Question

I created two jar files, my.common.jar which contain helper classes and methods (mostly static methods). I also created a jar file, test.jar with a main method that calls a static method in a class in my.common.jar.

Everything works fine when I launch main like this:

java -classpath path/to/myjars/my.common.jar:./test.jar test.Tester

Tester is the class in test.jar that contains method main.

But I get NoClassDefFoundError my/common/Myclass when I run it this way:

java -classpath path/to/myjars/my.common.jar -jar test.jar

I tried so hard, but I am not able to figure out why it fails or how to resolve this issue. I do appreciate your help.

—– addendum —-
I forgot to mention that the manifest file in test.jar looks like so:

    Manifest-Version: 1.0
    Build-Jdk: 1.6.0_13
    Created-By: Apache Maven
    Main-Class: test.Tester
    Archiver-Version: Plexus Archiver

Answer 1

You cannot use both -classpath and -jar options on the command line. Use one or the other … but not both.

When you use the -jar option, the command expects to find the entry point class AND the runtime classpath in the JAR file manifest. Your -classpath argument will be ignored, as will the CLASSPATH environment variable. To quote from the java manual page:

“When you use this option, the JAR file is the source of all user classes, and other user class path settings are ignored.”

If your (executable) JAR file needs to use things in other JARs, then it need a Class-Path attribute in the manifest. This attributes value is a space separated list of URLs; see here.

So in your case, you would need to add something like this to your JAR’s manifest:

Class-path: /path/to/myjars/my.common.jar

This page of the Java Tutorial covers this topic, and includes the warning that the Class-path manifest line must be properly terminated with a CR or NL for the JVM to recognize it.