SpringMVC----ModelAttribute注解使用

index.jsp

<!-- 模拟修改操作
        1.原始数据：1，Tom,123456,tom@qq.com,25,BJ
        2.要求密码不能被修改
        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="25"/>
         <br>
         <input type="submit" value="submit" />
     </form>



测试代码：

@RequestMapping("/springmvc")
@Controller
public class SpringMVCTest {
    
    private static final String SUCCESS = "success";
    
    @RequestMapping("/testModelAttribute")
    public String testModelAttribute(User user){
        System.out.println("修改："+user);
        return SUCCESS;
    }
}


结果：
修改：User [id=1, username=Tom, password=null, email=tom@qq.com, age=11111]

测试代码：

@RequestMapping("/springmvc")
@Controller
public class SpringMVCTest {
    
    private static final String SUCCESS = "success";
    
    @ModelAttribute
    public void getUser(@RequestParam(value="id",required=false) Integer id,
            Map<String,Object> map){
        if(id!=null){
            //模拟从数据库中获取对象，把对象放进map里面
            User user = new User(1, "Tom", "123456", "tom@qq.com", 25);
            System.out.println("从数据库中获取一个对象"+user);    
            map.put("user", user);
        }
    }
    
    @RequestMapping("/testModelAttribute")
    public String testModelAttribute(User user){
        System.out.println("修改："+user);
        return SUCCESS;
    }
}


结果：
从数据库中获取一个对象User [id=1, username=Tom, password=123456, email=tom@qq.com, age=25]
修改：User [id=1, username=Tom, password=123456, email=tom@qq.com, age=22222]