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  • How can i resolve the N+1 Selects problem ?

    - by Maxime ARNSTAMM
    Hello everyone, I have trouble understanding how to avoid the n+1 select in jpa or hibernate. From what i read, there's the 'left join fetch', but i'm not sure if it still works with more than one list (oneToMany).. Could someone explain it to me, or give me a link with a clear complete explanation please ? I'm sorry if this is a noob question, but i can't find a real clear article or doc on this issue. Thanks

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  • why toString method does not work here??

    - by user329820
    Hi this is my whole class ,I have added number 2 to the doubly linked list and then I want it to be be print in the concole but it will show this "datastructureproject.Node@f62373" thanks! package datastructureproject; public class DoublyLinkedList { private Node head = new Node(0); private Node tail = new Node(0); private int length = 0; public DoublyLinkedList() { head.setPrev(null); head.setNext(tail); tail.setPrev(head); tail.setNext(null); } public void add(int index, int value) throws IndexOutOfBoundsException { Node cursor = get(index); Node temp = new Node(value); temp.setPrev(cursor); temp.setNext(cursor.getNext()); cursor.getNext().setPrev(temp); cursor.setNext(temp); length++; } private Node get(int index) throws IndexOutOfBoundsException { if (index < 0 || index > length) { throw new IndexOutOfBoundsException(); } else { Node cursor = head; for (int i = 0; i < index; i++) { cursor = cursor.getNext(); } return cursor; } } public long size() { return length; } public boolean isEmpty() { return length == 0; } @Override public String toString() { StringBuffer result = new StringBuffer(); result.append("(head) - "); Node temp = head; while (temp.getNext() != tail) { temp = temp.getNext(); result.append(temp.getValue() + " - "); } result.append("(tail)"); return result.toString(); } public static void main(String[] args){ DoublyLinkedList list = new DoublyLinkedList(); list.add(0,2 ); System.out.println(list.get(0).toString()); } }

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  • log4j rootLogger seems to inherit log level of other logger. Why?

    - by AndrewR
    I've got a log4J setup in which the root logger is supposed to log ERROR level messages and above to the console and another logger logs everything to syslog. log4j.properties is: # Root logger option log4j.rootLogger=ERROR,R log4j.appender.R=org.apache.log4j.ConsoleAppender log4j.appender.R.layout=org.apache.log4j.PatternLayout log4j.appender.R.layout.ConversionPattern=%d %p %t %c - %m%n log4j.logger.SGSearch=DEBUG,SGSearch log4j.appender.SGSearch=org.apache.log4j.net.SyslogAppender log4j.appender.SGSearch.SyslogHost=localhost log4j.appender.SGSearch.Facility=LOCAL6 log4j.appender.SGSearch.layout=org.apache.log4j.PatternLayout log4j.appender.SGSearch.layout.ConversionPattern=[%-5p] %m%n In code I do private static final Logger logger = Logger.getLogger("SGSearch"); . . . logger.info("Commencing snapshot index [" + args[1] + " -> " + args[2] + "]"); What is happening is that I get the console logging for all logging levels. What seems to be happening is that the level for SGSearch overrides the level set for the root logger somehow. I can't figure it out. I have confirmed that Log4J is reading then properties file I think it is, and no other (via the -Dlog4j.debug option)

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  • What is annotations and how do it actually works for frameworks like Spring ?

    - by Rachel
    I am new to Spring and now a days I hear a lot about Spring Framework. I have two sets of very specific questions: Set No. 1: What are annotations in general ? How does annotations works specifically with Spring framework ? Can annotations be used outside Spring Framework or are they Framework specific ? Set No. 2: What module of Spring Framework is widely used in Industry ? I think it is Spring MVC but why it is the most used module, if am correct or correct me on this ? I am newbie to Spring and so feel free to edit this questions to make more sense.

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  • Jakarta Regexp 1.5 Backreferences?

    - by Matt Smith
    Why does this match: String str = "099.9 102.2" + (char) 0x0D; RE re = new RE("^([0-9]{3}.[0-9]) ([0-9]{3}.[0-9])\r$"); System.out.println(re.match(str)); But this does not: String str = "099.9 102.2" + (char) 0x0D; RE re = new RE("^([0-9]{3}.[0-9]) \1\r$"); System.out.println(re.match(str)); The back references don't seem to be working... What am I missing?

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  • ResultSet and aggregation

    - by kachanov
    Ok, I admit my situation is special There is a data system that supports SQL-92 and JDBC interface However the SQL requets are pretty expensive, and in my application I need to retreive the same data multiple times and aggregate it ("group by") on different fields to show different dimensions of the same data. For example on one screen I have three tables that show the same set or records but aggregated by City (1st grid), by Population (2nd grid), by number of babies (3rd grid) This amounts to 3 SQL queries (which is very slow), UNLESS anyone of you can suggest any idea any library from apache commons or from google code, so that I can select all records into ResultSet and get 3 arrays of data group by different fields from this single ResultSet. Am I'm missing some obvious and unexpected solution to this problem?

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  • Spring Form: Submitting extra parameter on submit buttons

    - by theringostarrs
    Hi, I am working on a form with a bunch of selection criteria that will generate a report when the form is submitted. I also have a number of different reports that can be generated form this same criteria, and want the type of report to be selectable by using a tab system where each tab clicked on submits the form and generates the correct report. I was to do this by passing an extra parameter into the form to switch onto the right form type I am new to Spring, and from the guidance of an elder was told to use an input button for each tab with the following approximate syntax: <input type="submit" name="${form.selectionValues.tabSelection}" value="1" /> tabSelection form property of the SelectionValues object is not being set. I wasn't surprised ;) DIdn't think this would work. So I am wondering how can I can submit a post back from a button in Spring containing the form values plus an extra tabSelection parameter and value? How should I mark up this mechanism? Will I have to do anything to the form controller to register this extra parameter? The original markup I was using to build this page, was using HTML anchor tags instead of buttons for the tab links, which would be much better for the CSS, is there any way to trigger a full form submit using an anchor href? I know this will be a GET request instead of a POST, and not associated with the form.. so I dont expect this to work.. just trying to think of solutions! I would prefer to use the priginal markup, as the styles are there. Any help would be appreciated

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  • Is J2SE a framework?

    - by Alvin
    Hello, I want to know is this legitimate to say J2SE a framework? If J2SE is a framework, then why there is a collection framework? Isn't collection framework inside J2SE? Please help me!

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  • Creating custom Android project templates in Eclipse?

    - by Rich
    Every app I make starts out with a number of common base classes, interfaces, utility classes and a basic package structure that has been working for me. Is there a way for me to set up a project template in Eclipse that will give me all of the basic Android project stuff PLUS a bunch of custom packages, classes and interfaces? I guess I could just put all of this stuff into one or more libraries as opposed to creating a whole project template, so if you have a preferred approach or information/links/etc on how to do any of the above, please share (I'm relatively inexperienced with Eclipse, so the more detail the better). Thanks.

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  • Testing code that uses SoftReference<T>

    - by bmargulies
    To get any code with SoftReference<T> to be fully tested, one must come up with some way to test the 'yup, it's been nulled' case. One might more or less mock this by using a 'for-test' code path to force the reference to be null, but that won't manage the queue exactly as the GC does. I wonder if anyone out can share experience in setting up a repeatable, controlled, environment, in which the GC is, in fact, provoked into collecting and nulling?

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  • How do I retain a requested url with parameters after redirecting to a login page?

    - by Brent Parker
    I have been asked to set up some authentication for some content on our website using JSP. What I would like to do seems simple to me but I can't quite figure out how to do it in JSP. What I would like to do is this: When a user requests a page that you must be logged in to see, I have a tag that checks their cookies for an authentication token. If it is not there, they are redirected to a login page. After they log in, I want to redirect them back to the page they first requested along with any parameters they were sending. Now, I have the tag that is checking their authentication and redirecting them to the login page. That part is working just fine. But I'm not sure how to maintain the first requested url and parameters so they can be redirected after they login. How might I accomplish this?

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  • final and private static

    - by xdevel2000
    I read that doing: public final void foo() {} is equals to: private static void foo() {} both meaning that the method is not overridable! But I don't see the equivalence if a method is private it's automatically not accessible...

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  • stop thread that does not get interrupted

    - by prmatta
    I have a thread that sits and reads objects off of an ObjectInputStream: public void run() { try { ois = new ObjectInputStream(clientSocket.getInputStream()); Object o; while ((o = ois.readObject()) != null) { //do something with object } } catch (Exception ex) { //Log exception } } readObject does not throw InterruptedException and as far as I can tell, no exception is thrown when this thread is interrupted. How do I stop this thread?

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  • Compare Long values Struts2

    - by Marquinio
    Hi everyone I'm trying to compare two values using struts2 s:if tag but its not working. If I hardcode the values it works but I want it to be dynamic. The variable stringValue is of type String. The variable currentLongValue is of type Long. <s:set var="stringValue" value="order"/> <s:iterator value="listTest"> <s:set var="currentLongValue" value="value"/> <s:if test="#currentLongValue.toString() == #stringValue" > //Do something </s:if> <s:else> //Do something else </s:else> </s:iterator> For the s:if I have tried toString and also the equals(). It only works if I hardcode the values. Example: <s:if test="#currentLongValue == 1234"> Any clues? Thank you.

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  • Servlets, long operations

    - by asrijaal
    Hi there, I'm refactoring a big piece of code atm where a long taking operation is executed in a servlet. Now sometimes I don't get a response after the operation has finished. (It has finished because it is printed into the logs) What I wish to achieve would some "fire and forget" behavior by the servlet. I would pass my params to the action and the servlet would immediately return a status (something like: the operation has started, check your logs for further info) Is this possible with servlet 2.5 spec? I think I could get such a behavior with JMS maybe any other solutions out there?

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  • Maven Ant BuildException with maven-antrun-plugin ... unable to find javac compiler

    - by robsbobs
    Im trying to make Maven call an ANT build for some legacy code. the ant build builds correctly through ant however when i call it using the maven ant plugin it fails with the following error: [ ERROR] Failed to execute goal org.apache.maven.plugins:maven-antrun-plugin:1.6:run (default) on project CoreServices: An Ant BuildException has occured: The following error occurred while executing this line: [ERROR] C:\dev\projects\build\build.xml:158: The following error occurred while executing this line: [ERROR] C:\dev\projects\build\build.xml:62: The following error occurred while executing this line: [ERROR] C:\dev\projects\build\build.xml:33: The following error occurred while executing this line: [ERROR] C:\dev\projects\ods\build.xml:41: Unable to find a javac compiler; [ERROR] com.sun.tools.javac.Main is not on the classpath. [ERROR] Perhaps JAVA_HOME does not point to the JDK. [ERROR] It is currently set to "C:\bea\jdk150_11\jre" My javac exists at C:\bea\jdk150_11\bin and this works for all other things. Im not sure where Maven is getting this version of JAVA_HOME. JAVA_HOME in windows envionrmental variables is set to C:\bea\jdk150_11\ as it should be. The Maven code that im using to call the build.xml is <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-antrun-plugin</artifactId> <version>1.6</version> <executions> <execution> <phase>install</phase> <configuration> <target> <ant antfile="../build/build.xml" target="deliver" > </ant> </target> </configuration> <goals> <goal>run</goal> </goals> </execution> </executions> </plugin> </plugins> </build>

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  • checking boolean property in XML(Spring)

    - by Abhishek Bhandari
    I am using Spring Framework . While writing coustum SQL queries , i am unable check a parameter of boolean value. For example this is not working .. do some SQl cods The above checking is not working , it is evaluating as equal in both the cases when booleanVariable is true and false . i tried to replace compareValue ="tree" and "false". As that is a monkey work i do sometimes . is it possible to check the boolean property in XML like above .

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  • How to write a jUnit test for this class?

    - by flash
    Hi, I would like to know what's the best approach to test the method "pushEvent()" in the following class with a jUnit test. My problem is, that the private method "callWebsite()" always requires a connection to the network. How can I avoid this requirement or refactor my class that I can test it without a connection to the network? class MyClass { public String pushEvent (Event event) { //do something here String url = constructURL (event); //construct the website url String response = callWebsite (url); return response; } private String callWebsite (String url) { try { URL requestURL = new URL (url); HttpURLConnection connection = null; connection = (HttpURLConnection) requestURL.openConnection (); String responseMessage = responseParser.getResponseMessage (connection); return responseMessage; } catch (MalformedURLException e) { e.printStackTrace (); return e.getMessage (); } catch (IOException e) { e.printStackTrace (); return e.getMessage (); } } }

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  • Reg Google app engine datastore -primarykey

    - by megala
    hi, I created table in google Big table datastore ,In that the i set primary key using @annotations as follows @Id @Column(name = "groupname") private String groupname; @Basic private String groupdesc; I worked corretly,but it override the previous record,how to solve this for eg if i entered groupname=group1 groupdesc=groupdesc than it accept after that i enter same groupname it override previous record for eg groupname=group1 groupdesc=groups this record override previous one.

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  • Using enums or a set of classes when I know I have a finite set of different options?

    - by devoured elysium
    Let's say I have defined the following class: public abstract class Event { public DateTime Time { get; protected set; } protected Event(DateTime time) { Time = time; } } What would you prefer between this: public class AsleepEvent : Event { public AsleepEvent(DateTime time) : base(time) { } } public class AwakeEvent : Event { public AwakeEvent(DateTime time) : base(time) { } } and this: public enum StateEventType { NowAwake, NowAsleep } public class StateEvent : Event { protected StateEventType stateType; public MealEvent(DateTime time, StateEventType stateType) : base(time) { stateType = stateType; } } and why? I am generally more inclined to the first option, but I can't explain why. Is it totally the same or are any advantages in using one instead of the other? Maybe with the first method its easier to add more "states", altough in this case I am 100% sure I will only want two states: now awake, and now asleep (they signal the moments when one awakes and one falls asleep).

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  • class not found when running

    - by captfrank
    I'm getting "could not find class" error when I run my app. Understand that copulation and execution path different but I followed the recommendations of another question to create a sub dir under my project of lib and put the jar there but still no luck. using Eclipse and it is when I run on a device from eclipse (unable to get the broadcast events I want to trigger this code from simulator, i.e. wifi and blue-tooth). Any way to look at the apk to see what's in it like this jar file? looking around did not see anything.

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  • How do I make my custom Swing component visible?

    - by Alex
    I have no idea why it won't show. First I create an instance of the component and then add it to a certain element in a two-dimensional JPanel array. Then I loop through that array and add each JPanel to another JPanel container which is to hold all the JPanels. I then add that final container to my JFrame window and set visibility to true, it should be visible? public class View extends JFrame { Board gameBoard; JFrame gameWindow = new JFrame("Chess"); JPanel gamePanel = new JPanel(); JPanel[][] squarePanel = new JPanel[8][8]; JMenuBar gameMenu = new JMenuBar(); JButton restartGame = new JButton("Restart"); JButton pauseGame = new JButton("Pause"); JButton log = new JButton("Log"); View(Board board){ gameWindow.setDefaultCloseOperation(EXIT_ON_CLOSE); gameWindow.setSize(400, 420); gameWindow.getContentPane().add(gamePanel, BorderLayout.CENTER); gameWindow.getContentPane().add(gameMenu, BorderLayout.NORTH); gameMenu.add(restartGame); gameMenu.add(pauseGame); gameMenu.add(log); gameBoard = board; drawBoard(gameBoard); gameWindow.setResizable(false); gameWindow.setVisible(true); } public void drawBoard(Board board){ for(int row = 0; row < 8; row++){ for(int col = 0; col < 8; col++){ Box box = new Box(board.getSquare(col, row).getColour(), col, row); squarePanel[col][row] = new JPanel(); squarePanel[col][row].add(box); } } for(JPanel[] col : squarePanel){ for(JPanel square : col){ gamePanel.add(square); } } } } @SuppressWarnings("serial") class Box extends JComponent{ Color boxColour; int col, row; public Box(Color boxColour, int col, int row){ this.boxColour = boxColour; this.col = col; this.row = row; repaint(); } protected void paintComponent(Graphics drawBox){ drawBox.setColor(boxColour); drawBox.drawRect(50*col, 50*row, 50, 50); drawBox.fillRect(50*col, 50*row, 50, 50); } } A final question as well. Notice how each Box component has a position, what happens to the position when I add the component to a JPanel and add the JPanel to my JFrame? Does it still have the same position in relation to the other Box components?

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  • Use ObjectOutputStream and FileOutputStream with FileWriter

    - by wishi
    Hi! Is there any way to use ObjectOutputStream like this: <tag>output of the ObjectOutputStream</tag> If I try: FileOutputStream fos = new FileOutputStream(filename); ObjectOutputStream oos = new ObjectOutputStream(fos); FileWriter fw = new FileWriter(fos); And for example: fw.write("<tag>"); oos.write(cool_object); fw.wrote("</tag>"); I don't get that result. It seems the ObjectOutputStream overwrites the file completly each and every time.

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