Hibernate实体关系

Hibernate实体关系：双向关联，mappedBy必设

注解方式

1、一对一单向

@Entity       

public class Husband{

           @Id
​
           @GenerateValue

             pirvate int id;

             private String name;

            @OneToOne

            @JoinColumn(name="wifeId")

             private Wife wife;

      }

        @Entity

     public class Wife{

           @Id

           @GenerateValue

         private int id;

         private String name;

    }

2.、一对一双向

@Entity       

public class Husband{

           @Id

           @GenerateValue

             pirvate int id;

             private String name;

            @OneToOne

            @JoinColumn(name="wifeId")

             private Wife wife;

      }

 

        @Entity

     public class Wife{

           @Id

           @GenerateValue

         private int id;

         private String name;

       @OneToOne(mappedBy="wife")

        private Husband husband;

    }

3.、一对多单向

package com.bjsxt.hibernate;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity
@Table(name="t_group")
public class Group {
private int id;
private String name;
private Set<User> users = new HashSet<User>();
@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;
}
@OneToMany
@JoinColumn(name="groupId") //不加出现3张表
public Set<User> getUsers() {
   return users;
}
public void setUsers(Set<User> users) {
   this.users = users;
}
}

package com.bjsxt.hibernate;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Entity
@Table(name="t_user")
public class User {
private int id;
private String name;
@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;
}
}

4、多对一单向

package com.bjsxt.hibernate;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="t_group")
public class Group {
private int id;
private String name;
@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;
}
}

 

package com.bjsxt.hibernate;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Entity
@Table(name="t_user")
public class User {
private int id;
private String name;
private Group group;
@ManyToOne

public Group getGroup() {
   return group;
}
public void setGroup(Group group) {
   this.group = group;
}
@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;
}
}

5、一对多双向

package com.bjsxt.hibernate;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
@Entity
@Table(name="t_group")
public class Group {
private int id;
private String name;
private Set<User> users = new HashSet<User>();
@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;

}

@OneToMany(mappedBy="group") //ManyToOne没有mappedBy
public Set<User> getUsers() {
   return users;
}
public void setUsers(Set<User> users) {
   this.users = users;
}
}

package com.bjsxt.hibernate;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
@Entity
@Table(name="t_user")
public class User {
private int id;
private String name;
private Group group;
@ManyToOne
public Group getGroup() {
   return group;
}
public void setGroup(Group group) {
   this.group = group;
}
@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;
}
}

6、多对多单向

@Entity
public class Student {
private int id;
private String name;
@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;
}
}

@Entity
public class Teacher {
private int id;
private String name;
private Set<Student> students = new HashSet<Student>();
@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;
}
@ManyToMany
@JoinTable(name="t_s",
  joinColumns={@JoinColumn(name="teacher_id")},
  inverseJoinColumns={@JoinColumn(name="student_id")}
   )     //改变中间表的名字和字段名字
public Set<Student> getStudents() {
   return students;
}
public void setStudents(Set<Student> students) {
   this.students = students;
}
}

7、多对多双向

@Entity
public class Student {
private int id;
private String name;
private Set<Teacher> teachers = new HashSet<Teacher>();
@ManyToMany(mappedBy="students")
public Set<Teacher> getTeachers() {
   return teachers;
}
public void setTeachers(Set<Teacher> teachers) {
   this.teachers = teachers;
}
@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;
}
}

@Entity
public class Teacher {
private int id;
private String name;
private Set<Student> students = new HashSet<Student>();
@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;
}
@ManyToMany
@JoinTable(name="t_s",
  joinColumns={@JoinColumn(name="teacher_id")},
  inverseJoinColumns={@JoinColumn(name="student_id")}
   )
public Set<Student> getStudents() {
   return students;
}
public void setStudents(Set<Student> students) {
   this.students = students;
}
}