Spring Web MVC：简单的控制器 - $表达式不起作用

问题描述：

我从Spring Web MVC开始。我有很简单的控制器和视图，但是当我打开页http://localhost:8080/springonly/spring/hello我得到：${message}，不Hello World

任何人都知道什么是错？为什么$-expression没有被识别？

视图 - hello.jsp：

${message}

控制器 - HelloController.java：

import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import org.springframework.stereotype.Controller; 
import org.springframework.web.bind.annotation.RequestMapping; 
import org.springframework.web.servlet.ModelAndView; 

@Controller 
public class HelloController { 

    @RequestMapping("/hello") 
    public ModelAndView hello(HttpServletRequest request, 
      HttpServletResponse response) throws Exception { 
     return new ModelAndView("hello", "message", "Hello World"); 
    } 

}

web.xml：

<web-app> 
    <display-name>Spring Only WebApp</display-name> 

    <servlet> 
     <servlet-name>springonly</servlet-name> 
     <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> 
     <init-param> 
      <param-name>contextConfigLocation</param-name> 
      <param-value>/WEB-INF/config/applicationContext.xml</param-value> 
     </init-param> 
     <load-on-startup>1</load-on-startup> 
    </servlet> 

    <servlet-mapping> 
     <servlet-name>springonly</servlet-name> 
     <url-pattern>/spring/*</url-pattern> 
    </servlet-mapping> 

</web-app>

applicationContext.xml：

<!-- scan for Controllers --> 
<context:component-scan base-package="net.marioosh.spring.springonly" /> 

<!-- view resolver --> 
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"> 
    <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" /> 
    <property name="prefix" value="/WEB-INF/pages/" /> 
    <property name="suffix" value=".jsp" /> 
</bean>

日志说：

2011-03-15 13:43:12,703 DEBUG [DispatcherServlet:693] : DispatcherServlet with name 'springonly' processing GET request for [/springonly/spring/hello] 
2011-03-15 13:43:12,718 DEBUG [DefaultAnnotationHandlerMapping:221] : Mapping [/hello] to HandlerExecutionChain with handler [[email protected]] and 1 interceptor 
2011-03-15 13:43:12,718 DEBUG [DispatcherServlet:769] : Last-Modified value for [/springonly/spring/hello] is: -1 
2011-03-15 13:43:12,718 DEBUG [HandlerMethodInvoker:173] : Invoking request handler method: public org.springframework.web.servlet.ModelAndView net.marioosh.spring.springonly.HelloController.hello(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse) throws java.lang.Exception 
2011-03-15 13:43:12,718 DEBUG [DispatcherServlet:1045] : Rendering view [org.springframework.web.servlet.view.JstlView: name 'hello'; URL [/WEB-INF/pages/hello.jsp]] in DispatcherServlet with name 'springonly' 
2011-03-15 13:43:12,718 DEBUG [JstlView:328] : Added model object 'message' of type [java.lang.String] to request in view with name 'hello' 
2011-03-15 13:43:12,718 DEBUG [JstlView:236] : Forwarding to resource [/WEB-INF/pages/hello.jsp] in InternalResourceView 'hello' 
2011-03-15 13:43:12,718 DEBUG [DispatcherServlet:674] : Successfully completed request

答

你web.xml缺少正确的标题，它应该是这样的：

<web-app 
    xmlns="http://java.sun.com/xml/ns/j2ee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" 
    version="2.4">

如果你离开了这一点，而只是有一个裸露<web-app>，则容器将默认使用旧的EL版本的JSP。

Spring Web MVC：简单的控制器 - $表达式不起作用

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