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/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 org.apache.jasper.servlet.JspServlet.service(JspServlet.java:343) javax.servlet.http.HttpServlet.service(HttpServlet.java:722) 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/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 org.apache.jsp.index_jsp._jspInit(index_jsp.java:31) org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:49) org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:180) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:369) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334) javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
That will happen when you include server-specific libraries of a different server make/version in the/WEB-INF/lib of your web application, such as jsp-api.jar, el-api.jar, servlet-api.jar, etc. You need to remove them all. The /WEB-INF/lib should not contain any server-specific libraries. They belongs in the specific server itself (Tomcat has them in its /lib folder already).
This is by the way a pretty common beginner's mistake whenever they encounter compilation errors on the JSP/Servlet API in their IDE project. This should have been solved differently, namely by integrating the server in the IDE and adding the server as "Target runtime" to the project.
一句话 就是你不能在项目的lib目录中再包含 服务器类提供过jar 比如jsp-api.jar, el-api.jar, servlet-api.jar, 等等