struts2是使用jstl

不是吧，难道我做错了
jstl.jar  standard.jar我都导入了
jsp页面也有<%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %>
但是当<c:out value="${1+1}" />时页面就爆了org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:39)
org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:405)
org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:146)
org.apache.jasper.compiler.Validator$ValidateVisitor.checkXmlAttributes(Validator.java:955)
org.apache.jasper.compiler.Validator$ValidateVisitor.visit(Validator.java:710)
org.apache.jasper.compiler.Node$CustomTag.accept(Node.java:1441)
org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2163)
org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2213)
org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2219)
org.apache.jasper.compiler.Node$Root.accept(Node.java:456)
org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2163)
org.apache.jasper.compiler.Validator.validate(Validator.java:1489)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:157)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:286)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:267)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:255)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:556)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:293)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.struts2.dispatcher.ServletDispatcherResult.doExecute(ServletDispatcherResult.java:139)
org.apache.struts2.dispatcher.StrutsResultSupport.execute(StrutsResultSupport.java:178)
com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:348)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253)
com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:221)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224)
com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223)
com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221)