Resin can't load sun.tools.javac.Main

Question

也面错误：

500 Servlet Exception
Resin can't load sun.tools.javac.Main.  Usually this means that the JDK
tools.jar is missing from the classpath, possibly because of using a JRE
instead of the JDK.  You can either add tools.jar to the classpath or change
the compiler to an external one with <java compiler='javac'/>; or jikes.

java.lang.ClassNotFoundException: sun.tools.javac.Main

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Resin 2.1.6 (built Fri Nov 8 08:18:18 PST 2002)

求助！！！