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MyBatis 级联查询一对一与一对多

时间：2015-09-19 19:45:34      阅读：222      评论：0      收藏：0      [点我收藏+]

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mybatis是通过映射sql语句把关系模型(数据库中的表)与领域模型(java中的实体类)关联起的
 简单分析级联查询：
       关系模型中：表与表只有主外键关联
       领域模型中：实体类与实体类这间关联，只有一和多的关系。
                            一是指别一个实体类以对象属性存在当前实体类中。
                            多是指别一个实体类以集合对象属性存在当前实体类中


下面我以例子的形式给大家说明:
数据库脚本如下：
drop table student;
drop table classes;
drop table teacher;
 
create table student
(
stuId number(4) primary key,
stuName varchar2(20) not null,
stuSex varchar2(4),
stuBirthday date,
classId number(4)
);
 
create table classes
(
clsId number(4) primary key,
clsName varchar2(20) not null,
teacherId number(4)
);
 
create table teacher
(
teacherId number(4) primary key,
teacherName varchar2(20) not null,
workYear number(2),
professional varchar2(20)
);
 
insert into student values(1001, ‘张三‘, ‘男‘, to_date(‘1989-12-2‘, ‘yyyy-mm-dd‘), 3001);
insert into student values(1002, ‘王五‘, ‘女‘, to_date(‘1991-6-21‘, ‘yyyy-mm-dd‘), 3001);
insert into student values(1003, ‘赵六‘, ‘女‘, to_date(‘1990-1-15‘, ‘yyyy-mm-dd‘), 3001);
insert into student values(1004, ‘田七‘, ‘男‘, to_date(‘1992-11-25‘, ‘yyyy-mm-dd‘), 3002);
 
insert into classes values(3001, ‘计本1103‘, 5001);
insert into classes values(3002, ‘信本1102‘, 5002);
 
insert into teacher values(5001, ‘李四‘, 3, ‘计算机科学与技术‘);
insert into teacher values(5002, ‘王八‘, 5, ‘计算机信息‘);
 
commit;

mybatis.xml配制文件 
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
<configuration>
<properties resource="db.properties"/>
<typeAliases>
<package name="com.yc.mybatis.entity"/>
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC" />
<dataSource type="POOLED">
<property name="driver" value="${driver}" />
<property name="url" value="${url}" />
<property name="username" value="${username}" />
<property name="password" value="${password}" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/yc/mybatis/entity/ClassesMapper.xml"/>
<mapper resource="com/yc/mybatis/entity/StudentMapper.xml"/>
<mapper resource="com/yc/mybatis/entity/TeacherMapper.xml"/>
</mappers>
</configuration>
          
mybatis工具类
package com.yc.mybatis.util;
 
import java.io.IOException;
import java.io.InputStream;
 
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
 
public class MyBatisUtil
{
private static SqlSessionFactory  sqlSessionFactory;
 
static
{
try
{
InputStream in = Resources.getResourceAsStream("mybatis.xml");
sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
}
catch (IOException e)
{
throw new RuntimeException("读取mybatis.xml配制失败", e);
}
 
}
 
 
public static SqlSession getSession()
{
SqlSession session = null;
if (sqlSessionFactory != null)
{
session = sqlSessionFactory.openSession();
}
 
return session;
}
 
public static SqlSession getSession(boolean isAuto)
{
SqlSession session = null;
if (sqlSessionFactory != null)
{
session = sqlSessionFactory.openSession(isAuto);
}
return session;
}
 
public static void close(SqlSession session)
{
if (session != null)
{
session.close();
}
}
}

MyBatis 级联查询一对一实体类(Classes与Teacher):
Classes类 
package com.yc.mybatis.entity;
 
public class Classes
{
private String clsId;
private String clsName;
private Teacher teacher;
 
public String getClsId()
{
return clsId;
}
 
public void setClsId(String clsId)
{
this.clsId = clsId;
}
 
public String getClsName()
{
return clsName;
}
 
public void setClsName(String clsName)
{
this.clsName = clsName;
}
 
public Teacher getTeacher()
{
return teacher;
}
 
public void setTeacher(Teacher teacher)
{
this.teacher = teacher;
}
 
@Override
public String toString()
{
return "Classes [clsId=" + clsId + ", clsName=" + clsName + ", teacher=" + teacher + "]";
}
 
}

 Teacher类
package com.yc.mybatis.entity;
 
public class Teacher
{
private Integer teacherId;
private String teacherName;
private Integer workYear;
private String professional;
 
public Integer getTeacherId()
{
return teacherId;
}
 
public void setTeacherId(Integer teacherId)
{
this.teacherId = teacherId;
}
 
public String getTeacherName()
{
return teacherName;
}
 
public void setTeacherName(String teacherName)
{
this.teacherName = teacherName;
}
 
public Integer getWorkYear()
{
return workYear;
}
 
public void setWorkYear(Integer workYear)
{
this.workYear = workYear;
}
 
public String getProfessional()
{
return professional;
}
 
public void setProfessional(String professional)
{
this.professional = professional;
}
 
 
@Override
public String toString()
{
return "Teacher [teacherId=" + teacherId + ", teacherName=" + teacherName + ", workYear=" + workYear + ", professional=" + professional + "]";
}
 
}

MyBatis 级联查询一对一映射sql语句第一种
ClassesMapper.xml 
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mapper namespace="com.yc.mybatis.mapper.ClassesMapper">
<!-- 嵌套查询
select * from classes where clsId = 3001; 通过clsId = 3001,获得teacherId = 5001
  select * from teacher where teacherId = 5001; 然后通过查询到的eacherId = 5001查询
-->
<resultMap type="Classes" id="ClassesMap">
<id property="clsId" column="clsId"/>
<result property="clsName" column="clsName"/>
<association property="teacher" column="teacherId" 
select="com.yc.mybatis.mapper.TeacherMapper.getTeacherById"/>
</resultMap>
 
<select id="getTeacherByClasses" parameterType="int" resultMap="ClassesMap">
select * from classes where clsId = #{id}
</select>
</mapper> 

TeacherMapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mapper namespace="com.yc.mybatis.mapper.TeacherMapper">
<select id="getTeacherById" parameterType="int" resultType="Teacher">
select * from teacher where teacherId = #{teacherId}
</select>
</mapper> 
 
MyBatis 级联查询一对一映射sql语句第二种
ClassesMapper.xml 
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mapper namespace="com.yc.mybatis.mapper.ClassesMapper">
<!-- 嵌套结果 连接查询: 一次查询出所有数据
select * from classes c join teacher t on c.clsId = 3001 and c.teacherId = t.teacherId  -->
 
<resultMap type="Classes" id="ClassesMap">
<id property="clsId" column="clsId"/>
<result property="clsName" column="clsName"/>
                  <!-- 第一种方法  直接映射字段
                <association property="teacher">
                    <id property="teacherId" column="teacherId"/>
<result property="teacherName" column="teacherName"/>
<result property="workYear" column="workYear"/>
<result property="professional" column="professional"/> 
                </association> -->
                 <!-- 第二种方法引用外部resultMap -->  
<association property="teacher" 
resultMap="com.yc.mybatis.mapper.TeacherMapper.TeacherMap"/>
</resultMap>
<select id="getTeacherByClasses" parameterType="int" resultMap="ClassesMap">
select * from classes c join teacher t on c.clsId = #{id} and c.teacherId = t.teacherId
</select>
</mapper>

TeacherMapper.xml
 <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mapper namespace="com.yc.mybatis.mapper.TeacherMapper">
<resultMap type="Teacher" id="TeacherMap">
<id property="teacherId" column="teacherId"/>
<result property="teacherName" column="teacherName"/>
<result property="workYear" column="workYear"/>
<result property="professional" column="professional"/>
</resultMap>
</mapper>

MyBatis 级联查询一对一映射接口
package com.yc.mybatis.mapper;
 
import com.yc.mybatis.entity.Classes;
 
public interface ClassesMapper
{
Classes getTeacherByClasses(int id);
}

MyBatis 级联查询一对一测试
 package com.yc.mybatis.mapper;
 
import static org.junit.Assert.*;
 
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
 
import com.yc.mybatis.entity.Classes;
import com.yc.mybatis.util.MyBatisUtil;
 
public class ClassesMapperTest
{
 
private SqlSession session;
 
@Before
public void setUp() throws Exception
{
session = MyBatisUtil.getSession();
}
 
@After
public void tearDown() throws Exception
{
MyBatisUtil.close(session);
}
 
@Test
public void testGetTeacherByClasses()
{
ClassesMapper cm = session.getMapper(ClassesMapper.class);
Classes c = cm.getTeacherByClasses(3001);
System.out.println(c);
assertNotNull(c);
}
 
}

 MyBatis 级联查询一对多实体类(Classes与Student):
 Classes类
package com.yc.mybatis.entity;
 
import java.util.List;
 
public class Classes
{
private String clsId;
private String clsName;
private List<Student> stus;
 
public String getClsId()
{
return clsId;
}
 
public void setClsId(String clsId)
{
this.clsId = clsId;
}
 
public String getClsName()
{
return clsName;
}
 
public void setClsName(String clsName)
{
this.clsName = clsName;
}
 
public List<Student> getStus()
{
return stus;
}
 
public void setStus(List<Student> stus)
{
this.stus = stus;
}
 
@Override
public String toString()
{
return "Classes [clsId=" + clsId + ", clsName=" + clsName + ", stus=" + stus + "]";
}
 
}

Student类
  package com.yc.mybatis.entity;
 
import java.io.Serializable;
 
public class Student implements Serializable
{
private int stuId;
private String stuName;
private String stuSex;
private String stuBirthday;
 
public int getStuId()
{
return stuId;
}
 
public void setStuId(int stuId)
{
this.stuId = stuId;
}
 
public String getStuName()
{
return stuName;
}
 
public void setStuName(String stuName)
{
this.stuName = stuName;
}
 
public String getStuSex()
{
return stuSex;
}
 
public void setStuSex(String stuSex)
{
this.stuSex = stuSex;
}
 
public String getStuBirthday()
{
return stuBirthday;
}
 
public void setStuBirthday(String stuBirthday)
{
this.stuBirthday = stuBirthday;
}
 
@Override
public String toString()
{
return "Student [stuId=" + stuId + ", stuName=" + stuName + ", stuSex=" + stuSex + ", stuBirthday=" + stuBirthday + "]";
}
 
}
 
MyBatis 级联查询一对多映射sql语句第一种
ClassesMapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mapper namespace="com.yc.mybatis.mapper.ClassesMapper">
 
<!--  一对多嵌套查询   两条sql语句
select * from classes where clsId = 3001;
select * from student where classId = 3001;-->
<resultMap type="Classes" id="ClassesMap">
<id property="clsId" column="clsId"/>
<result property="clsName" column="clsName"/>
<collection property="stus" column="clsId" 
select="com.yc.mybatis.mapper.StudentMapper.getStusById"/>
</resultMap>
 
<select id="getStusByClasses" parameterType="int" resultMap="ClassesMap">
select * from classes where clsId = #{id}
</select>
</mapper>

StudentMapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mapper namespace="com.yc.mybatis.mapper.StudentMapper">
<select id="getStusById" parameterType="int" resultType="Student">
select * from student where classId = #{clsId}
</select>
</mapper> 
 
MyBatis 级联查询一对多映射sql语句第二种
ClassesMapper.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mapper namespace="com.yc.mybatis.mapper.ClassesMapper">
<!-- 嵌套结果  连接查询
select * from classes c join student s on c.clsId = 3001 and c.clsId = s.classId-->
<resultMap type="Classes" id="ClassesMap">
<id property="clsId" column="clsId"/>
<result property="clsName" column="clsName"/>
<!-- 第一种方法  直接映射字段
<collection property="stus" ofType="Student" >
<id property="stuId" column="stuId"/>
<result property="stuName" column="stuName"/>
<result property="stuSex" column="stuSex"/>
<result property="stuBirthday" column="stuBirthday"/>
</collection> -->
   <!-- 第二种方法引用外部resultMap --> 
  <collection property="stus" ofType="Student" 
  resultMap="com.yc.mybatis.mapper.StudentMapper.StudentMap"/> 
</resultMap>
<select id="getStusByClasses" parameterType="int" resultMap="ClassesMap">
select * from classes c join student s on c.clsId = #{id} and c.clsId = s.classId
</select>
</mapper>

StudentMapper.xml
 <?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
<mapper namespace="com.yc.mybatis.mapper.StudentMapper">
<resultMap type="Student" id="StudentMap">
<id property="stuId" column="stuId"/>
<result property="stuName" column="stuName"/>
<result property="stuSex" column="stuSex"/>
<result property="stuBirthday" column="stuBirthday"/>
</resultMap>
</mapper>

MyBatis 级联查询一对多映射接口 
package com.yc.mybatis.mapper;
 
import com.yc.mybatis.entity.Classes;
 
public interface ClassesMapper
{
Classes getStusByClasses(int id);
}
 
MyBatis 级联查询一对多测试 
package com.yc.mybatis.mapper;
 
import static org.junit.Assert.*;
 
import org.apache.ibatis.session.SqlSession;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
 
import com.yc.mybatis.entity.Classes;
import com.yc.mybatis.util.MyBatisUtil;
 
public class ClassesMapperTest
{
 
private SqlSession session;
 
@Before
public void setUp() throws Exception
{
session = MyBatisUtil.getSession();
}
 
@After
public void tearDown() throws Exception
{
MyBatisUtil.close(session);
}
 
@Test
public void testGetStusByClasses()
{
ClassesMapper cm = session.getMapper(ClassesMapper.class);
Classes c = cm.getStusByClasses(3001);
System.out.println(c);
assertNotNull(c);
}
 
}

MyBatis 级联查询一对一与一对多

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原文地址：http://www.cnblogs.com/xiaocunchu/p/4822037.html
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