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:
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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; } @Overridepublic String toString() { return "[goods include:Id="+this.getId()+",name="+this.getName()+ ",orderNo="+this.getOrderNo()+",cateId="+this.getCateId()+ ",updateTime="+this.getTimeStamp()+"]"; } } |
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<?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> |
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<?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> |
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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> |
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<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:
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<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> |
以上所述是小编给大家介绍的MyBatis中关于resultType和resultMap的区别介绍，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对服务器之家网站的支持！
原文链接：http://blog.csdn.net/caolipeng_918/article/details/39344783?utm_source=tuicool&utm_medium=referral
