So yesterday I was attempting to debug an issue in a batch processing module within one of our applications. In short, an assertion was failing deep within Hibernate as it attempted to flush the session. Using a combination of various log statements, I had isolated the problem down to a particular record that the batch process was attempting to update. (BTW: I know you shouldn't be using Hibernate for batch processing - however, we're talking about batches of at most 1000 records here, not millions!) What I really wanted to do was set a breakpoint and examine the state of the objects at runtime; however, I dreaded the thought of clicking through the breakpoint time and time again until I got to the particular record that was causing the problem. "Surely," I thought, "there must be a way to tell the debugger to only break under certain conditions."

So, here's the code I wanted to examine:

public Publication parsePublication(String inputLine) throws ParseException {
        Publication publication = new Publication();

        String[] fields = inputLine.split("\t");

        publication.setPublicationType(fields[0]);
        ...
        return publication;
} 

Essentially, I wanted to break after inputLine.split("\t"); if and only if fields[35] existed and was equal to "PM:16732581." After examining IDEA [1]'s Breakpoint dialog, I noticed a section in the bottom right-hand corner that I'd never played with before:



As it turns out, this is exactly what I needed. If you click on the ellipsis next to the drop menu, you get a context-sensitive editor equipped with code completion:

 

Enter the desired conditions and voila! A conditional breakpoint. It worked like a charm the very first time, and I only had to inspect the breakpoint when the problematic record came up.

Another nice feature of the conditional breakpoint is that if some sort of exception (such as a NullPointerException) occurs while attempting to evaluate the conditional expression, IDEA pops up a dialog informing you what happened and asking if you want to stop at the breakpoint or continue. Nice.