java.lang.LinkageError: loader constraint violation: when resolving interface.

java.lang.LinkageError: loader constraint violation: when resolving interface...

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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 signatureorg.apache.jsp.index_jsp._jspInit(index_jsp.java:23)org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:52)org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:159)org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:329)org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)

JBPM4在Tomca6.0上运行的时候报出上面的异常，是EL的问题，上网找了下资料，原来项目中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

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解决办法如下：

一：把Tomcat6换成Tomcat5.5就ok了。

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，把WEB-INF\lib中的juel.jar, juel-engine.jar, juel-impl.jar删除。

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