Developing SCM Plugin for JDev9i... Deadlock

Question

Hi!
I'm currentlly developing a SCM plugin for JDev9i with the option to use MS Visual Source Safe. I've experienced problems with hanging for a while. I'm using the oracle.ide.scm packages bundled with JDev, and I think I've found where the hangup is caused.
There's a class called oracle.ide.scm.util.SCMProcess which is a process wrapper around another class called oracle.ide.scm.util.SCMShellRunner. The process will recieve output text from standard out and standard error. These outputs must be caught and displayed as they are given to the system. If they are not displayed, JDev will go into deadlock it seams.
These classes have their equals respectivelly in java.lang.Process and java.lang.Runtime. I've used these classes to run a command from disk and they work if you properlly handle the output. The problem with this way of doing things is that these classes does not report back to the scm systems and can cause unexpected results from the other interfaces and classes in the oracle.ide.scm...
Does anybody have any experience in coding plugins of this kind? Have you experienced the same problem and have you found a way around it?
This does not work as it should:
SCMShellRunner rt = SCMShellRunner.getInstance();
SCMProcess p = rt.run(cmd, envArr);
while(!p.isFinished()) {
System.err.println(p.getErrorText());
System.out.println(p.getOutputText());

Answer 1

Hi.
The SCMShellRunner and SCMProcess classes are utilities which you
may find useful in implementing your SCM support; you can still
use java.lang.Runtime and java.lang.Process if you prefer.
However, we strongly recommend that you use SCMShellRunner because:
- On windows systems, the external process is launched in the
context of a shell.
- The output and error streams of the external process are
monitored separate threads to prevent blocking issues because of
buffer overruns.
- A native workaround is used to prevent console windows popping
up every time external processes are launched under Windows.
Not sure what could be causing the deadlock, but I did notice in
your code snippet that you are attempting to print output from the
process before it is finished.
The 'error text' and 'output text' will become available only
when the process has successfully terminated, so I guess you're
seeing an awful lot of "null" in your debug window.
Also, I would suggest using SCMProcess.waitFor() to block until
the process has completed; it will not be so greedy with CPU.
Try something like the following:
SCMShellRunner rt = SCMShellRunner.getInstance();
SCMProcess p = rt.run(cmd, envArr);
p.waitFor();
if (p.getExitCode().intValue() != 0)
// throw SCM exception.
System.err.println(p.getErrorText()); // should be non-null
System.out.println(p.getOutputText()); // should be non-null
Thanks,
Paul. JDev SCM