList is just another list field I have in that entity, not the one I modified. Is there any reason manually changing a field would adversely throw something off such that the server gets confused? Is this a known bug? I wrote an http handler to alter the field through server code and it works fine if I take that approach. Update: (adding details) I am using the python google app engine server. Basically if I go into the Google App Engine Launcher and press the SDK Console button, then go into one of my entities and edit a field that is a float (i.e. change it from 0 to 3.5, for instance), I get the "Items in the mMyList list must all be Key instance" suddenly when I query the entity like this: query = DataModels.RegionData.gql("WHERE mRegion = :1", region) entry = query.get() the RegionData entity is what has the mMyList member. As mentioned previously, if I do not manually change the field but rather do so through server code, i.e. query = DataModels.RegionData.gql("WHERE mRegion = :1", region) entry = query.get() entry.mMyFloat = 3.5 entry.put() Then it works.

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  • Delete only reference to child object

    - by Al
    I'm running in to a bit of a problem where any attempt to delete just the reference to a child also deletes the child record. My schema looks like this Person Organisation OrganisationContacts : Person OrgId PersonId Role When removing an Organisation i want to only delete the record in OrgnaisationContacts, but not touch the Person record. My Mapping looks like this Code: public OrganisationMap() { Table("Organsations"); .... HasMany<OrganisationContact>(x => x.Contacts) .Table("OrganisationContacts ") .KeyColumn("OrgId") .Not.Inverse() .Cascade.AllDeleteOrphan(); } public class OrganisationContactMap : SubclassMap<OrganisationContact> { public OrganisationContactMap() { Table("OrganisationContacts"); Map(x => x.Role, "PersonRole"); Map(x => x.IsPrimary); } } At the moment just removing a contact from the IList either doesn't reflect in the database at all, or it issues two delete statements DELETE FROM OrganisationContact & DELETE FROM Person, or tries to set PersonId to null in the OrganisationContacts table. All of which are not desirable. Any help would be great appreciated.

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  • Orbited exception Data must not be unicode.

    - by Sid
    I am working with orbited and once I switch on orbited in production mode it throws the following error on my screen -- <exception caught here> --- File "/usr/lib/python2.6/dist-packages/twisted/web/server.py", line 150, in process self.render(resrc) File "/usr/lib/python2.6/dist-packages/twisted/web/server.py", line 157, in render body = resrc.render(self) File "/usr/local/lib/python2.6/dist-packages/orbited-0.7.10-py2.6.egg/orbited/transports/base.py", line 21, in render self.conn.transportOpened(self) File "/usr/local/lib/python2.6/dist-packages/orbited-0.7.10-py2.6.egg/orbited/cometsession.py", line 322, in transportOpened self.cometTransport.flush() File "/usr/local/lib/python2.6/dist-packages/orbited-0.7.10-py2.6.egg/orbited/transports/base.py", line 45, in flush self.write(self.packets) File "/usr/local/lib/python2.6/dist-packages/orbited-0.7.10-py2.6.egg/orbited/transports/htmlfile.py", line 42, in write self.request.write(payload); File "/usr/lib/python2.6/dist-packages/twisted/web/http.py", line 862, in write self.transport.write(data) File "/usr/lib/python2.6/dist-packages/twisted/internet/tcp.py", line 420, in write abstract.FileDescriptor.write(self, bytes) File "/usr/lib/python2.6/dist-packages/twisted/internet/abstract.py", line 170, in write raise TypeError("Data must not be unicode") exceptions.TypeError: Data must not be unicode I have absolutely no clue as to what could be the problem. Could anyone point me in the right direction.

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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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  • How to check for a null object reference when validating forms in MVC

    - by quakkels
    Hello SO, I'm experimenting with validating forms in the asp.net MVC framework. I'm focusing on server side validation for the time being. I've come across an error that I'm not sure how to rectify. System.NullReferenceException: Object reference not set to an instance of an object. The code that throws the error is: [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create([Bind(Exclude="ID")] MembersCreate mc ) { mc.Modules = ModuleListDataContext.GetModuleList(); ViewData.Model = mc; //Validation using ModelState // // //line below errors when form field is empty // if ((string)mc.Member.Username.Trim() == "") ModelState.AddModelError("Member.Username", "Username is required."); if (!ModelState.IsValid) return View(); try { // TODO: Add insert logic here return RedirectToAction("Index","Home"); } catch { return View(); } } When I put spaces in the field it performs exactly as i want, but if I leave the field blank and press submit I get the error. What's the best way to avoid this error and still validate blank form fields? Thanks all -

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  • targeting sprites from a method in the document class - null object reference

    - by Freddyk
    Hi I am trying to code a flash app entirely in the document class. I am using GestureWorks with a touch screen. When a user essentially presses a button it calls a method that should hide a specific graphic but not the graphic they touched. Essentially I need a way to refer to a graphic on the screen using a method besides 'e.target'. //This code works because it can access 'e.target'. private function photo1SpriteFlickHandler(e:GestureEvent):void { var openTween:Tween = new Tween(e.target, "x", Strong.easeOut, 232, 970, 5, true); } //this code gives me a null object reference because I am using 'photo1Sprite' rather than 'e.target' private function photo1SpriteFlickHandler(e:GestureEvent):void { var openTween:Tween = new Tween(photo1Sprite, "x", Strong.easeOut, 232, 970, 5, true); } //photo1Sprite has already been programatically added to the screen as so: var photo1Sprite = new TouchSprite(); var photo1Loader=new Loader(); photo1Loader.load(new URLRequest("media/photos1/photo1.jpg")); photo1Loader.contentLoaderInfo.addEventListener(Event.COMPLETE,loaderComplete); photo1Sprite.x = 232; photo1Sprite.y = 538; photo1Sprite.scaleX = .3; photo1Sprite.scaleY = .3; photo1Sprite.blobContainerEnabled = true; photo1Sprite.addEventListener(TouchEvent.TOUCH_DOWN, startDrag_Press); photo1Sprite.addEventListener(TouchEvent.TOUCH_UP, stopDrag_Release); photo1Sprite.addChild(photo1Loader); addChild(photo1Sprite); So I can make photo1Sprite react if my method is attached to it directly using 'e.target' but not if I am trying to call it from a method that was called from another element on the screen.

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  • NoClassDefFoundError when trying to reference external jar files

    - by opike
    I have some 3rd party jar files that I want to reference in my tomcat web application. I added this line to catalina.properties: shared.loader=/home/ollie/dev/java/googleapi_samples/gdata/java/lib/*.jar but I'm still getting this error: org.apache.jasper.JasperException: javax.servlet.ServletException: java.lang.NoClassDefFoundError: com/google/gdata/util/ServiceException org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:491) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:401) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260) javax.servlet.http.HttpServlet.service(HttpServlet.java:717) I verified that the com.google.gdata.util.ServiceException is in the gdata-core-1.0.jar file which is in the directory: /home/ollie/dev/java/googleapi_samples/gdata/java/lib I did bounce tomcat after I modified catalina.properties. Update 1: I tried copying the gdata-core-1.0.jar file into /var/lib/tomcat6/webapp/examples/WEB-INF/lib as a test but that didn't fix the problem either. Update 2: It actually does work when I copy the jar file directly into the WEB-INF/lib directory. There was a permissions issue that I had to resolve. But it's still not working when I use the shared.loader setting. I reconfirmed that the path is correct.

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  • Hibernate Exception Fixed By Alt+Tab

    - by Lee Theobald
    Hi all, I've got a very curious problem in Hibernate that I would like some opinions on. In my code if I do the following: Go to page A Click a link on page A to be taken to page B Click on data item on page B Exception thrown I get an error telling me: failed to lazily initialize a collection of role: XYZ, no session or session was closed Fair enough. But when I do the same thing but add an alt+tab in the middle, everything is fine. E.g. Go to page A Click a link on page A to be taken to page B Hit ALt+Tab to switch to another application Hit ALt+Tab to switch back to the web browser Click on data item on page B Everything is fine. I'm a little confused as to how switching focus from my application makes it act as I want it to. Does anyone have any light to shine on the subject? I don't think it's a locking issue as even if I do the second set of steps quicker than the first, still no error. It's a Seam application using Hibernate 3.3.2.GA & 3.4.0.GA.

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  • Retruning reference to object not changing the address in c++

    - by ashish-sangwan
    I am trying to understand function returning reference. For that i have written a simple program :- include using namespace std; class test { int i; friend test& func(); public: test(int j){i=j;} void show(){cout< }; test& func() { test temp(10); return temp; //// Address of temp=0xbfcb2874 } int main() { test obj1(50); // Address of obj1=0xbfcb28a0 func()=obj1; <= Problem:The address of obj1 is not changing obj1.show(); // // Address of obj1=0xbfcb28a0 return 0; } I run the program using gdb and observed that the address of obj1 still remains same but i expect it to get changed to 0xbfcb2874. I am not clear with the concept. Please help. Thanks in advance

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  • Returning reference to object is not changing the address in c++

    - by ashish-sangwan
    I am trying to understand functions returning a reference. For that I have written a simple program: #include<iostream> using namespace std; class test { int i; friend test& func(); public: test(int j){i=j;} void show(){cout<<i<<endl;} }; test& func() { test temp(10); return temp; //// Address of temp=0xbfcb2874 } int main() { test obj1(50); // Address of obj1=0xbfcb28a0 func()=obj1; <= Problem:The address of obj1 is not changing obj1.show(); // // Address of obj1=0xbfcb28a0 return 0; } I ran the program using gdb and observed that the address of obj1 still remains same, but I expect it to get changed to 0xbfcb2874. I am not clear with the concept. Please help.

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  • When is a try catch not a try catch?

    - by Dearmash
    I have a fun issue where during application shutdown, try / catch blocks are being seemingly ignored in the stack. I don't have a working test project (yet due to deadline, otherwise I'd totally try to repro this), but consider the following code snippet. public static string RunAndPossiblyThrow(int index, bool doThrow) { try { return Run(index); } catch(ApplicationException e) { if(doThrow) throw; } return ""; } public static string Run(int index) { if(_store.Contains(index)) return _store[index]; throw new ApplicationException("index not found"); } public static string RunAndIgnoreThrow(int index) { try { return Run(index); } catch(ApplicationException e) { } return ""; } During runtime this pattern works famously. We get legacy support for code that relies on exceptions for program control (bad) and we get to move forward and slowly remove exceptions used for program control. However, when shutting down our UI, we see an exception thrown from "Run" even though "doThrow" is false for ALL current uses of "RunAndPossiblyThrow". I've even gone so far as to verify this by modifying code to look like "RunAndIgnoreThrow" and I'll still get a crash post UI shutdown. Mr. Eric Lippert, I read your blog daily, I'd sure love to hear it's some known bug and I'm not going crazy. EDIT This is multi-threaded, and I've verified all objects are not modified while being accessed

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  • Haskell: Dealing With Types And Exceptions

    - by Douglas Brunner
    I'd like to know the "Haskell way" to catch and handle exceptions. As shown below, I understand the basic syntax, but I'm not sure how to deal with the type system in this situation. The below code attempts to return the value of the requested environment variable. Obviously if that variable isn't there I want to catch the exception and return Nothing. getEnvVar x = do { var <- getEnv x; Just var; } `catch` \ex -> do { Nothing } Here is the error: Couldn't match expected type `IO a' against inferred type `Maybe String' In the expression: Just var In the first argument of `catch', namely `do { var <- getEnv x; Just var }' In the expression: do { var <- getEnv x; Just var } `catch` \ ex -> do { Nothing } I could return string values: getRequestURI x = do { requestURI <- getEnv x; return requestURI; } `catch` \ex -> do { return "" } however, this doesn't feel like the Haskell way. What is the Haskell way?

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  • @ManyToMany Duplicate Entry Exception

    - by zp26
    I have mapped a bidirectional many-to-many exception between the entities Course and Trainee in the following manner: Course { ... private Collection<Trainee> students; ... @ManyToMany(targetEntity = lesson.domain.Trainee.class, cascade = {CascadeType.All}, fetch = {FetchType.EAGER}) @Jointable(name="COURSE_TRAINEE", joincolumns = @JoinColumn(name="COURSE_ID"), inverseJoinColumns = @JoinColumn(name = "TRAINEE_ID")) @CollectionOfElements public Collection<Trainee> getStudents() { return students; } ... } Trainee { ... private Collection<Course> authCourses; ... @ManyToMany(cascade = {CascadeType.All}, fetch = {FetchType.EAGER}, mappedBy = "students", targetEntity = lesson.domain.Course.class) @CollectionOfElements public Collection<Course> getAuthCourses() { return authCourses; } ... } Instead of creating a table where the Primary Key is made of the two foreign keys (imported from the table of the related two entities), the system generates the table "COURSE_TRAINEE" with the following schema: I am working on MySQL 5.1 and my App. Server is JBoss 5.1. Does anyone guess why?

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  • i have this code but when i run it i get an exception:

    - by nisnis84
    i have this code but when i run it i get an exception: java.security.AccessControlException: access denied (java.net.SocketPermission 127.0.0.1:8081 connect,resolve) this is the code, the server running good but the client dont work <OBJECT classid="clsid:8AD9C840-044E-11D1-B3E9-00805F499D93" width="615" height="360" codebase="http://java.sun.com/products/plugin/autodl/jinstall-1_4-windows-i586.cab#Version=1,4,0,mn"> <PARAM name="code" value="client/LlamaChat.class"> <PARAM name="archive" value="LlamaChat.jar"> <PARAM name="type" value="application/x-java-applet;version=1.4"> <PARAM name="scriptable" value="true"> <PARAM name="username" value="[replace with username]"> <PARAM name="port" value="[replace with port]"> <COMMENT> <EMBED type="application/x-java-applet;version=1.4" width="615" height="360" code="client/LlamaChat.class" archive="LlamaChat.jar" pluginspage="http://java.sun.com/j2se/1.4.1/download.html" username="nis" port="8081" <NOEMBED> No Java 1.4 plugin </NOEMBED></EMBED> </COMMENT> </OBJECT>

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  • ASP.NET Image Upload Parameter Not Valid. Exception

    - by pennylane
    Hi Guys, Im just trying to save a file to disk using a posted stream from jquery uploadify I'm also getting Parameter not valid. On adding to the error message so i can tell where it blew up in production im seeing it blow up on: var postedBitmap = new Bitmap(postedFileStream) any help would be most appreciated public string SaveImageFile(Stream postedFileStream, string fileDirectory, string fileName, int imageWidth, int imageHeight) { string result = ""; string fullFilePath = Path.Combine(fileDirectory, fileName); string exhelp = ""; if (!File.Exists(fullFilePath)) { try { using (var postedBitmap = new Bitmap(postedFileStream)) { exhelp += "got past bmp creation" + fullFilePath; using (var imageToSave = ImageHandler.ResizeImage(postedBitmap, imageWidth, imageHeight)) { exhelp += "got past resize"; if (!Directory.Exists(fileDirectory)) { Directory.CreateDirectory(fileDirectory); } result = "Success"; postedBitmap.Dispose(); imageToSave.Save(fullFilePath, GetImageFormatForFile(fileName)); } exhelp += "got past save"; } } catch (Exception ex) { result = "Save Image File Failed " + ex.Message + ex.StackTrace; Global.SendExceptionEmail("Save Image File Failed " + exhelp, ex); } } return result; }

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  • Could not load SWT library on Windows 32-bit

    - by Firzen
    I am almost done with one Java project that I have been developing on Linux. Now I need to build and test it on Windows. So I have installed Eclipse on Windows XP 32-bit, and imported my project. All dependencies of project are in jar files in lib folder, and on Linux everything works well, but on Windows XP I get following error: Exception in thread "main" java.lang.UnsatisfiedLinkError: Could not load SWT library. Reasons: no swt-pi-gtk-4234 in java.library.path no swt-pi-gtk in java.library.path Can't load library: C:\Documents and Settings\firzen\.swt\lib\win32\x86\swt-pi-gtk-4234.dll Can't load library: C:\Documents and Settings\firzen\.swt\lib\win32\x86\swt-pi-gtk.dll at org.eclipse.swt.internal.Library.loadLibrary(Library.java:331) at org.eclipse.swt.internal.Library.loadLibrary(Library.java:240) at org.eclipse.swt.internal.gtk.OS.<clinit>(OS.java:22) at org.eclipse.swt.internal.Converter.wcsToMbcs(Converter.java:63) at org.eclipse.swt.internal.Converter.wcsToMbcs(Converter.java:54) at org.eclipse.swt.widgets.Display.<clinit>(Display.java:133) at gui.Frontend.<init>(Frontend.java:51) at Fighter.main(Fighter.java:18) I have searched for these DLLs, but I have failed to find them. Where can I download these DLL files? Thanks in advance.

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  • [WPF] ExceptionValidationRule doesn't react to exceptions...

    - by Darmak
    Hi, I have an ExceptionValidationRule on my TextBox: <Window.Resources> <Style x:Key="textStyleTextBox" TargetType="TextBox"> <Style.Triggers> <Trigger Property="Validation.HasError" Value="true"> <Setter Property="ToolTip" Value="{Binding RelativeSource={RelativeSource Self}, Path=(Validation.Errors)[0].ErrorContent}" /> </Trigger> </Style.Triggers> </Style> </Window.Resources> <TextBox x:Name="myTextBox" {Binding Path=MyProperty, ValidatesOnExceptions=True}" Style="{StaticResource ResourceKey=textStyleTextBox}" /> and MyProperty looks like that: private int myProperty; public int MyProperty { get { return myProperty; } set { if(value > 10) throw new ArgumentException("LOL that's an error"); myProperty = value; } } In DEBUG mode, application crashes with unhandled exception "LOL that's an error" (WPF Binding Engine doesn't catch this and I think it should...). In RELEASE mode, everything works fine. Can someone tell me, why the hell is this happening? And how can I fix this?

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  • Internal Java code best practice for dealing with invalid REST API parameters

    - by user326389
    My colleague wrote the following stackoverflow question: other stack overflow question on this topic The question seems to have been misinterpreted and I want to find out the answer, so I'm starting this new question... hopefully a little more clear. Basically, we have a REST API. Users of our API call our methods with parameters. But sometimes users call them with the wrong parameters!! Maybe a mistake in their code, maybe they're just trying to play with us, maybe they're trying to see how we respond, who knows! We respond with HTTP status error codes and maybe a detailed description of the invalid parameter in the XML response. All is well. But internally we deal with these invalid parameters by throwing exceptions. For example, if someone looks up a Person object by giving us their profile id, but the profile id doesn't exist... we throw a PersonInvalidException when looking them up. Then we catch this exception in our API controller and send back an HTTP 400 status error code. Our question is... is this the best practice, throwing exceptions internally for this kind of user error? These exceptions never get propogated back to the user, this is a REST API. They only make our code cleaner. Otherwise we could have a validation method in each of our API controllers to make sure the parameters all make sense, but that seems inefficient. We have to look up things in our database potentially twice. Or we could return nulls and check for them, but that sucks... What are your thoughts?

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  • Blackberry: Getting uncaught exception java.lang.securityexception

    - by Maxim Xion
    here is my code to open an image file from SDcard in Blackberry import javax.microedition.midlet.*; import javax.microedition.lcdui.*; import java.io.*; public class DisplayAnImage extends MIDlet { private Display mDisplay; private Form mForm; private Image pngBackground; public void startApp() { try{ pngBackground = Image.createImage("file:///Media Card/test_image.png"); ImageItem img = new ImageItem("bg",pngBackground, ImageItem.LAYOUT_EXPAND,"background",ImageItem.PLAIN); mForm = new Form("MIDlet Developer Guide: Display an image."); mForm.append(img); mDisplay = Display.getDisplay(this); mDisplay.setCurrent(mForm); } catch(IOException e) { mForm.append(e.getMessage()); } } public void pauseApp() { } public void destroyApp(boolean flag) { } } While I am running this app with giving all permission to app it shows me "uncaught exception java.lang.securityexception". Please somebody help me on this. Thanks in advance.. :-)

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  • workaround for ORA-03113: end-of-file on communication channel

    - by Jefferstone
    The call to TEST_FUNCTION below fails with "ORA-03113: end-of-file on communication channel". A workaround is presented in TEST_FUNCTION2. I boiled down the code as my actual function is far more complex. Tested on Oracle 11G. Anyone have any idea why the first function fails? CREATE OR REPLACE TYPE "EMPLOYEE" AS OBJECT ( employee_id NUMBER(38), hire_date DATE ); CREATE OR REPLACE TYPE "EMPLOYEE_TABLE" AS TABLE OF EMPLOYEE; CREATE OR REPLACE FUNCTION TEST_FUNCTION RETURN EMPLOYEE_TABLE IS table1 EMPLOYEE_TABLE; table2 EMPLOYEE_TABLE; return_table EMPLOYEE_TABLE; BEGIN SELECT CAST(MULTISET ( SELECT user_id, created FROM all_users WHERE LOWER(username) < 'm' ) AS EMPLOYEE_TABLE) INTO table1 FROM dual; SELECT CAST(MULTISET ( SELECT user_id, created FROM all_users WHERE LOWER(username) >= 'm' ) AS EMPLOYEE_TABLE) INTO table2 FROM dual; SELECT CAST(MULTISET ( SELECT employee_id, hire_date FROM TABLE(table1) UNION SELECT employee_id, hire_date FROM TABLE(table2) ) AS EMPLOYEE_TABLE) INTO return_table FROM dual; RETURN return_table; END TEST_FUNCTION; CREATE OR REPLACE FUNCTION TEST_FUNCTION2 RETURN EMPLOYEE_TABLE IS table1 EMPLOYEE_TABLE; table2 EMPLOYEE_TABLE; return_table EMPLOYEE_TABLE; BEGIN SELECT CAST(MULTISET ( SELECT user_id, created FROM all_users WHERE LOWER(username) < 'm' ) AS EMPLOYEE_TABLE) INTO table1 FROM dual; SELECT CAST(MULTISET ( SELECT user_id, created FROM all_users WHERE LOWER(username) >= 'm' ) AS EMPLOYEE_TABLE) INTO table2 FROM dual; WITH combined AS ( SELECT employee_id, hire_date FROM TABLE(table1) UNION SELECT employee_id, hire_date FROM TABLE(table2) ) SELECT CAST(MULTISET ( SELECT * FROM combined ) AS EMPLOYEE_TABLE) INTO return_table FROM dual; RETURN return_table; END TEST_FUNCTION2; SELECT * FROM TABLE (TEST_FUNCTION()); -- Throws exception ORA-03113. SELECT * FROM TABLE (TEST_FUNCTION2()); -- Works

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  • How to use interfaces in exception handling

    - by vikp
    Hi, I'm working on the exception handling layer for my application. I have read few articles on interfaces and generics. I have used inheritance before quite a lot and I'm comfortable with in that area. I have a very brief design that I'm going to implement: public interface IMyExceptionLogger { public void LogException(); // Helper methods for writing into files,db, xml } I'm slightly confused what I should be doing next. public class FooClass: IMyExceptionLogger { // Fields // Constructors } Should I implement LogException() method within FooClass? If yes, than I'm struggling to see how I'm better of using an interface instead of the concrete class... I have a variety of classes that will make a use of that interface, but I don't want to write an implementation of that interface within each class. In the same time If I implement an interface in one class, and then use that class in different layers of the application I will be still using concrete classes instead of interfaces, which is a bad OO design... I hope this makes sense. Any feedback and suggestions are welcome. Please notice that I'm not interested in using net4log or its competitors because I'm doing this to learn. Thank you Edit: Wrote some more code. So I will implement variety of loggers with this interface, i.e. DBExceptionLogger, CSVExceptionLogger, XMLExceptionLogger etc. Than I will still end up with concrete classes that I will have to use in different layers of my application.

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  • Null Ref when adding TabPages at runtimes

    - by BDotA
    This is a sample code I wrote to add some tab pages with the controls in them at run time. but when I run it , I get a Null Ref exception error. what part I am doing wrong? TabPage[] tabPages = new TabPage[2]; CheckBox ck  = new CheckBox();       tabPages[0].BackColor = Color.Firebrick;     tabPages[0].Controls.Add(ck);       tabPages[1].BackColor = Color.Firebrick;     tabPages[1].Controls.Add(ck);   tabGuy.SuspendLayout();     tabGuy.TabPages.Add(tabPages[0]);     tabGuy.TabPages.Add(tabPages[1]); tabGuy.ResumeLayout();

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  • Why aren't variables declared in "try" in scope in "catch" or "finally"?

    - by Jon Schneider
    In C# and in Java (and possibly other languages as well), variables declared in a "try" block are not in scope in the corresponding "catch" or "finally" blocks. For example, the following code does not compile: try { String s = "test"; // (more code...) } catch { Console.Out.WriteLine(s); //Java fans: think "System.out.println" here instead } In this code, a compile-time error occurs on the reference to s in the catch block, because s is only in scope in the try block. (In Java, the compile error is "s cannot be resolved"; in C#, it's "The name 's' does not exist in the current context".) The general solution to this issue seems to be to instead declare variables just before the try block, instead of within the try block: String s; try { s = "test"; // (more code...) } catch { Console.Out.WriteLine(s); //Java fans: think "System.out.println" here instead } However, at least to me, (1) this feels like a clunky solution, and (2) it results in the variables having a larger scope than the programmer intended (the entire remainder of the method, instead of only in the context of the try-catch-finally). My question is, what were/are the rationale(s) behind this language design decision (in Java, in C#, and/or in any other applicable languages)?

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  • VB.net avoiding cross thread exception with extension method

    - by user574632
    Hello I am trying to implement a solution for updating form controls without using a delegate. I am attempting to use the 1st solution on this page: http://www.dreamincode.net/forums/blog/143/entry-2337-handling-the-dreaded-cross-thread-exception/ Imports System.ComponentModel Imports System.Runtime.CompilerServices Public Module MyInvoke <Extension()> _ Public Sub CustomInvoke(Of T As ISynchronizeInvoke)(ByVal control As T, ByVal toPerform As Action(Of T)) If control.InvokeRequired Then control.Invoke(toPerform, New Object() {control}) toPerform(control) End If End Sub End Module The site gives this as example of how to use: Label1.CustomInvoke(l => l.Text = "Hello World!") But i get 'l' is not declared error. As you can see im very new to VB or any OOP. I can get the second solution on that page to work (using delegates) but i have quite a few things to do in this thread and it seems like i would need to write a new delegate sub for each thing, which seems wasteful. What i need to do is select the 1st item from a combobox, update a textbox.text with the selected item, and pass the selected item to a function. Then wait for x seconds and start again, selecting the second item. I can get it to work in a single threaded application, but i need the interface to remain responsive. Any help greatly appreciated. EDIT: OK so changing the syntax worked for the example. However if i change it from Label1.CustomInvoke(Sub(l) l.text = "hello world!") (which worked just fine) to: Dim indexnumber As Integer = 0 ComboBox1.CustomInvoke(Sub(l) l.SelectedIndex = indexnumber) I get a cross threading error as though i didnt even use this method: Cross-thread operation not valid: Control 'ComboBox1' accessed from a thread other than the thread it was created on. So now im back to where i started? Any further help very much appreciated.

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  • Silverlight logging out causes "Object reference not set to an instance"

    - by Alex
    I am using the Silverlight 4 Business Application Template. I've created a DomainDataSource in XAML like so: <riaControls:DomainDataSource x:Name="LogData" QueryName="GetLogs" AutoLoad="True" LoadSize="20" > <riaControls:DomainDataSource.DomainContext> <local:AdminDomainContext /> </riaControls:DomainDataSource.DomainContext> <riaControls:DomainDataSource.QueryParameters> <riaControls:Parameter ParameterName="UserLoginID" Value="{Binding Path=User.UserLoginID, Source={StaticResource WebContext}}" /> </riaControls:DomainDataSource.QueryParameters> </riaControls:DomainDataSource> The problem I'm experiencing is that whenever I log out, I get: Load operation failed for query 'GetLogs'. Object reference not set to an instance of an object. I assume that because I've logged out, User.UserLoginID is now null and is causing the exception. So... anybody know a good way for me to solve this? I don't really want to set the QueryParameter programmatically.

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