Saturday, October 07, 2006

Tip: debug (and patch at runtime) an installed eclipse

Today I had a problem that occurred only in my installed eclipse but not in my runtime workbench.

How to start eclipse so you can attach a debugger?

You have to add the following to the vmargs: -vmargs -Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=9009
The 9009 is used later to attach to eclipse.

How attach to eclipse?
  • create a new Debug->Remote Java Application.
  • Set the port to to 9009 (or whatever you use as the address argument in your eclipse launch)
  • On the Sources tab add the projects that you want to debug..

How to "patch" the running eclipse?

Just modify the code. Actually, I discovered this by accident. My problem was an obvious bug (missing check for null), so I fixed in during the debug session. And the usual eclipse "magic" fixed the bug in my running eclipse. It's the hot code replacement that normally happens. I (falsely) though that would only work when I start a runtime eclipse from within eclipse. But it works in any case.

Now I can fix my running eclipse while I'm normally working. The only downside is, that the two eclipse must use two different workspaces. Too bad.

Here's a flash demo video that shows how to do this step by step.

1 comment:

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