Hibernate一对多报collection owner not associated with session 一对一,多对多,一对多

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mob6454cc6dcf7f 2024-04-03 20:28:10

文章标签 mysql sql 数据库配置文件实体类 文章分类 架构后端开发

前言：为了方便起见，一对一和一对多用相同的数据库表

理解：（以下面的数据库表为例子）

一对一：相当于一个学生对应一个老师
一对多：相当于一个老师对应多个学生（也可以使用一个学生对应多个老师）
多对多：相当于多个老师对应多个学生（也就是一个老师对应多个学生，一个学生对应多个老师的合并）

1.一对一

先建立对应的数据库表

/*创建student表 */
DROP TABLE IF EXISTS `student`;
/*设置student表的字段 */
CREATE TABLE `student` (
  `id` int(10) NOT NULL,
  `name` varchar(30) DEFAULT NULL,
  `tid` int(10) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `fktid` (`tid`),
  CONSTRAINT `fktid` FOREIGN KEY (`tid`) REFERENCES `teacher` (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
/*往student表中插入一些数据 */
insert  into `student`(`id`,`name`,`tid`) values (1,'小明',1),(2,'小红',1),(3,'小张',1),(4,'小李',1),(5,'小王',1),(6,'小黄',2),(7,'小吕',2),(8,'小绿',2),(9,'小蓝',2),(10,'小兰',2),(11,'小天',3),(12,'小田',3),(13,'小花',3),(14,'小华',3),(15,'小宗',3),(16,'小芬',4),(17,'小分',4),(18,'小亲',4),(19,'小琴',4),(20,'小新',4);
/*创建teacher表 */
DROP TABLE IF EXISTS `teacher`;
/*设置teacher表的字段 */
CREATE TABLE `teacher` (
  `id` int(10) NOT NULL,
  `name` varchar(30) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
/*往teacher表中插入一些数据 */
insert  into `teacher`(`id`,`name`) values (1,'秦老师'),(2,'黄老师'),(3,'蔡老师'),(4,'马老师');

创建实体类
创建Student实体类

package com.bjpowernode.ba01.pojo;

public class Student {
    private Integer id;
    private String name;
    private Teacher teacher;

    public Student(Integer id, String name, Teacher teacher) {
        this.id = id;
        this.name = name;
        this.teacher = teacher;
    }

    public Student() {
    }

    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 Teacher getTeacher() {
        return teacher;
    }

    public void setTeacher(Teacher teacher) {
        this.teacher = teacher;
    }


    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", teacher=" + teacher +
                '}';
    }
}

创建Teacher实体类

package com.bjpowernode.ba01.pojo;

public class Teacher {
    private Integer id;
    private String name;

    public Teacher(Integer id, String name) {
        this.id = id;
        this.name = name;
    }

    public Teacher() {
    }

    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;
    }


    @Override
    public String toString() {
        return "Teacher{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}

写接口

package com.bjpowernode.ba01.dao;

import com.bjpowernode.ba01.pojo.Student;

public interface StudentDao {

    public Student getstuandteaById(Integer id);
}

写接口的配置文件

<?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.bjpowernode.ba01.dao.StudentDao">
    <!-- 定义结果集，column表示sql查询列,property表示映射到实体的属性 -->
<resultMap id="mystu" type="com.bjpowernode.ba01.pojo.Student">
    <id  property="sid"  column="id"/>
    <result property="sname" column="name"/>
    <association property="teacher" javaType="com.bjpowernode.ba01.pojo.Teacher">
        <id property="tid" column="id" />
        <result property="tname" column="name"/>
    </association>
</resultMap>
    <select id="getstuandteaById" resultMap="mystu">
        select s.id sid,s.name sname,t.id tid,t.name tname
        from student s,teacher t
        where s.tid=t.id and s.id=#{id}
    </select>
</mapper>

在主配置文件添加配置文件

<?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>
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>
    <environments default="mydev">
        <environment id="mydev">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!--数据库的驱动类名-->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <!--连接数据库的url字符串-->
                <property name="url" value="jdbc:mysql://localhost:3306/task?useUnicode=true&characterEncoding=utf-8"/>
                <!--访问数据库的用户名-->
                <property name="username" value="root"/>
                <!--密码-->
                <property name="password" value="123456"/>
            </dataSource>
        </environment>

    </environments>

    <mappers>
<!--        <mapper resource="com/bjpowernode/dao/StudentDao.xml"/>-->
        <package name="com.bjpowernode.ba01"/>
    </mappers>
</configuration>

编写测试类

package com.bjpowernode;

import com.bjpowernode.ba01.dao.StudentDao;
import com.bjpowernode.ba01.pojo.Student;
import com.bjpowernode.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

public class MyTest1 {
    @Test
    public void test01(){
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        StudentDao mapper = sqlSession.getMapper(StudentDao.class);
        Student student = mapper.getstuandteaById(2);
        System.out.println(student);
        sqlSession.close();
    }
}

测试结果

Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@61322f9d]
==>  Preparing: select s.id sid,s.name sname,t.id tid,t.name tname from
student s,teacher t where s.tid=t.id and s.id=? 
==> Parameters: 2(Integer)
<==    Columns: sid, sname, tid, tname
<==        Row: 2, 小红, 1, 秦老师
<==      Total: 1
Student{id=2, name='小红', teacher=Teacher{id=1, name='秦老师'}}
Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@61322f9d]
Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@61322f9d]
Returned connection 1630678941 to pool.

2.一对多

先建立对应的数据库表**（使用一对一的数据库表）**
创建实体类
创建Student实体类

package com.bjpowernode.ba02.pojo;

public class Student {
    private Integer id;
    private String name;
    private Integer tid;

    public Student(Integer id, String name, Integer tid) {
        this.id = id;
        this.name = name;
        this.tid = tid;
    }

    public Student() {
    }


    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", tid=" + tid +
                '}';
    }


    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 getTid() {
        return tid;
    }

    public void setTid(Integer tid) {
        this.tid = tid;
    }
}

创建Teacher实体类

package com.bjpowernode.ba02.pojo;

import java.util.List;

public class Teacher {
    private Integer id;
    private String name;
    private List<Student> student;

    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 List<Student> getStudent() {
        return student;
    }

    public void setStudent(List<Student> student) {
        this.student = student;
    }


    public Teacher() {
    }

    public Teacher(Integer id, String name, List<Student> student) {
        this.id = id;
        this.name = name;
        this.student = student;
    }

    @Override
    public String toString() {
        return "Teacher{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", student=" + student +
                '}';
    }
}

写接口

package com.bjpowernode.ba02.dao;

import com.bjpowernode.ba02.pojo.Teacher;

public interface TeacherDao {
   Teacher getteastu(Integer id);
}

写接口的配置文件

<?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.bjpowernode.ba02.dao.TeacherDao">
    <resultMap id="mytea" type="com.bjpowernode.ba02.pojo.Teacher">
        <id column="tid" property="id"/>
        <result column="tname" property="name"/>
        <collection property="student"  ofType="com.bjpowernode.ba02.pojo.Student">
            <result column="sid" property="id"/>
            <result column="sname" property="name"/>
            <result column="stid" property="tid"/>
        </collection>
    </resultMap>
<select id="getteastu" resultMap="mytea">
    select t.id tid,t.name tname,s.id sid,s.name sname,s.tid stid
    from teacher t,student s
    where t.id=s.tid and t.id=#{id}
</select>

</mapper>

在主配置文件添加配置文件

<!--        其余部分与一对一的主配置文件一样--> 
<mappers>
<!--        <mapper resource="com/bjpowernode/dao/StudentDao.xml"/>-->
        <package name="com.bjpowernode.ba02"/>
 </mappers>

编写测试类

package com.bjpowernode;

import com.bjpowernode.ba02.dao.TeacherDao;
import com.bjpowernode.ba02.pojo.Teacher;
import com.bjpowernode.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

public class MyTest2 {
    @Test
    public void test01(){
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        TeacherDao mapper = sqlSession.getMapper(TeacherDao.class);
        Teacher getteastu = mapper.getteastu(1);
        System.out.println(getteastu);
        sqlSession.close();
    }
}

7.测试结果

Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@61322f9d]
==>  Preparing: select t.id tid,t.name tname,s.id sid,s.name sname,s.tid stid from teacher t,student s where t.id=s.tid and t.id=? 
==> Parameters: 1(Integer)
<==    Columns: tid, tname, sid, sname, stid
<==        Row: 1, 秦老师, 1, 小明, 1
<==        Row: 1, 秦老师, 2, 小红, 1
<==        Row: 1, 秦老师, 3, 小张, 1
<==        Row: 1, 秦老师, 4, 小李, 1
<==        Row: 1, 秦老师, 5, 小王, 1
<==      Total: 5
Teacher{id=1, name='秦老师', student=[Student{id=1, name='小明', tid=1}, Student{id=2, name='小红', tid=1}, Student{id=3, name='小张', tid=1}, Student{id=4, name='小李', tid=1}, Student{id=5, name='小王', tid=1}]}
Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@61322f9d]
Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@61322f9d]
Returned connection 1630678941 to pool.

3.多对多

先建立对应的数据库表

/*创建stu表 */
DROP TABLE IF EXISTS `stu`;

/*设置stu表的字段 */
CREATE TABLE `stu` (
  `sid` int(10) NOT NULL AUTO_INCREMENT,
  `sname` varchar(50) NOT NULL,
  PRIMARY KEY (`sid`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8;

/*往stu表中插入数据 */

insert  into `stu`(`sid`,`sname`) values (1,'张三'),(2,'李四'),(3,'王五'),(4,'赵六'),(5,'力力'),(6,'缓缓'),(7,'拍拍');

/*创建stu_tea表 */
DROP TABLE IF EXISTS `stu_tea`;

/*设置 stu_tea表的字段*/

CREATE TABLE `stu_tea` (
  `s_id` int(10) NOT NULL,
  `t_id` int(10) NOT NULL,
  KEY `s_id` (`s_id`),
  KEY `t_id` (`t_id`),
  CONSTRAINT `stu_tea_ibfk_1` FOREIGN KEY (`s_id`) REFERENCES `stu` (`sid`),
  CONSTRAINT `stu_tea_ibfk_2` FOREIGN KEY (`t_id`) REFERENCES `tea` (`tid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;


/*往stu_tea表中插入数据 */
insert  into `stu_tea`(`s_id`,`t_id`) values (1,1),(2,2),(3,1),(4,2),(5,3),(6,3),(4,1),(3,3),(2,1);

/*创建tea表 */
DROP TABLE IF EXISTS `tea`;

/*设置tea表的字段 */
CREATE TABLE `tea` (
  `tid` int(10) NOT NULL AUTO_INCREMENT,
  `tname` varchar(50) NOT NULL,
  PRIMARY KEY (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;


/*往tea表中插入数据 */
insert  into `tea`(`tid`,`tname`) values (1,'李老师'),(2,'王老师'),(3,'张老师');

创建实体类
创建stu实体类

package com.bjpowernode.ba04.pojo;

import java.util.List;

public class Stu {
    private Integer sid;
    private String sname;
    private List<Tea> teas;

    public Stu() {
    }

    public Stu(Integer sid, String sname, List<Tea> teas) {
        this.sid = sid;
        this.sname = sname;
        this.teas = teas;
    }

    public Integer getSid() {
        return sid;
    }

    public void setSid(Integer sid) {
        this.sid = sid;
    }

    public String getSname() {
        return sname;
    }

    public void setSname(String sname) {
        this.sname = sname;
    }

    public List<Tea> getTeas() {
        return teas;
    }

    public void setTeas(List<Tea> teas) {
        this.teas = teas;
    }

    @Override
    public String toString() {
        return "Stu{" +
                "sid=" + sid +
                ", sname='" + sname + '\'' +
                ", teas=" + teas +
                '}';
    }
}

创建tea实体类

package com.bjpowernode.ba04.pojo;

import java.util.List;
import java.util.Set;

public class Tea {
    private Integer tid;
    private String tname;

    public Tea() {
    }


    public Tea(Integer tid, String tname) {
        this.tid = tid;
        this.tname = tname;

    }

    public Integer getTid() {
        return tid;
    }

    public void setTid(Integer tid) {
        this.tid = tid;
    }

    public String getTname() {
        return tname;
    }

    public void setTname(String tname) {
        this.tname = tname;
    }

    @Override
    public String toString() {
        return "Tea{" +
                "tid=" + tid +
                ", tname='" + tname + '\'' +
                '}';
    }
}

创建stu_tea实体类（该表在本次测试用不到）

package com.bjpowernode.ba04.pojo;

public class Stu_Tea {

    private Stu stu;
    private Tea tea;

    public Stu_Tea() {
 }


    public Stu_Tea(Stu stu, Tea tea) {
        this.stu = stu;
        this.tea = tea;
    }

    public Stu getStu() {
        return stu;
    }

    public void setStu(Stu stu) {
        this.stu = stu;
    }

    public Tea getTea() {
        return tea;
    }

    public void setTea(Tea tea) {
        this.tea = tea;
    }


    @Override
    public String toString() {
        return "Stu_Tea{" +
                "stu=" + stu +
                ", tea=" + tea +
                '}';
    }
}

写接口

package com.bjpowernode.ba04.dao;

import com.bjpowernode.ba04.pojo.Stu;

import java.util.List;

public interface StuDao {
    List<Stu> getstuandtea();
}

写接口的配置文件

<?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.bjpowernode.ba04.dao.StuDao">
    <select id="getstuandtea" resultMap="getStuMap">
      SELECT s.`sid`,s.`sname`,t.tid,t.tname
      FROM stu s
      INNER JOIN stu_tea st
      ON st.t_id=s.sid
      INNER JOIN tea t
      ON st.`s_id`=t.`tid`
</select>

    <resultMap id="getStuMap" type="com.bjpowernode.ba04.pojo.Stu">
        <id property="sid" column="sid"/>
        <result property="sname" column="sname"/>
        <collection property="teas" ofType="com.bjpowernode.ba04.pojo.Tea">
            <id property="tid" column="tid"/>
            <result property="tname" column="tname"/>
        </collection>
    </resultMap>


</mapper>

在主配置文件添加配置文件

<!--        其余部分与一对一的主配置文件一样--> 
<mappers>
<!--        <mapper resource="com/bjpowernode/dao/StudentDao.xml"/>-->
        <package name="com.bjpowernode.ba04"/>
 </mappers>

编写测试类

package com.bjpowernode;

import com.bjpowernode.ba04.dao.StuDao;
import com.bjpowernode.ba04.pojo.Stu;
import com.bjpowernode.utils.MyBatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class MyTest4 {

    @Test
    public void test01(){
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        StuDao mapper = sqlSession.getMapper(StuDao.class);
        List<Stu> getstuandtea = mapper.getstuandtea();
        for (Stu s:getstuandtea) {
            System.out.println(s);
        }
        sqlSession.close();
    }
}

7.测试结果

Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@45c7e403]
==>  Preparing: SELECT s.`sid`,s.`sname`,t.tid,t.tname FROM stu s INNER JOIN stu_tea st ON st.t_id=s.sid INNER JOIN tea t ON st.`s_id`=t.`tid` 
==> Parameters: 
<==    Columns: sid, sname, tid, tname
<==        Row: 1, 张三, 1, 李老师
<==        Row: 2, 李四, 2, 王老师
<==        Row: 1, 张三, 2, 王老师
<==        Row: 1, 张三, 3, 张老师
<==        Row: 3, 王五, 3, 张老师
<==      Total: 5
Stu{sid=1, sname='张三', teas=[Tea{tid=1, tname='李老师'}, Tea{tid=2, tname='王老师'}, Tea{tid=3, tname='张老师'}]}
Stu{sid=2, sname='李四', teas=[Tea{tid=2, tname='王老师'}]}
Stu{sid=3, sname='王五', teas=[Tea{tid=3, tname='张老师'}]}
Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@45c7e403]
Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@45c7e403]
Returned connection 1170727939 to pool.

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