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  • Why is hibernate open session in view considered a bad practice?

    - by HeDinges
    And what kind of alternative strategies do you use for avoiding LazyLoadExceptions? I do understand that open session in view has issues with: Layered applications running in different jvm's Transactions are committed only at the end, and most probably you would like the results before. But, if you know that your application is running on a single vm, why not ease your pain by using an open session in view strategy?

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  • Jave JIT compiler compiles at compile time or runtime ?

    - by Tony
    From wiki: In computing, just-in-time compilation (JIT), also known as dynamic translation, is a technique for improving the runtime performance of a computer program. So I guess JVM has another compiler, not javac, that only compiles bytecode to machine code at runtime, while javac compiles sources to bytecode,is that right?

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  • How mature is java.lang.instrument?

    - by Juan Tamayo
    Hi Everyone, I'll be working on a project for instrumenting a relatively complex java application, and I'm planning to use java.lang.instrument to hook into the JVM and redefine classes before they're loaded. What is your take on this package? Is it well supported across JVMs? Does it work well with Hotspot? Thanks!

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  • Does generation of debug information to JSP classes add much to javac execution time?

    - by Rich
    Hi I am looking looking into the options for tweaking the performance of JBoss 5.1.0 and one of the options available to me is to disable the generation of debug information when compiling JSPs. I know that the presence/absence of debug information for the JVM makes no real difference, but does the generation of that debug information add much to compile time? Thanks in advance Richard

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  • What language/compiler for native running of application in any windows(XP/Vista/7) platform?

    - by Xinxua
    Hi, I want to develop an application that runs on any windows platform (XP, Vista, 7) but does not require a dependency like .NET Framework or JVM. I have given the other requirements below: Runs in any windows platform Must have GUI libraries to create windows/primitive controls I also want the output file size of the application to be minimal (So cannot include .net frameword etc in the exe file) Any suggestions for this requirement?

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  • Is Tomcat 6 ready for continuous integration or how to get it work?

    - by Philipp Sende
    Hello stackoverflow community, I'm looking for a hint how to make tomcat CI ready or an servlet container / application container which stand often redeploys like they happen when using hudson ci. I experienced that Tomcat 6 does not properly undeploy webapps, leaving classes in jvm. For example I monitored tomcat 6 with VisualVM: on start 2000 classes, on deploy of an app 3000 after redeploy 4000 and redeploy 5000 classes and so on - leading to crashes, memory leaks... Okay hope one have a hint on tomcat and continuous-integration or other app servers. Best,

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  • Having another static method as the entry point of the java program?

    - by GK
    As we all know java program will start executing from the main method of the class. So was curious to know that is there any other way by which we can make another static method as the entry point, that is can we override this property of the JVM to start with some other method than main? many of you will ask why do you want to do this? so want to make it clear that its just a curiosity to know about. And if it is there then it might help in many ways

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  • Java Beginner question about String[] args in the main method

    - by happysoul
    So I just tried excluding String[] args from the main method It compiled alright ! But JVM is showing an exception Why did it compile when String[] args HAS to be included every time ? What is going on here ? Why won't it show a compilation error ? typing this made me think that may be compiler did not see it as THE main method ..is that so ?

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  • How to lock files in a tomcat web application?

    - by yankee
    The Java manual says: The locks held on a particular file by a single Java virtual machine do not overlap. The overlaps method may be used to test whether a candidate lock range overlaps an existing lock. I guess that if I lock a file in a tomcat web application I can't be sure that every call to this application is done by a different JVM, can I? So how can I lock files within my tomcat application in a reliable way?

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  • Meaning of message "operations coalesced during safepoint"

    - by elec
    A java app runs with the following flag: -XX:+PrintSafepointStatistics, and then produces the following line on the standard output console: 2 VM operations coalesced during safepoint Anyone cares to explain what this mean ? More generally - is there a Java reference manual somewhere detailling all JVM flags, their use and, most importantly, the expected output, with relevant explanations ?

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  • Can you make a living as a system programmer?

    - by Helper Method
    Is there still a market for C system programmers? I love Java and some of the newer JVM languages but at the same time I really enjoy low-level system programming under Unix, using C and the GNU toolchain (it makes you feel elitist ;-)). Now I wonder a) is there still a market for C system programmers and b) how much do you earn compared to an app programmer c) is it that much fun in a large scale project?

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  • Using static variables in Android

    - by michael
    Hi, In android, are using static variables a recommended practice? E.g, implementing a Singleton pattern in Java, I usually do: private static A the_instance; public static A getInstance() { if (the_instance == null) { the_instance = new A(); } return the_instance; } Also, when does this get cleaned up by the Android JVM? Thank you.

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  • Concatenative language inrepreter in Java

    - by Vojislav Stojkovic
    I'm interested in finding a concatenative language interpreter in Java. Ideally, it should satisfy the following conditions: It has an interpreter, not (only) a bytecode compiler for JVM. The language itself has decent documentation, not only a few examples and a "I'll document the rest someday" notice. The project is not completely abandoned. In short, I'm looking for a reasonably "alive" concatenative language that can be embedded into Java easily.

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  • What is the best way to manage unix process from java?

    - by erotsppa
    I'm looking for some simple tasks like listing all the running process of a user, or kill a particular process by pid etc. Basic unix process management from Java. Is there a library out there that is relatively mature and documented? I could run a external command from the JVM and then parse the standard output/error but that seems like a lot of work and not robust at all. Any suggestions?

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  • SWT Windows64 bit

    - by Palani
    I am My application it throws the exception below. Exception in thread "main" java.lang.UnsatisfiedLinkError: Cannot load 32-bit SW T libraries on 64-bit JVM. How to solve this?what is the name of jar file needed?

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  • Environment variable expansion in persistence.xml (JPA)

    - by user342495
    I am developing a Eclipse RCP plugin which uses JPA. I tried to specify the database path via a variable give to the JVM on runtime. The property is set correctly but the database is created in a folder named after the variable name (here: ${DBHOME}). <property name="javax.persistence.jdbc.url" value="jdbc:derby:${DBHOME};create=true"/> Is there a possibility to fix this? Thx

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  • Getting version of java in runtime

    - by list
    I need to write version-independent java code, because of some bugs in JDK 1.5 which was fixed in JDK 1.6 now i use the following condition: if (System.getProperty("java.version").startsWith("1.5.")) { ... } else{ ... } Is there another possibility to check this? Will it work for JVM from IBM?

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  • Bad class file error when using Scala 2.8.0-rc1 in Javafx 1.2

    - by aoprisan
    When trying to import scala.Option in a javafx script, I get the following javafxc error: bad class file: scala/Option$$anonfun$orNull$1.class(scala:Option$$anonfun$orNull$1.class) undeclared type variable: A1 Please remove or make sure it appears in the correct subdirectory of the classpath. import scala.Option; ^ I am using Scala 2.8.0-RC1, Javafxc 1.2.3_b36, JVM 1.6.0_18-b07, OS Ubuntu 9.10. The same code was working in Scala 2.7.7 .

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  • JNA array structure

    - by Burny
    I want to use a dll (IEC driver) in Java, for that I am using JNA. The problem in pseudo code: start the server allocate new memory for an array (JNA) client connect writing values from an array to the memory sending this array to the client client disconnect new client connect allocate new memory for an array (JNA) - JVM crash (EXCEPTION_ACCESS_VIOLATION) The JVM crash not by primitve data types and if the values will not writing from the array to the memory. the code in c: struct DataAttributeData CrvPtsArrayDAData = {0}; CrvPtsArrayDAData.ucType = DATATYPE_ARRAY; CrvPtsArrayDAData.pvData = XYValDAData; XYValDAData[0].ucType = FLOAT; XYValDAData[0].uiBitLength = sizeof(Float32)*8; XYValDAData[0].pvData = &(inUpdateValue.xVal); XYValDAData[1].ucType = FLOAT; XYValDAData[1].uiBitLength = sizeof(Float32)*8; XYValDAData[1].pvData = &(inUpdateValue.yVal); Send(&CrvPtsArrayDAData, 1); the code in Java: DataAttributeData[] data_array = (DataAttributeData[]) new DataAttributeData() .toArray(d.bitLength); for (DataAttributeData d_temp : data_array) { d_temp.data = new Memory(size / 8); d_temp.type = type_iec; d_temp.bitLength = size; d_temp.write(); } d.data = data_array[0].getPointer(); And then writing values whith this code: for (int i = 0; i < arraySize; i++) { DataAttributeData dataAttr = new DataAttributeData(d.data.share(i * d.size())); dataAttr.read(); dataAttr.data.setFloat(0, f[i]); dataAttr.write(); } the struct in c: struct DataAttributeData{ unsigned char ucType; int iArrayIndex; unsigned int uiBitLength; void * pvData;}; the struct in java: public static class DataAttributeData extends Structure { public DataAttributeData(Pointer p) { // TODO Auto-generated constructor stub super(p); } public DataAttributeData() { // TODO Auto-generated constructor stub super(); } public byte type; public int iArrayIndex; public int bitLength; public Pointer data; @Override protected List<String> getFieldOrder() { // TODO Auto-generated method stub return Arrays.asList(new String[] { "type", "iArrayIndex", "bitLength", "data" }); } } Can anybody help me?

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  • Using database in Android

    - by Paul
    Does anyone know a good step by step tutorial for using sqlite on Android? I've found this: http://developer.android.com/guide/topics/data/data-storage.html#db and it ok to start with, but then it wants me to jump into other source code then its difficult to follow. I've tried others on the web, one from screaming penguin and that just kept causing errors with JVM. Advice greatly appreciated. I need to: Create database, with several tables (auto id, declare type) update get

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  • Linux configurations that would affect Java memory usage?

    - by wmacura
    Hi, Background: I have a set of java background workers I start as part of my webapp. I develop locally on Ubuntu 10.10 and deploy to an Ubuntu 10.04LTS server (a media temple (ve) instance). They're both running the same JVM: Sun JVM 1.6.0_22-b04. As part of the initialization script each worker is started with explicit Xmx, Xms, and XX:MaxPermGen settings. Yet somehow locally all 10 workers use 250MB, while on the server they use more than 2.7GB. I don't know how to begin to track this down. I thought the Ubuntu (and thus, kernel) version might make a difference, but I tried an old 10.04 VM and it behaves as expected. I've noticed that the machine does not seem to ever use memory for buffer or cache (according to htop), which seems a bit strange, but perhaps normal for a server? (edited) Some info: (server) root@devel:/app/axir/target# uname -a Linux devel 2.6.18-028stab069.5 #1 SMP Tue May 18 17:26:16 MSD 2010 x86_64 GNU/Linux (local) wiktor@beastie:~$ uname -a Linux beastie 2.6.35-25-generic #44-Ubuntu SMP Fri Jan 21 17:40:44 UTC 2011 x86_64 GNU/Linux (edited) Comparing PS output: (ps -eo "ppid,pid,cmd,rss,sz,vsz") PPID PID CMD RSS SZ VSZ (local) 1588 1615 java -cp axir-distribution. 25484 234382 937528 1615 1631 java -cp /home/wiktor/Code/ 83472 163059 652236 1615 1657 java -cp /home/wiktor/Code/ 70624 89135 356540 1615 1658 java -cp /home/wiktor/Code/ 37652 77625 310500 1615 1669 java -cp /home/wiktor/Code/ 38096 77733 310932 1615 1675 java -cp /home/wiktor/Code/ 37420 61395 245580 1615 1684 java -cp /home/wiktor/Code/ 38000 77736 310944 1615 1703 java -cp /home/wiktor/Code/ 39180 78060 312240 1615 1712 java -cp /home/wiktor/Code/ 38488 93882 375528 1615 1719 java -cp /home/wiktor/Code/ 38312 77874 311496 1615 1726 java -cp /home/wiktor/Code/ 38656 77958 311832 1615 1727 java -cp /home/wiktor/Code/ 78016 89429 357716 (server) 22522 23560 java -cp axir-distribution. 24860 285196 1140784 23560 23585 java -cp /app/axir/target/a 100764 161629 646516 23560 23667 java -cp /app/axir/target/a 72408 92682 370728 23560 23670 java -cp /app/axir/target/a 39948 97671 390684 23560 23674 java -cp /app/axir/target/a 40140 81586 326344 23560 23739 java -cp /app/axir/target/a 39688 81542 326168 They look very similar. In fact, the question now is why, if I add up the virtual memory usage on the server (3.2GB) does it more closely reflect 2.4GB of memory used (according to free), yet locally the virtual memory used adds up to a much more substantial 4.7GB but only actually uses ~250MB. It seems that perhaps memory isn't being shared as aggressively. (if that's even possible) Thank you for your help, Wiktor

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  • Tomcat memory issue

    - by user305210
    Hello, I have noticed that my application that is running on Tomcat 5 starts with 1gig of memory and as soon as it starts receiving requests from client, the memory starts dropping until it is down to 100MBs and troubles start from there. I am looking at /manager/status page of tomcat under JVM section where "Free Memory", "Total Memory", "Max Memory" is listed. Is this an indicator of memory leak? Memory does not seem to be freed-up automatically even if there are no requests coming from client machines.

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  • Installer for web application

    - by Xinus
    We have developed a web application which is to be deployed by nontechnical person. Therefor I want to create an installer for it. Installer has functions of installing JVM, Apache Tomcat, and the web application war file depending on whether they are installed or not. Is there any installation suit which I can use to achieve this?

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