java.lang.ClassNotFoundException while executing a class file from inside a jar

Question

I created a jar file in windows & copied it to linux and tried to execute with the following command:

java -jar Test.jar com.dcat2.messaging.datatransfer.Test

I am getting an exception as follows:

Exception in thread "main" java.lang.NoClassDefFoundError: Test
Caused by: java.lang.ClassNotFoundException: Test
    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
Could not find the main class: Test. Program will exit.

I am executing this command in the same location where i have the jar file.

Here is my java code:

package com.dcat2.messaging.datatransfer;

public class Test {
public static void main(String[] args) {
    System.out.println("Test App : " + args[0]);

}
}

The jar -tf command's output is as follows:

jar -tf Test.jar
META-INF/
META-INF/MANIFEST.MF
com/
com/dcat2/
com/dcat2/messaging/
com/dcat2/messaging/datatransfer/
com/dcat2/messaging/datatransfer/Test.class

Can anyone help please?

JB Nizet · Accepted Answer · 2012-06-28 07:12:41Z

1

java -cp Test.jar com.dcat2.messaging.datatransfer.Test

The -jar option launches the class that is indicated as the main class in the manifest of the jar file (and which must be the Test class, in the default package, in your case).

The -cp option sets the classpath to use for the app which, in this case, only contains your test jar.

answered Jun 28, 2012 at 7:12

JB Nizet

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4 Comments

user1407668 Over a year ago

Thank you so much ...It worked :) One more doubt...So, If I am executing this command from some another location, how should i set the classpath and execute?

JB Nizet Over a year ago

java -cp /path/to/the/Test.jar com.dcat2.messaging.datatransfer.Test. The path can be absolute or relative.

Tomer Over a year ago

BTW, it is possible , using Eclipse, to package the jar with its dependencies so your jar will contain all the other jars it needs. and then you can run it with no '-cp'

user1407668 Over a year ago

I tried that... But it says "Could not find or load main class Test.jar"

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