关于jstl中c:cout标签的输出问题

项目中，配置文件都正确
jstl标签库引入也正确
在jsp页面中，只是EL表达式输出值正确
如果用<c:out value="hello">,能够正确输出
但是如果使用<c:out value="${el表达式}"，则报错
错误信息如下：HTTPステータス 500 - --------------------------------------------------------------------------------type 例外レポートメッセージ 説明 The server encountered an internal error () that prevented it from fulfilling this request.例外 javax.servlet.ServletException: /jstlTest.jsp(33,8) TLD又はタグファイル中のattribute指示子に従って属性valueはどんな式も受け付けません
org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:286)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:449)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
原因 org.apache.jasper.JasperException: /jstlTest.jsp(33,8) TLD又はタグファイル中のattribute指示子に従って属性valueはどんな式も受け付けません
org.apache.jasper.compiler.DefaultErrorHandler.jspError(DefaultErrorHandler.java:40)
org.apache.jasper.compiler.ErrorDispatcher.dispatch(ErrorDispatcher.java:407)
org.apache.jasper.compiler.ErrorDispatcher.jspError(ErrorDispatcher.java:148)
org.apache.jasper.compiler.Validator$ValidateVisitor.checkXmlAttributes(Validator.java:952)
org.apache.jasper.compiler.Validator$ValidateVisitor.visit(Validator.java:706)
org.apache.jasper.compiler.Node$CustomTag.accept(Node.java:1442)
org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2164)
org.apache.jasper.compiler.Node$Visitor.visitBody(Node.java:2214)
org.apache.jasper.compiler.Node$Visitor.visit(Node.java:2220)
org.apache.jasper.compiler.Node$Root.accept(Node.java:457)
org.apache.jasper.compiler.Node$Nodes.visit(Node.java:2164)
org.apache.jasper.compiler.Validator.validate(Validator.java:1484)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:167)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:296)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:277)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:265)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:564)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:299)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.struts.chain.commands.servlet.PerformForward.handleAsForward(PerformForward.java:113)
org.apache.struts.chain.commands.servlet.PerformForward.perform(PerformForward.java:96)
org.apache.struts.chain.commands.AbstractPerformForward.execute(AbstractPerformForward.java:54)
org.apache.struts.chain.commands.ActionCommandBase.execute(ActionCommandBase.java:51)
org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
org.apache.commons.chain.generic.LookupCommand.execute(LookupCommand.java:305)
org.apache.commons.chain.impl.ChainBase.execute(ChainBase.java:191)
org.apache.struts.chain.ComposableRequestProcessor.process(ComposableRequestProcessor.java:283)
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1913)
org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:449)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)