Hi I was getting following error when tried running a JSP in a simple JSP + Servlet based application on JBoss4.0 03:09:08,236 ERROR [Engine] StandardWrapperValve[jsp]: Servlet.service() for servlet jsp threw exception Unable to find a javac compiler; com.sun.tools.javac.Main is not on the classpath. Perhaps JAVA_HOME does not point to the JDK at org.apache.tools.ant.taskdefs.compilers.CompilerAdapterFactory.getCompiler(CompilerAdapterFactory.java:105) I ensured tools.jar was present in: 1. project library 2. %JAVA_HOME%\lib 3. C:\JBoss4\server\default\lib I also ensured that JAVA_HOME was my JDK root folder. i.e. set JAVA_HOME=C:\Program Files\Java\jre1.6.0_04 But the problem got solved ONLY after placing "tools.jar" inside the "ext" folder like this C:\Program Files\Java\jre1.6.0_04\lib\ext\tools.jar I think there is class loader's problem in JBoss4. Kindly give some helpful comments. Anup Jani View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4223481#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...