Jar文件无法运行，提取的类运行良好

Question

I apoligize if this has been asked before but I have been unable to find anything that is the same.

I created a simple jar(myFailingJar.jar) file with two classes a main class and a simple class that accesses a class and its functions from another jar file (CCJAPI.jar).

The main class just instantiates the simple class, the simple class loads a shared library object and calls a function within CCJAPI.jar that crosses over JNI.

When run as a jar file with this command it fails because it can't find a class in CCJAPI.jar which is on the classpath: java -classpath /home/scott:/home/scott/CCJAPI.jar -jar myFailingJar.jar

Starting

Exception in thread "main" java.lang.NoClassDefFoundError: ccjni/DeviceManager
    at DetachedManager.DetachedDeviceManager.startManager(DetachedDeviceManager.java:24)
    at DetachedManager.Main.main(Main.java:19)
Caused by: java.lang.ClassNotFoundException: ccjni.DeviceManager
    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:323)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
    at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:336)

If I extract the contents of the myFailingJar.jar file and run with this command it works, which as far as I can tell just goes to the extracted class files and runs the : java -classpath /home/scott:/home/scott/CCJAPI.jar DetachedManager.Main

Starting ** Started ** Success = - Going to crash now

Here is both source files contents:

Source of Main

package DetachedManager;

public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        DetachedDeviceManager devMgr = new DetachedDeviceManager();
        if( devMgr.startManager() )
        {
            System.out.println("Success = - Going to crash now");
        }

    }

}

Source of simple class:

package DetachedManager;

import ccjni.DeviceManager;

public class DetachedDeviceManager {

    {
        System.load("/usr/lib/libccJNI.so");
    }

    public boolean startManager()
    {
        System.out.println("Starting");
        DeviceManager.start();
        System.out.println("** Started ** ");
        return true;
    }

}

The only difference is that one is tyring to run the compiled class from within the jar file and the other is running it outside the jar file. It must be some type of classpath or path issue that I have not been able to figure out. Any help would be much appreciated.

Answer 1

You probably are not creating the correct jar with the correct dependancies . Use the eclipse export (Right click on a project --> Export ), This will also create the required manifest file.

Using this should be helpful.

Answer 2

When I specified the classpath on the command line I thought that should be sufficient for any jar file loaded into the java environment to find a jar file, apparently it is not. I ended up having to add the class path into the manifest file even though that path was specified on the command line.

Here is the failing manifest:

Manifest-Version: 1.0
Created-By: 1.6.0_0 (Sun Microsystems Inc.)
Main-Class: DetachedManager.Main

Here is the successful manifest

Manifest-Version: 1.0
Created-By: 1.6.0_0 (Sun Microsystems Inc.)
Class-Path: lib/CCAPI.jar
Main-Class: DetachedManager.Main

Thanks to all for listening and giving me an idea of where and what to look at.