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; } @Override public 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