升级Struts2从2.3.20.1版本升级到2.5.5版本后可能报告如下错误：
HTTP Status 500 - Unable to compile class for JSP: type Exception report message Unable to compile class for JSP: description The server encountered an internal error that prevented it from fulfilling this request. exception org.apache.jasper.JasperException: Unable to compile class for JSP: An error occurred at line: [38] in the generated java file: [/var/lib/tomcat7/work/Catalina/localhost/Tools/org/apache/jsp/index_jsp.java] The method getJspApplicationContext(ServletContext) is undefined for the type JspFactory Stacktrace: org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:103) org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:366) org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:468) org.apache.jasper.compiler.Compiler.compile(Compiler.java:378) org.apache.jasper.compiler.Compiler.compile(Compiler.java:353) org.apache.jasper.compiler.Compiler.compile(Compiler.java:340) org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:657) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:357) 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:727) org.apache.struts2.dispatcher.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:110) note The full stack trace of the root cause is available in the Apache Tomcat/7.0.52 (Ubuntu) logs.
也有可能发生如下错误信息：
HTTP Status 500 - java.lang.ClassNotFoundException: org.apache.jsp.index_jsp
具体信息如下图：
比较诡异的是，在Tomcat 8的环境下，是可以正常运行的，但是在Tomcat 7环境下却会报错。造成这个现象的原因就是在引入的Jar包中包含了jsp-api.jar这个Jar包，只要在最后生成的war包中排除这个文件即可。