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ByteBuddy IllegalStateException: Attachment provider cannot connect on current JVM

I'm trying to mock a class that gets loaded by some process to return another value.

Say I have

Class A 
{ 
    public static IClassType getTheClass()
    { 
       new ClassB();
    } 
}

And I want that if some process calls ClassA.getTheClass() to return ClassC (which of course implements IClassType)

Somehow I figured out this should be possible with Byte Buddy's hot swapping capabilities. But I fail to install an agent. I tried with the -javaagent:C:\byte-buddy-agent-0.7.1.jar switch wich gives me

java.lang.IllegalStateException: The Byte Buddy agent is not installed or not accessible

as well as with ByteBuddyAgent.install(); which produces

java.lang.IllegalStateException: Attachment provider cannot connect on the current JVM: ByteBuddyAgent.AttachmentProvider.Compound{attachmentProviders=[ByteBuddyAgent.AttachmentProvider.ForJigsawVm.INSTANCE, ByteBuddyAgent.AttachmentProvider.ForToolsJarVm.JVM_ROOT, ByteBuddyAgent.AttachmentProvider.ForToolsJarVm.JDK_ROOT, ByteBuddyAgent.AttachmentProvider.ForToolsJarVm.MACINTOSH]}

on my machine. Does this only work for OpenJDK? Am I missing something?

Solution

  • There was an error in the byte-buddy-agent.jar until recently. Try using a newer version and it should function without a problem.

    The ByteBuddyAgent does indeed only work on JVM's that support some form of tools.jar. (Currently, OpenJDK, OracleJDK and J9.)