上一篇文章分析了数据模型，这篇文章就给出一个需求，这个需求是一对一查询，并完成这个需求。
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需求：
查询订单信息，关联查询创建订单的用户信息。
记住：用Mybatis开发的顺序就是
1.写sql语句
2.创建pojo类来完成映射
3.写Mapper.xml
4.写Mapper.java接口
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我们知道Mybatis中mapper.xml中分为resultType和resultMap两种，这两种我们都讲：
一：先讲resultMap:
先给出案例结构:
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" 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cn.itcast.mybatis.po包下面的类（items,orderdetail,Orders,User）都是根据数据库的4张表创建的实体类。
1.我们先来分析一下怎么写sql语句：
写sql语句时要先根据需求确定查询的主表和查询的关联表：
根据“查询订单信息，关联查询创建订单的用户信息” 很明显，查询的主表是订单表，查询的关联是用户表。
关联查询使用内链接？还是外链接？由于orders表中有一个外键（user_id），通过外键关联查询用户表只能查询出一条记录，可以使用内链接。
sql如下：
SELECT
orders.*,
USER.username,
USER.sex,
USER.address
FROM
orders,
USER
WHERE orders.user_id = user.id
2.根据select（orders.*,USER.username,USER.sex,USER.address）语句 创建Pojo类
我们创建的pojo类要满足orders.*,USER.username,USER.sex,USER.address这些映射，很明显单纯依靠数据库的映射（Orders.java和User.java）不能满足，所以要新写一个类OrdersCustom.java。
如下：
package cn.itcast.mybatis.po;
import java.util.Date;
public class OrdersCustom extends Orders{
private String username;
private String sex;
private String address;
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
}为什么这个类要继承Orders而不是继承User.java因为根据orders.*,USER.username,USER.sex,USER.address，很明显，要映射的数据是order表中的全部数据以及user
表中的username,sex,address这些数据，直接继承Order类的话就可以少定义一些属性，只要定义username，sex，address。就可以了。
3.写Mapper.xml和Mapper.java接口(放在同一个包下面，用接口的方式去加载)
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OrderMapperCustom.xml的代码如下：
<?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">
<!-- nanmespace:命名空间。 作用就是对sql进行分类话管理，理解Sal分离 注意：使用mapper代理方式，namespace有特殊重要的作用
--> <mapper namespace="cn.itcast.mybatis.mapper.OrdersMapperCustom"> <select id="findOrdersUser" resultType="cn.itcast.mybatis.po.OrdersCustom">
SELECT ORDERS.* ,
user.`username`,
user.`sex`,
user.`address`
FROM orderS,USER
WHERE ORDERS.`user_id`=USER.`id` </select> </mapper>
OrdersMapperCustom.java代码如下：
package cn.itcast.mybatis.mapper;
import java.util.List;
import cn.itcast.mybatis.po.OrdersCustom;
public interface OrdersMapperCustom {
public List<OrdersCustom> findOrdersUser();
}同时不要忘了在SqlMapConfig.xml。
<?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> <!-- properties的配置必须写在typeAliases的上面 -->
<properties resource="db.properties"></properties> <!-- 和spring整合后 environments配置将废除-->
<environments default="development">
<environment id="development">
<!-- 使用jdbc事务管理-->
<transactionManager type="JDBC" />
<!-- 数据库连接池-->
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
</dataSource>
</environment>
</environments> <mappers> <!-- 用mapper接口的方式加载-->
<!--
遵循一些规范：需要将mapper接口类名和mapper.xml映射文件名称保持一致
且在一个目录中。
当着这个规范的前提是：使用mapper代理方法。 -->
<mapper class="cn.itcast.mybatis.mapper.OrdersMapperCustom"/> </mappers> </configuration>
4.编写测试代码Mybatis_mappertest.java：
package cn.itcast.mybatis.test; import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
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 org.junit.Before;
import org.junit.Test; import cn.itcast.mybatis.mapper.OrdersMapperCustom;
import cn.itcast.mybatis.mapper.userMapper;
import cn.itcast.mybatis.po.User;
import cn.itcast.mybatis.po.UserCustom;
import cn.itcast.mybatis.po.UserQueryVo; public class Mybatis_mappertest { private SqlSessionFactory sqlSessionFactory;
@Before
public void setup() throws IOException
{ String resource="SqlMapConfig.xml";
InputStream inputStream= Resources.getResourceAsStream(resource);
//主要是生成SqlsessionFactory。
this.sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
}
@Test
public void testMaper()
{
SqlSession sqlSession=null; sqlSession=sqlSessionFactory.openSession();
//生成代理类
OrdersMapperCustom orderMapper=sqlSession.getMapper(OrdersMapperCustom.class); orderMapper.findOrdersUser(); } }
运行结果：一切正常。
二：再讲resultMap（重点）:
resultMap映射的思想：
使用resultMap将查询结果中的订单信息映射到Orders对象中，在orders类中添加User属性，将关联查询出来的用户信息映射到orders对象中的user属性中。也就是说查出来的user信息都要映射在orders中新开的一个user属性中。
还是按照第一sql语句，第二pojo类，第三mapper.xml，mapper.java接口这种顺序来写。
1.sql语句：和之前的resulrType的sql语句一样：
SELECT
orders.*,
USER.username,
USER.sex,
USER.address
FROM
orders,
USER
WHERE orders.user_id = user.id
2.写pojo类：在原来的Orders.java中新增一个User属性：
User类：
package cn.itcast.mybatis.po; import java.util.Date;
//对应数据库中的user表
public class User {
private int id;//对应数据库中主键
private String username;//对应数据库中用户的名称
private Date birthday;//对应数据库中的生日
private String sex;//性别
private String address;//地址
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
} }
Orders.java类：
package cn.itcast.mybatis.po;
import java.util.Date;
public class Orders {
private Integer id;
private Integer user_id;
private String number;
private Date createtime;
private String note;
//新增了一个User属性，为了保存查询得到的关联的User表的信息
private User user;
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Integer getUser_id() {
return user_id;
}
public void setUser_id(Integer user_id) {
this.user_id = user_id;
}
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public Date getCreatetime() {
return createtime;
}
public void setCreatetime(Date createtime) {
this.createtime = createtime;
}
public String getNote() {
return note;
}
public void setNote(String note) {
this.note = note;
}
}3.写mapper.xml和mapper.java接口
OrdersMapperCustom.xml:
<?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">
<!-- nanmespace:命名空间。 作用就是对sql进行分类话管理，理解Sal分离 注意：使用mapper代理方式，namespace有特殊重要的作用
--> <mapper namespace="cn.itcast.mybatis.mapper.OrdersMapperCustom"> <!-- 配置映射的订单信息 -->
<!-- id：指定查询列中的唯 一标识，订单信息的中的唯 一标识，如果有多个列组成唯一标识，配置多个id
就是说id要能唯一的标识出数据库中的Order表。
column：订单信息的唯 一标识 列
property：订单信息的唯 一标识 列所映射到Orders中哪个属性 --> <resultMap type="cn.itcast.mybatis.po.Orders" id="OrdersUserResultMap">
<!-- 这一行的作用是要能唯一的识别出order表的，那么很明显是主键id -->
<id column="id" property="id"/> <!-- 以下的几行result column就是表中的字段 property就是对应到相应pojo类中的属性-->
<result column="user_id" property="user_id"/>
<result column="number" property="number"/>
<result column="createtime" property="createtime"/>
<result column="note" property="note"/> <!-- 配置映射的关联的用户信息 -->
<!-- association：用于映射关联查询单个对象的信息
property：要将关联查询的用户信息映射到Orders中哪个属性
-->
<!-- 下面的代码比较特殊，因为Order表是直接关联到user表，下面这么写的目的是把user表映射到Order类中
<association property="user"这里的user指的是orders类中的user,对应的是cn.itcast.mybatis.po.User -->
<association property="user" javaType="cn.itcast.mybatis.po.User">
<!--
<id column="user_id" property="id"/>这里的是user_id指的是order表中只有这个属性能表示唯一的user表
-->
<id column="user_id" property="id"/> <!-- 接下来的result property什么的都是为了把user表中的字段能匹配到
cn.itcast.mybatis.po.User这个类的属性中
-->
<result column="username" property="username"/>
<result column="sex" property="sex"/>
<result column="address" property="address"/>
</association> </resultMap> <select id="findOrdersUser" resultType="cn.itcast.mybatis.po.OrdersCustom">
SELECT ORDERS.* ,
user.`username`,
user.`sex`,
user.`address`
FROM orderS,USER
WHERE ORDERS.`user_id`=USER.`id` </select> <select id="findOrdersUseResultMap" resultMap="OrdersUserResultMap">
SELECT ORDERS.* ,
user.`username`,
user.`sex`,
user.`address`
FROM orderS,USER
WHERE ORDERS.`user_id`=USER.`id` </select>
</mapper>
OrdersMapperCustom.java接口
package cn.itcast.mybatis.mapper; import java.util.List; import cn.itcast.mybatis.po.Orders;
import cn.itcast.mybatis.po.OrdersCustom; public interface OrdersMapperCustom {
//这里的的函数名字要和OrdersMapperCustom.xml中的id一模一样
public List<OrdersCustom> findOrdersUser();
public List<Orders> findOrdersUseResultMap(); }
Junit测试代码：
package cn.itcast.mybatis.test; import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
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 org.junit.Before;
import org.junit.Test; import cn.itcast.mybatis.mapper.OrdersMapperCustom;
import cn.itcast.mybatis.mapper.userMapper;
import cn.itcast.mybatis.po.Orders;
import cn.itcast.mybatis.po.User;
import cn.itcast.mybatis.po.UserCustom;
import cn.itcast.mybatis.po.UserQueryVo; public class Mybatis_mappertest { private SqlSessionFactory sqlSessionFactory;
@Before
public void setup() throws IOException
{ String resource="SqlMapConfig.xml";
InputStream inputStream= Resources.getResourceAsStream(resource);
//主要是生成SqlsessionFactory。
this.sqlSessionFactory=new SqlSessionFactoryBuilder().build(inputStream);
}
@Test
public void testMaper()
{
SqlSession sqlSession=null; sqlSession=sqlSessionFactory.openSession();
//生成代理类
OrdersMapperCustom orderMapper=sqlSession.getMapper(OrdersMapperCustom.class);
//创建包装对象，设置查询条件
//orderMapper.findOrdersUser(); @SuppressWarnings("unused")
List<Orders>list=orderMapper.findOrdersUseResultMap(); } }
运行结果：一切正常。
resultType和resultMap实现一对一查询小结
实现一对一查询：
resultType：使用resultType实现较为简单，如果pojo中没有包括查询出来的列名，需要增加列名对应的属性，即可完成映射。
如果没有查询结果的特殊要求建议使用resultType。
resultMap：需要单独定义resultMap，实现有点麻烦，如果对查询结果有特殊的要求，使用resultMap可以完成将关联查询映射pojo的属性中。
resultMap可以实现延迟加载，resultType无法实现延迟加载。