Question

Is it possible to load a premain-class from a jar library packed within a jar library? I’have the following setup:

Contets of my library:

# jar -tf myLibrary.jar
META-INF/
META-INF/MANIFEST.MF
agent/
agent/myAgent.jar
com/
com/package/
com/package/subpackage/
com/package/subpackage/A.class
com/package/subpackage/B.class
com/package/subpackage/C.class

Now within my MANIFEST.MF I would like to use something like:

Manifest-Version: 1.0
Premain-Class: com.agentpackage.AgentClass
Class-Path: agent/myAgent.jar

But unfortunately if I “use” this setup with -javaagent:myLibrary.jar it gives me the following error message:

java.lang.ClassNotFoundException: com.agentpackage.AgentClass
FATAL ERROR in native method: processing of -javaagent failed

Is it somehow possible to access a premain-class within a .jar file?

My (truncated) ANT build file for myLibrary.jar:

<jar destfile="myLibrary.jar" update="true">
    <zipfileset dir="lib" includes="myAgent.jar" prefix="agent" />
    <manifest>
        <attribute name="Class-Path" value="agent/myAgent.jar" />
        <attribute name="Premain-Class" value="com.agentpackage.AgentClass" />      
    </manifest>
</jar>

I know I could do the following:

<jar destfile="myLibrary.jar" update="true">
    <zipgroupfileset dir="lib" includes="myAgent.jar" />
    <manifest>
        <attribute name="Premain-Class" value="com.agentpackage.AgentClass" />
    </manifest>
</jar>

But then the contents of myAgent.jar gets inflated within myLibrary.jar and thats not what I want. Thanks for any help.

Answer 1

Java doesn’t support loading nested jars.

You’ll have to use inflated version or place these two jars in the same folder and update classpath correspondingly.