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  • Is this the right way to write a ProtocolDecoder in MINA?

    - by phpscriptcoder
    public class CustomProtocolDecoder extends CumulativeProtocolDecoder{ byte currentCmd = -1; int currentSize = -1; boolean isFirst = false; @Override protected boolean doDecode(IoSession is, ByteBuffer bb, ProtocolDecoderOutput pdo) throws Exception { if(currentCmd == -1) { currentCmd = bb.get(); currentSize = Packet.getSize(currentCmd); isFirst = true; } while(bb.remaining() > 0) { if(!isFirst) { currentCmd = bb.get(); currentSize = Packet.getSize(currentCmd); } else isFirst = false; //System.err.println(currentCmd + " " + bb.remaining() + " " + currentSize); if(bb.remaining() >= currentSize - 1) { Packet p = PacketDecoder.decodePacket(bb, currentCmd); pdo.write(p); } else { bb.flip(); return false; } } if(bb.remaining() == 0) return true; else return false; } } Anyone see anything wrong with this code? When a lot of packets are received at once, even when only one client is connected, one of them might get cut off at the end (12 bytes instead of 15 bytes, for example) which is obviously bad.

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  • how to share a variable between two threads

    - by prmatta
    I just inherited some code, two threads within this code need to perform a system task. One thread should do the system task before the other thread. They should not be performing the system task together. The two threads do not have references to each other. Now, I know I can use some sort of a semaphore to achieve this. But my question is what is the right way to get both threads to access this semaphore. I could create a static variable/method a new class : public class SharedSemaphore { private static Semaphore s = new Semaphore (1, true); public static void performSystemTask () { s.acquire(); } public static void donePerformingSystemTask() { s.release(); } } This would work (right?) but this doesn't seem like the right thing to do. Because, the threads now have access to a semaphore, without ever having a reference to it. This sort of thing doesn't seem like a good programming practice. Am I wrong?

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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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  • 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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  • Pointers, links, object and reference count

    - by EugeneP
    String a = "a"; // allocate memory and write address of a memory block to a variable String b = "b"; // in a and b hold addresses b = a; // copy a address into b. // Now what? b value is completely lost and will be garbage collected //* next step a = null; // now a does not hold a valid address to any data, // still data of a object exist somewhere, yet we cannot get access to it. Correct me if there's a mistake somewhere in my reflexions. My question is: suppose anInstance object of type Instance has a property ' surname ' anInstance.getSurname() returns "MySurname". now String s = anInstance.getSurname(); anInstance = null; question is - is it true that getSurname value, namely MySurname will not be garbage collected because and only because it has active reference counter 0, and if other properties of anInstance have a zero reference counter, they'll be garbage collected?

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  • Primary reasons why programming language runtimes use stacks?

    - by manuel aldana
    Many programming language runtime environments use stacks as their primary storage structure (e.g. see JVM bytecode to runtime example). Quickly recalling I see following advantages: Simple structure (pop/push), trivial to implement Most processors are anyway optimized for stack operations, so it is very fast Less problems with memory fragmentation, it is always about moving memory-pointer up and down for allocation and freeing complete blocks of memory by resetting the pointer to the last entry offset. Is the list complete or did I miss something? Are there programming language runtime environments which are not using stacks for storage at all?

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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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  • How to solve following issues?

    - by lakshmi
    hi im using postgresql database, I want to insert my datas into database,but whenever i run the server,it was display the following Error. Error:org.postgresql.util.PSQLException: FATAL: sorry, too many clients already How to solve this problem.My server.properties file is following. Sever.properties File: serverPortData=9042 serverPortCommand=9078 simocoConnectionURL=jdbc:postgresql://127.0.0.1:5432/vTrack?user=postgres&password=postgres dst=1 DatabaseName=vTrack ServerName=127.0.0.1 User=postgres Password=admin MaxConnections=90 InitialConnections=80 PoolSize=100 MaxPoolSize=100 KeepAliveTime=100 SimocoPoolSize=120 SimocoMaxPoolSize=120 SimocoKeepAliveTime=100 PortNumber=5432 Logging=1 Thanks.

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  • Duplicate Prefix Error in Jsp page with Struts

    - by Cricandcric.com
    Hi, i am creating and Configuring the Struts for the first time, when I place the following Code in my jsp page <%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean"%> <%@ taglib uri="http://struts.apache.org/tags-html" prefix="html"%> <%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic"%> <%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles"%> I am getting the error when i move the mouse over the 1st Line "Duplicate Prefix "html" When I move the mouse over the 2nd Line, I am getting as "Duplicate Prefix "html" Similarly for 3rd and 4th Line, Can any one tell me why is this error all about Thanks in advance

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  • How to set a bean property before executing this f:event listener

    - by user
    How to set a bean property from jsf page before executing this f:event listener: <f:event type="preRenderComponent" listener="bean.method}"/> I tried the below code but it does not set the value to the bean property. <f:event type="preRenderComponent" listener="bean.method}"> <f:setPropertyActionListener target="#{bean.howMany}" value="2"/> </f:event> JSF2.1.6 with PF 3.3 EDIT Any issues with this below code? (This works! but I just want to confirm if there are any issues with this!?) <f:event type="preRenderComponent" listener="#{bean.setHowMany(15)}"/> <f:event type="preRenderComponent" listener="#{bean.method}"/>

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  • MacPorts 1.8.2 fails to build db46 on Mac OS X 1.6.3

    - by themoch
    I'm trying to put a development environment on my Mac, and to do so I need to install several packages which require db46. When running sudo port install db46 I get the following error: ---> Computing dependencies for db46 ---> Fetching db46 ---> Attempting to fetch patch.4.6.21.1 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.2 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.3 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.4 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch db-4.6.21.tar.gz from http://distfiles.macports.org/db4/4.6.21_6 ---> Verifying checksum(s) for db46 ---> Extracting db46 ---> Applying patches to db46 ---> Configuring db46 ---> Building db46 Error: Target org.macports.build returned: shell command " cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_databases_db46/work/db-4.6.21/build_unix" && /usr/bin/make -j2 all " returned error 2 Command output: ../dist/../libdb_java/db_java_wrap.c:9464: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9487: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9509: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9532: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9563: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:9588: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9613: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:9638: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9666: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9691: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9716: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9739: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9771: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9796: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9819: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9842: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9867: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jobject' ../dist/../libdb_java/db_java_wrap.c:9899: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9920: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9943: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9966: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jstring' ../dist/../libdb_java/db_java_wrap.c:9991: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:10010: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:10046: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:10071: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' make: *** [db_java_wrap.lo] Error 1 make: *** Waiting for unfinished jobs.... Note: Some input files use unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. cd ./classes && jar cf ../db.jar ./com/sleepycat Error: Status 1 encountered during processing. I have removed my /usr/local folder completely and it does not seem to help.

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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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  • oracle connectivity

    - by jayprakash
    String serverName = "127.0.0.1"; String portNumber = "1521"; String sid = "database"; String url = "jdbc:oracle:thin:@" + serverName + ":" + portNumber + ":" + sid; String username = "scott"; String password = "tiger"; connection = DriverManager.getConnection(url, username, password); Could not connect to the database

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  • Android - Parsing XML with XPath

    - by Ruben Deig Ramos
    First of all, thanks to all the people who's going to spend a little time on this question. Second, sorry for my english (not my first language! :D). Well, here is my problem. I'm learning Android and I'm making an app which uses a XML file to store some info. I have no problem creating the file, but trying to read de XML tags with XPath (DOM, XMLPullParser, etc. only gave me problems) I've been able to read, at least, the first one. Let's see the code. Here is the XML file the app generates: <dispositivo> <id>111</id> <nombre>Name</nombre> <intervalo>300</intervalo> </dispositivo> And here is the function which reads the XML file: private void leerXML() { try { XPathFactory factory=XPathFactory.newInstance(); XPath xPath=factory.newXPath(); // Introducimos XML en memoria File xmlDocument = new File("/data/data/com.example.gps/files/devloc_cfg.xml"); InputSource inputSource = new InputSource(new FileInputStream(xmlDocument)); // Definimos expresiones para encontrar valor. XPathExpression tag_id = xPath.compile("/dispositivo/id"); String valor_id = tag_id.evaluate(inputSource); id=valor_id; XPathExpression tag_nombre = xPath.compile("/dispositivo/nombre"); String valor_nombre = tag_nombre.evaluate(inputSource); nombre=valor_nombre; } catch (Exception e) { e.printStackTrace(); } } The app gets correctly the id value and shows it on the screen ("id" and "nombre" variables are assigned to a TextView each one), but the "nombre" is not working. What should I change? :) Thanks for all your time and help. This site is quite helpful! PD: I've been searching for a response on the whole site but didn't found any.

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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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  • 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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  • Does a HashSet make an internal copy of added Objects?

    - by praks5432
    Let's say I have a function that is recursive and is like this public void someRecur(List<Integer>someList){ if(someBreakCondition) Set.add(someList); for(int i = 0; i < someLen ; i++){ someList.add(someInt); someRecur(someList); someList.remove(someInt); } } Does the remove affect the list that has been put into the set? What should I do to give the set an actual copy of the list?

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  • Where to handle fatal exceptions

    - by Stephen Swensen
    I am considering a design where all fatal exceptions will be handled using a custom UncaughtExceptionHandler in a Swing application. This will include unanticipated RuntimeExceptions but also custom exceptions which are thrown when critical resources are unavailable or otherwise fail (e.g. a settings file not found, or a server communication error). The UncaughtExceptionHandler will do different things depending on the specific custom exception (and one thing for all the unanticipated), but in all cases the application will show the user an error message and exit. The alternative would be to keep the UncaughtExceptionHandler for all unanticipated exceptions, but handle all other fatal scenarios close to their origin. Is the design I'm considering sound, or should I use the alternative?

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