hibernate ——关联关系

2022-05-23 23:56:12

1、一对一单向外键关联

<?xml version='1.0' encoding='utf-8'?>

<!DOCTYPE hibernate-configuration PUBLIC

        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"

        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <!-- Database connection settings -->

        <!-- <property name="connection.driver_class">org.hsqldb.jdbcDriver</property>

                    <property name="connection.url">jdbc:hsqldb:hsql://localhost/TestDB</property> -->

        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>

        <property name="connection.url">jdbc:mysql://localhost/test?useUnicode=true&amp;characterEncoding=UTF-8</property>

        <property name="connection.username">root</property>

        <property name="connection.password"></property>

        <property name="hbm2ddl.auto">update</property>

        <!-- SQL dialect -->

        <property name="dialect">

            org.hibernate.dialect.MySQL5InnoDBDialect

        </property>

        <property name="show_sql">true</property>

        <property name="format_sql">true</property>

         <mapping class="com.pt.hibernate.Husband" />

         <mapping class="com.pt.hibernate.Wife" />

    </session-factory>

</hibernate-configuration>

hibernate.cfg.xml

package com.pt.hibernate;

import java.util.Date;

import javax.annotation.Generated;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.OneToOne;

@Entity

public class Husband {

    int id;

    String name;

    Date bornTime;

    Wife myWife ;

    @OneToOne

    @JoinColumn(name="wifiId")    //指定外键字段名

    public Wife getMyWife() {

        return myWife;

    }

    public void setMyWife(Wife myWife) {

        this.myWife = myWife;

    }

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public Date getBornTime() {

        return bornTime;

    }

    public void setBornTime(Date bornTime) {

        this.bornTime = bornTime;

    }

}

Husband.java

package com.pt.hibernate;

import java.util.Date;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

@Entity

public class Wife {

    int id;

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public Date getBornTime() {

        return bornTime;

    }

    public void setBornTime(Date bornTime) {

        this.bornTime = bornTime;

    }

    String name;

    Date bornTime;

}

Wife

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

public class Test {

    public static void main(String[] arges){

        Configuration cfg = new Configuration();

        SessionFactory factory = cfg.configure().buildSessionFactory();

    }

}

Test

2、一对一双向外键关联

　　两个相关联的实体类都写上@OneToOne即可，如果指定OneToOne的(mappedBy="")属性，这样就不会在两个表中都保留对方的ID，只会在其中一个表中保留对方的ID。只要有双向关联，该属性必设置。

package com.pt.hibernate;

import java.util.Date;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.OneToOne;

@Entity

public class Wife {

    int id;

    String name;

    Date bornTime;

    Husband myHusband ;

    @OneToOne(mappedBy="myWife")

    public Husband getMyHusband() {

        return myHusband;

    }

    public void setMyHusband(Husband myHusband) {

        this.myHusband = myHusband;

    }

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public Date getBornTime() {

        return bornTime;

    }

    public void setBornTime(Date bornTime) {

        this.bornTime = bornTime;

    }

}

Wife

3、多对一单向外键关联

　　多对一，数据库中的表现是在多的一方记录一的一方的ID，添加Son类，同时在配置文件中配置，Son类如下：

package com.pt.hibernate;

import javax.persistence.Entity;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.ManyToOne;

@Entity

public class Son {

    int id;

    String name;

    Husband myFather;

    @ManyToOne

    @JoinColumn(name="fatherId")

    public Husband getMyFather() {

        return myFather;

    }

    public void setMyFather(Husband myFather) {

        this.myFather = myFather;

    }

    @Id

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

}

Son

4、多对一双向外键关联

　　在3、的基础上，修改Husband类，如下：

package com.pt.hibernate;

import java.util.Date;

import java.util.Set;

import javax.annotation.Generated;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.JoinColumn;

import javax.persistence.OneToMany;

import javax.persistence.OneToOne;

@Entity

public class Husband {

    int id;

    String name;

    Date bornTime;

    Wife myWife ;

    Set<Son> sons;

    @OneToMany(mappedBy="myFather")

    public Set<Son> getSons() {

        return sons;

    }

    public void setSons(Set<Son> sons) {

        this.sons = sons;

    }

    @OneToOne

    @JoinColumn(name="wifiId")    //指定外键字段名

    public Wife getMyWife() {

        return myWife;

    }

    public void setMyWife(Wife myWife) {

        this.myWife = myWife;

    }

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public Date getBornTime() {

        return bornTime;

    }

    public void setBornTime(Date bornTime) {

        this.bornTime = bornTime;

    }

}

Husband

5、一对一单向主键关联

　　修改husband和wife类，这时候husband依赖于wife，如果没有wife对应的ID，则husband插不进去记录！

package com.pt.hibernate;

import java.util.Date;

import java.util.Set;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.OneToMany;

import javax.persistence.OneToOne;

import javax.persistence.PrimaryKeyJoinColumn;

@Entity

public class Husband {

    int id;

    String name;

    Date bornTime;

    Wife myWife ;

    Set<Son> sons;

    @OneToMany(mappedBy="myFather")

    public Set<Son> getSons() {

        return sons;

    }

    public void setSons(Set<Son> sons) {

        this.sons = sons;

    }

    @OneToOne(optional=false)        //optional表示该属性是否可以为null 默认为true

    //@JoinColumn(name="wifiId")    //指定外键字段名

    @PrimaryKeyJoinColumn

    public Wife getMyWife() {

        return myWife;

    }

    public void setMyWife(Wife myWife) {

        this.myWife = myWife;

    }

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public Date getBornTime() {

        return bornTime;

    }

    public void setBornTime(Date bornTime) {

        this.bornTime = bornTime;

    }

}

Husband.java

package com.pt.hibernate;

import java.util.Date;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.OneToOne;

@Entity

public class Wife {

    int id;

    String name;

    Date bornTime;

//    Husband myHusband ;

//    @OneToOne(mappedBy="myWife")

//    public Husband getMyHusband() {

//        return myHusband;

//    }

//    public void setMyHusband(Husband myHusband) {

//        this.myHusband = myHusband;

//    }

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public Date getBornTime() {

        return bornTime;

    }

    public void setBornTime(Date bornTime) {

        this.bornTime = bornTime;

    }

}

Wife.java

6、一对一双向向主键关联

　　修改Wife类

package com.pt.hibernate;

import java.util.Date;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.OneToOne;

@Entity

public class Wife {

    int id;

    String name;

    Date bornTime;

    Husband myHusband ;

    @OneToOne(mappedBy="myWife")

    public Husband getMyHusband() {

        return myHusband;

    }

    public void setMyHusband(Husband myHusband) {

        this.myHusband = myHusband;

    }

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public Date getBornTime() {

        return bornTime;

    }

    public void setBornTime(Date bornTime) {

        this.bornTime = bornTime;

    }

}

Wife.java

7、多对多单向关联

　　在数据库中，针对多对多的关系，如：学生与老师的关系，一般都是有一张中间表维护！同时，需要建立一张中间表对应的类~~

 package com.pt.hibernate;

 import java.util.Set;

 import javax.persistence.CascadeType;

 import javax.persistence.Entity;

 import javax.persistence.Id;

 import javax.persistence.IdClass;

 import javax.persistence.JoinColumn;

 import javax.persistence.JoinTable;

 import javax.persistence.ManyToMany;

 import org.hibernate.engine.internal.Cascade;

 @Entity

 @IdClass(value=UnionId.class)

 public class Student {

     String schoolName;

     int id;

     String stuName;

     Set<Teacher> myTeachers;

     @ManyToMany(cascade=CascadeType.ALL)

     @JoinTable(

             name="teacher_stu",

             joinColumns={//当前类的ID

                     @JoinColumn(name="stu_id"),

                     @JoinColumn(name="school_id")

             },

             inverseJoinColumns={//与当前类关联的类的ID

                     @JoinColumn(name="teacher_id"),

             }

     )

     public Set<Teacher> getMyTeachers() {

         return myTeachers;

     }

     public void setMyTeachers(Set<Teacher> myTeachers) {

         this.myTeachers = myTeachers;

     }

     public String getStuName() {

         return stuName;

     }

     public void setStuName(String stuName) {

         this.stuName = stuName;

     }

     @Id

     public String getSchoolName() {

         return schoolName;

     }

     public void setSchoolName(String schoolName) {

         this.schoolName = schoolName;

     }

     @Id

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

 }

Student.java

 package com.pt.hibernate;

 import java.util.Set;

 import javax.persistence.CascadeType;

 import javax.persistence.Entity;

 import javax.persistence.GeneratedValue;

 import javax.persistence.Id;

 import javax.persistence.ManyToMany;

 import org.hibernate.engine.internal.Cascade;

 @Entity

 public class Teacher {

     int id;

     String name;

     String courese;            //教授课程

     Set<Student> myStudents;

     @ManyToMany(mappedBy="myTeachers",cascade=CascadeType.ALL)

     public Set<Student> getMyStudents() {

         return myStudents;

     }

     public void setMyStudents(Set<Student> myStudents) {

         this.myStudents = myStudents;

     }

     @Id

     @GeneratedValue

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public String getCourese() {

         return courese;

     }

     public void setCourese(String courese) {

         this.courese = courese;

     }

 }

Teacher.java

　　生成的表结构如下：

CREATE TABLE `student` (

  `id` int(11) NOT NULL,

  `schoolName` varchar(255) NOT NULL,

  `stuName` varchar(255) DEFAULT NULL,

  PRIMARY KEY (`id`,`schoolName`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8

CREATE TABLE `teacher` (

  `id` int(11) NOT NULL,

  `courese` varchar(255) DEFAULT NULL,

  `name` varchar(255) DEFAULT NULL,

  PRIMARY KEY (`id`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8

CREATE TABLE `teacher_stu` (

  `stu_id` int(11) NOT NULL,

  `school_id` varchar(255) NOT NULL,

  `teacher_id` int(11) NOT NULL,

  PRIMARY KEY (`stu_id`,`school_id`,`teacher_id`),

  KEY `FK3913g7i2hhmoifd6umlvicvck` (`teacher_id`),

  CONSTRAINT `FK3913g7i2hhmoifd6umlvicvck` FOREIGN KEY (`teacher_id`) REFERENCES `teacher` (`id`),

  CONSTRAINT `FKiv4krpyoes8tqxfy89uewaimm` FOREIGN KEY (`stu_id`, `school_id`) REFERENCES `student` (`id`, `schoolName`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8

学生-老师

8、多对多双向关联

　　在7、基础上，修改Teacher.java类

package com.pt.hibernate;

import java.util.Set;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.ManyToMany;

@Entity

public class Teacher {

    int id;

    String name;

    String courese;            //教授课程

    Set<Student> myStudents;

    @ManyToMany(mappedBy="myTeachers")

    public Set<Student> getMyStudents() {

        return myStudents;

    }

    public void setMyStudents(Set<Student> myStudents) {

        this.myStudents = myStudents;

    }

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public String getCourese() {

        return courese;

    }

    public void setCourese(String courese) {

        this.courese = courese;

    }

}

Teacher.java

总结：1、双向关联，必用mappedBy属性

　　　2、单向与双向关联，对于数据库结构是没有区别的，区别在于程序中是否可以通过一方寻找另一方；

　　　　　　如：A与B单向关联，只可以通过A找B，通过B找不到A，

　　　　　　　　双向关联，则可以通过A找B，也可以通过B找A；

多对多补充：

 package com.pt.hibernate;

 import javax.persistence.CascadeType;

 import javax.persistence.Entity;

 import javax.persistence.GeneratedValue;

 import javax.persistence.Id;

 import javax.persistence.JoinColumn;

 import javax.persistence.JoinColumns;

 import javax.persistence.ManyToOne;

 import javax.persistence.Table;

 @Entity

 @Table(name="teacher_stu")

 public class Teacher_stu {

     int id;

     Student student;

     Teacher teacher;

     public Teacher_stu() {

     }

     public Teacher_stu(int in_id,Student in_student,Teacher in_teacher) {

         this.id = in_id;

         this.student = in_student;

         this.teacher = in_teacher;

     }

     @ManyToOne

     //最好指定列名  别用默认的

     @JoinColumns({

         @JoinColumn(name="stu_id"),

         @JoinColumn(name="school_id")

     }

     )

     public Student getStudent() {

         return student;

     }

     public void setStudent(Student student) {

         this.student = student;

     }

     @Id

     @GeneratedValue

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

     @ManyToOne

     @JoinColumn(name="teacher_id")

     public Teacher getTeacher() {

         return teacher;

     }

     public void setTeacher(Teacher teacher) {

         this.teacher = teacher;

     }

 }

Teacher_stu

 package com.pt.hibernate;

 import java.io.Serializable;

 import java.util.Set;

 import javax.persistence.CascadeType;

 import javax.persistence.Entity;

 import javax.persistence.GeneratedValue;

 import javax.persistence.Id;

 import javax.persistence.ManyToMany;

 import javax.persistence.OneToMany;

 import org.hibernate.engine.internal.Cascade;

 @Entity

 public class Teacher {

     int id;

     String name;

     String courese;            //教授课程

     Set<Student> myStudents;

     Set<Teacher_stu> t_s;

     public Teacher() {

     }

     public Teacher(int in_id,String in_name) {

         this.id = in_id;

         this.name = in_name;

     }

     @OneToMany(mappedBy="teacher")

     public Set<Teacher_stu> getT_s() {

         return t_s;

     }

     public void setT_s(Set<Teacher_stu> t_s) {

         this.t_s = t_s;

     }

     @ManyToMany(mappedBy="myTeachers")

     public Set<Student> getMyStudents() {

         return myStudents;

     }

     public void setMyStudents(Set<Student> myStudents) {

         this.myStudents = myStudents;

     }

     @Id

     //@GeneratedValue

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

     public String getName() {

         return name;

     }

     public void setName(String name) {

         this.name = name;

     }

     public String getCourese() {

         return courese;

     }

     public void setCourese(String courese) {

         this.courese = courese;

     }

 }

Teacher.java

 package com.pt.hibernate;

 import java.io.Serializable;

 import java.util.HashSet;

 import java.util.Set;

 import javax.persistence.CascadeType;

 import javax.persistence.Entity;

 import javax.persistence.Id;

 import javax.persistence.IdClass;

 import javax.persistence.JoinColumn;

 import javax.persistence.JoinTable;

 import javax.persistence.ManyToMany;

 import javax.persistence.OneToMany;

 import org.hibernate.engine.internal.Cascade;

 @Entity

 @IdClass(value=UnionId.class)

 public class Student implements Serializable{

     String schoolName;

     int id;

     String stuName;

     Set<Teacher> myTeachers;

     Set<Teacher_stu> t_s;

     public Student() {

         myTeachers = new HashSet<Teacher>();

         t_s = new HashSet<Teacher_stu>();

     }

     public Student(int in_id,String in_stuName,String in_schoolName) {

         this.id = in_id;

         this.stuName = in_stuName;

         this.schoolName = in_schoolName;

         myTeachers = new HashSet<Teacher>();

         t_s = new HashSet<Teacher_stu>();

     }

     @OneToMany(mappedBy="student")

     public Set<Teacher_stu> getT_s() {

         return t_s;

     }

     public void setT_s(Set<Teacher_stu> t_s) {

         this.t_s = t_s;

     }

     @ManyToMany(cascade=CascadeType.ALL)

     @JoinTable(

             name="teacher_stu",

             joinColumns={//当前类的ID

                     @JoinColumn(name="stu_id"),

                     @JoinColumn(name="school_id")

             },

             inverseJoinColumns={//与当前类关联的类的ID

                     @JoinColumn(name="teacher_id"),

             }

     )

     public Set<Teacher> getMyTeachers() {

         return myTeachers;

     }

     public void setMyTeachers(Set<Teacher> myTeachers) {

         this.myTeachers = myTeachers;

     }

     public String getStuName() {

         return stuName;

     }

     public void setStuName(String stuName) {

         this.stuName = stuName;

     }

     @Id

     public String getSchoolName() {

         return schoolName;

     }

     public void setSchoolName(String schoolName) {

         this.schoolName = schoolName;

     }

     @Id

     public int getId() {

         return id;

     }

     public void setId(int id) {

         this.id = id;

     }

 }

Student.java

 import java.sql.Connection;

 import java.util.HashSet;

 import java.util.Set;

 import org.hibernate.Session;

 import org.hibernate.SessionFactory;

 import org.hibernate.cfg.Configuration;

 import com.pt.hibernate.Student;

 import com.pt.hibernate.Teacher;

 import com.pt.hibernate.Teacher_stu;

 import com.pt.treeStrut.ArticleTree;

 public class Test {

     public static void main(String[] arges){

         Configuration cfg = new Configuration();

         SessionFactory factory = cfg.configure().buildSessionFactory();

         Student stu = new Student(20111913,"潘腾5","独羊岗中学");

         Teacher tea = new Teacher(1011,"JinLei");

         tea.getMyStudents().add(stu);

         stu.getMyTeachers().add(tea);

         Teacher_stu s_t= new Teacher_stu(1012,stu,tea);

         stu.getT_s().add(s_t);

         Session ss = factory.getCurrentSession();

         ss.beginTransaction();

         ss.save(stu);

         ss.getTransaction().commit();

         factory.close();

     }

     public static void printTree(ArticleTree parent,int level){

         for(int i = 0; i< level; i++){

             System.out.print("--");

         }

         System.out.println(parent);

         for(ArticleTree article : parent.getSons()){

             printTree(article, level + 1);

         }

     }

 }

Test.java

码农公寓

1、一对一单向外键关联

2、一对一双向外键关联

3、多对一单向外键关联

4、多对一双向外键关联

5、一对一单向主键关联

6、一对一双向向主键关联

7、多对多单向关联

8、多对多双向关联

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