关于MyBatis中映射对象关系的举例

//销售单对象
public class SaleBill {
    private Long id;
    private String sn;
    private Set<</span>SaleBillItem> items = new HashSet<</span>SaleBillItem>();
    //getter & setter
}  
        
//销售单明细对象
public class SaleBillItem {
    private Long id;
    private Double price;
    private SaleBill bill;
    //getter & setter
}

<mapper namespace="cd.itcast.mybatis.salebill.SaleBillMapper">
<!-- 保存SaleBill对象，该调用必须放在SaleBillItem对象保存之前 -->
    <insert id="saveSaleBill" keyProperty="id" parameterType="SaleBill"
                useGeneratedKeys="true">
                INSERT INTO salebill(sn) values (#{sn})
    </insert>
<!-- 保存SaleBillItem对象 -->
    <insert id="saveSaleBillItem" keyProperty="id" parameterType="SaleBillItem" useGeneratedKeys="true">
            INSERT INTO salebillitem(price,bill_id) values (#{price},#{bill.id})
</insert>
<!-- 内嵌映射SaleBill对象，注意，因为是组合关系，所以不会出现单独去拿SaleBillItem对象的情况，所以只需要映射SaleBill主对象即可 -->
<resultMap type="SaleBill" id="salebillmap">
            <id property="id" column="id"/>
            <result column="sn" property="sn"/>
            <collection property="items" column="id" ofType="SaleBillItem" >
            <id column="item_id" property="id"/>
            <result column="item_price" property="price"/>
            <association property="bill" column="bill_id" resultMap="salebillmap" />
           </collection>
</resultMap>
 
<!-- 因为列表和单独的get方法都是采用内联的查询，所以把公用的SQL提取出来 -->
    <sql id="select">
            SELECT b.*,item.id as item_id,item.price as item_price FROM salebill b LEFT JOIN salebillitem item ON b.id = item.bill_id
     </sql>
 
<!-- get -->
    <select id="get" parameterType="long" resultMap="salebillmap">
            <include refid="select"/> WHERE b.id = #{id}
     </select>
 
<!-- 列表查询 -->
    <select id="list" resultMap="salebillmap">
            <include refid="select"/>
     </select>
 
<!-- 删除SaleBill对象 -->
    <delete id="delete" parameterType="long">
            DELETE FROM salebill WHERE id = #{id}      
    </delete>
 
<!-- 删除SaleBill对象对应的Item对象，注意，因为有外键的约束，这条删除语句应该放在delete SaleBill之前执行。注意，传入的这个id应该是SaleBill的id -->
    <delete id="deleteItems" parameterType="long">
     DELETE FROM salebillitem WHERE bill_id = #{id}
    </delete>
</mapper>

//先创建一个Mapper接口，使用接口来完成映射
public interface SaleBillMapper {
    void saveSaleBill(SaleBill sb);
    void saveSaleBillItem(SaleBillItem sbi);
    SaleBill get(Long id);
    //在接口中可以直接映射分页对象
    List<</span>SaleBill> list(RowBounds rb);
    void delete(Long id);
    void deleteItems(Long billId);
}

@Test
public void testSave() {
    //创建SaleBill对象
    SaleBill sb = new SaleBill();
    sb.setSn("001");
    //创建一个明细对象
    SaleBillItem sbi = new SaleBillItem();
    sbi.setPrice(100d);
    sbi.setBill(sb);
    //创建一个明细对象
    SaleBillItem sbi2 = new SaleBillItem();
    sbi2.setPrice(300d);
    sbi2.setBill(sb);
    //处理关系
    sb.getItems().add(sbi);
    sb.getItems().add(sbi2);
    //保存
    SqlSession session = MyBatisUtil.openSession();
    SaleBillMapper mapper = session.getMapper(SaleBillMapper.class);
    //注意，先保存SaleBill对象
    mapper.saveSaleBill(sb);
    //保存明细对象
    mapper.saveSaleBillItem(sbi);
    mapper.saveSaleBillItem(sbi2);
    session.commit();
    session.close();
}
 
@Test
public void testGet() {
    SqlSession session = MyBatisUtil.openSession();
    //得到SaleBill对象
    SaleBillMapper mapper = session.getMapper(SaleBillMapper.class);
    SaleBill sb = mapper.get(5l);
    Set<</span>SaleBillItem> items = sb.getItems();
    for (SaleBillItem item : items) {
            System.out.println(item.getPrice());
    }
    session.close();
}
 
@Test
public void testDelete() {
    SqlSession session = MyBatisUtil.openSession();
    SaleBillMapper mapper = session.getMapper(SaleBillMapper.class);
    mapper.deleteItems(1l);
    mapper.delete(1l);
    session.commit();
    session.close();
}    

<?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="com.cnpiec.ireader.dao.GetBookDataDao">
    <insert id="batchInsertBook" parameterType="Book">
        INSERT INTO BOOK (BOOKID,NAME,PARTNERNAME) VALUES
        <foreach collection="list" item="book" separator=",">
            (#{book.bookId}, #{book.name}, #{book.partnerName})
        </foreach>
    </insert>
</mapper>

<mappers>
    <mapper resource=” tk/mybatis/simple/mapper/CountryMapper.xml ” / >
    <mapper resource=” tk/mybatis/simple/mapper/UserMapper . xml ” / >
    <mapper resource=” tk/mybatis/simple/mapper/RoleMapper.xml ” />
    <mapper resource=” tk/mybatis/simple/mapper/PrivilegeMapper . xml ” />
    <mapper resource=” tk/mybatis/simple/mapper/UserRoleMapper . xml ” />
    <mapper resource=” tk/mybatis/simple/mapper / RolePrivilegeMapper.xml ” />
</mappers>

<mappers>
    <package name= ” tk.mybatis . simple . mapper ” />
</mappers>