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  • Filling combobox from database by using hibernate in Java

    - by denny
    Heyy; I am developing a small swing based application with hibernate in java. And I want fill combobox from database coloumn.How i can do that ? And I don't know in where(under initComponents, buttonActionPerformd) i need to do. For saving i'am using jbutton and it's code is here : private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) { int idd=Integer.parseInt(jTextField1.getText()); String name=jTextField2.getText(); String description=jTextField3.getText(); Session session = null; SessionFactory sessionFactory = new Configuration().configure() .buildSessionFactory(); session = sessionFactory.openSession(); Transaction transaction = session.getTransaction(); try { ContactGroup con = new ContactGroup(); con.setId(idd); con.setGroupName(name); con.setGroupDescription(description); transaction.begin(); session.save(con); transaction.commit(); } catch (Exception e) { e.printStackTrace(); } finally{ session.close(); } }

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  • puzzled with java if else performance

    - by user1906966
    I am doing an investigation on a method's performance and finally identified the overhead was caused by the "else" portion of the if else statement. I have written a small program to illustrate the performance difference even when the else portion of the code never gets executed: public class TestIfPerf { public static void main( String[] args ) { boolean condition = true; long time = 0L; int value = 0; // warm up test for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } else { value = 1 + 3; } } // benchmark if condition only time = System.nanoTime(); for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } } time = System.nanoTime() - time; System.out.println( "1) performance " + time ); time = System.nanoTime(); // benchmark if else condition for( int count=0; count<10000000; count++ ) { if ( condition ) { value = 1 + 2; } else { value = 1 + 3; } } time = System.nanoTime() - time; System.out.println( "2) performance " + time ); } } and run the test program with java -classpath . -Dmx=800m -Dms=800m TestIfPerf. I performed this on both Mac and Linux Java with 1.6 latest build. Consistently the first benchmark, without the else is much faster than the second benchmark with the else section even though the code is structured such that the else portion is never executed because of the condition. I understand that to some, the difference might not be significant but the relative performance difference is large. I wonder if anyone has any insight to this (or maybe there is something I did incorrectly). Linux benchmark (in nano) performance 1215488 performance 2629531 Mac benchmark (in nano) performance 1667000 performance 4208000

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  • Noob question about a statement in a Java program

    - by happysoul
    I am beginner to java and was trying out this code puzzle from the book head first java which I solved as follows and got the output correct :D class DrumKit { boolean topHat=true; boolean snare=true; void playSnare() { System.out.println("bang bang ba-bang"); } void playTopHat() { System.out.println("ding ding da-ding"); } } public class DrumKitTestDriver { public static void main(String[] args) { DrumKit d =new DrumKit(); if(d.snare==true) { d.playSnare(); } d.playTopHat(); } } Output is :: bang bang ba-bang ding ding da-ding Now the problem is that in that code puzzle one code snippet is left that I did not include..it's as follows d.snare=false; Even though I did not write it , I got the output like the book. I am wondering why is there need for us to set it's value as false even when we know the code is gonna run without it too !?? I am wondering what the coder had in mind ..I mean what could be the possible future use and motive behind doing this ? I am sorry if it's a dumb question. I just wanna know why or why not to include that particular statement ? It's not like there's a loop or something that we need to come out of. Why is that statement there ?

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  • Android - BroadcastReceiver CONNECTIVITY ACTION

    - by Marc Ortiz
    in my project there's a service that listens for changes in the connectivity. When wifi is switched off to on then it gets called. The problem it's that i'm using a fragment and inside a fragment there's a button with the setonclicklistener(); and onclick(); SOMETIMES when i touch the button then the service receives an intent that the connectivity has changed (the method gets called without any reason...). Here's the code of my fragment activity for the viewpager layout: public static class FragmentSelection extends Fragment { int mNum; static FragmentSelection newInstance(int num) { FragmentSelection f = new FragmentSelection(); // Supply num input as an argument. Bundle args = new Bundle(); args.putInt("num", num); f.setArguments(args); return f; } /** * When creating, retrieve this instance's number from its arguments. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mNum = (getArguments() != null ? getArguments().getInt("num") : 1) + 1; } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { final View v = inflater.inflate(R.layout.fragment_intro_contenido, container, false); Button btStart = (Button) v.findViewById(R.id.btChanged); final CheckBox cbSMS = (CheckBox) v.findViewById(R.id.checkBoxSms); final CheckBox cbCalls = (CheckBox) v .findViewById(R.id.checkBoxLlamadas); final CheckBox cbApps = (CheckBox) v .findViewById(R.id.checkBoxApps); final CheckBox cbPosition = (CheckBox) v .findViewById(R.id.checkBoxPosicion); final CheckBox cbContacts = (CheckBox) v .findViewById(R.id.checkBoxContactos); final CheckBox cbAll = (CheckBox) v.findViewById(R.id.checkBoxAll); cbSMS.setChecked(true); cbCalls.setChecked(true); cbApps.setChecked(true); cbPosition.setChecked(true); cbContacts.setChecked(true); cbAll.setChecked(true); btStart.setOnClickListener(new View.OnClickListener() { public void onClick(View c) { Intent i = new Intent(); i.setClass(v.getContext(), AnonymeActivity.class); if (!cbSMS.isChecked()) { i.putExtra("sms", 0); } else { i.putExtra("sms", 1); } if (!cbCalls.isChecked()) { i.putExtra("calls", 0); } else { i.putExtra("calls", 1); } if (cbContacts.isChecked()) { i.putExtra("contacts", 1); } else { i.putExtra("contacts", 0); } if (cbApps.isChecked()) { i.putExtra("apps", 1); } else { i.putExtra("apps", 0); } if (!cbPosition.isChecked()) { i.putExtra("gps", 0); } else { i.putExtra("gps", 1); } if (!cbAll.isChecked()) { if (cbSMS.isChecked() && cbCalls.isChecked() && cbContacts.isChecked() && cbApps.isChecked() && cbPosition.isChecked()) { i.putExtra("all", 1); } else { i.putExtra("all", 0); } } else { i.putExtra("all", 1); } startActivity(i); } }); return v; } @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); } } My BroadcastReceiver class: class Broadcast_Reciver extends BroadcastReceiver implements Variables { CheckConexion cc; @Override public void onReceive(Context contxt, Intent intent) { // Cuando hay un evento, lo diferenciamos y hacemos una acción. if (intent.getAction().equals(SMS_RECEIVED)) { Sms sms = new Sms(null, contxt); sms.uploadNewSms(intent); } else if (intent.getAction().equals(Intent.ACTION_BATTERY_LOW)) { // st.batterylow(contxt); } else if (intent.getAction().equals(Intent.ACTION_POWER_CONNECTED)) { // st.power(1, contxt); } else if (intent.getAction().equals(Intent.ACTION_POWER_DISCONNECTED)) { // st.power(0, contxt); } else if (intent.getAction().equals(Intent.ACTION_CALL_BUTTON)) { // Notify } else if (intent.getAction().equals(Intent.ACTION_CAMERA_BUTTON)) { // Notify } else if (intent.getAction().equals(Intent.ACTION_PACKAGE_ADDED) || intent.getAction().equals(Intent.ACTION_PACKAGE_CHANGED) || intent.getAction().equals(Intent.ACTION_PACKAGE_REMOVED)) { Database db = new Database(contxt); if (db.open().Preferences(4)) { Uri data = intent.getData(); new ListApps(contxt).import_app(intent, contxt, data, intent.getAction()); } db.close(); } else if (intent.getAction().equals( ConnectivityManager.CONNECTIVITY_ACTION)) { cc = new CheckConexion(contxt); if (cc.isOnline()) { Database db = new Database(contxt); if (db.open().move() == 1) { new UploadOffline(contxt); } db.close(); } } } } And the errors: 9-03 23:20:37.887: E/SqliteDatabaseCpp(2715): CREATE TABLE android_metadata failed 09-03 23:20:37.887: E/SQLiteDatabase(2715): Failed to open the database. closing it. 09-03 23:20:37.887: E/SQLiteDatabase(2715): android.database.sqlite.SQLiteDatabaseLockedException: database is locked 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.database.sqlite.SQLiteDatabase.native_setLocale(Native Method) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.database.sqlite.SQLiteDatabase.setLocale_(SQLiteDatabase.java:2211) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.database.sqlite.SQLiteDatabase.setLocale(SQLiteDatabase.java:2199) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:1130) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:1081) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:1167) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.app.ContextImpl.openOrCreateDatabase(ContextImpl.java:833) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:221) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:157) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at com.background.Database.open(Database.java:127) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at <b><b><b><h3>com.background.Broadcast_Reciver.onReceive(BroadcastService.java:100)</h3> 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:728) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.os.Handler.handleCallback(Handler.java:605) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.os.Handler.dispatchMessage(Handler.java:92) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.os.Looper.loop(Looper.java:137) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at android.app.ActivityThread.main(ActivityThread.java:4507) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at java.lang.reflect.Method.invokeNative(Native Method) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at java.lang.reflect.Method.invoke(Method.java:511) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557) 09-03 23:20:37.887: E/SQLiteDatabase(2715): at dalvik.system.NativeStart.main(Native Method) 09-03 23:20:37.887: D/AndroidRuntime(2715): Shutting down VM 09-03 23:20:37.887: W/dalvikvm(2715): threadid=1: thread exiting with uncaught exception (group=0x40c3b1f8) 09-03 23:20:37.902: E/AndroidRuntime(2715): FATAL EXCEPTION: main 09-03 23:20:37.902: E/AndroidRuntime(2715): java.lang.RuntimeException: Error receiving broadcast Intent { act=android.net.conn.CONNECTIVITY_CHANGE flg=0x10000010 (has extras) } in com.background.Broadcast_Reciver@415203f8 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:737) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.os.Handler.handleCallback(Handler.java:605) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.os.Handler.dispatchMessage(Handler.java:92) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.os.Looper.loop(Looper.java:137) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.app.ActivityThread.main(ActivityThread.java:4507) 09-03 23:20:37.902: E/AndroidRuntime(2715): at java.lang.reflect.Method.invokeNative(Native Method) 09-03 23:20:37.902: E/AndroidRuntime(2715): at java.lang.reflect.Method.invoke(Method.java:511) 09-03 23:20:37.902: E/AndroidRuntime(2715): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:790) 09-03 23:20:37.902: E/AndroidRuntime(2715): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:557) 09-03 23:20:37.902: E/AndroidRuntime(2715): at dalvik.system.NativeStart.main(Native Method) 09-03 23:20:37.902: E/AndroidRuntime(2715): Caused by: android.database.sqlite.SQLiteDatabaseLockedException: database is locked 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.database.sqlite.SQLiteDatabase.native_setLocale(Native Method) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.database.sqlite.SQLiteDatabase.setLocale_(SQLiteDatabase.java:2211) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.database.sqlite.SQLiteDatabase.setLocale(SQLiteDatabase.java:2199) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:1130) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:1081) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.database.sqlite.SQLiteDatabase.openOrCreateDatabase(SQLiteDatabase.java:1167) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.app.ContextImpl.openOrCreateDatabase(ContextImpl.java:833) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:221) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:157) 09-03 23:20:37.902: E/AndroidRuntime(2715): at com.background.Database.open(Database.java:127) 09-03 23:20:37.902: E/AndroidRuntime(2715): at com.background.Broadcast_Reciver.onReceive(BroadcastService.java:100) 09-03 23:20:37.902: E/AndroidRuntime(2715): at android.app.LoadedApk$ReceiverDispatcher$Args.run(LoadedApk.java:728) 09-03 23:20:37.902: E/AndroidRuntime(2715): ... 9 more Checkout that the program goes into BroadcastReceiver class and i don't understand why!

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  • ArrayList in Java, adding code to methods

    - by yaz
    Why am I getting a compile time error for the two method headers at the end of my code in my class ArrayListTest? ArrayListTest: http://pastebin.com/dUHn9vPr Student: http://pastebin.com/3Vz1Aytr I have a compiler error at the two lines: delete(CS242, s3) replace(CS242, s, s4); When I try to run the code it states: Exception in thread "main" java.lang.Error: Unresolved compilation problems: The method replace(ArrayList<Student>, Student, Student)in the type ArrayListTest is not applicable for the arguments (List<Student>, Student, Student) The method delete(ArrayList<Student>, Student) in the type ArrayListTest is not applicable for the arguments (List<Student>, Student) at ArrayListTest.main(ArrayListTest.java:54) I fixed the compile time errors since I use Eclipse and Eclipse gives options of code you can use to fix the compile time error. I chose to "Change method to 'replace(ArrayList, Student, Student)' to 'replace(List, Student, Student)' Although it fixed that compile time error, I don't understand why I was getting a compile time error to begin with and why that effectively fixed the error I don't really know what missing code I need to write to correct these two methods below: public static void replace(List<Student> cS242, Student oldItem, Student newItem) { public static void delete(List<Student> cS242, Student target){

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  • How to use a int2 database-field as a boolean in Java using JPA/Hibernate

    - by mg
    Hello... I write an application based on an already existing database (postgreSQL) using JPA and Hibernate. There is a int2-column (activeYN) in a table, which is used as a boolean (0 = false (inactive), not 0 = true (active)). In the Java application i want to use this attribute as a boolean. So i defined the attribute like this: @Entity public class ModelClass implements Serializable { /*..... some Code .... */ private boolean active; @Column(name="activeYN") public boolean isActive() { return this.active; } /* .... some other Code ... */ } But there ist an exception because Hibernate expects an boolean database-field and not an int2. Can i do this mapping i any way while using a boolean in java?? I have a possible solution for this, but i don't really like it: My "hacky"-solution is the following: @Entity public class ModelClass implements Serializable { /*..... some Code .... */ private short active_USED_BY_JPA; //short because i need int2 /** * @Deprecated this method is only used by JPA. Use the method isActive() */ @Column(name="activeYN") public short getActive_USED_BY_JPA() { return this.active_USED_BY_JPA; } /** * @Deprecated this method is only used by JPA. * Use the method setActive(boolean active) */ public void setActive_USED_BY_JPA(short active) { this.active_USED_BY_JPA = active; } @Transient //jpa will ignore transient marked methods public boolean isActive() { return getActive_USED_BY_JPA() != 0; } @Transient public void setActive(boolean active) { this.setActive_USED_BY_JPA = active ? -1 : 0; } /* .... some other Code ... */ } Are there any other solutions for this problem? The "hibernate.hbm2ddl.auto"-value in the hibernate configuration is set to "validate". (sorry, my english is not the best, i hope you understand it anyway)..

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  • java partial classes

    - by Dewfy
    Hello colleagues, Small preamble. I was good java developer on 1.4 jdk. After it I have switched to another platforms, but here I come with problem so question is strongly about jdk 1.6 (or higher :) ). I have 3 coupled class, the nature of coupling concerned with native methods. Bellow is example of this 3 class public interface A { public void method(); } final class AOperations { static native method(. . .); } public class AImpl implements A { @Override public void method(){ AOperations.method( . . . ); } } So there is interface A, that is implemented in native way by AOperations, and AImpl just delegates method call to native methods. These relations are auto-generated. Everything ok, but I have stand before problem. Sometime interface like A need expose iterator capability. I can affect interface, but cannot change implementation (AImpl). Saying in C# I could be able resolve problem by simple partial: (C# sample) partial class AImpl{ ... //here comes auto generated code } partial class AImpl{ ... //here comes MY implementation of ... //Iterator } So, has java analogue of partial or something like.

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  • Can't download pdf with java

    - by gedemagt
    I'm trying to download a file from http://aula.au.dk/main/document/document.php?action=download&id=%2F%D8velsesvejledning+2012.pdf but it dosen't appear to be a pdf, when i try downloading it with this code import java.io.*; import java.net.*; public class DownloadFile { public static void download(String address, String localFileName) throws IOException { URL url1 = new URL(address); byte[] ba1 = new byte[1024]; int baLength; FileOutputStream fos1 = new FileOutputStream(localFileName); try { // Contacting the URL System.out.print("Connecting to " + url1.toString() + " ... "); URLConnection urlConn = url1.openConnection(); // Checking whether the URL contains a PDF if (!urlConn.getContentType().equalsIgnoreCase("application/pdf")) { System.out.println("FAILED.\n[Sorry. This is not a PDF.]"); } else { try { // Read the PDF from the URL and save to a local file InputStream is1 = url1.openStream(); while ((baLength = is1.read(ba1)) != -1) { fos1.write(ba1, 0, baLength); } fos1.flush(); fos1.close(); is1.close(); } catch (ConnectException ce) { System.out.println("FAILED.\n[" + ce.getMessage() + "]\n"); } } } catch (NullPointerException npe) { System.out.println("FAILED.\n[" + npe.getMessage() + "]\n"); } } } Can you help me out here?

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  • Building Reducisaurus URLs

    - by Alix Axel
    I'm trying to use Reducisaurus Web Service to minify CSS and Javascript but I've run into a problem... Suppose I've two unminified CSS at: http:/domain.com/dynamic/styles/theme.php?color=red http:/domain.com/dynamic/styles/typography.php?font=Arial According to the docs I should call the web service like this: http:/reducisaurus.appspot.com/css?url=http:/domain.com/dynamic/styles/theme.php?color=red And if I want to minify both CSS files at once: http:/reducisaurus.appspot.com/css?url1=http:/domain.com/dynamic/styles/theme.php?color=red&url2=http:/domain.com/dynamic/styles/theme.php?color=red If I wanted to specify a different number of seconds for the cache (3600 for instance) I would use: http:/reducisaurus.appspot.com/css?url=http:/domain.com/dynamic/styles/theme.php?color=red&expire_urls=3600 And again for both CSS files at once: http:/reducisaurus.appspot.com/css?url1=http:/domain.com/dynamic/styles/theme.php?color=red&url2=http:/domain.com/dynamic/styles/theme.php?color=red&expire_urls=3600 Now my question is, how does Reducisaurus knows how to separate the URLs I want? How does it know that &expire_urls=3600 is not part of my URL? And how does it know that &url2=... is not a GET argument of url1? I'm I doing this right? Do I need to urlencode my URLs? I took a peek into the source code and although my Java is very poor it seems that the methods acquireFromRemoteUrl() and getSortedParameterNames() from the BaseServlet.java file hold the answers to my question - if a GET argument name contains - or _ they should be ignored?! What about multiple &url(n)s?

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  • How to draw a circle in java with a radius and points around the edge

    - by windopal
    Hi, I'm really stuck on how to go about programming this. I need to draw a circle within a JFrame with a radius and points around the circumference. i can mathematically calculate how to find the coordinates of the point around the edge but i cant seem to be able to program the circle. I am currently using a Ellipse2D method but that doesn't seem to work and doesn't return a radius, as under my understanding, it doesn't draw the circle from the center rather from a starting coordinate using a height and width. My current code is on a separate frame but i need to add it to my existing frame. import java.awt.*; import javax.swing.*; import java.awt.geom.*; public class circle extends JFrame { public circle() { super("circle"); setSize(410, 435); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); Panel sp = new Panel(); Container content = getContentPane(); content.add(sp); setContentPane(content); setVisible(true); } public static void main (String args[]){ circle sign = new circle(); } } class Panel extends JPanel { public void paintComponent(Graphics comp) { super.paintComponent(comp); Graphics2D comp2D = (Graphics2D) comp; comp2D.setColor(Color.red); Ellipse2D.Float sign1 = new Ellipse2D.Float(0F, 0F, 350F, 350F); comp2D.fill(sign1); } }

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  • synchronized block in JSP tag class

    - by Sudhakar
    Hi, I am trying to find answer for the following ,for the past couple of days ,but couldnt find comprehensive answer Problem Statement I have a custom JSP tag class which handles a web form submission ,captures data and write it to same file in the filesystem. As all web applications,this can be triggeredsimultaneosly ,and i fear that multiple threads would be in action handling each of the submission (we all know thats how Servlet works.) CODE synchronized (this){ final String reportFileName = "testReport.csv"; File reportDir = new File( rootCsDirectory, "reports" ); if(!reportDir.isDirectory())reportDir.mkdir(); File reportFile = new File (reportDir, reportFileName); logReport(reportFile,reportContent.toString()); } ISSUE: - A File object can be opened by one thread for writing and at same time another thread might try to access and fail and throw an exception So i thought of synchronizing (on the object ) should solve the issue , but read some where that jsp engine would have pool of jsp tag objects, so i am afraid that synchronized (this) wont work and it should be changed to synchronized (this.getClass())

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  • Java: how to debug an invalid JSTL declaration?

    - by Webinator
    I've seen this kind of issue on SO (and on the Net overall) quite a few times. For example here: http://stackoverflow.com/questions/1884529 Earlier today I was trying on a JSP (regular .jsp, not .jspx) to do this, because I stupidly cut/pasted some example found on the net: <%@ taglib prefix = "c" uri = "http://java.sun.com/jstl/core"%> Then my .jsp was giving a blank page. No error message in the Tomcat log. No nothing. Just a blank page. While, of course (I'm being sarcastic here), the correct line was this: <%@ taglib prefix = "c" uri = "http://java.sun.com/jsp/jstl/core"%> There was a "jsp/" missing (which I found a hint to in yet another SO question). So obviously such issues are common. I can't believe you have to wait for things "not to work" to know you've there's an error and I'm honestly a bit confuzzabled by the number of questions found on the net (and here on SO) where the answer is basically "fix your declaration". My question here is simple: how do you know that it's a declaration issue? What thought process is required here to diagnose and troubleshoot such issues? Are there tools that can help here? (I don't know, like, say, IntelliJ IDEA or Eclipse or Emacs in nxml-mode warning you in real time that the declared URI is invalid?)

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  • Java (or possibly other languages) learning path

    - by bgo
    I am familiar (as a self-learner) with C, python and php such that i can solve some problems involving simple steps (for example, i easily do calculations for physics lab reports with python which normally would take 4x-5x times longer with a calculator). The point here is, as doing such things, i learnt the idea / concepts of programming language and problem solving along with oop or fuctional programming etc. Recently i have started Java and, with the familiarity of other languages, i am doing well for starters but i need guidence. -I am thinking of learning syntax from sun java tutorials and then practicing with codingbat.com or similar sites. I need a reference book that i can study deeper aspects of the topics i am learning. What do you suggest about these? -The problem is (and always have been) the lack of practice. I need coding and problem-solving practices sources. I stuck at the point where i can't figure out what to do next. Can you suggest any source (possibly like codingbat)? If i could plan a learning trail, i can progress faster and efficiently. So i need ideas, comments, suggestions. Thanks in advance.

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  • Ruby as a scripting language for web server

    - by Olivier Lalonde
    Is it possible to use Ruby as a scripting language with a HTTP server ? I'd like to be able to simply put some Ruby files in a web directory and be able to execute them from my browser - just like I did with PHP. I have absolutely nothing against frameworks such as RoR, but I was told that I should first learn Ruby and only then move on with higher level frameworks. Of course, I could write some Ruby scripts and run them in the console, but I would prefer getting the input/output from my browser :) Is that possible at all ? Otherwise, how hard would it be for me to build a quick and simple web framework ?

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  • Pass Variable to Java Method from an Ant Target

    - by user200317
    At the moment I have a .properties file to store settings related to the framework. Example: default.auth.url=http://someserver-at008:8080/ default.screenshots=false default.dumpHTML=false And I have written a class to extract those values and here is the method of that class. public static String getResourceAsStream(String defaultProp) { String defaultPropValue = null; //String keys = null; try { InputStream inputStream = SeleniumDefaultProperties.class.getClassLoader().getResourceAsStream(PROP_FILE); Properties properties = new Properties(); //load the input stream using properties. properties.load(inputStream); defaultPropValue = properties.getProperty(defaultProp); }catch (IOException e) { log.error("Something wrong with .properties file, check the location.", e); } return defaultPropValue; } Throughout the application I use method like follows to just exact property needed, public String getBrowserDefaultCommand() { String bcmd = SeleniumDefaultProperties.getResourceAsStream("default.browser.command"); if(bcmd.equals("")) handleMissingConfigProperties(SeleniumDefaultProperties.getResourceAsStream("default.browser.command")); return bcmd; } But I have not decided do a change to this and use ant and pass a parameter instead of using it from .properties file. I was wondering how could I pass a value to a Java Method using ANT. Non of these classes have Main methods and will not have any main. Due to this I was unable to use it as a java system properties. Thanks in advance.

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  • Help with java executors: wait for task termination.

    - by Raffo
    I need to submit a number of task and then wait for them until all results are available. Each of them adds a String to a Vector (that is synchronized by default). Then I need to start a new task for each result in the Vector but I need to do this only when all the previous tasks have stopped doing their job. I want to use Java Executor, in particular I tried using Executors.newFixedThreadPool(100) in order to use a fixed number of thread (I have a variable number of task that can be 10 or 500) but I'm new with executors and I don't know how to wait for task termination. This is something like a pseudocode of what my program needs to do: EecutorService e = Executors.newFixedThreadPool(100); while(true){ /*do something*/ for(...){ <start task> } <wait for all task termination> for each String in result{ <start task> } <wait for all task termination> } I can't do a e.shutdown because I'm in a while(true) and I need to reuse the executorService... Can you help me? Can you suggest me a guide/book about java executors??

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  • Java Iterators - Trying to get a for each loop to work

    - by CS Student
    So I have a Tree<E> class where E is the datatype held and organized by the tree. I'd like to iterate through the Tree like this, or in a way similar to this: 1. Tree<String> tree=new Tree<String>(); 2. ...add some nodes... 3. for (String s : tree) 4. System.out.println(s); It gives me an error on line 3 though. Incompatible types required: java.lang.String found: java.lang.Object The following works fine and as expected though, performing a proper in-order traversal of the tree and printing each node out as it should: for (TreeIterator<String> i = tree.iterator(); i.hasNext(); ) System.out.println(i.next()); Any idea what I'm doing wrong? Do you need to see more of the code?

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  • Why does the Java Collections Framework offer two different ways to sort?

    - by dvanaria
    If I have a list of elements I would like to sort, Java offers two ways to go about this. For example, lets say I have a list of Movie objects and I’d like to sort them by title. One way I could do this is by calling the one-argument version of the static java.util.Collections.sort( ) method with my movie list as the single argument. So I would call Collections.sort(myMovieList). In order for this to work, the Movie class would have to be declared to implement the java.lang.Comparable interface, and the required method compareTo( ) would have to be implemented inside this class. Another way to sort is by calling the two-argument version of the static java.util.Collections.sort( ) method with the movie list and a java.util.Comparator object as it’s arguments. I would call Collections.sort(myMovieList, titleComparator). In this case, the Movie class wouldn’t implement the Comparable interface. Instead, inside the main class that builds and maintains the movie list itself, I would create an inner class that implements the java.util.Comparator interface, and implement the one required method compare( ). Then I'd create an instance of this class and call the two-argument version of sort( ). The benefit of this second method is you can create an unlimited number of these inner class Comparators, so you can sort a list of objects in different ways. In the example above, you could have another Comparator to sort by the year a movie was made, for example. My question is, why bother to learn both ways to sort in Java, when the two-argument version of Collections.sort( ) does everything the first one-argument version does, but with the added benefit of being able to sort the list’s elements based on several different criteria? It would be one less thing to have to keep in your mind while coding. You’d have one basic mechanism of sorting lists in Java to know.

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  • Updating to Spring 2.5.5 causes a javax.servlet.UnavailableException: org.springframework.web.struts

    - by Averroes
    I have been told to update some application from Spring 2.0.8 to Spring 2.5.5. This application is using Struts 1.2.7. Once I change the Spring.jar I get the following exception while loading in JBoss 4.0.5: 10:14:57,579 ERROR [[/PortalRRHH]] Servlet /PortalRRHH threw load() exception javax.servlet.UnavailableException: org.springframework.web.struts.DelegatingTilesRequestProcessor This is defined in the struts-config.xml this way: <controller locale="true"> <set-property property="processorClass" value="org.springframework.web.struts.DelegatingTilesRequestProcessor"/> </controller> I have no clue of what is happening since it works with the old version of Spring and the DelegatingTilesRequestProcessor is still available in Spring 2.5.5. I have no previous experience with Struts so if you need anything else to figure what the problem is please ask and I will update the question. Thanks.

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  • Issue encondig java->xls

    - by Xerg
    This is not a pure java question and can also be related to HTML I've written a java servlet that queries a database table and shows the result as a html table. The user can also ask to receive the result as an Excel sheet. Im creating the Excel sheet by printing the same html table, but with the content-type of "application/vnd.ms-excel". The Excel file is created fine. The problem is that the tables may contain non-english data so I want to use a UTF-8 encoding. PrintWriter out = response.getWriter(); response.setContentType("application/vnd.ms-excel:ISO-8859-1"); //response.setContentType("application/vnd.ms-excel:UTF-8"); response.setHeader("cache-control", "no-cache"); response.setHeader("Content-Disposition", "attachment; filename=file.xls"); out.print(src); out.flush(); The non-english characters appear as garbage (áéíóú) Also I tried converting to bytes from String byte[] arrByte = src.getBytes("ISO-8859-1"); String result = new String(arrByte, "UTF-8"); But I Still getting garbage, What can I do?. Thanks

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  • Establishing persistent connection to a database in Java

    - by gmile
    I've ran through several examples over the web, and found that every single time I need something from the DB, I should write the following code: try { // Step 1: Load the JDBC driver. Class.forName("mysql_driver_name"); // Step 2: Establish the connection to the database. String url = "jdbc:string_to_mysql_server"; Connection conn = DriverManager.getConnection(url,"user1","password"); // fetch from the DB ... } catch (Exception e) { System.err.println("Got an exception! "); System.err.println(e.getMessage()); } It's very annoying to put up this code every time I want something from the DB, so the question is - is there a way to only once connect entirely all my app to the DB somehow at the very start point, avoiding copy-pasting mentioned code, and then be able to do everything I want with DB? I've quickly looked through NetBeans's Project menu, but didn't find any clue on how to configurate a persistent connection to a selected DB. If it's important, i'm writing a purely desktop app, i.e. using Java EE. Also, it's worth mentioning that I'm a kinda beginner in Java.

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  • Webpage data scraping using Java

    - by Gemma
    I am now trying to implement a simple HTML webpage scraper using Java.Now I have a small problem. Suppose I have the following HTML fragment. <div id="sr-h-left" class="sr-comp"> <a class="link-gray-underline" id="compare_header" rel="nofollow" href="javascript:i18nCompareProd('/serv/main/buyer/ProductCompare.jsp?nxtg=41980a1c051f-0942A6ADCF43B802');"> <span style="cursor: pointer;" class="sr-h-o">Compare</span> </a> </div> <div id="sr-h-right" class="sr-summary"> <div id="sr-num-results"> <div class="sr-h-o-r">Showing 1 - 30 of 1,439 matches, The data I am interested is the integer 1.439 shown at the bottom.I am just wondering how can I get that integer out of the HTML. I am now considering using a regular expression,and then use the java.util.Pattern to help get the data out,but still not very clear about the process. I would be grateful if you guys could give me some hint or idea on this data scraping. Thanks a lot.

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  • Java: using endpoint to publish webservice to tomcat server

    - by Will
    hi all, i am creating a simple SOAP web service. i am to ensure that it runs on a tomcat web service. im trying to implement this with JAX-WS (see code) my question is: does the Endpoint.publish use the tomcat server to host this or is it a mini glassfish kind of server? should i be extending UnicastRemoveObject or something similiar instead? ideally it would be able to be packaged into a .WAR and dropped in the directory and just work. It doesn't seem to work with my installed tomcat server as is because it says the port is already in use. I'm using Ubuntu karmic with the tomcat6 package installed, it could also be my user doesnt have permissions to publish to the running tomcat on 8080 i hope this question is clear enough sample code: @WebService public class UserAttributes { public static void main(String[] args) { UserAttributes instance = new UserAttributes(); Endpoint.publish("http://localhost:8082/WebServices/userattributes", instance); } public string Hello() { return "Hello World"; } }

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  • Creating a QMainWindow from Java using JNI

    - by ebasconp
    Hi everybody: I'm trying to create a Qt main windows from Java using JNI directly and I got a threading error. My code looks like this: Test class: public class Test { public static void main(String... args) { System.out.println(System.getProperty("java.library.path")); TestWindow f = new TestWindow(); f.show(); } } TestWindow class: public class TestWindow { static { System.loadLibrary("mylib"); } public native void show(); } C++ impl: void JNICALL Java_testpackage_TestWindow_show (JNIEnv *, jobject) { int c = 0; char** a = NULL; QApplication* app = new QApplication(c, a); QMainWindow* mw = new QMainWindow(); mw->setWindowTitle("Hello"); mw->setGeometry(150, 150, 400, 300); mw->show(); QApplication::exec(); } and I get my window painted but frozen (it does not receive any event) and the following error message when instantiating the QMainWindow object: QCoreApplication::sendPostedEvents: Cannot send posted events for objects in another thread I know all the UI operations must done in the UI thread but in my example I created the QApplication in the only thread I have running, so, everything should work properly. I did some tests executing the code of my "show" method from a QMetaObject::invokeMethod stuff using Qt::QueuedConnection but nothing works properly. I know I could use Jambi... but I know that it could be done natively too and that is what I want to do :) Any ideas on this? Thanks in advance! Ernesto

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