MyBatis中resultType和resultMap的区别

我不是女神ヾ 2022-06-08 01:36 232阅读 0赞

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>
    		
    		<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>
    	
    	<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();
                            
                            //使用resultType的情况
    			Goods goods = (Goods)session.selectOne("clark.selectGoodById", 4);
    			System.out.println(goods.toString());</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:

\---使用resultType的结果---

\[goods include:Id=4,name=clark,orderNo=null,cateId=null,updateTime=null\]

\---使用resultMap的结果---

\[goods include:Id=4,name=clark,orderNo=5,cateId=12,updateTime=Wed Sep 17 15:29:58 CST 2014\]\[goods include:Id=1,name=诺基亚N85,orderNo=1,cateId=1,updateTime=Wed Sep 17 13:52:51 CST 2014\]  
\[goods include:Id=2,name=金立 A30,orderNo=2,cateId=1,updateTime=Wed Sep 17 13:53:11 CST 2014\]\[goods include:Id=3,name=金立 A30,orderNo=3,cateId=2,updateTime=Wed Sep 17 15:07:38 CST 2014\]