在JVM中调试多线程Web服务器

Question

I'm developing a multithreaded webserver applet and have been dealing with system.out.println's for the past week or so as my "debugging" tool. As far as I understand it, the .jar I build is split by a builder and put into .html files and then spit out when I access the web server.

I am wondering if there is some way that I would be able to attach a debugger (plugin?) to Java's virtual machine that would allow me to step through the code as I operate the webserver- there are some critical exceptions that are very frustrating to track down. I believe they're timing issues related to the multithreading which makes them even more unreliable when attempting to locate, and may mean that the debugger won't process appropriately. I don't think it matters, but the IDE I'm building in is Netbeans.

I've taken over a previous developer's hastily-not-quite-finished project and am in well over my head. =/ Thanks in advance for any possible solutions, I appreciate it.

Answer 1

Sure you can.

You need to start the web server JVM with suitable arguments allowing it to be debugged remotely. You can see at http://download.oracle.com/javase/1.3/docs/tooldocs/win32/jdb.html how to do it. jdb is available in the JDK along with javac. You then launch your IDE debugger to connect to your JVM and tell it where the source for your classes is located. Remember to compile with debug information.

As you have it inside Netbeans already then consider just launching it in debug mode as then all the extra work described above will be done automatically for you.