Google app engine demo app jsp page creates 500 error

Hello I am trying out Google app engine and eclipse. I ihave installed the google plug in and have copied the code in the demo exactly. I saw a similar question posted here and I tried the solution of making sure the JDK was checked instead of JRE. I am using the guestbook demo for java and when I get to the part where I add the jsp page I am still getting this error :

HTTP ERROR 500 Problem accessing /. Reason:

Error running javac.exe compiler

Caused by: Error running javac.exe compiler at org.apache.tools.ant.taskdefs.compilers.DefaultCompilerAdapter.executeExternalCompile(DefaultCompilerAdapter.java:509) at org.apache.tools.ant.taskdefs.compilers.JavacExternal.execute(JavacExternal.java:61) at org.apache.tools.ant.taskdefs.Javac.compile(Javac.java:1065) at org.apache.tools.ant.taskdefs.Javac.execute(Javac.java:882) at org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:382) at org.apache.jasper.compiler.Compiler.compile(Compiler.java:472) at org.apache.jasper.compiler.Compiler.compile(Compiler.java:451) at org.apache.jasper.compiler.Compiler.compile(Compiler.java开发者_如何学运维:439) at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:511) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:295) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)

You may have run the ant target before switching JRE to JDK so the launch configuration is old and refers to the JRE which doesn't have a javac.exe.

Try opening the launch configuration (by selecting the Run As... menu entry - the dots are important), and verify that this Java Runtime points to the JDK also. This should fix it. Also verify that you actually have switched the JRE correctly for all of Eclipse in the Preferences.