An Oracle JDeveloper How To Document
Written by Shay Shmeltzer, Oracle Corporation
Debugging is probably the activity that Java developers spend the most time on (right after coding and drinking coffee/cola). While there are many Java debugger out there, JDeveloper's debugger isn't "just another debugger". In fact the debugger in JDeveloper has some tricks up-its-sleeve that you won't find in other debuggers. In this article will look at some of these and guide you through using them.
A Java program can have hundreds of variables and parameters. When debugging your code, however, you are usually interested in just some of these variables. This is what the "smart-data" window automatically does for you. It analyzes the source code at the point where you are and finds the variables, fields and expressions that are used at this area. You can always see the full list of variables in the Data tab. You can set the scope that smart data analyzes in the code debugger preferences entry.
In the screenshot you can see that while in the loop only the i,a, and my_str variables are shown. The other strings and the arguments to the method are not shown.
Don't you whish sometimes you could turn back time? Well the JDeveloper debugger let you do just that. No matter where you are in the code while debugging, if you want to go back to a statement you already passed, just place the cursor there, right click and choose "Set Next Statement".
Another sample of when this feature can become useful is if you did a step-over and you actually wanted to do step into. Just set the next statement to be the method call and do "step-in". By the way, you can also skip code execution by placing the curser after that code section.
In JDeveloper a breakpoint doesn't have to mean you are stopping execution, you can tell a breakpoint to do something else. For example one breakpoint can enable another breakpoint. An example of when such a thing will be useful is when you only want to break in one area (will call this B) if another area (we'll call this A) was executed first. To do this show your breakpoint window (CTRL+Shift+R).
Right click on the B breakpoint and set the "Breakpoint Group Name" for it.
Then edit the A breakpoint - in the action-tab uncheck the "Halt Execution" checkbox, and set the "Enable a Group of Breakpoints" to the name you specified for B.
Sometime you want to know what is going on in your Java Heap, this is helpful utility when you are looking to find out if you have memory leaks. The debugger's classes window (View->Debugger->classes menu option) gives you a look into the heap, showing you which classes (and how many instances of each one) are currently in the heap. If you are noticing too many instances you might want to force a garbage collection action. To do this simply choose the Debug->Garbage Collect menu option.
If you need a deeper look into what is the source of each instance, right click on the class and choose Display in Heap. The heap window that comes up shows you all the objects of this specific class. When you have identified a problematic object in this window you can right click on it and choose Show Reference Paths, this will show you the roots of the object.
The Debugger in Oracle JDeveloper offers many utilities that can make your development experience easier. To learn more about the powerful Oracle JDeveloper Debugger check out the online help section : Working with Application Design Tools >
Building and Tuning Applications > Debugging in JDeveloper.