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:
packagecom.clark.model;
importjava.util.Date;
publicclassGoods{
privateIntegerid;
privateIntegercateId;
privateStringname;
privatedoubleprice;
privateStringdescription;
privateIntegerorderNo;
privateDateupdateTime;
publicGoods(){
}
publicGoods(Integerid,IntegercateId,Stringname,doubleprice,
Stringdescription,IntegerorderNo,DateupdateTime){
super();
this.id=id;
this.cateId=cateId;
this.name=name;
this.price=price;
this.description=description;
this.orderNo=orderNo;
this.updateTime=updateTime;
}
publicIntegergetId(){
returnid;
}
publicvoidsetId(Integerid){
this.id=id;
}
publicIntegergetCateId(){
returncateId;
}
publicvoidsetCateId(IntegercateId){
this.cateId=cateId;
}
publicStringgetName(){
returnname;
}
publicvoidsetName(Stringname){
this.name=name;
}
publicdoublegetPrice(){
returnprice;
}
publicvoidsetPrice(doubleprice){
this.price=price;
}
publicStringgetDescription(){
returndescription;
}
publicvoidsetDescription(Stringdescription){
this.description=description;
}
publicIntegergetOrderNo(){
returnorderNo;
}
publicvoidsetOrderNo(IntegerorderNo){
this.orderNo=orderNo;
}
publicDategetTimeStamp(){
returnupdateTime;
}
publicvoidsetTimeStamp(DateupdateTime){
this.updateTime=updateTime;
}
@Override
publicStringtoString(){
return"[goodsinclude:Id="+this.getId()+",name="+this.getName()+
",orderNo="+this.getOrderNo()+",cateId="+this.getCateId()+
",updateTime="+this.getTimeStamp()+"]";
}
}
<?xmlversion="1.0"encoding="UTF-8"?> <!DOCTYPEconfigurationPUBLIC"-//mybatis.org//DTDConfig3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <typeAliases> <!--giveaaliasformodel--> <typeAliasalias="goods"type="com.clark.model.Goods"></typeAlias> </typeAliases> <environmentsdefault="development"> <environmentid="development"> <transactionManagertype="JDBC"/> <dataSourcetype="POOLED"> <propertyname="driver"value="oracle.jdbc.driver.OracleDriver"/> <propertyname="url"value="jdbc:oracle:thin:@172.30.0.125:1521:oradb01"/> <propertyname="username"value="settlement"/> <propertyname="password"value="settlement"/> </dataSource> </environment> </environments> <mappers> <mapperresource="com/clark/model/goodsMapper.xml"/> </mappers> </configuration></span>
<?xmlversion="1.0"encoding="UTF-8"?>
<!DOCTYPEmapperPUBLIC"-//mybatis.org//DTDMapper3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mappernamespace="clark">
<resultMaptype="com.clark.model.Goods"id="t_good">
<idcolumn="id"property="id"/>
<resultcolumn="cate_id"property="cateId"/>
<resultcolumn="name"property="name"/>
<resultcolumn="price"property="price"/>
<resultcolumn="description"property="description"/>
<resultcolumn="order_no"property="orderNo"/>
<resultcolumn="update_time"property="updateTime"/>
</resultMap>
<!--resultMap和resultType的使用区别-->
<selectid="selectGoodById"parameterType="int"resultType="goods">
selectid,cate_id,name,price,description,order_no,update_time
fromgoodswhereid=#{id}
</select>
<selectid="selectAllGoods"resultMap="t_good">
selectid,cate_id,name,price,description,order_no,update_timefromgoods
</select>
<insertid="insertGood"parameterType="goods">
insertintogoods(id,cate_id,name,price,description,order_no,update_time)
values(#{id},#{cateId},#{name},#{price},#{description},#{orderNo},#{updateTime})
</insert>
</mapper>
packagecom.clark.mybatis;
importjava.io.IOException;
importjava.io.Reader;
importjava.util.List;
importorg.apache.ibatis.io.Resources;
importorg.apache.ibatis.session.SqlSession;
importorg.apache.ibatis.session.SqlSessionFactory;
importorg.apache.ibatis.session.SqlSessionFactoryBuilder;
importcom.clark.model.Goods;
publicclassTestGoods{
publicstaticvoidmain(String[]args){
Stringresource="configuration.xml";
try{
Readerreader=Resources.getResourceAsReader(resource);
SqlSessionFactorysessionFactory=newSqlSessionFactoryBuilder().build(reader);
SqlSessionsession=sessionFactory.openSession();</span>
<spanstyle="font-size:18px;"><spanstyle="white-space:pre"></span>//使用resultType的情况
Goodsgoods=(Goods)session.selectOne("clark.selectGoodById",4);
System.out.println(goods.toString());</span>
[html]viewplaincopy在CODE上查看代码片派生到我的代码片
<spanstyle="font-size:18px;"><spanstyle="white-space:pre"></span>//使用resultMap的情况
List<Goods>gs=session.selectList("clark.selectAllGoods");
for(Goodsgoods2:gs){
System.out.println(goods2.toString());
}
//Goodsgoods=newGoods(4,12,"clark",12.30,"testisok",5,newDate());
//session.insert("clark.insertGood",goods);
//session.commit();
}catch(IOExceptione){
e.printStackTrace();
}
}
}
结果输出为:
<spanstyle="color:#cc0000;">[goodsinclude:Id=4,name=clark,orderNo=null,cateId=null,updateTime=null]---使用resultType的结果</span> <spanstyle="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毛票票网站的支持！