tomcat6整合jbpm4.4报错javax/el/ExpressionFactory找不到的解决办法

tomcat6跑jbpm4.4应用中，启动访问时正常成功，但是任何一个jsp页面时报一下错误：

javax.servlet.ServletException: java.lang.LinkageError: loader constraint violation: loader (instance of org/apache/catalina/loader/WebappClassLoader) previously initiated loading for a different type with name "javax/el/ExpressionFactory"
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:275)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	org.displaytag.filter.ResponseOverrideFilter.doFilter(ResponseOverrideFilter.java:125)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:343)
	org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:99)
	org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)
	org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:355)
	org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:109)
	org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:83)

解决办法如下：

删除tomcat6/lib 下面的el-api.jar

把你的应用里的juel-api.jar剪贴到tomcat6/lib下， 注意应用下面不要留juel-api.jar了。

否则会报如下错误：

java.lang.ClassNotFoundException: javax.el.ELResolver