MyBatis中关于resultType和resultMap的区别

时间 2014-09-17 16:53:22 CSDN博客

原文  http://blog.csdn.net/caolipeng_918/article/details/39344783

主题 MyBatis 数据库

MyBatis中关于resultType和resultMap的区别

MyBatis中在查询进行select映射的时候，返回类型可以用resultType，也可以用resultMap，resultType是直接表示返回类型的(对应着我们的model对象中的实体)，而resultMap则是对外部ResultMap的引用(提前定义了db和model之间的隐射key-->value关系)，但是resultType跟resultMap不能同时存在。

在MyBatis进行查询映射时，其实查询出来的每一个属性都是放在一个对应的Map里面的，其中键是属性名，值则是其对应的值。

①当提供的返回类型属性是resultType时，MyBatis会将Map里面的键值对取出赋给resultType所指定的对象对应的属性。所以其实MyBatis的每一个查询映射的返回类型都是ResultMap，只是当提供的返回类型属性是resultType的时候，MyBatis对自动的给把对应的值赋给resultType所指定对象的属性。

②当提供的返回类型是resultMap时，因为Map不能很好表示领域模型，就需要自己再进一步的把它转化为对应的对象，这常常在复杂查询中很有作用。

  下面给出一个例子说明两者的使用差别:

package com.clark.model;import java.util.Date;public class Goods {  private Integer id;  private Integer cateId;  private String name;  private double price;  private String description;  private Integer orderNo;  private Date updateTime;    public Goods(){      }    public Goods(Integer id, Integer cateId, String name, double price,      String description, Integer orderNo, Date updateTime) {    super();    this.id = id;    this.cateId = cateId;    this.name = name;    this.price = price;    this.description = description;    this.orderNo = orderNo;    this.updateTime = updateTime;  }  public Integer getId() {    return id;  }  public void setId(Integer id) {    this.id = id;  }  public Integer getCateId() {    return cateId;  }  public void setCateId(Integer cateId) {    this.cateId = cateId;  }  public String getName() {    return name;  }  public void setName(String name) {    this.name = name;  }  public double getPrice() {    return price;  }  public void setPrice(double price) {    this.price = price;  }  public String getDescription() {    return description;  }  public void setDescription(String description) {    this.description = description;  }  public Integer getOrderNo() {    return orderNo;  }  public void setOrderNo(Integer orderNo) {    this.orderNo = orderNo;  }  public Date getTimeStamp() {    return updateTime;  }  public void setTimeStamp(Date updateTime) {    this.updateTime = updateTime;  }  @Override  public String toString() {    return "[goods include:Id="+this.getId()+",name="+this.getName()+        ",orderNo="+this.getOrderNo()+",cateId="+this.getCateId()+        ",updateTime="+this.getTimeStamp()+"]";  }}

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN"  "http://mybatis.org/dtd/mybatis-3-config.dtd"><configuration>  <typeAliases>    <!-- give a alias for model -->    <typeAlias alias="goods" type="com.clark.model.Goods"></typeAlias>  </typeAliases>  <environments default="development">    <environment id="development">      <transactionManager type="JDBC" />      <dataSource type="POOLED">        <property name="driver" value="oracle.jdbc.driver.OracleDriver" />        <property name="url" value="jdbc:oracle:thin:@172.30.0.125:1521:oradb01" />        <property name="username" value="settlement" />        <property name="password" value="settlement" />      </dataSource>    </environment>  </environments>  <mappers>    <mapper resource="com/clark/model/goodsMapper.xml" />  </mappers></configuration></span>

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"  "http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="clark">  <resultMap type="com.clark.model.Goods" id="t_good">    <id column="id" property="id"/>    <result column="cate_id" property="cateId"/>    <result column="name" property="name"/>    <result column="price" property="price"/>    <result column="description" property="description"/>    <result column="order_no" property="orderNo"/>    <result column="update_time" property="updateTime"/>  </resultMap>  <!--resultMap 和   resultType的使用区别-->  <select id="selectGoodById" parameterType="int" resultType="goods">    select id,cate_id,name,price,description,order_no,update_time     from goods where id = #{id}  </select>    <select id="selectAllGoods" resultMap="t_good">    select id,cate_id,name,price,description,order_no,update_time from goods  </select>    <insert id="insertGood" parameterType="goods">    insert into goods(id,cate_id,name,price,description,order_no,update_time)      values(#{id},#{cateId},#{name},#{price},#{description},#{orderNo},#{updateTime})  </insert></mapper>

package com.clark.mybatis;import java.io.IOException;import java.io.Reader;import java.util.List;import org.apache.ibatis.io.Resources;import org.apache.ibatis.session.SqlSession;import org.apache.ibatis.session.SqlSessionFactory;import org.apache.ibatis.session.SqlSessionFactoryBuilder;import com.clark.model.Goods;public class TestGoods {  public static void main(String[] args) {    String resource = "configuration.xml";    try {      Reader reader = Resources.getResourceAsReader(resource);      SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(reader);      SqlSession session = sessionFactory.openSession();</span>

<span style="font-size:18px;"><span style="white-space:pre"></span>//使用resultType的情况      Goods goods = (Goods)session.selectOne("clark.selectGoodById", 4);      System.out.println(goods.toString());</span>

<span style="font-size:18px;"><span style="white-space:pre"></span>//使用resultMap的情况      List<Goods> gs = session.selectList("clark.selectAllGoods");      for (Goods goods2 : gs) {        System.out.println(goods2.toString());      }//Goods goods = new Goods(4, 12, "clark", 12.30, "test is ok", 5, new Date());//session.insert("clark.insertGood", goods);//session.commit();    } catch (IOException e) {      e.printStackTrace();    }  }}

结果输出为:

<span style="color:#cc0000;">[goods include:Id=4,name=clark,orderNo=null,cateId=null,updateTime=null]---使用resultType的结果</span>

<span style="color:#33ff33;">-------使用resultMap的结果-----------------</span>

[goods include:Id=4,name=clark,orderNo=5,cateId=12,updateTime=Wed Sep 17 15:29:58 CST 2014][goods include:Id=1,name=诺基亚N85,orderNo=1,cateId=1,updateTime=Wed Sep 17 13:52:51 CST 2014]

[goods include:Id=2,name=金立 A30,orderNo=2,cateId=1,updateTime=Wed Sep 17 13:53:11 CST 2014][goods include:Id=3,name=金立 A30,orderNo=3,cateId=2,updateTime=Wed Sep 17 15:07:38 CST 2014]