用Eclipse启动Tomcat5.0后动行JSP时出现java.lang.NoClassDefFoundError: org/apache/commons/el/ExpressionEvaluatorImpl错误,如何解决?

用Eclipse启动Tomcat5.0后动行JSP时出现java.lang.NoClassDefFoundError: org/apache/commons/el/ExpressionEvaluatorImpl错误,如何解决? 用Eclipse启动Tomcat5.0后动行JSP时出现java.lang.NoClassDe