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>

 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