mybatis的強大之處一：resultMap

場景：

model：

package com.lgy.model;

public class User {
	private Integer userId;
	
	private String username;
	
	private Integer age;

	public Integer getUserId() {
		return userId;
	}

	public void setUserId(Integer userId) {
		this.userId = userId;
	}

	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public Integer getAge() {
		return age;
	}

	public void setAge(Integer age) {
		this.age = age;
	}
}
 

CREATE TABLE `user` (
  `user_id` int(11) NOT NULL AUTO_INCREMENT,
  `username` varchar(32) DEFAULT NULL,
  `age` int(11) DEFAULT NULL,
  PRIMARY KEY (`user_id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

Mappers片段：

<select id="findOneById"  parameterType="java.lang.Integer" resultType="user">
    select * from user where user_id = #{id}
  </select>
 

1.配置resultMap，resultMap會根據property和column進行隱射：

  <resultMap type="com.lgy.model.User" id="userResultMap">
  		<id column="user_id" property="userId" />
  		<result column="username" property="username" />
  		<result column="age" property="age" />
  </resultMap>
 

2.書寫sql語句寫成別名

<select id="findOneById"  parameterType="java.lang.Integer" resultType="user">
    select user_id as userId,username,age from user where user_id = #{id}
  </select>