Spring MVC 模型数据解析

JSP 四大作用域对应的内置对象：pageContext、request、session、application。

模型数据的绑定是由 ViewResolver 来完成的，实际开发中，我们需要先添加模型数据，再交给 ViewResolver 来绑定。

Spring MVC 提供了以下几种方式添加模型数据：

Map
Model
ModelAndView
@ModelAttribute
@SessionAttribute

将模式数据绑定到 request 对象

其实以下方法的目的都是将模式数据绑定到 request 对象。有的直接存入request ，有的间接而已。

1，Map

map会自动封装进去view视图？？？

@RequestMapping("/map")
public String map(Map<String,User> map){
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    map.put("user",user);
    return "view";
}

JSP

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page isELIgnored="false" %>  表示忽略el表达式
<html>
<head>
    <title>Title</title>
</head>
<body>
    ${requestScope.user}
</body>
</html>

2，Model

@RequestMapping("/model")
public String model(Model model){
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    model.addAttribute("user",user);
    return "view";
}

3，ModelAndView

@RequestMapping("/test")
public ModelAndView test(){
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    ModelAndView modelAndView = new ModelAndView();
    modelAndView.addObject("user",user);
    modelAndView.setViewName("view");
    return modelAndView;
}

@RequestMapping("/test2")
public ModelAndView test2(){
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    ModelAndView modelAndView = new ModelAndView();
    modelAndView.addObject("user",user);
    View view = new InternalResourceView("/view.jsp");
    modelAndView.setView(view);
    return modelAndView;
}

@RequestMapping("/test3")
public ModelAndView test3(){
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    ModelAndView modelAndView = new ModelAndView("view");
    modelAndView.addObject("user",user);
    return modelAndView;
}

@RequestMapping("/test4")
public ModelAndView test4(){
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    View view = new InternalResourceView("/view.jsp");
    ModelAndView modelAndView = new ModelAndView(view);
    modelAndView.addObject("user",user);
    return modelAndView;
}

@RequestMapping("/test5")
public ModelAndView test5(){
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    Map<String,User> map = new HashMap<>();
    map.put("user",user);
    ModelAndView modelAndView = new ModelAndView("view",map);
    return modelAndView;
}

@RequestMapping("/test6")
public ModelAndView test6(){
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    Map<String,User> map = new HashMap<>();
    map.put("user",user);
    View view = new InternalResourceView("/view.jsp");
    ModelAndView modelAndView = new ModelAndView(view,map);
    return modelAndView;
}

@RequestMapping("/test7")
public ModelAndView test7(){
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    ModelAndView modelAndView = new ModelAndView("view","user",user);
    return modelAndView;
}

@RequestMapping("/test8")
public ModelAndView test8(){
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    View view = new InternalResourceView("/view.jsp");
    ModelAndView modelAndView = new ModelAndView(view,"user",user);
    return modelAndView;
}

4，HttpServletRequest

@RequestMapping("/request")
public String request(HttpServletRequest request){
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    request.setAttribute("user",user);
    return "view";
}

5，@ModelAttribute

定义一个方法，该方法有注解@ModelAttribute表示在业务方法return之前会被调用，专门用来返回要填充到模型数据中的对象。将对象放入request对象中

@ModelAttribute
public User getUser(){  // 得到pojo对象
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    return user;
}

@ModelAttribute
public void getUser(Map<String,User> map){  // 得到Map对象
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    map.put("user",user);
}

@ModelAttribute
public void getUser(Model model){ // 得到Model对象
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    model.addAttribute("user",user);
}

业务方法中无需再处理模型数据，只需返回视图即可。

@RequestMapping("/test")
public String test(){
    return "view";
}

将模型数据绑定到 session 对象

1、直接使用原生的 Servlet API。

@RequestMapping("/testSession") //从request中取session
public String testSession(HttpServletRequest request){ 
    HttpSession session = request.getSession();
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    session.setAttribute("user",user);
    return "view";
}

@RequestMapping("/testSession2") //直接获取session
public String testSession2(HttpSession session){
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    session.setAttribute("user",user);
    return "view";
}

2、@SessionAttribute

@SessionAttributes(value = {"user","address"})
public class ViewHandler { //注意这里是给类加注解
}

对于 ViewHandler 中的所有业务方法，只要向 request 中添加了 key = “user”、key = “address” 的对象时，Spring MVC 会自动将该数据添加到 session 中，保存 key 不变。

@SessionAttributes(types = {User.class,Address.class})
public class ViewHandler {
}

对于 ViewHandler 中的所有业务方法，只要向 request 中添加了数据类型是 User 、Address 的对象时，Spring MVC 会自动将该数据添加到 session 中，保存 key 不变。

将模型数据绑定到 application 对象

@RequestMapping("/application")
public String application(HttpServletRequest request){
    ServletContext application = request.getServletContext();
    User user = new User();
    user.setId(1L);
    user.setName("张三");
    application.setAttribute("user",user);
    return "view";
}

乱码

<filter>
    <filter-name>encoding</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <init-param>
        <param-name>encoding</param-name>
        <param-value>utf-8</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>encoding</filter-name>
    <url-pattern>/</url-pattern>   这里写成/*
</filter-mapping>

vayneXiao

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