SpringMVC学习（8）：ModelAttribute

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由@ModelAttribute标记的方法会在每个目标方法执行之前被SpringMVC调用

可以在提交表单时从数据库中取出数据，然后使用表单数据更新

在java文件中：

写一个User类：

package springmvc;public class User {private Integer id;private String username;private String password;private String email;private int age;public User(Integer id, String username, String password, String email,int age) {super();this.id = id;this.username = username;this.password = password;this.email = email;this.age = age;}public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}public String getEmail() {return email;}public void setEmail(String email) {this.email = email;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}@Overridepublic String toString() {return "User [id=" + id + ", username=" + username + ", password="+ password + ", email=" + email + ", age=" + age + "]";}}

在方法处理类中：

package springmvc;import java.util.Map;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 springmvc.User;@Controller@RequestMapping("/springmvc")public class HelloWorld {private static final String SUCCESS = "success";@ModelAttributepublic void getUser(@RequestParam(value="id", required=false) Integer id,Map<String, Object> map) {if (id != null) { //模拟访问数据库User user = new User(1, "Tom", "123456", "tom@qq.com", 12);System.out.println("从数据库中获取一个对象: " + user);map.put("user", user);}}@RequestMapping("/testModelAttribute")//public String testModelAttribute(@ModelAttribute("user") User user) {public String testModelAttribute(User user) {System.out.println("修改： " + user);return SUCCESS;}}

在index.jsp中：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"    pageEncoding="ISO-8859-1"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>SpringMVC</title></head><body><!-- 模拟修改操作1.原始数据为:1,Tom,123456,tom@qq.com,122.密码不能修改3.表单回显，模拟操作直接在表单填写对应的属性值 --><form action="springmvc/testModelAttribute" method="post"><input type="hidden" name="id" value="1"/>username: <input type="text" name="username" value="Tom"/><br>email: <input type="text" name="email" value="tom@qq.com"><br>age: <input type="text" name="age" value="12"><br><input type="submit" value="Submit"></form></body></html>

运行起来可以看到效果：

可以看到成功修改了age属性

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