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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~~

 1 package com.pt.hibernate;
 2 
 3 import java.util.Set;
 4 
 5 import javax.persistence.CascadeType;
 6 import javax.persistence.Entity;
 7 import javax.persistence.Id;
 8 import javax.persistence.IdClass;
 9 import javax.persistence.JoinColumn;
10 import javax.persistence.JoinTable;
11 import javax.persistence.ManyToMany;
12 
13 import org.hibernate.engine.internal.Cascade;
14 
15 @Entity
16 @IdClass(value=UnionId.class)
17 public class Student {
18     String schoolName;
19     int id;
20     String stuName;
21     Set<Teacher> myTeachers;
22     @ManyToMany(cascade=CascadeType.ALL)
23     @JoinTable(
24             name="teacher_stu",
25             joinColumns={//当前类的ID
26                     @JoinColumn(name="stu_id"),
27                     @JoinColumn(name="school_id")
28             },
29             inverseJoinColumns={//与当前类关联的类的ID
30                     @JoinColumn(name="teacher_id"),
31             }
32             
33     )
34     public Set<Teacher> getMyTeachers() {
35         return myTeachers;
36     }
37     public void setMyTeachers(Set<Teacher> myTeachers) {
38         this.myTeachers = myTeachers;
39     }
40     public String getStuName() {
41         return stuName;
42     }
43     public void setStuName(String stuName) {
44         this.stuName = stuName;
45     }
46     @Id
47     public String getSchoolName() {
48         return schoolName;
49     }
50     public void setSchoolName(String schoolName) {
51         this.schoolName = schoolName;
52     }
53     @Id
54     public int getId() {
55         return id;
56     }
57     public void setId(int id) {
58         this.id = id;
59     }
60 
61 }

Student.java

 1 package com.pt.hibernate;
 2 
 3 import java.util.Set;
 4 
 5 import javax.persistence.CascadeType;
 6 import javax.persistence.Entity;
 7 import javax.persistence.GeneratedValue;
 8 import javax.persistence.Id;
 9 import javax.persistence.ManyToMany;
10 
11 import org.hibernate.engine.internal.Cascade;
12 
13 @Entity
14 public class Teacher {
15     int id;
16     String name;
17     String courese;            //教授课程
18     Set<Student> myStudents;
19     @ManyToMany(mappedBy="myTeachers",cascade=CascadeType.ALL)
20     public Set<Student> getMyStudents() {
21         return myStudents;
22     }
23     public void setMyStudents(Set<Student> myStudents) {
24         this.myStudents = myStudents;
25     }
26     @Id
27     @GeneratedValue
28     public int getId() {
29         return id;
30     }
31     public void setId(int id) {
32         this.id = id;
33     }
34     public String getName() {
35         return name;
36     }
37     public void setName(String name) {
38         this.name = name;
39     }
40     public String getCourese() {
41         return courese;
42     }
43     public void setCourese(String courese) {
44         this.courese = courese;
45     }
46     
47 }

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：

 1 package com.pt.hibernate;
 2 
 3 import javax.persistence.CascadeType;
 4 import javax.persistence.Entity;
 5 import javax.persistence.GeneratedValue;
 6 import javax.persistence.Id;
 7 import javax.persistence.JoinColumn;
 8 import javax.persistence.JoinColumns;
 9 import javax.persistence.ManyToOne;
10 import javax.persistence.Table;
11 
12 @Entity
13 @Table(name="teacher_stu")
14 public class Teacher_stu {
15     int id;
16     Student student;
17 
18     Teacher teacher;
19     public Teacher_stu() {
20     }
21     
22     public Teacher_stu(int in_id,Student in_student,Teacher in_teacher) {
23         this.id = in_id;
24         this.student = in_student;
25         this.teacher = in_teacher;
26     }
27     
28     
29     @ManyToOne
30     //最好指定列名  别用默认的
31     @JoinColumns({
32         @JoinColumn(name="stu_id"),
33         @JoinColumn(name="school_id")
34     }
35     )
36     public Student getStudent() {
37         return student;
38     }
39     public void setStudent(Student student) {
40         this.student = student;
41     }
42     @Id
43     @GeneratedValue
44     public int getId() {
45         return id;
46     }
47     public void setId(int id) {
48         this.id = id;
49     }
50     @ManyToOne
51     @JoinColumn(name="teacher_id")
52     public Teacher getTeacher() {
53         return teacher;
54     }
55     public void setTeacher(Teacher teacher) {
56         this.teacher = teacher;
57     }
58     
59 }

Teacher_stu

 1 package com.pt.hibernate;
 2 
 3 import java.io.Serializable;
 4 import java.util.Set;
 5 
 6 import javax.persistence.CascadeType;
 7 import javax.persistence.Entity;
 8 import javax.persistence.GeneratedValue;
 9 import javax.persistence.Id;
10 import javax.persistence.ManyToMany;
11 import javax.persistence.OneToMany;
12 
13 import org.hibernate.engine.internal.Cascade;
14 
15 @Entity
16 public class Teacher {
17     int id;
18     String name;
19     String courese;            //教授课程
20     Set<Student> myStudents;
21     Set<Teacher_stu> t_s;
22     
23     public Teacher() {
24     }
25     
26     public Teacher(int in_id,String in_name) {
27         this.id = in_id;
28         this.name = in_name;
29     }
30     
31     
32     @OneToMany(mappedBy="teacher")
33     public Set<Teacher_stu> getT_s() {
34         return t_s;
35     }
36     public void setT_s(Set<Teacher_stu> t_s) {
37         this.t_s = t_s;
38     }
39     
40     @ManyToMany(mappedBy="myTeachers")
41     public Set<Student> getMyStudents() {
42         return myStudents;
43     }
44     public void setMyStudents(Set<Student> myStudents) {
45         this.myStudents = myStudents;
46     }
47     @Id
48     //@GeneratedValue
49     public int getId() {
50         return id;
51     }
52     public void setId(int id) {
53         this.id = id;
54     }
55     public String getName() {
56         return name;
57     }
58     public void setName(String name) {
59         this.name = name;
60     }
61     public String getCourese() {
62         return courese;
63     }
64     public void setCourese(String courese) {
65         this.courese = courese;
66     }
67     
68 }

Teacher.java

 1 package com.pt.hibernate;
 2 
 3 import java.io.Serializable;
 4 import java.util.HashSet;
 5 import java.util.Set;
 6 
 7 import javax.persistence.CascadeType;
 8 import javax.persistence.Entity;
 9 import javax.persistence.Id;
10 import javax.persistence.IdClass;
11 import javax.persistence.JoinColumn;
12 import javax.persistence.JoinTable;
13 import javax.persistence.ManyToMany;
14 import javax.persistence.OneToMany;
15 
16 import org.hibernate.engine.internal.Cascade;
17 
18 @Entity
19 @IdClass(value=UnionId.class)
20 public class Student implements Serializable{
21     String schoolName;
22     int id;
23     String stuName;
24     Set<Teacher> myTeachers;
25     Set<Teacher_stu> t_s;
26     
27     public Student() {
28         myTeachers = new HashSet<Teacher>();
29         t_s = new HashSet<Teacher_stu>();
30     }
31     
32     public Student(int in_id,String in_stuName,String in_schoolName) {
33         this.id = in_id;
34         this.stuName = in_stuName;
35         this.schoolName = in_schoolName;
36         myTeachers = new HashSet<Teacher>();
37         t_s = new HashSet<Teacher_stu>();
38     }
39     
40     @OneToMany(mappedBy="student")
41     public Set<Teacher_stu> getT_s() {
42         return t_s;
43     }
44     public void setT_s(Set<Teacher_stu> t_s) {
45         this.t_s = t_s;
46     }
47     
48     @ManyToMany(cascade=CascadeType.ALL)
49     @JoinTable(
50             name="teacher_stu",
51             joinColumns={//当前类的ID
52                     @JoinColumn(name="stu_id"),
53                     @JoinColumn(name="school_id")
54             },
55             inverseJoinColumns={//与当前类关联的类的ID
56                     @JoinColumn(name="teacher_id"),
57             }
58             
59     )
60     public Set<Teacher> getMyTeachers() {
61         return myTeachers;
62     }
63     public void setMyTeachers(Set<Teacher> myTeachers) {
64         this.myTeachers = myTeachers;
65     }
66     public String getStuName() {
67         return stuName;
68     }
69     public void setStuName(String stuName) {
70         this.stuName = stuName;
71     }
72     @Id
73     public String getSchoolName() {
74         return schoolName;
75     }
76     public void setSchoolName(String schoolName) {
77         this.schoolName = schoolName;
78     }
79     @Id
80     public int getId() {
81         return id;
82     }
83     public void setId(int id) {
84         this.id = id;
85     }
86 
87 }

Student.java

 1 import java.sql.Connection;
 2 import java.util.HashSet;
 3 import java.util.Set;
 4 
 5 import org.hibernate.Session;
 6 import org.hibernate.SessionFactory;
 7 import org.hibernate.cfg.Configuration;
 8 
 9 import com.pt.hibernate.Student;
10 import com.pt.hibernate.Teacher;
11 import com.pt.hibernate.Teacher_stu;
12 import com.pt.treeStrut.ArticleTree;
13 
14 
15 public class Test {
16     public static void main(String[] arges){
17         Configuration cfg = new Configuration();
18         SessionFactory factory = cfg.configure().buildSessionFactory();
19         Student stu = new Student(20111913,"潘腾5","独羊岗中学");
20         Teacher tea = new Teacher(1011,"JinLei");
21         tea.getMyStudents().add(stu);
22         stu.getMyTeachers().add(tea);
23         Teacher_stu s_t= new Teacher_stu(1012,stu,tea);
24         stu.getT_s().add(s_t);
25         
26         Session ss = factory.getCurrentSession();
27         ss.beginTransaction();
28         ss.save(stu);
29         ss.getTransaction().commit();
30         factory.close();
31     }
32     
33     public static void printTree(ArticleTree parent,int level){
34         for(int i = 0; i< level; i++){
35             System.out.print("--");
36         }
37         System.out.println(parent);
38         for(ArticleTree article : parent.getSons()){
39             printTree(article, level + 1);
40         }
41     }
42 }

Test.java

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原文地址：https://www.cnblogs.com/tengpan-cn/p/5551323.html