What's wrong with my classpath?
Question
I'm trying to make an applet with jPCT. Using jPCT requires that the jPCT jar be added to the classpath. I thought I had it, but I'm still getting a class not found exception about one of jPCT's classes.
My commands:
$ javac -classpath /var/www/html/jpct.jar:. /var/www/html/HelloWorld.java
$ jar cf /var/www/html/HelloWorld.jar /var/www/html/HelloWorld.class
My HTML:
<html>
<head>
<title>Hello World</title>
</head>
<body>
<applet code="HelloWorld"
width=640
height=480
archive="http://applet/HelloWorld.jar,http://applet/jpct.jar">
</applet>
</body>
</html>
I'm using Apache and I have verified that my jars are downloadable from the URLs in my code.
The exact error message:
$ firefox http://applet/HelloWorld.html
java version "1.6.0_22"
OpenJDK Runtime Environment (IcedTea6 1.10.2) (6b22-1.10.2-0ubuntu1~11.04.1)
OpenJDK Server VM (build 20.0-b11, mixed mode)
(firefox-bin:15296): LIBDBUSMENU-GTK-CRITICAL **: dbusmenu_menuitem_property_set_shortcut: assertion `gtk_accelerator_valid(key, modifier)' failed
Unable to use Firefox's proxy settings. Using "DIRECT" as proxy type.
java.lang.NoClassDefFoundError: com/threed/jpct/World
at HelloWorld.init(HelloWorld.java:18)
at sun.applet.AppletPanel.run(AppletPanel.java:436)
at net.sourceforge.jnlp.NetxPanel.run(NetxPanel.java:69)
at java.lang.Thread.run(Thread.java:679)
Caused by: java.lang.ClassNotFoundException: com.threed.jpct.World
at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
at net.sourceforge.jnlp.runtime.JNLPClassLoader$CodeBaseClassLoader.findClass(JNLPClassLoader.java:1348)
at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
... 4 more
Exception in thread "TimerQueue" java.lang.IllegalMonitorStateException
at java.util.concurrent.locks.ReentrantLock$Sync.tryRelease(ReentrantLock.java:155)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.release(AbstractQueuedSynchronizer.java:1262)
at java.util.concurrent.locks.ReentrantLock.unlock(ReentrantLock.java:459)
at java.util.concurrent.DelayQueue.take(DelayQueue.java:205)
at javax.swing.TimerQueue.run(TimerQueue.java:167)
at java.lang.Thread.run(Thread.java:679)
What am I doing wrong?
2 answers
solution1
1 ACCPTED
You have to put your dependencies on the same web server that is serving the Applet .jar file and give the locations either absolutely or relative to the root context of the Applet.
And you have to load your Applet into your web browser from the web server, not from the file system.
Here is the relevant reading materials.
ARCHIVE = archiveList
This OPTIONAL attribute describes one or more archives containing classes and other resources that will be "preloaded". The classes are loaded using an instance of an AppletClassLoader with the given CODEBASE. The archives in archiveList are separated by ",". NB: in JDK1.1, multiple APPLET tags with the same CODEBASE share the same instance of a ClassLoader. This is used by some client code to implement inter-applet communication. Future JDKs may provide other mechanisms for inter-applet communication. For security reasons, the applet's class loader can read only from the same codebase from which the applet was started. This means that archives in archiveList must be in the same directory as, or in a subdirectory of, the codebase. Entries in archiveList of the form ../a/b.jar will not work unless explicitly allowed for in the security policy file (except in the case of an http codebase, where archives in archiveList must be from the same host as the codebase, but can have ".."'s in their paths. )
if your applet is at /var/www/html/Applet.jar then the simplest thing to do is put your dependencies in the exact same location /var/www/html/jcpt.jar and then you can just refer to it without having to worry about calculating the relative path.
Example
<applet code="HelloWorld"
width=640
height=480
archive="HelloWorld.jar,jpct.jar">
</applet>
solution2
-2 2011-06-20 02:24:58
Have you used any server like Tomcat ? If you have, you may need to assign the path of your jar file to it or copy the jpct.jar to the tomcat/lib/ dir .
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