debug JSP from eclipse

Question

Does anyone know of a good tool for debugging JSPs from within Eclipse? I'd like to be able to set and watch breakpoints, step through the Java code/tags, etc within Eclipse while the app is running (under JBoss in my case).

Presumably, it's reasonably straightforward to debug the servlet class that's generated from a JSP, but it's also fairly unappealing.

Solution 1

If you have WTP installed, you can set breakpoints within a JSP and they work fine in a regular "remote debug" session. However, once you've stopped on a breakpoint, stepping through the code is nigh on impossible and finding whatever it is that you wish to inspect takes a lot of digging around in the "Variables" view.

Solution 2

If you are having to use a debugger in a JSP, chances are very good that you are doing things in the JSP that you shouldn't be. I recommend that you think very hard about whether your current implementation is using good MVC design practice. JSPs really should be about presentation, which should rarely (if ever) require debugging.

If you have certain logic constructs that you are having to implement in JSP, consider implementing them using a custom tag (which is easy to debug in an IDE), or do the processing in controller servlet that presents the data in an easy to digest form for the JSP.

Solution 3

Within Eclipse, you can put breakpoints to your jsp file, step through the Java code/tags, etc.
However the only view you can use while debugging is the Variables view to inspect the value of any variable.

And one more thing, you can not see the value for example of this expression:
<%= response.encodeURL("ProcessLogin.jsp") %>
just the value of the variable response.