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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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  • Long running method causing race condition

    - by keeleyt83
    Hi, I'm relatively new with hibernate so please be gentle. I'm having an issue with a long running method (~2 min long) and changing the value of a status field on an object stored in the DB. The pseudo-code below should help explain my issue. public foo(thing) { if (thing.getStatus() == "ready") { thing.setStatus("finished"); doSomethingAndTakeALongTime(); } else { // Thing already has a status of finished. Send the user back a message. } } The pseudo-code shouldn't take much explanation. I want doSomethingAndTakeALongTime() to run, but only if it has a status of "ready". My issue arises whenever it takes 2 minutes for doSomethingAndTakeALongTime() to finish and the change to thing's status field doesn't get persisted to the database until it leaves foo(). So another user can put in a request during those 2 minutes and the if statement will evaluate to true. I've already tried updating the field and flushing the session manually, but it didn't seem to work. I'm not sure what to do from here and would appreciate any help. PS: My hibernate session is managed by spring.

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  • which toString() method can be used performance wise??

    - by Mrityunjay
    hi, I am working on one project for performance enhancement. I had one doubt, while we are during a process, we tend to trace the current state of the DTO and entity used. So, for this we have included toString() method in all POJOs for the same. I have now implemented toString() in three different ways which are following :- public String toString() { return "POJO :" + this.class.getName() + " RollNo :" + this.rollNo + " Name :" + this.name; } public String toString() { StringBuffer buff = new StringBuffer("POJO :").append(this.class.getName()).append(" RollNo :").append(this.rollNo).append(" Name :").append(this.name); return buff.toString(); } public String toString() { StringBuilder builder = new StringBuilder("POJO :").append(this.class.getName()).append(" RollNo :").append(this.rollNo).append(" Name :").append(this.name); return builder .toString(); } can anyone please help me to find out which one is best and should be used for enhancing performance.

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  • How to retrieve the ordered list of best articles having a minimum number of votes by using HSQL ?

    - by fabien7474
    I have a Vote domain class from my grails application containing properties like article_id and note I want to HQL query the Vote domain class in order to retrieve the 5 best rated articles having at least 10 votes. I tried : SELECT v.article_id, avg(v.note), count(*) FROM vote v where count(*) >= 10 group by v.article_id order by avg(v.note) desc limit 5; But unfortunately the insertion of where count(*) >= 10 throws an error. How can I do that in a simple way? Thank you for your help.

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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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  • 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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  • Casting of object for a class loaded at runtime

    - by Steven
    hi, i load a class using Class.forName(klassname,false,loader) After this i create an instance using klass.newInstance(); It returns an object type.I want to cast it to specific type(ie.Klassnamw instance).I used normal casting but it gets hung because it is not resolved during runtime.How can i cast it?Hellp

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  • leiningen - how to add dependencies for local jars?

    - by signalseeker
    Hi, I want to use leiningen to build and develop my clojure project. Is there a way to modify project.clj to tell it to pick some jars from local directories? I have some proprietary jars that cannot be uploaded to public repos. Also, can leiningen be used to maintain a "lib" directory for clojure projects? If a bunch of my clojure projects share the same jars, I don't want to maintain a separate copy for each of them. Thanks

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  • Swing Timer in Conjunction with Possible Long-running Background Task

    - by javacavaj
    I need to perform a task repeatedly that affects both GUI-related and non GUI-related objects. One caveat is that no action should performed if the previous task had not completed when the next timer event is fired. My initial thoughts are to use a SwingTimer in conjunction with a javax.swing.SwingWorker object. The general setup would look like this. class { timer = new Timer(speed, this); timer.start(); public void actionPerformed(ActionEvent e) { SwingWorker worker = new SwingWorker() { @Override public ImageIcon[] doInBackground() { // potential long running task } @Override public void done() { // update GUI on event dispatch thread when complete } } } Some potential issues I see with this approach are: 1) Multiple SwingWorkers will be active if a worker has not completed before the next ActionEvent is fired by the timer. 2) A SwingWorker is only designed to be executed once, so holding a reference to the worker and reusing (is not?) a viable option. Is there a better way to achieve this?

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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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  • write behind cache Ehcache new feature?

    - by cometta
    Hi, i looking for guide/document/tutorial on how to use this new feature write-behind-cache in ehcache? Is there any demo in spring+jpa+ehcache+hibernate? just to clariyfing, write-behind-cache mean each time we persist entity, it will be written into cache rather than into database correct?

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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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  • 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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  • inserted in multiple tables of database at a time

    - by rajkumari
    can we work with multiple tables of database with same connection object of database at same time . suppose i have inserted value in table 1 and at same time also inserted value in table 2 of data base with same object of data base connection. I am using sqlite database in code and getting database locked exception while commit() .

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  • for loop will not loop

    - by Bjørn Jostein Aurheim
    I have a for loop that I will use to compute time intervals to add to an ArrayList. The problem is that I can not prove that the for loop is being executed. Nothing is printed when using the system.out.println() statement, and nothing is added to the array from inside the loop ... any sugestions? // lager tidspunkter og legger disse inn i en Array kalt tider tid.setTimer(16); tid.setMinutter(0); tid.setSekunder(0); tider.add(tid.asString());// String "16:00" is added as it should System.out.println("tiden er: "+tid.asString());// gives 16:00 printed for(int i=0;i>12;i++){ System.out.println("er i løkken");// gives nothing printed tid.increaseMinutter(30); System.out.println(tid.asString());// gives nothing printed tider.add(tid.asString()); }

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  • How to define RequestMapping prioritization

    - by James Skidmore
    I have a situation where I need the following RequestMapping: @RequestMapping(value={"/{section}"}) ...method implementation here... @RequestMapping(value={"/support"}) ...method implementation here... There is an obvious conflict. My hope was that Spring would resolve this automatically and map /support to the second method, and everything else to the first, but it instead maps /support to the first method. How can I tell Spring to allow an explicit RequestMapping to override a RequestMapping with a PathVariable in the same place? (Edit - this is simplified, I know that having those two RequestMapping alone wouldn't make much sense)

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  • Exception durin processing XSLT transformation!

    - by Artic
    I'm usin such code to generate contents file. try { StreamResult result = new StreamResult(); TransformerFactory tf = TransformerFactory.newInstance(); for (String item: groups){ item = item.replaceAll(" ", "-").toLowerCase(); result.setOutputStream(new FileOutputStream(path+item+".html")); Templates templ = tf.newTemplates(xsltSource); Transformer transf = templ.newTransformer(); transf.clearParameters(); transf.setParameter("group", item); transf.transform(xmlSource, result); } } catch (TransformerConfigurationException e) { throw new SinkException(e.getMessage()); } catch (TransformerException e) { throw new SinkException(e.getMessage()); } But on second iteration I have an exception ERROR: javax.xml.transform.TransformerException: com.sun.org.apache.xml.internal.utils.WrappedRuntimeException: Read error Cann't understand what is the reason?

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  • JAXB Annotated class - setting of a variable which is not an element

    - by sswdeveloper
    I have a JAXB annotated class say @XmlRootElement(namespace = "http://www.abc.com/customer") Class Customer{ @XmlElement(namespace = "http://www.abc.com/customer") private String Name; @XmlElement(namespace = "http://www.abc.com/customer") private String Address; @XmlTransient private HashSet set = new HashSet(); public String getName(){ return Name; } public void setName(String name){ this.Name = name; set.add("Name"); } public String getAddress(){ return Address; } public void setAddress(String address){ this.Address = address; set.add("Address"); } public void getSet(){ return set; } I have a XML of the form <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <Customer xmlns="http://www.abc.com/customer" > <Name>Ralph</Name> <Address>Newton Street</Address> </Customer> I use JAXB unmarshalling to get the object representation of the XML input. The values for Name and Address are set correctly. However the value of set gets lost(since it is @XMLTransient it gets ignored) Is there any way of ensuring that it is still set in the object which has been unmarshalled? Some other annotation which I can use?

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  • Ref to map vs. map to refs vs. multiple refs

    - by mikera
    I'm working on a GUI application in Swing+Clojure that requires various mutable pieces of data (e.g. scroll position, user data, filename, selected tool options etc.). I can see at least three different ways of handling this set of data: Create a ref to a map of all the data: (def data (ref { :filename "filename.xml" :scroll [0 0] })) Create a map of refs to the individual data elements: (def datamap { :filename (ref "filename.xml") :scroll (ref [0 0]) })) Create a separate ref for each in the namespace: (def scroll (ref [0 0])) (def filename (ref "filename.xml")) Note: This data will be accessed concurrently, e.g. by background processing threads or the Swing event handling thread. However there probably isn't a need for consistent transactional updates of multiple elements. What would be your recommended approach and why?

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