Debugging JSP in Intellij 2019 Ultimate
Answered
I have successfully configured the Tomcat in debug mode in Edit configurations. The break point in the JSP works as well.

But my problem is as follows :
a) How to evaluate the EL expressions in evaluate window ? If that is not possible what use can we get by putting breakpoints in JSP code ?
b) Can IntelliJ show me the servlet code that is generated out of this JSP ? From this stackoverflow question , I know how to see it manually.
c) In case of any error in JSP , like the 500 one , the tomcat shows the stacktrace of the servlet code generated out of this JSP. How should I map that in JSP line in IntelliJ ?
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IntelliJ IDEA doesn't support it:
https://youtrack.jetbrains.com/issue/IDEA-89604
https://youtrack.jetbrains.com/issue/IDEA-169951
You can view the generated code if you add a new content root for the module that will point to a directory with the generated classes like c:\Users\<user>\.IntelliJIdea2019.1\system\tomcat\Unnamed_TomcatHotDeploy\work\Catalina\localhost\ROOT\.
Mapping work automatically in the debugger, but there is no way to open the stacktrace and map it automatically.
You can copy/paste the statement from the generated Java code to the evaluation dialog like this:
(java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${u.param}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null);Adding all the Tomcat jars into the server library is needed for this to work properly:
Thnx for the reply.
It seems to me that putting a breakpoint in JSP in IntelliJ is of not much help. I was curious if there are some scenarios where it will be helpful ? Especially for end users who don't want to delve into all that Jasper code to get things evaluated.
You can debug the flow control (logic conditions, loops) and other aspects of the JSPs.