问题：在java代码中设置 了msg但是在jsp页面使用jstl取不出来
原因：创建maven工程时，idea自动添加的web.xml中的jsp页面头约束版本太低
解决方法：将“一”的代码替换为“二”的代码即可
“一”
<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd" >
<web-app>
</web-app>
“二”
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
</web-app>
java代码：
public class Hello implements Controller { @Override public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception { ModelAndView modelAndView=new ModelAndView(); modelAndView.setViewName("hello"); modelAndView.addObject("msg","springMVC的页面输出！"); return modelAndView; } }jsp页面代码：
<body> <h1>Hello页面！</h1> ${msg} </body>