MyBatis中关于resultType和resultMap的区别介绍
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>
[html] view plain copy 在CODE上查看代码片派生到我的代码片
<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>
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