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• Trouble binding command in grid menu item.

  - by Pete

  I have a grid that's inside a usercontrol derived class called MediatedUserControl. I'm adding a context menu to let the user delete an item, but I've been unable to figure out how to bind the command to my command property. I'm using MVVM and my viewmodel implements a public ICommand property called DeleteSelectedItemCommand. However, when the view is displayed, I get the following message in the output window: System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='BRO.View.MediatedUserControl', AncestorLevel='1''. BindingExpression:Path=DataContext.DeleteSelectedItemCommand; DataItem=null; target element is 'BarButtonItem' (HashCode=6860584); target property is 'Command' (type 'ICommand') I feel like I generally have a good handle on bindings like this and can't figure out what it is I'm missing here. Thanks for any help you can provide. <dxg:GridControl HorizontalAlignment="Left" Margin="12,88,0,0" x:Name="gridControl1" VerticalAlignment="Top" Height="500" Width="517" DataSource="{Binding ItemList}" BorderBrush="{StaticResource {x:Static SystemColors.ActiveBorderBrushKey}}" ShowBorder="True" Background="{StaticResource {x:Static SystemColors.ControlLightBrushKey}}" UseLayoutRounding="False" DataContext="{Binding}"> <dxg:GridControl.Columns> <dxg:GridColumn FieldName="Code" Header="Code" Width="107" /> <dxg:GridColumn FieldName="Name" Header="Item" Width="173" /> <dxg:GridColumn FieldName="PricePerItem" Header="Unit Price" Width="70"> <dxg:GridColumn.EditSettings> <dxe:TextEditSettings DisplayFormat="N2" /> </dxg:GridColumn.EditSettings> </dxg:GridColumn> <dxg:GridColumn FieldName="Quantity" Header="Qty" Width="50" AllowEditing="True" /> <dxg:GridColumn FieldName="TotalPrice" Header="Total Price" Width="90"> <dxg:GridColumn.EditSettings> <dxe:TextEditSettings DisplayFormat="N2" /> </dxg:GridColumn.EditSettings> </dxg:GridColumn> </dxg:GridControl.Columns> <dxg:GridControl.View> <dxg:TableView ShowIndicator="False" ShowGroupPanel="False" MultiSelectMode="Row" AllowColumnFiltering="False" AllowBestFit="False" AllowFilterEditor="False" AllowEditing="False" AllowGrouping="False" AllowSorting="False" AllowResizing="False" AllowMoving="False" AllowMoveColumnToDropArea="False" AllowDateTimeGroupIntervalMenu="False" > <dxg:TableView.RowCellMenuCustomizations> <dxb:BarButtonItem Name="deleteRowItem" Command="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=view:MediatedUserControl, AncestorLevel=1}, Path=DataContext.DeleteSelectedItemCommand}"> </dxb:BarButtonItem> </dxg:TableView.RowCellMenuCustomizations> </dxg:TableView> </dxg:GridControl.View>

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• Difference in output from use of synchronized keyword and join()

  - by user2964080

  I have 2 classes, public class Account { private int balance = 50; public int getBalance() { return balance; } public void withdraw(int amt){ this.balance -= amt; } } and public class DangerousAccount implements Runnable{ private Account acct = new Account(); public static void main(String[] args) throws InterruptedException{ DangerousAccount target = new DangerousAccount(); Thread t1 = new Thread(target); Thread t2 = new Thread(target); t1.setName("Ravi"); t2.setName("Prakash"); t1.start(); /* #1 t1.join(); */ t2.start(); } public void run(){ for(int i=0; i<5; i++){ makeWithdrawl(10); if(acct.getBalance() < 0) System.out.println("Account Overdrawn"); } } public void makeWithdrawl(int amt){ if(acct.getBalance() >= amt){ System.out.println(Thread.currentThread().getName() + " is going to withdraw"); try{ Thread.sleep(500); }catch(InterruptedException e){ e.printStackTrace(); } acct.withdraw(amt); System.out.println(Thread.currentThread().getName() + " has finished the withdrawl"); }else{ System.out.println("Not Enough Money For " + Thread.currentThread().getName() + " to withdraw"); } } } I tried adding synchronized keyword in makeWithdrawl method public synchronized void makeWithdrawl(int amt){ and I keep getting this output as many times I try Ravi is going to withdraw Ravi has finished the withdrawl Ravi is going to withdraw Ravi has finished the withdrawl Ravi is going to withdraw Ravi has finished the withdrawl Ravi is going to withdraw Ravi has finished the withdrawl Ravi is going to withdraw Ravi has finished the withdrawl Not Enough Money For Prakash to withdraw Not Enough Money For Prakash to withdraw Not Enough Money For Prakash to withdraw Not Enough Money For Prakash to withdraw Not Enough Money For Prakash to withdraw This shows that only Thread t1 is working... If I un-comment the the line saying t1.join(); I get the same output. So how does synchronized differ from join() ? If I don't use synchronize keyword or join() I get various outputs like Ravi is going to withdraw Prakash is going to withdraw Prakash has finished the withdrawl Ravi has finished the withdrawl Prakash is going to withdraw Ravi is going to withdraw Prakash has finished the withdrawl Ravi has finished the withdrawl Prakash is going to withdraw Ravi is going to withdraw Prakash has finished the withdrawl Ravi has finished the withdrawl Account Overdrawn Account Overdrawn Not Enough Money For Ravi to withdraw Account Overdrawn Not Enough Money For Prakash to withdraw Account Overdrawn Not Enough Money For Ravi to withdraw Account Overdrawn Not Enough Money For Prakash to withdraw Account Overdrawn So how does the output from synchronized differ from join() ?

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• Android Application Crashel

  - by deewangan

  hello everyone, i am trying to run an application on an android emulator, but it crashes. i am following a howto i don't know what to do, it just crashes. other applications are running fine, can anyone tell me what i am doing wrong.here is the code: public class Finder extends Activity { /** Called when the activity is first created. */ private LocationManager myLocationManager; private LocationListener myLocationListener; private TextView myLatitude, myLongitude; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); myLatitude = (TextView)findViewById(R.id.Latitude); myLongitude = (TextView)findViewById(R.id.Longitude); myLocationManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE); myLocationListener = new MyLocationListener(); myLocationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,0,0,myLocationListener); myLatitude.setText(String.valueOf( myLocationManager.getLastKnownLocation( LocationManager.GPS_PROVIDER).getLatitude())); myLongitude.setText(String.valueOf( myLocationManager.getLastKnownLocation( LocationManager.GPS_PROVIDER).getLongitude())); } private class MyLocationListener implements LocationListener{ public void onLocationChanged(Location argLocation) { // TODO Auto-generated method stub myLatitude.setText(String.valueOf( argLocation.getLatitude())); myLongitude.setText(String.valueOf( argLocation.getLongitude())); } public void onProviderDisabled(String provider) { // TODO Auto-generated method stub } public void onProviderEnabled(String provider) { // TODO Auto-generated method stub } public void onStatusChanged(String provider, int status, Bundle extras) { // TODO Auto-generated method stub } }; } i looked in the logcat after running the application, it seems that the following lines are cause of the problem but i don't understand it:( 01-18 22:12:46.017: WARN/dalvikvm(1091): threadid=3: thread exiting with uncaught exception (group=0x4001aa28) 01-18 22:12:46.017: ERROR/AndroidRuntime(1091): Uncaught handler: thread main exiting due to uncaught exception 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): java.lang.RuntimeException: Unable to start activity ComponentInfo{pro.googleLocation/pro.googleLocation.Finder}: java.lang.NullPointerException 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2401) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2417) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at android.app.ActivityThread.access$2100(ActivityThread.java:116) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at android.os.Handler.dispatchMessage(Handler.java:99) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at android.os.Looper.loop(Looper.java:123) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at android.app.ActivityThread.main(ActivityThread.java:4203) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at java.lang.reflect.Method.invokeNative(Native Method) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at java.lang.reflect.Method.invoke(Method.java:521) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at dalvik.system.NativeStart.main(Native Method) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): Caused by: java.lang.NullPointerException 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at pro.googleLocation.Finder.onCreate(Finder.java:28) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1123) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2364) 01-18 22:12:46.037: ERROR/AndroidRuntime(1091): ... 11 more

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• Revision control for writing programming lessons

  - by Dietrich Epp

  I'd like to write a series programming lessons that guide programmers to build a certain kind of program. After each lesson, I'd like to provide sample code that implements what that lesson covered, and the next lesson would use that code as a starting point. Right now I'm using Git to keep track of the code from lesson to lesson. Each lesson has its own branch. lesson1: A--B--C \ lesson2: D--E--F \ lesson3: G--H--I However, suppose that now I want to make it easier on the Windows programmers using my lessons, so I add a Visual Studio project to lesson 1 and then merge it into lessons 2 and 3. lesson1: A--B--C--------------J \ \ lesson2: D--E--F--------K \ \ lesson3: G--H--I--L And then someone points out a bug in lesson 2 that causes crashes on certain systems. (This diagram is where I am right now, and I'm having doubts about continuing along this path.) lesson1: A--B--C--------------J \ \ lesson2: D--E--F--------K--M \ \ \ lesson3: G--H--I--L--N Here are the problems I imagine having: If I had many lessons, and I fix something in lesson 1, am I going to have to spend fifteen minutes or more just merging that one simple change? I know I'll probably have to test all of those lessons again, but I can put that off. When I make a bunch of changes to various lessons on one computer, how do I pull all of the branches at the same time? If I decide to publish these lessons, I'd like a way to tag all of the branches to correspond with what I publish. I figure I'll just need to tag each branch separately, but it would be nice if there were a better way. When I look at the history, I imagine becoming terribly confused about what I've done. Compare the above diagram to a hypothetical diagram below, where I use rebase instead of merge (and rebase has its own problems): lesson1: A--B--C--J \ lesson2: D2--E2--F2--M \ lesson3: G2--H2--I2 Do any of you have experience working with a project like this? Should I consider using a different VCS, such as Darcs? (Note: it would be a real pain to use centralized VCS, so don't suggest one of those unless the benefits are clear.) Should I consider writing plugins or extra tools for a VCS (such as a "meta tag" which tags several branches)?

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• quartz: preventing concurrent instances of a job in jobs.xml

  - by Jason S

  This should be really easy. I'm using Quartz running under Apache Tomcat 6.0.18, and I have a jobs.xml file which sets up my scheduled job that runs every minute. What I would like to do, is if the job is still running when the next trigger time rolls around, I don't want to start a new job, so I can let the old instance complete. Is there a way to specify this in jobs.xml (prevent concurrent instances)? If not, is there a way I can share access to an in-memory singleton within my application's Job implementation (is this through the JobExecutionContext?) so I can handle the concurrency myself? (and detect if a previous instance is running) update: After floundering around in the docs, here's a couple of approaches I am considering, but either don't know how to get them to work, or there are problems. Use StatefulJob. This prevents concurrent access... but I'm not sure what other side-effects would occur if I use it, also I want to avoid the following situation: Suppose trigger times would be every minute, i.e. trigger#0 = at time 0, trigger #1 = 60000msec, #2 = 120000, #3 = 180000, etc. and the trigger#0 at time 0 fires my job which takes 130000msec. With a plain Job, this would execute triggers #1 and #2 while job trigger #0 is still running. With a StatefulJob, this would execute triggers #1 and #2 in order, immediately after #0 finishes at 130000. I don't want that, I want #1 and #2 not to run and the next trigger that runs a job should take place at #3 (180000msec). So I still have to do something else with StatefulJob to get it to work the way I want, so I don't see much of an advantage to using it. Use a TriggerListener to return true from vetoJobExecution(). Although implementing the interface seems straightforward, I have to figure out how to setup one instance of a TriggerListener declaratively. Can't find the docs for the xml file. Use a static shared thread-safe object (e.g. a semaphore or whatever) owned by my class that implements Job. I don't like the idea of using singletons via the static keyword under Tomcat/Quartz, not sure if there are side effects. Also I really don't want them to be true singletons, just something that is associated with a particular job definition. Implement my own Trigger which extends SimpleTrigger and contains shared state that could run its own TriggerListener. Again, I don't know how to setup the XML file to use this trigger rather than the standard <trigger><simple>...</simple></trigger>.

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• C# Finalize/Dispose pattern

  - by robUK

  Hello, C# 2008 I have been working on this for a while now. And I am still confused about some issues. My questions below 1) I know that you only need a finalizer if you are disposing of unmanaged resources. However, if you are using managed resources that make calls to unmanaged resources. Would you still need to implement a finalizer? 2) However, if you develop a class that doesn't use any unmanged resources directly or indirectly and you implement the IDisposable so that clients of your class can use the 'using statement'. Would it be acceptable to implement the IDisposable just so that clients of your class can use the using statement? using(myClass objClass = new myClass()) { // Do stuff here } 3) I have developed this simple code below to demostrate the Finalize/dispose pattern: public class NoGateway : IDisposable { private WebClient wc = null; public NoGateway() { wc = new WebClient(); wc.DownloadStringCompleted += wc_DownloadStringCompleted; } // Start the Async call to find if NoGateway is true or false public void NoGatewayStatus() { // Start the Async's download // Do other work here wc.DownloadStringAsync(new Uri(www.xxxx.xxx)); } private void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e) { // Do work here } // Dispose of the NoGateway object public void Dispose() { wc.DownloadStringCompleted -= wc_DownloadStringCompleted; wc.Dispose(); GC.SuppressFinalize(this); } } Question about the source code: 1) Here I have not added the finalizer. And normally the finalizer will be called by the GC, and the finalizer will call the Dispose. As I don't have the finalizer, when do I call the Dispose method? Is it the client of the class that has to call it? So my class in the example is called NoGateway and the client could use and dispose of the class like this: Would the Dispose method be automatically called when execution reaches the end of the using block? using(NoGateway objNoGateway = new NoGateway()) { // Do stuff here } Or does the client have to manually call the dispose method i.e.? NoGateway objNoGateway = new NoGateway(); // Do stuff with object objNoGateway.Dispose(); // finished with it Many thanks for helping with all these questions, 2) I am using the webclient class in my 'NoGateway' class. Because the webclient implements the IDisposable interface. Does this mean that the webclient indirectly uses unmanaged resources? Is there any hard and fast rule to follow about this. How do I know that a class uses unmanaged resources?

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• Spring AOP pointcut that matches annotation on interface

  - by seanizer

  Hello, this is my first post here, so I apologize in advance for any stupidity on my side. I have a service class implemented in Java 6 / Spring 3 that needs an annotation to restrict access by role. I have defined an annotation called RequiredPermission that has as its value attribute one or more values from an enum called OperationType: public @interface RequiredPermission { /** * One or more {@link OperationType}s that map to the permissions required * to execute this method. * * @return */ OperationType[] value();} public enum OperationType { TYPE1, TYPE2; } package com.mycompany.myservice; public interface MyService{ @RequiredPermission(OperationType.TYPE1) void myMethod( MyParameterObject obj ); } package com.mycompany.myserviceimpl; public class MyServiceImpl implements MyService{ public myMethod( MyParameterObject obj ){ // do stuff here } } I also have the following aspect definition: /** * Security advice around methods that are annotated with * {@link RequiredPermission}. * * @param pjp * @param param * @param requiredPermission * @return * @throws Throwable */ @Around(value = "execution(public *" + " com.mycompany.myserviceimpl.*(..))" + " && args(param)" + // parameter object " && @annotation( requiredPermission )" // permission annotation , argNames = "param,requiredPermission") public Object processRequest(final ProceedingJoinPoint pjp, final MyParameterObject param, final RequiredPermission requiredPermission) throws Throwable { if(userService.userHasRoles(param.getUsername(),requiredPermission.values()){ return pjp.proceed(); }else{ throw new SorryButYouAreNotAllowedToDoThatException( param.getUsername(),requiredPermission.value()); } } The parameter object contains a user name and I want to look up the required role for the user before allowing access to the method. When I put the annotation on the method in MyServiceImpl, everything works just fine, the pointcut is matched and the aspect kicks in. However, I believe the annotation is part of the service contract and should be published with the interface in a separate API package. And obviously, I would not like to put the annotation on both service definition and implementation (DRY). I know there are cases in Spring AOP where aspects are triggered by annotations one interface methods (e.g. Transactional). Is there a special syntax here or is it just plain impossible out of the box. PS: I have not posted my spring config, as it seems to be working just fine. And no, those are neither my original class nor method names. Thanks in advance, Sean PPS: Actually, here is the relevant part of my spring config: <aop:aspectj-autoproxy proxy-target-class="false" /> <bean class="com.mycompany.aspect.MyAspect"> <property name="userService" ref="userService" /> </bean>

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• ActionListener problem

  - by thegamer

  Hello, i am trying to make an actionListener on a button in another button which has also an actionlistener and i just couldn't figure it out for some way. I am trying to make an action on the 2nd button but i couldn't figure it out.If anyone helps me i'd appreciate! here is the code below: import java.awt.; import java.awt.event.; import javax.swing.; import java.io.; import java.util.*; public class basic implements ActionListener{ public static void main(String[] args) { basic process = new basic (); } public basic(){ JFrame fan = new JFrame("Scheme"); JPanel one = new JPanel(new BorderLayout()); fan.add(one); JPanel uno = new JPanel(); uno.setLayout(new BoxLayout(uno, BoxLayout.Y_AXIS)); JButton addB = new JButton("first choice"); addB.setAlignmentX(Component.CENTER_ALIGNMENT); uno.add(addB); addDButton.setActionCommand("hehe"); addDButton.addActionListener(this); one.add(uno,BorderLayout.CENTER); fan.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); fan.setSize(500,700); fan.setLocationByPlatform(true); fan.setVisible(true); } public void actionPerformed(ActionEvent evt) { JPanel markP = new JPanel(new FlowLayout(FlowLayout.RIGHT,10,20)); JDialog dialog = new JDialog((JFrame)null); dialog.getContentPane().add(markP,BorderLayout.CENTER); if (evt.getActionCommand().equals("hehe")) { JLabel title = new JLabel("Proceed"); title.setFont(new Font("Arial",Font.BOLD,15)); markP.add(title,BorderLayout.NORTH); JButton exit = new JButton("Exit"); markP.add(exit); //here i want to create another actionListener on the exit button only without affecting the other content which is in the button "addB " so that when i click on the addB button the J dialog pops up, and than when i click on exit button the program will return to the menu.I couldn't figure it out. dialog.toFront(); dialog.setModal(true); dialog.pack(); // dialog.setLocationRelativeTo(null); // dialog.setVisible(true); } // here the code goes on but the problem is that of the actionListener which is concerned.

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• Turn class "Interfaceable"

  - by scooterman

  Hi folks, On my company system, we use a class to represent beans. It is just a holder of information using boost::variant and some serialization/deserialization stuff. It works well, but we have a problem: it is not over an interface, and since we use modularization through dlls, building an interface for it is getting very complicated, since it is used in almost every part of our app, and sadly interfaces (abstract classes ) on c++ have to be accessed through pointers, witch makes almost impossible to refactor the entire system. Our structure is: dll A: interface definition through abstract class dll B: interface implementation there is a painless way to achieve that (maybe using templates, I don't know) or I should forget about making this work and simply link everything with dll B? thanks Edit: Here is my example. this is on dll A BeanProtocol is a holder of N dataprotocol itens, wich are acessed by a index. class DataProtocol; class UTILS_EXPORT BeanProtocol { public: virtual DataProtocol& get(const unsigned int ) const { throw std::runtime_error("Not implemented"); } virtual void getFields(std::list<unsigned int>&) const { throw std::runtime_error("Not implemented"); } virtual DataProtocol& operator[](const unsigned int ) { throw std::runtime_error("Not implemented"); } virtual DataProtocol& operator[](const unsigned int ) const { throw std::runtime_error("Not implemented"); } virtual void fromString(const std::string&) { throw std::runtime_error("Not implemented"); } virtual std::string toString() const { throw std::runtime_error("Not implemented"); } virtual void fromBinary(const std::string&) { throw std::runtime_error("Not implemented"); } virtual std::string toBinary() const { throw std::runtime_error("Not implemented"); } virtual BeanProtocol& operator=(const BeanProtocol&) { throw std::runtime_error("Not implemented"); } virtual bool operator==(const BeanProtocol&) const { throw std::runtime_error("Not implemented"); } virtual bool operator!=(const BeanProtocol&) const { throw std::runtime_error("Not implemented"); } virtual bool operator==(const char*) const { throw std::runtime_error("Not implemented"); } virtual bool hasKey(unsigned int field) const { throw std::runtime_error("Not implemented"); } }; the other class (named GenericBean) implements it. This is the only way I've found to make this work, but now I want to turn it in a truly interface and remove the UTILS_EXPORT (which is an _declspec macro), and finally remove the forced linkage of B with A.

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• Lifetime issue of IDisposable unmanaged resources in a complex object graph?

  - by stakx

  This question is about dealing with unmanaged resources (COM interop) and making sure there won't be any resource leaks. I'd appreciate feedback on whether I seem to do things the right way. Background: Let's say I've got two classes: A class LimitedComResource which is a wrapper around a COM object (received via some API). There can only be a limited number of those COM objects, therefore my class implements the IDisposable interface which will be responsible for releasing a COM object when it's no longer needed. Objects of another type ManagedObject are temporarily created to perform some work on a LimitedComResource. They are not IDisposable. To summarize the above in a diagram, my classes might look like this: +---------------+ +--------------------+ | ManagedObject | <>------> | LimitedComResource | +---------------+ +--------------------+ | o IDisposable (I'll provide example code for these two classes in just a moment.) Question: Since my temporary ManagedObject objects are not disposable, I obviously have no control over how long they'll be around. However, in the meantime I might have Disposed the LimitedComObject that a ManagedObject is referring to. How can I make sure that a ManagedObject won't access a LimitedComResource that's no longer there? +---------------+ +--------------------+ | managedObject | <>------> | (dead object) | +---------------+ +--------------------+ I've currently implemented this with a mix of weak references and a flag in LimitedResource which signals whether an object has already been disposed. Is there any better way? Example code (what I've currently got): LimitedComResource: class LimitedComResource : IDisposable { private readonly IUnknown comObject; // <-- set in constructor ... void Dispose(bool notFromFinalizer) { if (!this.isDisposed) { Marshal.FinalReleaseComObject(comObject); } this.isDisposed = true; } internal bool isDisposed = false; } ManagedObject: class ManagedObject { private readonly WeakReference limitedComResource; // <-- set in constructor ... public void DoSomeWork() { if (!limitedComResource.IsAlive()) { throw new ObjectDisposedException(); // ^^^^^^^^^^^^^^^^^^^^^^^ // is there a more suitable exception class? } var ur = (LimitedComResource)limitedComResource.Target; if (ur.isDisposed) { throw new ObjectDisposedException(); } ... // <-- do something sensible here! } }

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• How can I create specialized builders for semantic layout in rails?

  - by Paul Alexander

  This is how I'd like to write markup in say index.html.erb <%= page_for "Super Cool Page" do |p| %> <%= p.header do %> Ruby is Cool <% end %> <%= p.body do %> Witty discourse on Ruby. <% end %> <% if page.has_sidebar? %> <%= p.sidebar do %> <ul><li>Option 1</li></ul> <% end %> <% end %> <% end %> Which would output <div class="page"> <header><h1>Super Cool Page</h1></header> <section> Witty discourse on Ruby. </section> </div> and when page.has_sidebar? is true <div class="page"> <header><h1>Super Cool Page</h1></header> <asside><ul><li>Option 1</li></ul></asside> <section> Witty discourse on Ruby. </section> </div> I've taken a look at the FormHelper class in rails for guidance, but it seems like I'd have to duplicate a lot of work which I'm trying to avoid. I'm really just trying to figure out where to hang the classes/modules/methods in the framework and whit kind of object |p| should be. My first inclination was to create a PageBuilder class that implements header, body and sidebar methods. But I got stuck on the rendering pipeline to get everything output just right. Is there a gem that already provides this type of semantic generation? If not I'd love any insight on how to set this up.

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• design for a wrapper around command-line utilities

  - by hatchetman82

  im trying to come up with a design for a wrapper for use when invoking command line utilities in java. the trouble with runtime.exec() is that you need to keep reading from the process' out and err streams or it hangs when it fills its buffers. this has led me to the following design: public class CommandLineInterface { private final Thread stdOutThread; private final Thread stdErrThread; private final OutputStreamWriter stdin; private final History history; public CommandLineInterface(String command) throws IOException { this.history = new History(); this.history.addEntry(new HistoryEntry(EntryTypeEnum.INPUT, command)); Process process = Runtime.getRuntime().exec(command); stdin = new OutputStreamWriter(process.getOutputStream()); stdOutThread = new Thread(new Leech(process.getInputStream(), history, EntryTypeEnum.OUTPUT)); stdOutThread.setDaemon(true); stdOutThread.start(); stdErrThread = new Thread(new Leech(process.getErrorStream(), history, EntryTypeEnum.ERROR)); stdErrThread.setDaemon(true); stdErrThread.start(); } public void write(String input) throws IOException { this.history.addEntry(new HistoryEntry(EntryTypeEnum.INPUT, input)); stdin.write(input); stdin.write("\n"); stdin.flush(); } } public class Leech implements Runnable{ private final InputStream stream; private final History history; private final EntryTypeEnum type; private volatile boolean alive = true; public Leech(InputStream stream, History history, EntryTypeEnum type) { this.stream = stream; this.history = history; this.type = type; } public void run() { BufferedReader reader = new BufferedReader(new InputStreamReader(stream)); String line; try { while(alive) { line = reader.readLine(); if (line==null) break; history.addEntry(new HistoryEntry(type, line)); } } catch (Exception e) { e.printStackTrace(); } } } my issue is with the Leech class (used to "leech" the process' out and err streams and feed them into history - which acts like a log file) - on the one hand reading whole lines is nice and easy (and what im currently doing), but it means i miss the last line (usually the prompt line). i only see the prompt line when executing the next command (because there's no line break until that point). on the other hand, if i read characters myself, how can i tell when the process is "done" ? (either complete or waiting for input) has anyone tried something like waiting 100 millis since the last output from the process and declaring it "done" ? any better ideas on how i can implement a nice wrapper around things like runtime.exec("cmd.exe") ?

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• Getting problem in Java OpenCV code.

  - by Chetan

  I had successfully compile my java code in Eclipse with name FaceDetection.java... I am getting an Exception in thread "main" java.lang.NoSuchMethodError: main.... Please help me to remove this Exception.. Here is the code import java.awt.; import java.awt.event.; import java.awt.image.MemoryImageSource; import hypermedia.video.OpenCV; @SuppressWarnings("serial") public class FaceDetection extends Frame implements Runnable { /** * Main method. * @param String[] a list of user's arguments passed from the console to this program */ public static void main( String[] args ) { System.out.println( "\nOpenCV face detection sample\n" ); new FaceDetection(); } // program execution frame rate (millisecond) final int FRAME_RATE = 1000/30; OpenCV cv = null; // OpenCV Object Thread t = null; // the sample thread // the input video stream image Image frame = null; // list of all face detected area Rectangle[] squares = new Rectangle[0]; /** * Setup Frame and Object(s). */ FaceDetection() { super( "Face Detection Sample" ); // OpenCV setup cv = new OpenCV(); cv.capture( 320, 240 ); cv.cascade( OpenCV.CASCADE_FRONTALFACE_ALT ); // frame setup this.setBounds( 100, 100, cv.width, cv.height ); this.setBackground( Color.BLACK ); this.setVisible( true ); this.addKeyListener( new KeyAdapter() { public void keyReleased( KeyEvent e ) { if ( e.getKeyCode()==KeyEvent.VK_ESCAPE ) { // ESC : release OpenCV resources cv.dispose(); System.exit(0); } } } ); // start running program t = new Thread( this ); t.start(); } /** * Draw video frame and each detected faces area. */ public void paint( Graphics g ) { // draw image g.drawImage( frame, 0, 0, null ); // draw squares g.setColor( Color.RED ); for( Rectangle rect : squares ) g.drawRect( rect.x, rect.y, rect.width, rect.height ); } /** * Execute this sample. */ @SuppressWarnings("static-access") public void run() { while( t!=null && cv!=null ) { try { t.sleep( FRAME_RATE ); // grab image from video stream cv.read(); // create a new image from cv pixels data MemoryImageSource mis = new MemoryImageSource( cv.width, cv.height, cv.pixels(), 0, cv.width ); frame = createImage( mis ); // detect faces squares = cv.detect( 1.2f, 2, OpenCV.HAAR_DO_CANNY_PRUNING, 20, 20 ); // of course, repaint repaint(); } catch( InterruptedException e ) {;} } } }

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• How do I make my multicast program work between computers on different networks?

  - by George

  I made a little chat applet using multicast. It works fine between computers on the same network, but fails if the computers are on different networks. Why is this? import java.io.*; import java.net.*; import java.awt.*; import java.awt.event.*; import javax.swing.*; public class ClientA extends JApplet implements ActionListener, Runnable { JTextField tf; JTextArea ta; MulticastSocket socket; InetAddress group; String name=""; public void start() { try { socket = new MulticastSocket(7777); group = InetAddress.getByName("233.0.0.1"); socket.joinGroup(group); socket.setTimeToLive(255); Thread th = new Thread(this); th.start(); name =JOptionPane.showInputDialog(null,"Please enter your name.","What is your name?",JOptionPane.PLAIN_MESSAGE); tf.grabFocus(); }catch(Exception e) {e.printStackTrace();} } public void init() { JPanel p = new JPanel(new BorderLayout()); ta = new JTextArea(); ta.setEditable(false); ta.setLineWrap(true); JScrollPane sp = new JScrollPane(ta); p.add(sp,BorderLayout.CENTER); JPanel p2 = new JPanel(); tf = new JTextField(30); tf.addActionListener(this); p2.add(tf); JButton b = new JButton("Send"); b.addActionListener(this); p2.add(b); p.add(p2,BorderLayout.SOUTH); add(p); } public void actionPerformed(ActionEvent ae) { String message = name+":"+tf.getText(); tf.setText(""); tf.grabFocus(); byte[] buf = message.getBytes(); DatagramPacket packet = new DatagramPacket(buf,buf.length, group,7777); try { socket.send(packet); } catch(Exception e) {} } public void run() { while(true) { byte[] buf = new byte[256]; String received = ""; DatagramPacket packet = new DatagramPacket(buf, buf.length); try { socket.receive(packet); received = new String(packet.getData()).trim(); } catch(Exception e) {} ta.append(received +"\n"); ta.setCaretPosition(ta.getDocument().getLength()); } } }

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• How to design this ?

  - by Akku

  how can i make this entire process as 1 single event??? http://code.google.com/apis/visualization/documentation/dev/dsl_get_started.html and draw the chart on single click? I am new to servlets please guide me When a user clicks the "go " button with some input. The data goes to the servlet say "Test3". The servlet processes the data by the user and generates/feeds the data table dynamically Then I call the html page to draw the chart as shown in the tutorial link above. The problem is when I call the servlet it gives me a long json string in the browser as given in the tutorials "google.visualization.Query.setResponse({version:'0.6',status:'ok',sig:'1333639331',table:{cols:[{............................" Then when i manually call the html page to draw the chart i am see the chart. But when I call html page directly using the request dispatcher via the servlet I dont get the result. This is my code and o/p...... I need sugession as to how should be my approach to call the chart public class Test3 extends HttpServlet implements DataTableGenerator { protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { DataSourceHelper.executeDataSourceServletFlow(request, response, this , isRestrictedAccessMode() ); RequestDispatcher rd; rd = request.getRequestDispatcher("new.html");// it call's the html page which draws the chart as per the data added by the servlet..... rd.include(request, response);//forward(request, response); @Override public Capabilities getCapabilities() { return Capabilities.NONE; } protected boolean isRestrictedAccessMode() { return false; } @Override public DataTable generateDataTable(Query query, HttpServletRequest request) { // Create a data table. DataTable data = new DataTable(); ArrayList<ColumnDescription> cd = new ArrayList<ColumnDescription>(); cd.add(new ColumnDescription("name", ValueType.TEXT, "Animal name")); cd.add......... I get the following result along with unprocessed html page google.visualization.Query.setResponse({version:'0.6',statu..... <html> <head> <title>Getting Started Example</title> .... Entire html page as it is on the Browser. What I need is when a user clicks the go button the servlet should process the data and call the html page to draw the chart....Without the json string appearing on the browser.(all in one user click) What should be my approach or how should i design this.... there are no error in the code. since when i run the servlet i get the json string on the browser and then when i run the html page manually i get the chart drawn. So how can I do (servlet processing + html page drawing chart as final result) at one go without the long json string appearing on the browser. There is no problem with the html code....

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• HttpClient response handler always returns closed stream

  - by Alex Ciminian

  I'm new to Java development so please bear with me. Also, I hope I'm not the champion of tl;dr :). I'm using HttpClient to make requests over Http (duh!) and I'd gotten it to work for a simple servlet that receives an URL as a query string parameter. I realized that my code could use some refactoring, so I decided to make my own HttpResponseHandler, to clean up the code, make it reusable and improve exception handling. I currently have something like this: public class HttpResponseHandler implements ResponseHandler<InputStream>{ public InputStream handleResponse(HttpResponse response) throws ClientProtocolException, IOException { int statusCode = response.getStatusLine().getStatusCode(); InputStream in = null; if (statusCode != HttpStatus.SC_OK) { throw new HttpResponseException(statusCode, null); } else { HttpEntity entity = response.getEntity(); if (entity != null) { in = entity.getContent(); // This works // for (int i;(i = in.read()) >= 0;) System.out.print((char)i); } } return in; } } And in the method where I make the actual request: HttpClient httpclient = new DefaultHttpClient(); HttpGet httpget = new HttpGet(target); ResponseHandler<InputStream> httpResponseHandler = new HttpResponseHandler(); try { InputStream in = httpclient.execute(httpget, httpResponseHandler); // This doesn't work // for (int i;(i = in.read()) >= 0;) System.out.print((char)i); return in; } catch (HttpResponseException e) { throw new HttpResponseException(e.getStatusCode(), null); } The problem is that the input stream returned from the handler is closed. I don't have any idea why, but I've checked it with the prints in my code (and no, I haven't used them both at the same time :). While the first print works, the other one gives a closed stream error. I need InputStreams, because all my other methods expect an InputStream and not a String. Also, I want to be able to retrieve images (or maybe other types of files), not just text files. I can work around this pretty easily by giving up on the response handler (I have a working implementation that doesn't use it), but I'm pretty curious about the following: Why does it do what it does? How do I open the stream, if something closes it? What's the right way to do this, anyway :)? I've checked the docs and I couldn't find anything useful regarding this issue. To save you a bit of Googling, here's the Javadoc and here's the HttpClient tutorial (Section 1.1.8 - Response handlers). Thanks, Alex

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• IsAuthenticated is false! weird behaviour + review question

  - by Naor

  This is the login function (after I validate user name and password, I load user data into "user" variable and call Login function: public static void Login(IUser user) { HttpResponse Response = HttpContext.Current.Response; HttpRequest Request = HttpContext.Current.Request; FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(1, user.UserId.ToString(), DateTime.Now, DateTime.Now.AddHours(12), false, UserResolver.Serialize(user)); HttpCookie cookie = new HttpCookie(FormsAuthentication.FormsCookieName, FormsAuthentication.Encrypt(ticket)); cookie.Path = FormsAuthentication.FormsCookiePath; Response.Cookies.Add(cookie); string redirectUrl = user.HomePage; Response.Redirect(redirectUrl, true); } UserResolver is the following class: public class UserResolver { public static IUser Current { get { IUser user = null; if (HttpContext.Current.User.Identity.IsAuthenticated) { FormsIdentity id = (FormsIdentity)HttpContext.Current.User.Identity; FormsAuthenticationTicket ticket = id.Ticket; user = Desrialize(ticket.UserData); } return user; } } public static string Serialize(IUser user) { StringBuilder data = new StringBuilder(); StringWriter w = new StringWriter(data); string type = user.GetType().ToString(); //w.Write(type.Length); w.WriteLine(user.GetType().ToString()); StringBuilder userData = new StringBuilder(); XmlSerializer serializer = new XmlSerializer(user.GetType()); serializer.Serialize(new StringWriter(userData), user); w.Write(userData.ToString()); w.Close(); return data.ToString(); } public static IUser Desrialize(string data) { StringReader r = new StringReader(data); string typeStr = r.ReadLine(); Type type=Type.GetType(typeStr); string userData = r.ReadToEnd(); XmlSerializer serializer = new XmlSerializer(type); return (IUser)serializer.Deserialize(new StringReader(userData)); } } And the global.asax implements the following: void Application_PostAuthenticateRequest(Object sender, EventArgs e) { IPrincipal p = HttpContext.Current.User; if (p.Identity.IsAuthenticated) { IUser user = UserResolver.Current; Role[] roles = user.GetUserRoles(); HttpContext.Current.User = Thread.CurrentPrincipal = new GenericPrincipal(p.Identity, Role.ToString(roles)); } } First question: Am I do it right? Second question - weird thing! The user variable I pass to Login has 4 members: UserName, Password, Name, Id. When UserResolver.Current executed, I got the user instance. I descided to change the user structure - I add an array of Warehouse object. Since that time, when UserResolver.Current executed (after Login), HttpContext.Current.User.Identity.IsAuthenticated was false and I couldn't get the user data. When I removed the Warehouse[] from user structure, it starts to be ok again and HttpContext.Current.User.Identity.IsAuthenticated become true after I Login. What is the reason to this weird behaviour?

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• Android OnClick in ListView calling parent function

  - by user1321683

  I have an Android application with a ListView in it, the ListView will setup fine but now I want a image in the ListView to be clickable. I do this by using 2 classes, the Activity class (parent) and an ArrayAdapter to fill the list. In the ArrayAdapter I implement a OnClickListener for the image in the list that I want to be clickable. So far it all works. But now I want to run a function from the activity class when the onClick, for the image in the list, is run but I do not know how. Below are the 2 classes that I use. First the Activity class: public class parent_class extends Activity implements OnClickListener, OnItemClickListener { child_class_list myList; ListView myListView; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); // setup the Homelist data myList = new child_class_list (this, Group_Names, Group_Dates); myListView = (ListView) findViewById(R.id.list); // set the HomeList myListView.setAdapter( myList ); myListView.setOnItemClickListener(this); } void function_to_run() { // I want to run this function from the LiscView Onclick } public void onItemClick(AdapterView<?> arg0, View arg1, int arg2, long arg3) { // do something } } And the ArrayAdapter from where I want to call a function from the Activity class: public class child_class_list extends ArrayAdapter<String> { // private private final Context context; private String[] mName; private String[] mDate; public child_class_list (Context context, String[] Name, String[] Date) { super(context, R.layout.l_home, GroupName); this.context = context; this.mName = Name; this.mDate = Date; } @Override public View getView(int position, View convertView, ViewGroup parent) { LayoutInflater inflater = (LayoutInflater) context .getSystemService(Context.LAYOUT_INFLATER_SERVICE); View rowView = inflater.inflate(R.layout.l_home, parent, false); ImageView selectable_image = (ImageView) rowView.findViewById(R.id.l_selectable_image); selectable_image.setOnClickListener(new OnClickListener() { public void onClick(View v) { // I want to run the function_to_run() function from the parant class here } } ); // get the textID's TextView tvName = (TextView) rowView.findViewById(R.id.l_name); TextView tvDate = (TextView) rowView.findViewById(R.id.l_date); // set the text tvName.setText (mName[position]); tvDate.setText (mDate[position]); return rowView; } } If anyone knows how to run the function in the activity class from the arrayadapter or how to set the image onClickListener in the Activity Class I would greatly apriciate the help.

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• Android: Memory leak due to AsyncTask

  - by Manu

  Hello, I'm stuck with a memory leak that I cannot fix. I identified where it occurs, using the MemoryAnalizer but I vainly struggle to get rid of it. Here is the code: public class MyActivity extends Activity implements SurfaceHolder.Callback { ... Camera.PictureCallback mPictureCallbackJpeg = new Camera.PictureCallback() { public void onPictureTaken(byte[] data, Camera c) { try { // log the action Log.e(getClass().getSimpleName(), "PICTURE CALLBACK JPEG: data.length = " + data); // Show the ProgressDialog on this thread pd = ProgressDialog.show(MyActivity.this, "", "Préparation", true, false); // Start a new thread that will manage the capture new ManageCaptureTask().execute(data, c); } catch(Exception e){ AlertDialog.Builder dialog = new AlertDialog.Builder(MyActivity.this); ... dialog.create().show(); } } class ManageCaptureTask extends AsyncTask<Object, Void, Boolean> { protected Boolean doInBackground(Object... args) { Boolean isSuccess = false; // initialize the bitmap before the capture ((myApp) getApplication()).setBitmapX(null); try{ // Check if it is a real device or an emulator TelephonyManager telmgr = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE); String deviceID = telmgr.getDeviceId(); boolean isEmulator = "000000000000000".equalsIgnoreCase(deviceID); // get the bitmap if (isEmulator) { ((myApp) getApplication()).setBitmapX(BitmapFactory.decodeFile(imageFileName)); } else { ((myApp) getApplication()).setBitmapX(BitmapFactory.decodeByteArray((byte[]) args[0], 0, ((byte[])args[0]).length)); } ((myApp) getApplication()).setImageForDB(ImageTools.resizeBmp(((myApp) getApplication()).getBmp())); // convert the bitmap into a grayscale image and display it in the preview ((myApp) getApplication()).setImage(makeGrayScale()); isSuccess = true; } catch (Exception connEx){ errorMessageFromBkgndThread = getString(R.string.errcapture); } return isSuccess; } protected void onPostExecute(Boolean result) { // Pass the result data back to the main activity if (MyActivity.this.pd != null) { MyActivity.this.pd.dismiss(); } if (result){ ((ImageView) findViewById(R.id.apercu)).setImageBitmap(((myApp) getApplication()).getBmp()); ((myApp) getApplication()).setBitmapX(null); } else{ // there was an error ErrAlert(); } } } }; private void ErrAlert(){ // notify the user about the error AlertDialog.Builder dialog = new AlertDialog.Builder(this); ... dialog.create().show(); } } MemoryAnalyzer indicated the memory leak at: ((myApp) getApplication()).setBitmapX(BitmapFactory.decodeByteArray((byte[]) args[0], 0, ((byte[])args[0]).length)); I am grateful for any suggestion, thank you in advance.

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• One-to-many relationship with JDO in Google App Engine

  - by Marvin

  I've followed the GAE docs on setting up one-to-many relationship in JDO but I'm still having trouble in retrieving the collection data back. I have no problem getting the other non-collection fields back. Here are my classes: @PersistenceCapable public class User{ @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key key; @Persistent private String uniqueId; @Persistent private String email; @Persistent private List<Address> addresses = new ArrayList<Address>() ; ... } @PersistenceCapable public class Phone{ @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key key; @Persistent private String number; ... } public class UserDaoImpl implements UserDao { public void insertUser(User user) { if(user.getKey() == null) { com.google.appengine.api.datastore.Key key = KeyFactory.createKey(User.class.getSimpleName(), user.getEmail()); user.setKey(key); } PersistenceManager pm = PersistenceManagerWrapper.getPersistenceManager(); notNull(user); try { pm.makePersistent(user); } finally { pm.close(); } } @SuppressWarnings("unchecked") public User getUser(String uniqueId) { PersistenceManager pm = PersistenceManagerWrapper.getPersistenceManager(); Query query = pm.newQuery(User.class); query.setFilter("uniqueId == uniqueIdParam"); query.declareParameters("String uniqueIdParam"); User user = null; try { List<User> users = (List<User>)(query.execute(uniqueId)); //TODO abstract this if(users.size() > 0) user = users.get(0); } finally { pm.close(); } return user; } } public class UserDaoImplTest { @Test public void getUserTest() { User user = createTestUser(); assertNotNull("The user object should not be null", user); userDao.insertUser(user); User returnedUser = userDao.getUser(TEST_USER_ID); assertNotNull("The returnedUser object should not be null", returnedUser); Assert.assertPropertyEqualsExcludeProperties("User Object", user, returnedUser, ""); } } When I run the test, all the properties for User is populated but the list of Phone if I get is empty.

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• How to add Listview in tab activity?

  - by sandip armal

  I have one "SubjectTabActivity" and i need to show listview on this activity. But when i want to implement ListActivity it doesn't show listActivity. I have two(addchapter,addsubject) xml file with "SubjectTabActivity". and i need to show my database item il list view in respective xml file. but i don't understand how to do that? How to add Listactivity in TabActivity?. Please give me any reference or code. Thanks in advance.. Here is my reference code. public class MasterMainActivity extends TabActivity { LayoutInflater layoutInflater = null; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.master); Intent intent=getIntent(); setResult(RESULT_OK, intent); layoutInflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE); TabHost tabHost = getTabHost(); TabHost.TabSpec tab1spec = tabHost.newTabSpec("tabOneSpec"); ImageView imgView = new ImageView(this); imgView.setBackgroundResource(R.drawable.subject); tab1spec.setIndicator("Subject", imgView.getBackground()); tab1spec.setContent(new TabContentLayout()); TabHost.TabSpec tab2spec = tabHost.newTabSpec("tabTwoSpec"); tab2spec.setContent(new TabContentLayout()); ImageView imgView1 = new ImageView(this); imgView1.setBackgroundResource(R.drawable.chapter); tab2spec.setIndicator("Chapter", imgView1.getBackground()); tabHost.addTab(tab1spec); tabHost.addTab(tab2spec); } private class TabContentLayout implements TabHost.TabContentFactory { @Override public View createTabContent(String tag) { View view = null; if(tag.equals("tabOneSpec")) { try { //static final String[] FRUITS = new String[] { "Apple", "Avocado", "Banana", // "Blueberry", "Coconut", "Durian", "Guava", "Kiwifruit", //"Jackfruit", "Mango", "Olive", "Pear", "Sugar-apple" }; view = (LinearLayout) layoutInflater.inflate(R.layout.subjecttabview, null); //setListAdapter(new ArrayAdapter<String>(this, R.layout.subjecttabview,FRUITS)); } catch(Exception e) { e.printStackTrace(); } } if(tag.equals("tabTwoSpec")) { try { view = (LinearLayout) layoutInflater.inflate(R.layout.chaptertabview, null); } catch(Exception e) { e.printStackTrace(); } } return view; } } How to add ListActivity in this TabActivity

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• Component must be a valid peer (when i remove frame.add(Component);)

  - by boyd

  i have this code here for creating and drawing array of pixels into an image import javax.swing.JFrame; import java.awt.Canvas; import java.awt.Graphics; import java.awt.image.BufferStrategy; import java.awt.image.BufferedImage; import java.awt.image.DataBufferInt; public class test extends Canvas implements Runnable{ private static final long serialVersionUID = 1L; public static int WIDTH = 800; public static int HEIGHT = 600; public boolean running=true; public int[] pixels; public BufferedImage img; public static JFrame frame; private Thread thread; public static void main(String[] arg) { test wind = new test(); frame = new JFrame("WINDOW"); frame.add(wind); frame.setVisible(true); frame.setSize(WIDTH, HEIGHT); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); wind.init(); } public void init(){ thread=new Thread(this); thread.start(); img=new BufferedImage(WIDTH, HEIGHT,BufferedImage.TYPE_INT_RGB); pixels=((DataBufferInt)img.getRaster().getDataBuffer()).getData(); } public void run(){ while(running){ render(); try { thread.sleep(55); } catch (InterruptedException e) { e.printStackTrace(); } } } public void render(){ BufferStrategy bs=this.getBufferStrategy(); if(bs==null){ createBufferStrategy(4); return; } drawRect(0,0,150,150); Graphics g= bs.getDrawGraphics(); g.drawImage(img, 0, 0, WIDTH, HEIGHT, null); g.dispose(); bs.show(); } private void drawRect(int x, int y, int w, int h) { for(int i=x;i<w;i++) for(int j=x;j<h;j++) pixels[i+j*WIDTH]=346346; } } Why i get "Component must be a valid peer" error when i remove the line: frame.add(wind); Why I want to remove it? Because I want to create a frame using a class object(from another file) and use the code Window myWindow= new Window() to do exactly the same thing BTW: who knows Java and understands what i wrote please send me a message with your skype or yahoo messenger id.I want to cooperate with you for a project (graphics engine for games)

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• Multiple Connection Types for one Designer Generated TableAdapter

  - by Tim

  I have a Windows Forms application with a DataSet (.xsd) that is currently set to connect to a Sql Ce database. Compact Edition is being used so the users can use this application in the field without an internet connection, and then sync their data at day's end. I have been given a new project to create a supplemental web interface for displaying some of the same reports as the Windows Forms application so certain users can obtain reports without installing the Windows app. What I've done so far is create a new Web Project and added it to my current Solution. I have split both the reports (.rdlc) and DataSets out of the Windows Forms project into their own projects so they can be accessed by both the Windows and Web applications. So far, this is working fine. Here's my dilemma: As I said before, the DataSets are currently set up to connect to a local Sql Ce database file. This is correct for the Windows app, but for the Web application I would like to use these same TableAdapters and queries to connect to the Sql Server 2005 database. I have found that the designer generated, strongly-typed TableAdapter classes have a ConnectionModifier property that allows you to make the TableAdapter's Connection public. This exposes the Connection property and allows me to set it, however it is strongly-typed as a SqlCeConnection, whereas I would like to set it to a SqlConnection for my Web project. I'm assuming the DataSet Designer strongly-types the Connection, Command, and DataAdapter objects based on the Provider of the ConnectionString as indicated in the app.config file. Is there any way I can use some generic provider so that the DataSet Designer will use object types that can connect to both a Sql Ce database file AND the actual Sql Server 2005 database? I know that SqlCeConnection and SqlConnection both inherit from DbConnection, which implements IDbConnection. Relatively, the same goes for SqlCeCommand/SqlCommand:DbCommand:IDbCommand. It would be nice if I could just figure out a way for the designer to use the Interface types rather than the strong types, but I'm hesitant that that is possible. I hope my problem and question are clear. Any help is much appreciated. Let me know if there's anything I can clarify.

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• log4j performance

  - by Bob

  Hi, I'm developing a web app, and I'd like to log some information to help me improve and observe the app. (I'm using Tomcat6) First I thought I would use StringBuilders, append the logs to them and a task would persist them into the database like every 2 minutes. Because I was worried about the out-of-the-box logging system's performance. Then I made some test. Especially with log4j. Here is my code: Main.java public static void main(String[] args) { Thread[] threads = new Thread[LoggerThread.threadsNumber]; for(int i = 0; i < LoggerThread.threadsNumber; ++i){ threads[i] = new Thread(new LoggerThread("name - " + i)); } LoggerThread.startTimestamp = System.currentTimeMillis(); for(int i = 0; i < LoggerThread.threadsNumber; ++i){ threads[i].start(); } LoggerThread.java public class LoggerThread implements Runnable{ public static int threadsNumber = 10; public static long startTimestamp; private static int counter = 0; private String name; public LoggerThread(String name) { this.name = name; } private Logger log = Logger.getLogger(this.getClass()); @Override public void run() { for(int i=0; i<10000; ++i){ log.info(name + ": " + i); if(i == 9999){ int c = increaseCounter(); if(c == threadsNumber){ System.out.println("Elapsed time: " + (System.currentTimeMillis() - startTimestamp)); } } } } private synchronized int increaseCounter(){ return ++counter; } } } log4j.properties log4j.logger.main.LoggerThread=debug, f log4j.appender.f=org.apache.log4j.RollingFileAppender log4j.appender.f.layout=org.apache.log4j.PatternLayout log4j.appender.f.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n log4j.appender.f.File=c:/logs/logging.log log4j.appender.f.MaxFileSize=15000KB log4j.appender.f.MaxBackupIndex=50 I think this is a very common configuration for log4j. First I used log4j 1.2.14 then I realized there was a newer version, so I switched to 1.2.16 Here are the figures (all in millisec) LoggerThread.threadsNumber = 10 1.2.14: 4235, 4267, 4328, 4282 1.2.16: 2780, 2781, 2797, 2781 LoggerThread.threadsNumber = 100 1.2.14: 41312, 41014, 42251 1.2.16: 25606, 25729, 25922 I think this is very fast. Don't forget that: in every cycle the run method not just log into the file, it has to concatenate strings (name + ": " + i), and check an if test (i == 9999). When threadsNumber is 10, there are 100.000 loggings and if tests and concatenations. When it is 100, there are 1.000.000 loggings and if tests and concatenations. (I've read somewhere JVM uses StringBuilder's append for concatenation, not simple concatenation). Did I missed something? Am I doing something wrong? Did I forget any factor that could decrease the performance? If these figures are correct I think, I don't have to worry about log4j's performance even if I heavily log, do I?

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• Java problem cant find image file

  - by user363035

  I am a student working on a homework project. I spent DAYS trying to get the following code to display an image on my new windows 7 laptop. I compiled it and ran it on my old xp pc and it worked! I really want to use my laptop. Any suggestions on how to get it to display the image? import java.awt.*; import java.applet.*; import java.awt.event.*; import java.awt.image.*; public class MoveIt extends Applet implements ActionListener { // set variables and componets private Image cup; Panel keypad = new Panel(); public int top = 15; public int left = 15; private Button keysArray[]; public void init() { cup = getImage(getDocumentBase(), "cup.gif"); Canvas myCanvas = new Canvas(); keysArray = new Button[5]; setLayout(new BorderLayout(5,5)); setBackground(Color.blue); // set up keypad layout keypad.setLayout(new BorderLayout(0,0)); keysArray[0] = new Button("Up"); keysArray[1] = new Button("Left"); keysArray[2] = new Button("Center"); keysArray[3] = new Button("Right"); keysArray[4] = new Button("Down"); // add buttons to the keypad panel keypad.add(keysArray[0], BorderLayout.NORTH); keysArray[0].addActionListener(this); keypad.add(keysArray[1], BorderLayout.EAST); keysArray[1].addActionListener(this); keypad.add(keysArray[2], BorderLayout.CENTER); keysArray[2].addActionListener(this); keypad.add(keysArray[3], BorderLayout.WEST); keysArray[3].addActionListener(this); keypad.add(keysArray[4], BorderLayout.SOUTH); keysArray[4].addActionListener(this); // add canvas and keypad to the BorderLayout add(myCanvas, BorderLayout.NORTH); add(keypad, BorderLayout.SOUTH); } public void paint(Graphics g) { g.drawImage( cup, left, top, this ); } public void actionPerformed(ActionEvent e) { // test for menu item clicks String arg = e.getActionCommand(); if (arg == "Up") top -=15; else if (arg == "Down") top +=15; else if (arg == "Left") left -=15; else if (arg == "Right") left +=15; else { top = 60; left =125; } repaint(); } }

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