This section provides a tutorial example on how to run a Java application and the 'jdb' debugger separately in shared memory mode.
If you ask "Can I launch the debugger ('jdb') and the target application separately?",
the answer is "Yes, you can.". In JDK 1.5, both "jdb" and "java" have been enhanced to use the latest
JPDA (Java Platform Debugger Architecture) technology to give you the following options:
Debugger Target
Option jdb java
1 Shared memory client Shared memory server
2 Shared memory server Shared memory client
3 Socket client Socket server
4 Socket server Socket client
The shared memory options requires that the debugger and the target application to be on the same machine.
Of course, the socket options allow you to run them remotely.
Let's try option #1 first. Open a command window on a windows system and run:
C:\herong>java -agentlib:jdwp=transport=dt_shmem,address=MyHello,server=y,
suspend=y Hello
Listening for transport dt_shmem at address: MyHello
The target application is launched in "shared memory server" mode.
Its execution is suspended. Now open another command window and run:
C:\herong>jdb -attach MyHello
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
Initializing jdb ...
>
VM Started: No frames on the current call stack
main[1] stop in Hello.main
Deferring breakpoint Hello.main.
It will be set after the class is loaded.
main[1] cont
> Set deferred breakpoint Hello.main
Breakpoint hit: "thread=main", Hello.main(), line=3 bci=0
3 System.out.println("Hello world!");
main[1] list
1 public class Hello {
2 public static void main(String[] a) {
3 => System.out.println("Hello world!");
4 }
5 }
main[1] cont
>
The application exited
As you can see, the debugger successfully connected to the target application.
I used "next" command to let the target application to execute the current statement.
