JVMTI native agent (DLL) can not be loaded to a runing Java program - AgentLoadException - native

Question

I struggled on this issue for a few days but didn't get a right answer yet.
Here is the Problem Description:
I wrote a normal Java program (Program-A), and wrote a Windows-based native agent (*.dll, written in C/C++) with Agent_OnLoad, Agent_OnAttach, Agent_OnUnload method, which works fine if using Java command-line flag (-agentlib). Then I wrote another Java program to attach the native agent onto a runing the Java Program-A (see the below code piece for VM attach and loadAgentPath), however I got the exception:
com.sun.tools.attach.AgentLoadException: Failed to load agent library
I tried to change the agentPath (absolute or relative file path) this or that way, none of these works. Should I try some other way to make this work. What I need is to attach a native agent onto a runing java program rather than using command-line flag.
Does anyone know the root cause or a clue for the solution?
BTW, the command line to run attach VM Java code as:
java -Djava.library.path=D:\DevTools\Java7\jre7\bin -classpath .;./tools.jar com.xxx.TestAgentVMAttacher
...
VirtualMachine virtualMachine = com.sun.tools.attach.VirtualMachine.attach(pid); // Note: this code line is executed normally, I am sure the pid is correct
...
agentPath = theFilePath + "/myagent.dll"; // Note: I am sure the dll file path is correct
virtualMachine.loadAgentPath(agentPath,null); // Note: this code line would cause the exception (AgentLoadException) as I mentioned above, no matter how I set the agentPath, even I set it as null, same exception happened.
Environment related info:
- OS: Windows XP
- Java Version: Java(TM) SE Runtime Environment (build 1.7.0-b147)

Answer 1

Eventually I found the answer for my question, I had a wrong method name ('Agent_Attach') in Agent.cpp file, the correct one should be 'Agent_OnAttach', with this fix, my agent lib (.dll) can be loaded to a running Java program now.