ModelAttribute注解详细使用


org.springframework.web.bind.annotation.ModelAttribute注解类型将请求参数绑定到Model对象。
@ModelAttribute注解只支持一个属性value,类型为String,表示绑定的属性名称。

提示:被@ModelAttribute注释的方法会在Controller每个方法执行前被执行,因此在一个Controller映射到多个URL时,要谨慎使用。

实例:@ModelAttribute注解的使用

index.jsp
用于展示调用关于@ModelAttribute注解不同的使用方法。

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
  <h3>测试@ModelAttribute</h3>
  <a href="loginForm1">测试@ModelAttribute(value="")注释返回具体类的方法</a>
  <a href="loginForm2">测试@ModelAttribute注释void返回值的方法</a>
  <a href="loginForm3">测试@ModelAttribute注释返回具体类的方法</a>
  <a href="loginForm4">测试@ModelAttribute和@RequestMapping同时注释一个方法</a>
  <a href="loginForm5">测试@ModelAttribute注释一个方法的参数</a>
  </body>
</html>

FormController
用于接受index.jsp页,a标签(超链接)传递的地址。

@Controller
public class FormController {
    @RequestMapping(value = "/{formName}")
    public String loginForm(@PathVariable String formName){
        return formName;
    }
}

测试@ModelAttribute(value="")注释返回具体类的方法

loginForm1.jsp

<html>
<head>
    <title>Title</title>
</head>
<body>
<h3>测试@ModelAttribute(value="")注释返回具体类的方法 </h3>
<form action="login111" method="post">
    <label for="loginName">登录名:</label><input type="text" id="loginName" name="loginName">
    <input type="submit">
</form>
</body>
</html>

ModelAttribute1Controller

package com.wen.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

@Controller
public class ModelAttribute1Controller {
    //使用@ModelAttribute注释的value属性,来指定model属性的名称,model属性的值就是方法的返回值
    @ModelAttribute("loginName")
    public String userModel1(
            @RequestParam("loginName") String loginName){
        return loginName;
    }
    @RequestMapping(value = "/login111")
    public String login111(){
        return "result1";
    }

}

result1.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
${requestScope.loginName}
</body>
</html>

测试@ModelAttribute注释void返回值的方法

loginForm2.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h3>测试@ModelAttribute注释void返回值的方法</h3>
<form action="login222" method="post">
    <label for="loginName">登录名:</label><input type="text" id="loginName" name="loginName">
    <label for="password">密码:</label><input type="password" id="password" name="password">
    <input type="submit" value="登录">
</form>
</body>
</html>

ModelAttribute2Controller

package com.wen.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

@Controller
public class ModelAttribute2Controller {
    //model属性名称和值由model.addAttribute()实现,前提是要在方法中加入图个Model类型的参数
    @ModelAttribute
    public void userModel2(
            @RequestParam("loginName") String loginName,
            @RequestParam("password") String password,
            Model model) {
        model.addAttribute("loginName", loginName);
        model.addAttribute("password", password);
    }
    @RequestMapping(value = "/login222")
    public String login222(){
        return "result2";
    }
}

result2.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
${requestScope.loginName}
${requestScope.password}
</body>
</html>

测试@ModelAttribute注释访问具体类的方法

loginForm3.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h3>测试@ModelAttribute注释返回具体类的方法</h3>
<form action="login333" method="post">
    <label for="loginName">登录名:</label><input type="text" id="loginName" name="loginName">
    <label for="password">密码:</label><input type="password" id="password" name="password">
    <input type="submit" value="登录">
</form>
</body>
</html>

</body>
</html>

ModelAttribute3Controller

package com.wen.controller;

import com.wen.domain.User;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

import java.util.ArrayList;
import java.util.List;

@Controller
public class ModelAttribute3Controller {
    //静态List<User>集合,此处代替数据库用来保存注册的用户信息
    private static List<User> userList;

    //此构造器,初始化List<User>集合
    public ModelAttribute3Controller() {
        super();
        userList = new ArrayList<>();
        User user1 = new User("test", "123");
        User user2 = new User("admin", "456");
        userList.add(user1);
        userList.add(user2);
    }
    //根据登录名和密码查询用户,用户存在返回用户信息的User对象,不存在返回null
    private User find(String loginName, String password) {
        for (User user : userList) {
            if (user.getName().equals(loginName) && user.getPwd().equals(password)) {
                return user;
            }
        }
        return null;
    }
    //model属性的名称没有被锁定,它由返回类型隐含表示,如这个方法返回User类型,
    //那么这个model属性的名称就是user
    @ModelAttribute
    public User userModel3(
            @RequestParam("loginName") String loginName,
            @RequestParam("password") String password) {
        return find(loginName, password);
    }

    @RequestMapping(value = "/login333")
    public String login333() {
        return "result3";
    }
}

result3.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
${requestScope.user.name}
</body>
</html>

测试@ModelAttribute和@RequestMapping同时注释一个方法

loginForm4.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<body>
<h3>测试@ModelAttribute注释void返回值的方法</h3>
<form action="login444" method="post">
    <label for="loginName">登录名:</label><input type="text" id="loginName" name="loginName">
    <label for="password">密码:</label><input type="password" id="password" name="password">
    <input type="submit" value="登录">
</form>
</body>
</body>
</html>

ModelAttribute4Controller

package com.wen.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class ModelAttribute4Controller {
    /**
     * 视图名称是@RequestMapping的value值——"/login444",即跳转结果
     *
     * @return model属性名称就是value的值
     */
    @RequestMapping(value = "/login444")
    @ModelAttribute(value = "username")
    public String login444() {
        return "admin";
    }
}

login444.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
${requestScope.username}
</body>
</html>

测试@ModelAttribute注释一个方法的参数

loginForm5.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<body>
<h3>测试@ModelAttribute注释一个方法的参数</h3>
<form action="login555" method="post">
    <label for="loginName">登录名:</label><input type="text" id="loginName" name="loginName">
    <label for="password">密码:</label><input type="password" id="password" name="password">
    <input type="submit" value="登录">
</form>
</body>
</body>
</html>

ModelAttribute5Controller

package com.wen.controller;

import com.wen.domain.User;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;

@Controller
public class ModelAttribute5Controller {
    //model的属性名称就是value的值,即"user",model属性对象就是方法的返回值
    @ModelAttribute("user")
    public User userModel5(
            @RequestParam("loginName") String loginName,
            @RequestParam("password") String password){
        User user =new User();
        user.setName(loginName);
        user.setPwd(password);
        return user;
    }
    @RequestMapping(value = "/login555")
    public String login555(@ModelAttribute("user") User user){
        user.setName("管理员");
        return "result5";
    }
}

result5.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
${requestScope.user.name}
</body>
</html>

Tips:@ModelAttribute注解的使用的方法有很多种,非常灵活,我们可以根据业务需求选择使用。


原文链接:https://www.cnblogs.com/guowenrui/p/10363583.html