页面报错： have different Class objects for the type javax/el/ExpressionFactory used in the signature

详细信息如下：
javax.servlet.ServletException: 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/WEB_002dINF/jsp/addStudent_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
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:275)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168)
	org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
	org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1228)
	org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1011)
	org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:955)
	org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

root cause

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/WEB_002dINF/jsp/addStudent_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
	org.apache.jsp.WEB_002dINF.jsp.addStudent_jsp._jspInit(addStudent_jsp.java:33)
	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)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:168)
	org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
	org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1228)
	org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1011)
	org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:955)
	org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
	org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
	org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

问题根源：包冲突引起的，这个类javax/el/ExpressionFactory，在myeclipse的javaee.jar中有，在tomcat的el-api.jar中有，在jpbm的juel.jar中有。

删掉列出的包，用最新的javax.el-api-2.2.4.jar，javax.el-2.2.4.jar放在tomcat的lib中即可www.twitterchina.net