How do I start and suspend Java Application from say C++ program

Question

I want to start a Java application via C++ and on some condition i want to suspend the same program not terminate , but suspend

Answer 1

Have you tried running the virtual machine from your C++ application ? You can start Java applications from your C++ application using JNI after starting the Virtual machine from within your C++ application. According to the Java documentation you can even now stop the virtual machine from within your C++ program.
I haven't looked at the 'suspend' detail but I suppose it will not be a problem to call a method via JNI to set a flag to suspend a thread etc.
There is a tutorial: 'Invoking the Java Virtual Machine' at the following URL: http://java.sun.com/docs/books/tutorial/native1.1/invoking/invo.html.
This example seems to work only for version1.1 of the JDK. For JDK1.3, version 1.2, (I am not so sure whether I fully understand Sun's version numbers for Java yet) there is some updates on the JNI for starting the VM from C++. This article is called 'JNI Enhancements'. The URL for this article is:
http://java.sun.com/j2se/1.3.0/docs/guide/jni/jni-12.html
You have to set version to: JNI_VERSION_1_2
There is only one problem. I get an error when calling JNI_CreateJavaVM from C++. I could not find any documentation that indicates how you can go about diagnosing what is causing the problem. Normally in Visual C++ you can just get the probable cause by inspecting GetLastError() or the function itself can return helpful diagnostic (error) codes.
If you manage to start the VM correctly from within Visual C++ please let me know. My email address is [email protected]
good luck
Henko