oader constraint violation: when resolving interface method "javax.servlet.jsp.J

 Servlet.service() for servlet jsp threw exception
java.lang.LinkageError: loader constraint violation: when resolving interface method "javax.servlet.jsp.JspApplicationContext.getExpressionFactory()Ljavax/el/ExpressionFactory;" the class loader (instance of org/apache/jasper/servlet/JasperLoader) of the current class, org/apache/jsp/index_jsp, and the class loader (instance of org/apache/catalina/loader/StandardClassLoader) for resolved class, javax/servlet/jsp/JspApplicationContext, have different Class objects for the type javax/el/ExpressionFactory used in the signature

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jbpm4 在tomcat6 下面ssh2 这个错误！

原因是项目中WEB-INF/lib中的三个jar包(juel.jar, juel-engine.jar, juel-impl.jar)和

tomcat6下lib中jar包(el-api.jar)冲突

解决方法：

方法一：换成tomcat5.5 一点问题也没有了

方法二：将juel.jar, juel-engine.jar, juel-impl.jar这三个包复制到tomcat6下lib中，

并删除原来的el-api.jar，切记要把WEB-INF/lib中的juel.jar, juel-engine.jar, juel-impl.jar删除。

不然还是要冲突。