hibernate ——关联关系

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