Running a Class in a Jar

I created and deployed a program using Oracle JDeveloper. I tried to run the program in the produced jar using
C:\java -jar archive1.jar
I got the following error
Exception in thread "main" java.util.zip.ZipException: The system cannot find the file specifed
at java.util.zip.ZipFile.open(Native Method)
at java.util.zip.ZipFile.<init>(ZipFile.java:112)
. other similar messages
My classpath is:
classpath=D:\; C:\
path=C:\j2sdk1.4.0\bin
Note: The program compiles and runs successfully in JDeveloper, the error only arises when trying to run the program from command from the deployed archive1.jar.
thanks

Unless the .jar file is sitting in the current
directory, you'll need to give a complete path to it.Yes, the .jar file is in the current directory.

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I want to run .class file and .jar file in jdev9i,what should I do?
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Add the .class file containing the public static void main(...) method to the project by clicking on the + toolbar button in the navigator, open the project properties and properly set the additional classpath then right click on the .class in the navigator and say run. It should work, I've just tried it.
Doesn't work for a .jar yet, in JDeveloper 9.0.3 it works both for .class and .jar
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Dinamyc class loading and jar files

I'm new to java. I would like to load some plugins in my application (it's going to be packaged as a jar at the end). I managed to find some dinamyc class loading examples but they search for the classes to load in a directory.
This is the code:
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protected static IPlugin loadPlugin(String name) {
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Exception in thread "main" java.lang.NoClassDefFoundError: pluginsReloaded/plugins/plugin1 (wrong name: pluginsreloaded/plugins/plugin1)
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)
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        at java.lang.Class.forName0(Native Method)
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        at pluginsreloaded.PluginManager.loadPlugin(PluginManager.java:30)
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Java Result: 1As far as I can see it can't find the class. My question is how can I load the class/where can I find it?
Thanks.

You can use the java.util.jar.JarFile class to enumerate the contents of a jar. It's not good practice to search for plugins in this way though. A plugin may well involve serveral classes, which don't all have to be internal. Furthermore its wise to avoid any comitment about the mechaism by which class files are to be fetched. You might want to do it remotely, some time, or load them from a database.
What seesms to be the standard approach is to put a list of plugin classes into the jar as a text file.
Plugins for a given purpose usually implement some specified interface, or extend some abstract class to which their objects can be cast once loaded (without this they aren't really much use).
Say your plugins implment org.myorg.WidgetFactory then you put a list of them, one fully qualified name to a line, in a file or jar entry called META-INF/services/org.myorg.WidgetFactory. You framework picks up all such files from the classpath using ClassLoader.getResources() and loads all the classes whose names if finds, hence you can add new sets of plugins just by adding a new jar or class directory to the class path.

Could not find the main class (with every jar)

This isn't a developer question. I get the error Could not find the main class with every jar I try to open (for example the jar downloaded from https://gjar.dev.java.net/ gives the same problems - and I don't think there is something wrong with that JAR). It isn't a problem with the jar or MANIFEST because the same jar works fine on my laptop. So there is something wrong with my JRE installation, but what?
I tried to remove and reinstall the JRE 6 Update 18 but that didn't work. When I run the JAR with command line java -jar "file.jar" it works fine, but if I dubbelclick on it I get the error message (and it's irritating me).
I'm a bit desperate so I hope that someone here can help me ;)
Thanks in advanced

hai T.B.M ... Sorry to post here... I know that i posted my question in wrong thread..but i dont have another solution to contact with you.. I had seen your answers which are really excellent and helped to do my project..
Now i am having very less time to complete my project and i am very new to JMF.. I am not getting output in JMF video capture ..please check the code and guide me where i gone wrong.......please pardon me once again to post here.. Heres my code
import javax.media.*;
import java.awt.*;
import javax.swing.*;
import java.util.*;
import java.awt.event.*;
import javax.media.protocol.*;
import java.io.*;
import javax.media.control.StreamWriterControl;
public class webcam implements ActionListener,ControllerListener
boolean eomReached = false;
boolean realized = false;
JFrame f;
BorderLayout bd1;
CaptureDeviceInfo device;
MediaLocator m1;
Player player;
Component videoScreen;
JButton b1,b2;
Processor processor;
DataSource ds=null;
DataSink fileWriter=null;
JLabel status=new JLabel("");
public webcam()
try
JFrame f=new JFrame();
JPanel p =new JPanel();
JPanel p1=new JPanel();
device=CaptureDeviceManager.getDevice("vfw:Microsoft WDM Image Capture (Win32):0");
m1=device.getLocator();
System.out.println("1");
processor.configure();
processor = Manager.createProcessor(m1);
processor.setContentDescriptor(new
FileTypeDescriptor(FileTypeDescriptor.MSVIDEO));
ds=processor.getDataOutput();
player.addControllerListener(this);
MediaLocator dest = new MediaLocator("file://foo.avi");
fileWriter = Manager.createDataSink(ds, dest);
fileWriter.open();
ds.connect();
ds.start();
player=Manager.createPlayer(m1);
player.addControllerListener(this);
blockingRealize();
videoScreen=player.getVisualComponent();
b1=new JButton("START");
b2=new JButton("STOP");
bd1=new BorderLayout();
p.setLayout(bd1);
p1.add(b1);
p1.add(b2);
p.add("South",p1);
p.add("East",videoScreen);
f.getContentPane().add(p);
f.setVisible(true);
f.setSize(500,500);
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
b1.addActionListener(this);
b2.addActionListener(this);
catch(Exception e){}
public void actionPerformed(ActionEvent e)
if(e.getSource()==b1)
try{
processor.start();
player.start();
fileWriter.start();
catch(Exception e1){}
if(e.getSource()==b2)
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player.stop();
processor.stop();
processor.close();
fileWriter.close();
catch(Exception e2){}
public static void main(String args[])
webcam obj=new webcam();
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player.realize();
while (!realized) {
try {
wait();
} catch (java.lang.InterruptedException e) {
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System.exit(1);
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Can't load any classes from infobus.jar (WL 6.0 SP1)

Hi,
I am deploying an .ear file, which has one .war file in it. The war file, has
infobus.jar, inside it under \WEB-INF\lib. Whenever in my servlet code I try to
load a class from infobus.jar, I get the following exception :
About to load class javax.infobus.InfoBusDataConsumer<<<<<<<<<<java.lang.ClassNotFoundException: InfoBusDataConsumer
at weblogic.utils.classloaders.GenericClassLoader.findClass(GenericClassLoader.java:178)
at weblogic.utils.classloaders.ChangeAwareClassLoader.findClass(ChangeAwareClassLoader.java:45)
at java.lang.ClassLoader.loadClass(ClassLoader.java:297)
at java.lang.ClassLoader.loadClass(ClassLoader.java:253)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:313)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:120)
at XDILoginForm.init(XDILoginForm.java:99)
at weblogic.servlet.internal.ServletStubImpl.createServlet(ServletStubImpl.java:638)
at weblogic.servlet.internal.ServletStubImpl.createInstances(ServletStubImpl.java:581)
at weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.java:526)
at weblogic.servlet.internal.WebAppServletContext.preloadServlet(WebAppServletContext.java:1078)
at weblogic.servlet.internal.WebAppServletContext.preloadServlets(WebAppServletContext.java:1022)
at weblogic.servlet.internal.HttpServer.loadWARContext(HttpServer.java:499)
at weblogic.servlet.internal.HttpServer.loadWebApp(HttpServer.java:421)
at weblogic.j2ee.WebAppComponent.deploy(WebAppComponent.java:74)
at weblogic.j2ee.Application.deploy(Application.java:175)
at weblogic.j2ee.J2EEService.deployApplication(J2EEService.java:173)
at weblogic.management.mbeans.custom.Application.setLocalDeployed(Application.java:217)
at weblogic.management.mbeans.custom.Application.setDeployed(Application.java:187)
at java.lang.reflect.Method.invoke(Native Method)
at weblogic.management.internal.DynamicMBeanImpl.invokeSetter(DynamicMBeanImpl.java:1136)
at weblogic.management.internal.DynamicMBeanImpl.setAttribute(DynamicMBeanImpl.java:773)
at weblogic.management.internal.DynamicMBeanImpl.setAttribute(DynamicMBeanImpl.java:750)
at weblogic.management.internal.ConfigurationMBeanImpl.setAttribute(ConfigurationMBeanImpl.java:256)
at com.sun.management.jmx.MBeanServerImpl.setAttribute(MBeanServerImpl.java:1356)
at com.sun.management.jmx.MBeanServerImpl.setAttribute(MBeanServerImpl.java:1331)
at weblogic.management.internal.ConfigurationMBeanImpl.updateConfigMBeans(ConfigurationMBeanImpl.java:318)
at weblogic.management.internal.ConfigurationMBeanImpl.setAttribute(ConfigurationMBeanImpl.java:259)
at com.sun.management.jmx.MBeanServerImpl.setAttribute(MBeanServerImpl.java:1356)
at com.sun.management.jmx.MBeanServerImpl.setAttribute(MBeanServerImpl.java:1331)
at weblogic.management.internal.MBeanProxy.setAttribute(MBeanProxy.java:291)
at weblogic.management.internal.MBeanProxy.invoke(MBeanProxy.java:173)
at $Proxy7.setDeployed(Unknown Source)
at weblogic.management.console.pages._panels._mbean._application._jspService(_application.java:303)
at weblogic.servlet.jsp.JspBase.service(JspBase.java:27)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:213)
at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:1265)
at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:1622)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:137)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)
But if I put the infobus.jar on system classpath , everything works out fine.
Can somebody tell me, what is going on

Gseel is right: you try to instantiate an EJB with the BDK.
Enterprise Java Beans are totally different from graphical/GUI beans. EJBs are thought for dealing with business logic like accessing a database, ldap directory and so on. They run on a application server (simply speaking - a java enabled webserver) and do some processing to handle user requests. Enterprise Java Beans usually don't interact directly with the user, they only do the work in the background and forward their results, which are then rendered for the user. Typically they are employed for handling web requests (a user with a browser), but they can also be used for awt/swing applications. Though - let me repeat - they don't appear visually on the screen.
The only similarities between those two bean types are the following: they have getter/setter methods for their properties, they implement Serializeable (or a sub-interface like Externalizable, Remote) and they have a default no-argument constructor.
If you want to run your been you need an application server (your bean is pre-packaged for the Bea Weblogic app-server). If you want to do something graphical, you'll need to search for GUI beans.
dani3l

Applet inside a JAR: Cannot access other classes within the JAR

Hello,
Description
Web app + applet (packaged in a JAR)
I have followed this tutorial
JAR contents
package mypackage
SimpleApplet.class
SimpleObj.class
_"SimpleApplet" uses "SimpleObj"_
package mypackage;
public class SimpleApplet extends JApplet {
    @Override
    public void init() {
        SimpleObj obj = new SimpleObj();
HTML code
<applet archive="SimpleApplet.jar" codebase="." code="mypackage.SimpleApplet.class" width="800" height="600" />
SimpleObj cannot be found (Java Console)
java.lang.NoClassDefFoundError: mypackage/SimpleObj
at java.lang.Class.getDeclaredConstructors0(Native Method)
at java.lang.Class.privateGetDeclaredConstructors(Unknown Source)
at java.lang.Class.getConstructor0(Unknown Source)
at java.lang.Class.newInstance0(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source)
at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassNotFoundException: mypackage.SimpleObj
at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
... 8 more
Caused by: java.io.IOException: open HTTP connection failed:*http://localhost:8080/SimpleApp/mypackage/SimpleObj.class*
at sun.plugin2.applet.Applet2ClassLoader.getBytes(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader.access$000(Unknown Source)
at sun.plugin2.applet.Applet2ClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
... 12 more
Exception: java.lang.NoClassDefFoundError: mypackage/SimpleObj
It looks like JRE does not search for the SimpleObj class inside the JAR, but tries to get it from the server...
Any ideas?
Thanks in advance,
Gerard
Edited by: gsoldevila on Dec 10, 2008 2:05 AM

misread, deleted
Edited by: atmguy on Dec 10, 2008 1:12 PM

NoClassDefFoundError extending class in separate JAR

I have a class Foo which gets called from my servlet (extends HttpServlet) class. Both Foo and the servlet class are located in WEB-INF/classes and are deployed as part of the war file. Class Foo extends class Bar, which is a different .jar file located in the /WEB-INF/lib directory of the webapp. When I attempt to create an instance of Foo, I get the following exception:
java.lang.NoClassDefFoundError: /general/client/common/beans/Bar
     at java.lang.ClassLoader.defineClass1(Native Method)
     at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
     at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
     at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
     at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
     at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
     at java.security.AccessController.doPrivileged(Native Method)
     at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
     at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
     at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)
     at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
     at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1267)
     at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1198)
     at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
     at server.DBServlet.createFoo(DBServlet.java:236)
     at server.DBServlet.processInput(DBServlet.java:333)
     at server.DBServlet.doGet(DBServlet.java:154)
     at server.DBServlet.doPost(DBServlet.java:205)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
     at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:432)
     at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:541)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
     at org.apache.catalina.authenticator.SingleSignOn.invoke(SingleSignOn.java:419)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
     at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:667)
     at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
     at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
     at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
     at java.lang.Thread.run(Thread.java:595)
I'm running this on Windows, and found if I added the classpath the the jar file where the Bar class is located, that it worked fine. But my expectation is that the jar file should have been found because it is in the /WEB-INF/lib dir. There is a line the Tomcat docs that says:
"Last, any JAR containing servlet API classes will be ignored by the classloader. All other class loaders in Tomcat 5 follow the usual delegation pattern."
So maybe I need to do something special to load the Bar class, or there's something strange about the way the classes and jars are being loaded that I don't fully understand. I was able to instantiate the Bar class directly from w/in my servlet class, I just can't create an instance of the Foo class that is in /WEB-INF/classes along with the servlet class. So I'm not convinced that the Bar class or associated jar file isn't being loaded.
I don't want to have to set the classpath explicitly, so I'm looking for advice on why I'm getting this exception and how best to dynamically load the classes I need.
Thanks.
ab.

Thanks for hanging in there so far. Here's the specifics if you want to try to re-create this.
I have a webapp, which contains the class DBServlet:
package com.hm.dhca.server;
public class DBServlet extends HttpServlet
// Stuff
     public void processInput()
          Foo foo = new Foo();
The webapp also contains the class Foo:
package com.hm.dhca.common;
import com.general.client.common.beans.Bar;
public class Foo extends Bar
     public Foo()
          super();
          System.out.println("Foo");
Both of the classes are located in webapps\DHCA\WEB-INF\classes...
The Bar class is in a separate jar called HMJCommon.jar in the webapps\DHCA\WEB-INF\lib dir.
Class Bar looks like this:
package com.general.client.common.beans;
public class Bar
     public Bar()
          System.out.println("Bar");
DBServlet creates an instance of Foo as:
Foo foo = new Foo();
Which throws the Exception:
java.lang.NoClassDefFoundError: com/general/client/common/beans/Bar
     at java.lang.ClassLoader.defineClass1(Native Method)
     at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
     at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
     at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
     at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
     at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
     at java.security.AccessController.doPrivileged(Native Method)
     at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
     at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
     at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)
     at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
     at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1267)
     at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1198)
     at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
     at com.hm.dhca.server.DBServlet.processInput(DBServlet.java:236)
     at com.hm.dhca.server.DBServlet.doGet(DBServlet.java:154)
     at com.hm.dhca.server.DBServlet.doPost(DBServlet.java:205)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
     at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:432)
     at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:541)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
     at org.apache.catalina.authenticator.SingleSignOn.invoke(SingleSignOn.java:419)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
     at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:667)
     at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
     at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
     at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
     at java.lang.Thread.run(Thread.java:595)
Clues:
1. All three classes exist in the locations specified above - I have checked this manually.
2. Within DBServlet, I can create an instance of Bar. But I cannot create an instance of Foo without the exception.
3. If I move the Foo class from package com.hm.dhca.common to package com.hm.dhca.server (same package as DBSerlvet), everything works fine.
4. If I modify Tomcat's classpath to include the HMJCommon.jar, it works fine (as previously discussed).
Theory:
I have a vague theory that what is happening is that two different webappclassloaders are loading the Foo and Bar classes, for whatever reason. As a result, they can't see each other, because neither is up the hierarchy tree from the other.
This does not explain how I can instantiate Bar from DBServlet, but not Foo.
Hope this helps. I think I've corrected previous mistake w/ removing too much from package naming. I'm resorting to the workaround in clue #3 for the moment. But it's not the correct solution, and it's showing that I don't really understand what's going on here.

Don't know package of class in a jar using URLClassLoader

Hello,
i want to load a class out of a jar file but the only thing i know is the classname its the same as the jarname. the problem now is i packed the plugin as nice with packages and my Loader won't find the class without package, what can i do to know the package?
i don't have any main method because it's a plugin loading. i know der should be a possibility to loop through all classes?! or even to find a class implementing an interface (but that was something with ServiceLoader)...how can i do it?
for(int i = 0; files != null && i < files.length; i++) {
     MyClassLoader pluginLoader = null;
     try {
          pluginLoader = new MyClassLoader(MyConstants.MODULES_PATH+files);
     } catch(MalformedURLException e) {
          System.out.println("Exception: " + e.getMessage());
     // cut off extension for className
     int dot = files[i].lastIndexOf(MyConstants.MODULE_EXTENSION);
     String className = files[i].substring(0, dot);
     MyPluginInterface plugin = null;
     try {
          plugin = (MyPluginInterface)pluginLoader.findClass(className).newInstance();
     } catch(Exception e) {
          System.out.println("Exception: " + e.getMessage());
this works (for one of the jars with this package then):plugin = (MyPluginInterface)pluginLoader.findClass("my.package.in.jar."+className).newInstance();
public class MyClassLoader extends URLClassLoader {
     public MyClassLoader (String filenName) throws MalformedURLException {
          super(new URL[]{new File(filenName).toURI().toURL()}, MyClassLoader.class.getClassLoader());
     public Class<?> findClass(String name) throws ClassNotFoundException {
          return super.findClass(name);
thx for you help!

YES! just a bit of work and it's running nice :-)
if(!(Constants.MODULES_PATH.endsWith("/"))) Constants.MODULES_PATH = Constants.MODULES_PATH + "/";
File path = new File(Constants.MODULES_PATH);
if(path.exists() && path.isDirectory()) {
     // find all .jar files
     String[] files = path.list(new FilenameFilter() {
          public boolean accept(File d, String name) { return name.endsWith(Constants.MODULE_EXTENSION); }
     for(int i = 0; files != null && i < files.length; i++) {
          // create class loader for jar
          MySystemClassLoader classLoader = null;
          try {
               classLoader = new MySystemClassLoader(Constants.MODULES_PATH+files);
          } catch(MalformedURLException e) {
               System.out.println("Exception: " + e.getMessage());
          // load service(s)/module(s) (can be more than one in a jar!)
          ServiceLoader<ModuleInterface> moduleLoader = ServiceLoader.load(ModuleInterface.class, classLoader);
          for(ModuleInterface module : moduleLoader) {
               System.out.println("load module: "+module.getClass().getName()+"!");
}and this as class loader (given to the service loader)public class MySystemClassLoader extends URLClassLoader {
     public MySystemClassLoader(String filenName) throws MalformedURLException {
          super(new URL[]{new File(filenName).toURI().toURL()}, MySystemClassLoader.class.getClassLoader());
     public Class<?> findClass(String name) throws ClassNotFoundException {
          return super.findClass(name);
in the jar-file (module/service) you need a file named as the interface (path.to.package.ModuleInterface) inside of a folder "META-INF/services/" and contains just as a string (path.to.package.ModuleImplementation) the name of the implementaion class (in the jar-file)
Edited by: mrp_cologne on Jul 21, 2008 3:55 AM

Is it possible to load classes from a jar file

Using ClassLoader is it possible to load the classes from a jar file?

URL[] u = new URL[1] ;
u[0] = new URL( "file://" + jarLocation + jarFileName + "/" );
URLClassLoader jLoader = new URLClassLoader( u );
Object clsName = jLoader.loadClass( clsList.elementAt(i).toString() ).newInstance();
I get this error message.
java.lang.ClassNotFoundException: ExceptionTestCase
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:297)
at java.lang.ClassLoader.loadClass(ClassLoader.java:253)
// "file://" + fileLocation + fileName + "/" This works fine from a browser.
Is there anything I am missing? Thanks for the reply.

How to run test cases in a jar file using junit?

Hi,
I want to run test cases in a jar file using junit and the jar file is not in the class path. I wrote the following code, but it does not work.
import java.net.URL;
import java.net.URLClassLoader;
import junit.framework.TestResult;
import junit.textui.TestRunner;
public class MyTestRunner {
     public static void main(String[] args) throws Exception{
          URL url = new URL("file:///d:/case.jar");
          URLClassLoader loader = new URLClassLoader(new URL[]{url});
          loader.loadClass("TestCase1");
          TestRunner runner = new TestRunner();
          TestResult result = runner.start(new String[]{"TestCase1"});
          System.out.println(result.toString());
}Any ideas?
Thanks a lot.

Wouldn't it just be easier to put it on the classpath? You're trying to, anyway, with a URLClassLoader, albeit in an entirely unnecessarily complicated way

Small issue: Exception in running java class

I have created a java test.class through Eclipse in some workspace. This class is using mail.jar. It is working fine with eclipse.
But if i copy test.class and mail.jar to c:\ and try to run it. It is giving me runtime exception stating
"Exception in thread "main" java.lang.NoClassDefFoundError: test"
~Aman

You can try java -cp .;mail.jar testWhich should be OK provided that class test is not part of a package, and
that compiling test.java did not result in other .class files.

Loading classes from another jar file

I've set up my jnpl file so that it references a core jar file (contains main() function). The jnlp also references another jar file (app.jar) which contains class files that I load and instantiate dynamically (using ClassLoader). The core.jar file contains a manifest that includes a reference to app.jar.
The app works fine when I use "java -jar core.jar" from the command line.
However, when I wrap the jars using jnlp, I always get a null pointer exception because it cannot find any class that is in the app.jar file. I've tried different strategies, such as trying to load a class file that sits on the server (in a jar file and not in a jar file), but that also fails if I use jnlp (However, it works if I use "java -jar core.jar")
Any ideas what is going on?

This is the "OckCore.jar" manifest before signing:
Manifest-Version: 1.0
Main-Class: com.Ock.OckCore.OckApp
Class-Path: . OckMaths.jar
Created-By: 1.4.0-beta3 (Sun Microsystems Inc.)
Name: com.Ock.OckCore.OckApp.class
Java-Bean: FalseThis is the manifest after signing:
Manifest-Version: 1.0
Main-Class: com.Ock.OckCore.OckApp
Created-By: 1.4.0-beta3 (Sun Microsystems Inc.)
Class-Path: http://hazel/Ock/. http://hazel/Ock/OckMaths.jar
Name: com/Ock/OckCore/OckApp.class
SHA1-Digest: KRZmOryizx9o2L61nN+DbUYCgwo=I have removed a load of irrelevant stuff from the "after" manifest to keep it readable.
note that :-
The OckApp.class loads normally from webstart and tries to load a class from OckMaths.jar.
I can prove that OckApp.class does load because it creates a log file when it does.
The OckApp.class tries to load a class from the OckMaths.jar. This fails if webstart is used but works if OckCore is launched using "java -jar OckCore.jar".
The jars do exist at the location specified by the manifest.
The application launches normally if I use "java -Jar OckCore.jar"
Here is the jnlp file
<?xml version='1.0' encoding='UTF-8'?>
<jnlp
     spec="1.0"
     codebase="http://hazel/Ock"
     href="OckMaths.jnlp">
     <information>
          <title>Ock Maths Demo</title>
          <vendor>Rodentware Inc</vendor>
          <description>Demo of a ported app running as a Java Webstart application</description>
          <description kind="short">An app running as a Java Webstart application"></description>
          <offline-allowed/>
     </information>
     <security>
          <all-permissions/>
     </security>
     <resources>
          <j2se version="1.3"/>
          <jar href="OckCore.jar"/>
          <jar href="OckMaths.jar"/>
     </resources>
     <application-desc main-class="com.Ock.OckCore.OckApp">
</jnlp> I have also signed the jars outside of a webdirectory. I get the following manifest file:
Manifest-Version: 1.0
Main-Class: com.Ock.OckCore.OckApp
Created-By: 1.4.0-beta3 (Sun Microsystems Inc.)
Class-Path: . OckMaths.jar
Name: com/Ock/OckCore/OckApp.class
SHA1-Digest: KRZmOryizx9o2L61nN+DbUYCgwo=
note that :-
The jars do exist at the location specified by the manifest.
The application launches normally if I use "java -Jar OckCore.jar".
The application doesn't launch from webstart.
I've found that cache, but the jar files have been renamed.
OckCore.jar is anOckCore.jar, etc... so I'm not sure if trying to write a cmdline will work anyway.

Accessing classes in external jar files

I have a jar file called main. I want it to be able to acces the classes in another jar file say test.jar how do i do this.
Thank you

ok, if i have this right...
you have 2 directories that hold 2 .jars, right?
plugins/ -------- build/plugins .jar
systemModuals/ ------- DiaryUI and Loader .jar
Your main JAR is diary?
Diary.jar
you want Diary to run with the jars inside plugins and systemmoduals?
you set the "class-path:" tag like this....
write this manifest file. save it as Manifest.txt and put it in your home dir.
Main-Class: YourMainClass
Class-Path: Diary.jar plugins/this.jar systemmoduals/diaryui.jar
<make sure to hit enter, go to the next line>
command line to your parent directory.
jar cmf Manifest.txt Diary.jar build/main/*.class
you should be set to go.
use
jar xf META-INF/MANIFEST.MF
to read the present manifest that netbeans has created
if necessary

Can you only run one main() in a jar?

Hi,
I was just wondering if you can only ever run one main() method from a .jar file? I have a project being developed in Eclipse, consisting of several packages and then several classes with main()s in each of the packages. When the whole project is packaged into one big jar then I can run one of the main() methods by specifying it in the manifest, but as far as I'm aware I can't access the others.
Is there some cunning way to call the main() method of a different class to that specified in the jar manifest, or do I have to compile every class as a separate jar? And if that's the case, is there really any advantage to putting the classes into a jar as opposed to just running from the .class files?
Any help much appreciated. :)
h

Wow, thanks for the quick responses guys!
You can execute the other main methods byexecuting:
java -cp the-class-path TheMainClassIsn't that just what I'd use from the compiled .class
files though?Correct, but you specify the jar on your classpath. e.g.
java -cp myjar.jar TheMainClasss1 or
java -cp myjar.jar TheMainClasss2
For example:
java -cp the-class-path my.class1
java -cp the-class-path my.class2
How does this relate to a single .jar file containing
both of those classes? See above
If I try those commands in the
directory containing the .jar file, I just get a
NoClassDefFoundError (they work fine in the directory
with the .class files though).That's because you didn't specify the classpath in the correct way.
Kaj

Launching classes with java -jar option

hi all,
i have read how to launch a class using the -jar option.
Now i have one additional question.
Suppose that the class that i want to launch contains packages from other jar files.
Can i pack all the other jar files in the same jar, and have the code run by simply calling
java -jar MyClass?
if different jar packages are in the same jar file, can the main class that i want to launch see them?? or do i still
have to specify the -cp option??
thanx in advance and regars
marco

I don't know about having jar files in a jar file, but if you have class files in a jar file, you can make it so you just have to run it as
java -jar MyJar.jar
To make the jar file, you need to add an attribute to the manifest file. Make a text file and call it whatever you want, e.g. manifest.mf or manifest.txt.
Add this line to it:
Main-Class: MyMain
if MyMain is your class with the main method. If MyMain is in a package, then you need to add that too, e.g. mypackage.MyMain.
Now create your jar file as
jar cfm MyJar.jar manifest.mf *.class
After manifest.mf you add all the classes you have with spaces to separate them, or use wildcards.

Running a Class in a Jar

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