今天用jetty做嵌入式web container，来做web项目的integration test，结果发现出现在渲染使用EL表达式的jsp页面时出现异常：
javax.el.ExpressionFactory.newInstance()Ljavax/el/ExpressionFactory;
Caused by: java.lang.NoSuchMethodError: javax.el.ExpressionFactory.newInstance()Ljavax/el/ExpressionFactory;
at org.apache.jasper.compiler.JspUtil.getExpressionFactory(JspUtil.java:1189)
at org.apache.jasper.compiler.JspUtil.validateExpressions(JspUtil.java:651)
at org.apache.jasper.compiler.Validator$ValidateVisitor.visit(Validator.java:760)
at org.apache.jasper.compiler.Node$ELExpression.accept(Node.java:947)
at org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2297)
at org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2347)
at org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2353)
at org.apache.jasper.compiler.Node$Root.accept(Node.java:499)
at org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2297)
at org.apache.jasper.compiler.Validator.validate(Validator.java:1882)
at org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:223)
at org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)
at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:625)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:492)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:378)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:594)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:486)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:542)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:233)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1065)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:413)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:192)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:999)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)
at org.eclipse.jetty.server.Dispatcher.forward(Dispatcher.java:271)
at org.eclipse.jetty.server.Dispatcher.forward(Dispatcher.java:98)
at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:238)
at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:262)
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1157)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:927)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:827)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:735)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:594)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1366)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1337)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:484)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:524)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:233)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1065)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:413)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:192)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:999)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:111)
at org.eclipse.jetty.server.Server.handle(Server.java:351)
at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:454)
at org.eclipse.jetty.server.AbstractHttpConnection.headerComplete(AbstractHttpConnection.java:890)
at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.headerComplete(AbstractHttpConnection.java:944)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:634)
at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:230)
at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:77)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:609)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:45)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:599)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:534)
at java.lang.Thread.run(Thread.java:619)
检查了一下，发现javax.el.ExpressionFactory.newInstance()这个方法是EL2.2版本之后才有的方法，而在EL2.1之中是没有这个方法的，问题很明显：org.apache.jasper中试图调用2.2版本的EL，当时提供的EL的版本是2.1版本，所以解决的方式无非就是两个，要不降低org.apache.jasper的版本，要不提升el的版本。考虑到现在使用的jetty已经是最新的版本8.1.2.v20120308，因此提升EL的版本为2.2更为合适。
修改pom.xml文件，将
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>jsp-api</artifactId>
<version>2.1</version>
<scope>provided</scope>
</dependency>
修改为2.2版本，上述问题顺利解决，之前的el异常不再出现。