UserMapper.xml:

<select id="selectAllUser" resultType="HashMap">
		select * from user
</select>

UserDao介面：

List<HashMap<String, String>> selectAllUser();

UserService介面：

List<HashMap<String, String>> selectUser();

UserServiceImp：

public List<HashMap<String, String>> selectUser() {
	List<HashMap<String, String>> u = userDao.selectAllUser();
	return u;
}
 

UserController：

@RequestMapping(value="/selectUser")
@ResponseBody
public String selectUser(){
	List<HashMap<String, String>> u = userService.selectUser();
	System.out.println(u.toString()); 
    //結果：[{username=1, password=1221}, {username=2, password=1}]
	String jsonString = JSON.toJSONString(u);
	System.out.println(jsonString); 
    //結果：[{"username":"1","password":"1221"},{"username":"2","password":"1"}]
	return jsonString;
}