（四）MyBatis关系映射
2017-06-26 19:02
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第一节：一对一关系实现
需要实现一对一的关系，首先我们有两张表，t-addree和t_student。CREATE TABLE `t_address` ( `id` int(11) NOT NULL AUTO_INCREMENT, `sheng` varchar(20) DEFAULT NULL, `shi` varchar(20) DEFAULT NULL, `qu` varchar(20) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;
insert into `t_address`(`id`,`sheng`,`shi`,`qu`) values (1,'江苏省','苏州市','姑苏区'),(2,'江苏省','南京市','鼓楼区');
CREATE TABLE `t_student` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(20) DEFAULT NULL, `age` int(11) DEFAULT NULL, `addressId` int(11) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8;
insert into `t_student`(`id`,`name`,`age`,`addressId`) values (1,'张三',10,1),(2,'李四',11,2),(3,'李四',11,2),(4,'李四',11,2),(5,'李四',11,2),(6,'李四',11,2),(7,'李四',11,2);
然后写model层
Address.java
package com.javaxk.model;
public class Address {
private Integer id;
private String sheng;
private String shi;
private String qu;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getSheng() {
return sheng;
}
public void setSheng(String sheng) {
this.sheng = sheng;
}
public String getShi() {
return shi;
}
public void setShi(String shi) {
this.shi = shi;
}
public String getQu() {
return qu;
}
public void setQu(String qu) {
this.qu = qu;
}
@Override
public String toString() {
return "Address [id=" + id + ", sheng=" + sheng + ", shi=" + shi
+ ", qu=" + qu + "]";
}
}Student.java
package com.javaxk.model;
public class Student {
private Integer id;
private String name;
private Integer age;
private Address address;
public Student() {
super();
// TODO Auto-generated constructor stub
}
public Student(Integer id, String name, Integer age) {
super();
this.id = id;
this.name = name;
this.age = age;
}
public Student(String name, Integer age) {
super();
this.name = name;
this.age = age;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
@Override
public String toString() {
return "Student [id=" + id + ", name=" + name + ", age=" + age
+ ", address=" + address + "]";
}
}mappers映射类
AddressMapper.java
package com.javaxk.mappers;
import com.javaxk.model.Address;
public interface AddressMapper {
public Address findById(Integer id);
}StudentMapper.java
package com.javaxk.mappers;
import java.util.List;
import com.javaxk.model.Student;
public interface StudentMapper {
public Student findStudentWithAddress(Integer id);
}主程序运行类
StudentTest3.java
package com.javaxk.service;
import java.util.List;
import org.apache.ibatis.session.SqlSession;
import org.apache.log4j.Logger;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.javaxk.mappers.StudentMapper;
import com.javaxk.model.Student;
import com.javaxk.util.SqlSessionFactoryUtil;
public class StudentTest3 {
private static Logger logger=Logger.getLogger(StudentTest.class);
private SqlSession sqlSession=null;
private StudentMapper studentMapper=null;
/**
* 测试方法前调用
* @throws Exception
*/
@Before
public void setUp() throws Exception {
sqlSession=SqlSessionFactoryUtil.openSession();
studentMapper=sqlSession.getMapper(StudentMapper.class);
}
/**
* 测试方法后调用
* @throws Exception
*/
@After
public void tearDown() throws Exception {
sqlSession.close();
}
@Test
public void testFindStudentWithAddress() {
logger.info("查询学生(带地址)");
Student student=studentMapper.findStudentWithAddress(1);
System.out.println(student);
}
}Mapper映射文件的不同写法。。。
AddressMapper.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">
<mapper namespace="com.javaxk.mappers.AddressMapper">
<resultMap type="Address" id="AddressResult">
<result property="id" column="id"/>
<result property="sheng" column="sheng"/>
<result property="shi" column="shi"/>
<result property="qu" column="qu"/>
</resultMap>
<select id="findById" parameterType="Integer" resultType="Address">
select * from t_address where id=#{id}
</select>
</mapper>第一种方式：
<?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.javaxk.mappers.StudentMapper">
<resultMap type="Student" id="StudentResult">
<id property="id" column="id"/>
<result property="name" column="name"/>
<result property="age" column="age"/>
<result property="address.id" column="addressId"/>
<result property="address.sheng" column="sheng"/>
<result property="address.shi" column="shi"/>
<result property="address.qu" column="qu"/>
</resultMap>
<select id="findStudentWithAddress" resultMap="StudentResult" parameterType="Integer">
select * from t_student t1,t_address t2 where t1.addressId=t2.id and t1.id=#{id}
</select>
</mapper>第二种方式：
<?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.javaxk.mappers.StudentMapper">
<resultMap type="Address" id="AddressResult">
<result property="id" column="id"/>
<result property="sheng" column="sheng"/>
<result property="shi" column="shi"/>
<result property="qu" column="qu"/>
</resultMap>
<resultMap type="Student" id="StudentResult">
<id property="id" column="id"/>
<result property="name" column="name"/>
<result property="age" column="age"/>
<association property="address" resultMap="AddressResult"/>
</resultMap>
<select id="findStudentWithAddress" resultMap="StudentResult" parameterType="Integer">
select * from t_student t1,t_address t2 where t1.addressId=t2.id and t1.id=#{id}
</select>
</mapper>第三种方式：
<?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.javaxk.mappers.StudentMapper">
<resultMap type="Student" id="StudentResult">
<id property="id" column="id"/>
<result property="name" column="name"/>
<result property="age" column="age"/>
<association property="address" javaType="Address">
<result property="id" column="id"/>
<result property="sheng" column="sheng"/>
<result property="shi" column="shi"/>
<result property="qu" column="qu"/>
</association>
</resultMap>
<select id="findStudentWithAddress" resultMap="StudentResult" parameterType="Integer">
select * from t_student t1,t_address t2 where t1.addressId=t2.id and t1.id=#{id}
</select>
</mapper>第四种方式：
<?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.javaxk.mappers.StudentMapper">
<resultMap type="Student" id="StudentResult">
<id property="id" column="id"/>
<result property="name" column="name"/>
<result property="age" column="age"/>
<association property="address" column="id" select="com.javaxk.mappers.AddressMapper.findById"></association>
</resultMap>
<select id="findStudentWithAddress" resultMap="StudentResult" parameterType="Integer">
select * from t_student t1,t_address t2 where t1.addressId=t2.id and t1.id=#{id}
</select>
</mapper>第二节：一对多关系实现
StudentMapper.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">
<mapper namespace="com.javaxk.mappers.StudentMapper">
<resultMap type="Student" id="StudentResult">
<id property="id" column="id"/>
<result property="name" column="name"/>
<result property="age" column="age"/>
<association property="address" column="addressId" select="com.javaxk.mappers.AddressMapper.findById"></association>
<association property="grade" column="gradeId" select="com.javaxk.mappers.GradeMapper.findById"></association>
</resultMap>
<select id="findStudentWithAddress" resultMap="StudentResult" parameterType="Integer">
select * from t_student t1,t_address t2 where t1.addressId=t2.id and t1.id=#{id}
</select>
</mapper>AddressMapper.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">
<mapper namespace="com.javaxk.mappers.AddressMapper">
<resultMap type="Address" id="AddressResult">
<result property="id" column="id"/>
<result property="sheng" column="sheng"/>
<result property="shi" column="shi"/>
<result property="qu" column="qu"/>
</resultMap>
<select id="findById" parameterType="Integer" resultType="Address">
select * from t_address where id=#{id}
</select>
</mapper>GradeMapper.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">
<mapper namespace="com.javaxk.mappers.GradeMapper">
<resultMap type="Grade" id="GradeResult">
<result property="id" column="id"/>
<result property="gradeName" column="gradeName"/>
</resultMap>
<select id="findById" parameterType="Integer" resultType="Grade">
select * from t_grade where id=#{id}
</select>
</mapper>测试主类：
@Test
public void testFindStudentWithGrade(){
logger.info("查询学生(带年级)");
Student student=studentMapper.findStudentWithAddress(1);
System.out.println(student);
}
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