Use an external compiler
From Resin 3.0
Resin uses a compiler to compile the java code that is generated for jsp, xsl,
and php. The compiler is also used to compile java source files such as
servlets.
Resin's default is to use the "internal" compiler because it is the most likely to be available. Sometimes the internal compiler causes errors, creating exceptions or simply hanging and taking up a thread. The solution is to change the compiler to "javac" in resin.conf:
<javac compiler="javac" args=""/>
Jikes is another option for the compiler, as discussed in the documentation for javac.