JSP頁面代碼：
<form?action="springmvc/ModelAttribute"?method="POST">
????<input?type="hidden"?name="id"?value="1"/>
????age:<input?type="text"?name="age"?value="22"/><br><br>
????username:<input?type="text"?name="username"?value="Tom"/><br><br>
????email:<input?type="text"?name="email"?value="tom@163.com"/><br><br>
????<input?type="submit"?value="Test?ModelAttribute">
</form>

控制器層代碼：
@Controller
@RequestMapping("/springmvc")
//@SessionAttributes(value={"user"},types=String.class)
public?class?SpringMVCTest02?{
	private?static?final?String?SUCCESS?="success";
	
	/**
	?*?18.測(cè)試@ModelAttribute注解
	?*?@param?user
	?*?@return
	?*/
	@RequestMapping(value="/ModelAttribute",method=RequestMethod.POST)
	public?String?test18(UserBean?user)?{
		System.out.println("模擬需要進(jìn)行修改的user對(duì)象:"+user);
		return?SUCCESS;
	}
	
	@ModelAttribute
	public?void?getUser(@RequestParam(value="id",required=false)?Long?id,
						Map<String,?Object>?map)?{
		if?(id?!=?null)?{
			UserBean?user?=?new?UserBean();
			user.setAge((short)21);
			user.setId(new?Long(1));
			user.setUsername("Jerry");
			user.setPassword("123456");
			user.setEmail("jerry@163.com");
			System.out.println("模擬從數(shù)據(jù)庫(kù)獲取的User對(duì)象:"+user);
			map.put("user",?user);
		}
	}
}

這是控制臺(tái)輸出：

模擬從數(shù)據(jù)庫(kù)獲取的User對(duì)象:UserBean?[id=1,?age=21,?email=jerry@163.com,?username=Jerry,?password=123456,?address=null]
模擬需要進(jìn)行修改的user對(duì)象:UserBean?[id=1,?age=22,?email=tom@163.com,?username=Tom,?password=null,?address=null]

需求是把獲取到password賦值給為null的password