Finding Errors in Java classes

Hello,
I am relatively new to camunda and I found it difficult to get needed information about Errors in the Java classes and Html forms I am including in my processes. I am using tomcat and other then the catalina.out file I cannot find other logs which give me Information about Errors in the Java classes I am using.
My Problem is that the feedback which the webapps give me only show a short Error Message like this for example.


Are there log files which I just haven’t found yet that give more detailed information about where or at which lines in the java classes the errors occur? Or is there a way to check the classes for functionality in eclipse before I create the war file?The same problem with HTML code I include in Forms. The web console give me feedback to the error but not where in the code to exactly search for it.
I would appreciate some information here because this problem requires a lot of extra work I think I could use for better.