mybatis多對多關聯實戰教程(推)

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MyBatis3.0 新增了association和collection標籤專門用於對多個相關實體類資料進行級聯查詢,但仍不支援多個相關實體類資料的級聯儲存和級聯刪除操作

一、建立student、teacher和stu_teach_rel三張張表


DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
`id` int(11) NOT NULL,
`name` varchar(255) DEFAULT NULL,
`age` int(11) DEFAULT NULL,
`gender` varchar(255) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `student` VALUES ('1', '劉德華', '55', '0');
INSERT INTO `student` VALUES ('2', '張惠妹', '49', '1');
INSERT INTO `student` VALUES ('3', '謝霆鋒', '35', '0');
INSERT INTO `student` VALUES ('4', '王菲', '47', '1');
INSERT INTO `student` VALUES ('5', '汪峰', '48', '0');
INSERT INTO `student` VALUES ('6', '章子怡', '36', '1');

DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher` (
`id` int(11) NOT NULL,
`name` varchar(255) DEFAULT NULL,
`gender` varchar(255) DEFAULT NULL,
`subject` varchar(255) DEFAULT NULL,
`degree` varchar(255) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `teacher` VALUES ('1', '王晶', '0', 'CHINESE', '大專');
INSERT INTO `teacher` VALUES ('2', '馮小剛', '0', 'ENGLISH', '本科');
INSERT INTO `teacher` VALUES ('3', '吳京', '0', 'MATHEMATICS', '大專');
INSERT INTO `teacher` VALUES ('4', '王倦', '1', 'MATHEMATICS', '研究生');

DROP TABLE IF EXISTS `stu_teach_rel`;
CREATE TABLE `stu_teach_rel` (
`id` int(11) NOT NULL,
`stu_id` int(11) NOT NULL,
`teach_id` int(11) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
INSERT INTO `stu_teach_rel` VALUES ('1', '1', '1');
INSERT INTO `stu_teach_rel` VALUES ('2', '2', '1');
INSERT INTO `stu_teach_rel` VALUES ('3', '1', '2');
INSERT INTO `stu_teach_rel` VALUES ('4', '2', '2');
INSERT INTO `stu_teach_rel` VALUES ('5', '2', '3');
INSERT INTO `stu_teach_rel` VALUES ('6', '3', '1');
INSERT INTO `stu_teach_rel` VALUES ('7', '3', '2');
INSERT INTO `stu_teach_rel` VALUES ('8', '1', '3');
INSERT INTO `stu_teach_rel` VALUES ('9', '4', '1');
INSERT INTO `stu_teach_rel` VALUES ('10', '4', '2');
INSERT INTO `stu_teach_rel` VALUES ('11', '5', '3');
INSERT INTO `stu_teach_rel` VALUES ('12', '5', '4');
INSERT INTO `stu_teach_rel` VALUES ('13', '6', '1');
INSERT INTO `stu_teach_rel` VALUES ('14', '6', '3');

二、新建和表相關的實體類


package com.yihaomen.mybatis.model;
import com.yihaomen.mybatis.enums.Gender;
import java.util.List;
public class Student {
private String id;
private String name;
private int age;
private Gender gender;
private List<Teacher> teachers;
setters&getters
}

package com.yihaomen.mybatis.model;
import com.yihaomen.mybatis.enums.Gender;
import com.yihaomen.mybatis.enums.Subject;
import java.util.List;
public class Teacher {
private int id;
private String name;
private Gender gender;
private Subject subject;
private String degree;
private List<Student> students;
setters&getters
}

三、新建對映關係


package com.yihaomen.mybatis.dao;
import com.yihaomen.mybatis.model.Student;
import org.springframework.stereotype.Repository;
import java.util.List;
@Repository
public interface StudentMapper {
List<Student> selectStudents();
}

student.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.yihaomen.mybatis.dao.StudentMapper">
<resultMap id="studentMap" type="Student">
<id property="id" column="id" />
<result property="name" column="name" />
<result property="age" column="age" />
<result property="gender" column="gender" typeHandler="org.apache.ibatis.type.EnumOrdinalTypeHandler" />
</resultMap>
<resultMap id="collectionMap" type="Student" extends="studentMap">
<collection property="teachers" ofType="Teacher">
<id property="id" column="teach_id" />
<result property="name" column="tname"/>
<result property="gender" column="tgender" typeHandler="org.apache.ibatis.type.EnumOrdinalTypeHandler"/>
<result property="subject" column="tsubject" typeHandler="org.apache.ibatis.type.EnumTypeHandler"/>
<result property="degree" column="tdegree" javaType="string" jdbcType="VARCHAR"/>
</collection>
</resultMap>
<select id="selectStudents" resultMap="collectionMap">
SELECT
s.id, s.name, s.gender, t.id teach_id, t.name tname, t.gender tgender, t.subject tsubject, t.degree tdegree
FROM
student s
LEFT JOIN
stu_teach_rel str
ON
s.id = str.stu_id
LEFT JOIN
teacher t
ON
t.id = str.teach_id
</select>
</mapper>

四、在configuration.xml中配置相關mapper


<?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 resource="jdbc.properties"/>
<typeAliases>
<typeAlias alias="Student" type="com.yihaomen.mybatis.model.Student" />
<typeAlias alias="Teacher" type="com.yihaomen.mybatis.model.Teacher" />
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<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>
<mapper resource="com/yihaomen/mybatis/model/Student.xml"/>
</mappers>
</configuration>

五、測試


package com.yihaomen.service.student;
import com.yihaomen.mybatis.dao.StudentMapper;
import com.yihaomen.mybatis.model.Student;
import com.yihaomen.mybatis.model.Teacher;
import com.yihaomen.service.BaseTest;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import java.util.List;
public class TestStudent extends BaseTest {
public static void testStuTeachRela() {
SqlSessionFactory sqlSessionFactory = getSession();
SqlSession session = sqlSessionFactory.openSession();
StudentMapper mapper = session.getMapper(StudentMapper.class);
List<Student> list = mapper.selectStudents();
for(Student s : list) {
System.out.println("------------------");
System.out.println(s.getName()   ","   s.getAge()   ","   s.getGender());
for(Teacher t : s.getTeachers()) {
System.out.println(t.getName()   ","   t.getGender()   ","   t.getSubject());
}
}
}
public static void main(String[] args) {
testStuTeachRela();
}
}

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