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• Java method help

  - by dalton conley

  Ok, so I'm working on a project for a class I'm taking.. simple music library. Now I'm having some issues, the main issue is I'm getting "non-static method cannot be referenced from a static context" Here is a function I have public void addSong() { Scanner scan = new Scanner(System.in); Song temp = new Song(); int index = countFileLines(Main.databaseFile); index = index + 2; temp.index = index; System.out.print("Enter the artist name: "); temp.artist.append(scan.next()); } Now thats in a class file called LibraryFunctions. So I can access it with LibraryFunctions.addSong(); Now I'm trying to run this in my main java file and its giving me the error, I know why the error is happening, but what do I do about it? If I make addSong() a static function then it throws errors at me with the Song temp = new Song() being static. Kind of ironic. Much help is appreciated on this!

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• Blackberry (Java) - Can't get KeyListener to work

  - by paullb

  I am trying to get the KeyListener working for Blackberry, but none of the Dialogs pop up indicating that a key has been pressed (see code below, each action has a dialog popup in them). Any ideas on what i might be doing wrong? public class CityInfo extends UiApplication implements KeyListener { static CityInfo application; public static void main(String[] args) { //create a new instance of the application //and start the application on the event thread application.enterEventDispatcher(); } public CityInfo() { //display a new screen application = new CityInfo(); pushScreen(new WorkflowDisplayScreen()); this.addKeyListener(this); } public boolean keyChar(char arg0, int arg1, int arg2) { // TODO Auto-generated method stub Dialog.alert("key pressed : " + arg0); return true; } public boolean keyDown(int keycode, int time) { // TODO Auto-generated method stub Dialog.alert("keyDown : " + keycode); return false; } public boolean keyRepeat(int keycode, int time) { // TODO Auto-generated method stub Dialog.alert("keyRepeat : " + keycode); return false; } public boolean keyStatus(int keycode, int time) { // TODO Auto-generated method stub Dialog.alert("keyStatus : " + keycode); return false; } public boolean keyUp(int keycode, int time) { Dialog.alert("keyUp : " + keycode); // TODO Auto-generated method stub return false; } } I also tried implementing keyChar on the MainScreen class but that did not yield any results either.

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• Most awkward/misleading method in Java Base API ?

  - by JG

  I was recently trying to convert a string literal into a boolean, when the method "boolean Boolean.getBoolean(String name)" popped out of the auto-complete window. There was also another method ("boolean Boolean.parseBoolean(String s)") appearing right after, which lead me to search to find out what were the differences between these two, as they both seemed to do the same. It turns out that what Boolean.getBoolean(String name) really does is to check if there exists a System property (!) of the given name and if its value is true. I think this is very misleading, as I'm definitely not expecting that a method of Boolean is actually making a call to System.getProperty, and just by looking at the method signature, it sure looks (at least to me) like it should be used to parse a String as a boolean. Sure, the javadoc states it clearly, but I still think the method has a misleading name and is not in the right place. Other primitive type wrappers, such as Integer also have a similar method. Also, it doesn't seem to be a very useful method to belong in the base API, as I think it's not very common to have something like -Darg=true. Maybe it's a good question for a Java position interview: "What is the output of Boolean.getBoolean("true")?". I believe a more appropriate place for those methods would be in the System class, e.g., getPropertyAsBoolean; but again, I still think it's unnecessary to have these methods in the base API. It'd make sense to have these in something like the Properties class, where it's very common to do this kind of type conversions. What do you think of all this ? Also, if there's another "awkward" method that you're aware of, please post it. N.B. I know I can use Boolean.valueOf or Boolean.parseBoolean to convert a string literal into a boolean, but I'm just looking to discuss the API design.

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• Concurrency problem with arrays (Java)

  - by Johannes

  For an algorithm I'm working on I tried to develop a blacklisting mechanism that can blacklist arrays in a specific way: If "1, 2, 3" is blacklisted "1, 2, 3, 4, 5" is also considered blacklisted. I'm quite happy with the solution I've come up with so far. But there seem to be some serious problems when I access a blacklist from multiple threads. The method "contains" (see code below) sometimes returns true, even if an array is not blacklisted. This problem does not occur if I only use one thread, so it most likely is a concurrency problem. I've tried adding some synchronization, but it didn't change anything. I also tried some slightly different implementations using java.util.concurrent classes. Any ideas on how to fix this? public class Blacklist { private static final int ARRAY_GROWTH = 10; private final Node root = new Node(); private static class Node{ private volatile Node[] childNodes = new Node[ARRAY_GROWTH]; private volatile boolean blacklisted = false; public void blacklist(){ this.blacklisted = true; this.childNodes = null; } } public void add(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return; else if(currentNode.childNodes.length <= edge) { currentNode.childNodes = Arrays.copyOf(currentNode.childNodes, edge + ARRAY_GROWTH); } if(currentNode.childNodes[edge] == null) { currentNode.childNodes[edge] = new Node(); } currentNode = currentNode.childNodes[edge]; } currentNode.blacklist(); } } public boolean contains(final int[] array){ synchronized (root) { Node currentNode = this.root; for(final int edge : array){ if(currentNode.blacklisted) return true; else if(currentNode.childNodes.length <= edge || currentNode.childNodes[edge] == null) return false; currentNode = currentNode.childNodes[edge]; } return currentNode.blacklisted; } } }

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• Project Euler, Problem 10 java solution now working

  - by Dennis S

  Hi, I'm trying to find the sum of the prime numbers < 2'000'000. This is my solution in java but I can't seem get the correct answer. Please give some input on what could be wrong and general advice on the code is appreciated. Printing 'sum' gives: 1308111344, which is incorrect. /* The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below two million. */ class Helper{ public void run(){ Integer sum = 0; for(int i = 2; i < 2000000; i++){ if(isPrime(i)) sum += i; } System.out.println(sum); } private boolean isPrime(int nr){ if(nr == 2) return true; else if(nr == 1) return false; if(nr % 2 == 0) return false; for(int i = 3; i < Math.sqrt(nr); i += 2){ if(nr % i == 0) return false; } return true; } } class Problem{ public static void main(String[] args){ Helper p = new Helper(); p.run(); } }

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• Avoiding duplicate objects in Java deserialization

  - by YGL

  I have two lists (list1 and list2) containing references to some objects, where some of the list entries may point to the same object. Then, for various reasons, I am serializing these lists to two separate files. Finally, when I deserialize the lists, I would like to ensure that I am not re-creating more objects than needed. In other words, it should still be possible for some entry of List1 to point to the same object as some entry in List2. MyObject obj = new MyObject(); List<MyObject> list1 = new ArrayList<MyObject>(); List<MyObject> list2 = new ArrayList<MyObject>(); list1.add(obj); list2.add(obj); // serialize to file1.ser ObjectOutputStream oos = new ObjectOutputStream(...); oos.writeObject(list1); oos.close(); // serialize to file2.ser oos = new ObjectOutputStream(...); oos.writeObject(list2); oos.close(); I think that sections 3.4 and A.2 of the spec say that deserialization strictly results in the creation of new objects, but I'm not sure. If so, some possible solutions might involve: Implementing equals() and hashCode() and checking references manually. Creating a "container class" to hold everything and then serializing the container class. Is there an easy way to ensure that objects are not duplicated upon deserialization? Thanks.

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• Java JCheckBox ArrayList help needed

  - by user2929626

  I'm new to Java and struggling with something which I'm sure must have a simple answer but I can't seem to find it. I have an array of checkbox objects defined as: ArrayList<JCheckBox> checkBoxList A JPanel is created with a grid layout and the checkboxes are added to the JPanel and the ArrayList: for (int i = 0; i < 256; i++) { JCheckBox c = new JCheckBox(); c.setSelected(false); checkBoxList.add(c); mainPanel.add(c); } Yes, there are 256 checkboxes! The panel is added to a JFrame and eventually the GUI is displayed. The user can select any combination of the 256 checkboxes. My class implements Serializable and this ArrayList of checkboxes can be saved and restored using 'Save' and 'Load' GUI buttons. My code to load the saved object is as below: public class LoadListener implements ActionListener { public void actionPerformed(ActionEvent a) { try { // Prompt the user for a load file JFileChooser fileLoad = new JFileChooser(); fileLoad.showOpenDialog(mainFrame); // Create a object/file input stream linking to the selected file ObjectInputStream is = new ObjectInputStream(new FileInputStream(fileLoad.getSelectedFile())); // Read the checkBox array list checkBoxList = (ArrayList<JCheckBox>) is.readObject(); is.close(); } catch (Exception ex) { ex.printStackTrace(); } } On loading the ArrayList object, the values of the checkboxes are correctly populated, however I want to update the checkboxes on the GUI to reflect this. Is there an easy way to do this? I assumed as the array of checkboxes had the correct values that I could just repaint the panel / frame but this doesn't work. I'd like to understand why - does my loaded array of checkbox objects no longer reflect the checkbox objects on the GUI? Any help would be much appreciated. Thanks!

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• Send string from java (or other platform) to application

  - by MrSnowflake

  I want to send a barcode, read with my cellphone, to my computer. My computer has a simple server running, which listens to barcodes. When a barcode arrives, the server app should be able to input the value of the received barcode into the active application (I don't really care which application is going to get the input, the user should be able to select gedit, a terminal window or the browser if they choose to). My language at the moment is Java on GNU/Linux (Ubuntu), so I know about the Robot class. But the Robot class emulates a keyboard, which means: when you send VK_1 on a US keyboard layout, the output is '1' indeed, but when you send VK_1 on another layout (like belgian, which I use), which requires shift for the '1' key, the output is '&' (this is the character on the '1' key, when you don't hold shift). I also found xsendkeys, but this application too requires you to specify whether you need to hold shift. So it will be able to send an 'a' but for an 'A' (thus capital) you need to specify you want to hold shift with your 'a'. Isn't there an easy way to do this, for GNU/Linux and Windows, just using strings. I want to be able to send "12a68dd" to the active application. And I also would like to be able to send UTF-8 characters to the active application. I have been looking for a solution, but most require the breakdown in multiple keystrokes, which are often dependent on the keyboard layout.

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• Using same log4j logger in standalone java application

  - by ktaylorjohn

  I have some code which is a standalone java application comprising of 30+ classes. Most of these inherit from some other base classes. Each and every class has this method to get and use a log4j logger public static Logger getLogger() { if (logger != null) return logger; try { PropertyUtil propUtil = PropertyUtil.getInstance("app-log.properties"); if (propUtil != null && propUtil.getProperties() != null) PropertyConfigurator.configure(propUtil.getProperties ()); logger = Logger.getLogger(ExtractData.class); return logger; } catch (Exception exception) { exception.printStackTrace(); } } A) My question is whether this should be refactored to some common logger which is initialized once and used across by all classes? Is that a better practice? B) If yes, how can this be done ? How can I pass the logger around ? C) This is actually being used in the code not as Logger.debug() but getLogger().debug(). What is the impact of this in terms of performance?

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• Java loop to collect the second and third elements every three in an array

  - by mhollander38

  I have a file with data in the form timestamp, coordinate, coordinate, seperated by spaces, as here; 14:25:01.215 370.0 333.0 I need to loop through and add the coordinates only to an array. The data from the file is read in and put into as String[] called info, from split(" "). I have two problems, I think the end of the file has a extra " " which I need to lose appropriately and I also want confirmation/suggestions of my loop, at the moment I am getting sporadic out of bounds exceptions. My loop is as follows; String[] info; info = dataHolder.split(" "); ArrayList<String> coOrds1 = new ArrayList<String>(); for (int counter = 0; counter < info.length; counter = counter+3) { coOrds1.add(info[counter+1]); coOrds1.add(info[counter+2]); } Help and suggestions appreciated. The text file is here but the class receives in a UDP packet from another class so I am unsure if this potentially adds " " at the end or not.

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• Memory increases with Java UDP Server

  - by Trevor

  I have a simple UDP server that creates a new thread for processing incoming data. While testing it by sending about 100 packets/second I notice that it's memory usage continues to increase. Is there any leak evident from my code below? Here is the code for the server. public class UDPServer { public static void main(String[] args) { UDPServer server = new UDPServer(15001); server.start(); } private int port; public UDPServer(int port) { this.port = port; } public void start() { try { DatagramSocket ss = new DatagramSocket(this.port); while(true) { byte[] data = new byte[1412]; DatagramPacket receivePacket = new DatagramPacket(data, data.length); ss.receive(receivePacket); new DataHandler(receivePacket.getData()).start(); } } catch (IOException e) { e.printStackTrace(); } } } Here is the code for the new thread that processes the data. For now, the run() method doesn't do anything. public class DataHandler extends Thread { private byte[] data; public DataHandler(byte[] data) { this.data = data; } @Override public void run() { System.out.println("run"); } }

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• Strange behavior when overloading methods in Java

  - by Sep

  I came across this weird (in my opinion) behavior today. Take this simple Test class: public class Test { public static void main(String[] args) { Test t = new Test(); t.run(); } private void run() { List<Object> list = new ArrayList<Object>(); list.add(new Object()); list.add(new Object()); method(list); } public void method(Object o) { System.out.println("Object"); } public void method(List<Object> o) { System.out.println("List of Objects"); } } It behaves the way you expect, printing "List of Objects". But if you change the following three lines: List<String> list = new ArrayList<String>(); list.add(""); list.add(""); you will get "Object" instead. I tried this a few other ways and got the same result. Is this a bug or is it a normal behavior? And if it is normal, can someone explain why? Thanks.

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• Java How to find a value in a linked list iteratively and recursively

  - by Roxy

  Hi I have a method that has a reference to a linked list and a int value. So, this method would count and return how often the value happens in the linked list. So, I decided to make a class, public class ListNode{ public ListNode (int v, ListNode n) {value = v; next = n;) public int value; public ListNode next; } Then, the method would start with a public static int findValue(ListNode x, int valueToCount){ // so would I do it like this?? I don't know how to find the value, // like do I check it? for (int i =0; i< x.length ;i++){ valueToCount += valueToCount; } So, I CHANGED this part, If I did this recursively, then I would have public static int findValue(ListNode x, int valueToCount) { if (x.next != null && x.value == valueToCount { return 1 + findValue(x, valueToCount);} else return new findvalue(x, valueToCount); SO, is the recursive part correct now?

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• Inheritance concept java..help

  - by max

  Hi everyone. I'd be very grateful if someone could help me to understand the inheritance concept in Java. Is the following code an example of that? I mean the class WavPanel is actually a subclass of JPanel which acts as a superclass. Is that correct? If so it means that "what JPanel has, also WavPanel but it is more specific since through its methods you can do something else". Am I wrong? thank you. Max import javax.swing.JPanel; class WavPanel extends JPanel { List<Byte> audioBytes; List<Line2D.Double> lines; public WavPanel() { super(); setBackground(Color.black); resetWaveform(); } public void resetWaveform() { audioBytes = new ArrayList<Byte>(); lines = new ArrayList<Line2D.Double>(); repaint(); } }

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• Java using generics with lists and interfaces

  - by MirroredFate

  Ok, so here is my problem: I have a list containing interfaces - List<Interface> a - and a list of interfaces that extend that interface: List<SubInterface> b. I want to set a = b. I do not wish to use addAll() or anything that will cost more memory as what I am doing is already very cost-intensive. I literally need to be able to say a = b. I have tried List<? extends Interface> a, but then I cannot add Interfaces to the list a, only the SubInterfaces. Any suggestions? EDIT I want to be able to do something like this: List<SubRecord> records = new ArrayList<SubRecord>(); //add things to records recordKeeper.myList = records; The class RecordKeeper is the one that contains the list of Interfaces (NOT subInterfaces) public class RecordKeeper{ public List<Record> myList; }

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• Setting the type of a field in a superclass from a subclass (Java)

  - by Ibolit

  Hi. I am writing a project on Google App Engine, within it I have a number of abstract classes that I hope I will be able to use in my future projects, and a number of concrete classes inheriting from them. Among other abstract classes I have an abstract servlet that does user management, and I hava an abstract user. The AbstractUser has all the necessary fields and methods for storing it in the datastore and telling whether the user is registered with my service or not. It does not implement any project specific functionality. The abstract servlet that manages users, refers only to the methods declared in the AbstractUser class, which allows it to generate links for logging in, logging out and registering (for unregistered users). In order to implement the project-specific user functionality I need to subclass the Abstract user. The servlets I use in my project are all indirect descendants from that abstract user management servlet, and the user is a protected field in it, so the descendant servlets can use it as their own field. However, whenever i want to access any project specific method of the concrete user, i need to cast it to that type. i.e. (abstract user managing servlet) ... AbstractUser user = getUser(); ... abstract protected AbstractUser getUser(); (project-specific abstract servlet) @Override protected AbstractUser getUser() { return MyUserFactory.getUser(); } any other project specific servlet: int a = ((ConcreteUser) user).getA(); Well, what i'd like to do is to somehow make the type of “user” in the superclass depend on something in the project-specific abstract class. Is it at all possible? And i don't want to move all the user-management stuff into a project-specific layer, for i would like to have it for my future projects already written :) Thank you for your help.

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• java packets byte

  - by user303289

  Guys, I am implementing a protocol in one of the wireless project. I am stucked at one point. In of the java file i am suppose to receive a packet and that packet is 12 byte packet and I have to write different functions for reading different parts of packets and convert it to diferent type. Like I want first four byte in one of the function and convert it to int, next two bytes in string. and again next two in string, last two hop in string and followed by last two int. I want follwing function to implement: // here is the interface /* FloodingData should use methods defined in this class. */ class FloodingPacket{ public static void main(String arg[]){ byte FloodingPack[]; // just for example to test in code FloodingPack=new byte[12]; interface IFloodingPacket { // Returns the unique sequence number for the packet int getSequenceNumber() ; // Returns the source address for the packet String getSourceAddress(); // Returns the destination address for the packet String getDestinationAddress(); // Returns the last hop address for the packet String getLastHopAddress(); // Sets the last hop address to the address of the node // which the packet was received from void updateLastHopAddress(); // Returns the entire packet in bytes (for sending) byte[] getBytes(); // Sets the bytes of the packet (for receiving) void setBytes(byte[] packet); }

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• Unable to launch Eclipse 4.1.2 after installing the Eclipse e4 tooling

  - by Kuldeep Jain

  After installing Eclipse e4 Tools in my Eclipse 4.1.2 from update site. I am getting error when launching the eclipse.exe "An error has occurred. See the log file <my_workspace_path>\.metadata\.log". And the content of .log file are: !SESSION 2012-04-06 16:00:01.609 ----------------------------------------------- eclipse.buildId=M20120223-0900 java.fullversion=J2RE 1.6.0 IBM J9 2.4 Windows XP x86-32 jvmwi3260sr5-20090519_35743 (JIT enabled, AOT enabled) J9VM - 20090519_035743_lHdSMr JIT - r9_20090518_2017 GC - 20090417_AA BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=en_US Command-line arguments: -os win32 -ws win32 -arch x86 -clean -console !ENTRY org.eclipse.osgi 4 0 2012-04-06 16:00:17.343 !MESSAGE Application error !STACK 1 java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 1 at org.eclipse.emf.common.util.URI.segment(URI.java:1731) at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.getBundle(ReflectionContributionFactory.java:135) at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.doCreate(ReflectionContributionFactory.java:61) at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.create(ReflectionContributionFactory.java:53) at org.eclipse.e4.ui.internal.workbench.E4Workbench.processHierarchy(E4Workbench.java:196) at org.eclipse.e4.ui.internal.workbench.E4Workbench.init(E4Workbench.java:122) at org.eclipse.e4.ui.internal.workbench.E4Workbench.<init>(E4Workbench.java:73) at org.eclipse.e4.ui.internal.workbench.swt.E4Application.createE4Workbench(E4Application.java:293) at org.eclipse.ui.internal.Workbench$3.run(Workbench.java:534) at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332) at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:520) at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149) at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:123) at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196) at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110) at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79) at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:344) at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37) at java.lang.reflect.Method.invoke(Method.java:599) at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:622) at org.eclipse.equinox.launcher.Main.basicRun(Main.java:577) at org.eclipse.equinox.launcher.Main.run(Main.java:1410) I also tried the eclipse.exe -clean to launch it but getting same error.

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• Atomikos vs JOTM vs Bitronix vs ????

  - by HDave

  I am new to JTA and it's underlying transaction managers. Can anyone explain the pros/cons of each of these? Feel free to add others I didn't list in title. Also, don't the major applications servers (WebSphere, JBoss, Glassfish) have their own JTA compliant transaction manager? In those environments, would you still use these third party implementations?

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• JSF a4j:commandButton not working when 'disabled' is set

  - by Jon

  Hello, When I include a 'disabled' attribute on an a4j:commandButton, the button's action is not performed. Taking the 'disabled' attribute out causes it to work properly. I am not doing any special validation (that I'm aware of) and am not seeing any validation error messages. Here is part of my page: <t:dataTable id="myTable" var="region" value="#{MyPageBackingBean.regions}" width="100%"> ... <a4j:commandButton value="Update" action="#{region.doUpdate}" oncomplete="alert('done');" disabled="#{!empty region && region.messageEmpty}" immediate="true"/> ... </t:dataTable> Any ideas? Thanks! Edit: I tried setting preserveDataModel="true" on the t:dataTable to no avail. I also made a test having an a4j:commandButton and text box with no data table, but the backing bean action is still not being fired: <h:form> <a4j:region> <a4j:outputPanel id="testregion"> <h:messages id="messages"/> <a4j:status> <f:facet name="start"> <h:graphicImage value="/images/progress_indicator.gif"/> </f:facet> </a4j:status> <h:inputTextarea rows="5" value="#{MyPageBackingBean.myValue}" style="width:100%; border: 1px solid #99CCFF;"> <a4j:support event="onkeyup" reRender="testregion" eventsQueue="messageModificationQueue" ignoreDupResponses="true" requestDelay="500"/> </h:inputTextarea> <a4j:commandButton id="doDelete" value="Delete" action="#{MyPageBackingBean.dummy}" reRender="testregion" disabled="#{empty MyPageBackingBean.myValue}"/> <h:outputText value="#{MyPageBackingBean.myValue}"/> </a4j:outputPanel> </a4j:region> </h:form> Here is the new backing bean code used for testing: private String m_myValue = null; public String getMyValue() { return m_myValue; } public void setMyValue(String value) { m_myValue = value; } private String mystr2 = null; public String dummy() { mystr2 = "hello"; return null; } Thanks!

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• File upload and Download in a web app using struts2

  - by lakshmanan

  Hi In struts2 upload methods, can I choose where the uploaded file must be saved. I mean, all the examples in web ask me to store in WEB-INF which surely is not a good idea. I want to be able to store the uploaded file in any place in my disk. How should i do it? Can i do it with help of ServletContextAware interceptor ?

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• Type of object returned by an input from a web page

  - by controlfreak123

  I'm attempting to upload a file into a jsp and then use the file in some other code. My problem is that it comes into the servlet as an Object via the request.getAttribute() call so I don't know what to cast it to. I have this code so far to try and test what it is but I'm getting a NullPointerException. PrintWriter out = response.getWriter(); out.println(request.getAttribute("file1").getClass()); Is my understanding of whats going on flawed or am I just coding it up wrong?

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• spring security login pages?

  - by es11

  I have some confusion with how spring security works: In my application, I need to have a login page for users after which they are redirected back the page from where they came. I went through a few spring security tutorials and read some articles, and the examples work by securing a certain page on a site (managed by the <intercept url ..> tag). Then Spring security will generate a login page (or you can specify your own) in order to access the secured page. I am confused because I don't want to necessary secure a given page on my site: I want a login page for users to log into after which they have access to elevated features of the site (through spring security's authorization features). My question is: given what I described, what would be the strategy to create this login page which, after login, would grant the logged in user the appropriate authorities? The hack I thought of would be to create a simple JSP page who's only function is to redirect back to the previous page. Then I would use Spring Security to secure that JSP page. But it seems like there should be a better way of doing this... Thanks

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• Java3D: Painting 2D HUD over a Canvas3D

  - by Jim

  Hello, I'm using Java3D to render a three-dimensional scene. I would like to overlay a two-dimensional "heads-up-display" on top of the 3d image. How can I efficiently paint the 2d content on top of the 3d canvas? Thanks!

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• Problem reading from two separate InputStreams

  - by Emil H

  I'm building a Yammer client for Android in Scala and have encountered the following issue. When two AsyncTasks try to parse an XML response (not the same, each task has it's own InputStream) from the Yammer API the underlying stream throws a IOException with the message "null SSL pointer", as seen below: Uncaught handler: thread AsyncTask #1 exiting due to uncaught exception java.lang.RuntimeException: An error occured while executing doInBackground() at android.os.AsyncTask$3.done(AsyncTask.java:200) at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:234) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:258) at java.util.concurrent.FutureTask.run(FutureTask.java:122) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:648) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:673) at java.lang.Thread.run(Thread.java:1060) Caused by: java.io.IOException: null SSL pointer at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl.nativeread(Native Method) at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl.access$300(OpenSSLSocketImpl.java:55) at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl$SSLInputStream.read(OpenSSLSocketImpl.java:524) at org.apache.http.impl.io.AbstractSessionInputBuffer.fillBuffer(AbstractSessionInputBuffer.java:103) at org.apache.http.impl.io.AbstractSessionInputBuffer.read(AbstractSessionInputBuffer.java:134) at org.apache.http.impl.io.ContentLengthInputStream.read(ContentLengthInputStream.java:174) at org.apache.http.impl.io.ContentLengthInputStream.read(ContentLengthInputStream.java:188) at org.apache.http.conn.EofSensorInputStream.read(EofSensorInputStream.java:178) at org.apache.harmony.xml.ExpatParser.parseFragment(ExpatParser.java:504) at org.apache.harmony.xml.ExpatParser.parseDocument(ExpatParser.java:467) at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:329) at org.apache.harmony.xml.ExpatReader.parse(ExpatReader.java:286) at javax.xml.parsers.SAXParser.parse(SAXParser.java:361) at org.mediocre.util.XMLParser$.loadXML(XMLParser.scala:28) at org.mediocre.util.XMLParser$.loadXML(XMLParser.scala:12) ..... Searching for the error didn't give much clarity. Does this have something to do with the response from the server? Or is it something else? Complete code can be found at: http://github.com/archevel/YammerTime I get no error if I wait until the first repsponse is finished and then let the other complete. The request is made with the DefaultHttpClient, but this is supposedly thread safe. What am I missing? If anything needs to be clarified just ask :) Cheers, Emil H

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