hibernate一对一映射示例

一、主键一对一
1.建表

DROP TABLE student;
DROP TABLE friend;

//主表，一个学生有多个朋友
CREATE TABLE t2.student( id INT NOT NULL auto_increment, name VARCHAR(100), sex INT, age INT, CONSTRAINT `PRIMARY` PRIMARY KEY(id) );
//从表
CREATE TABLE friend( id INT NOT NULL auto_increment, friend_id INT, name VARCHAR(100), sex INT, CONSTRAINT `PRIMARY` PRIMARY KEY(id), CONSTRAINT friend_ibfk_1
FOREIGN KEY(id) REFERENCES student(id) );

2.建model
2.1 Student.java

package test1.model;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name = “student”, catalog = “t2”)
public class Student implements java.io.Serializable {

   private int id;
   private String name;
   private Integer sex;
   private Integer age;
   private Friend friend;

public Student() {
}

   public Student(int id) {
       this.id = id;
   }

   public Student(int id, String name, Integer sex, Integer age, Friend friend) {
       this.id = id;
       this.name = name;
       this.sex = sex;
       this.age = age;
       this.friend = friend;
   }

   @Id

   @GeneratedValue(strategy = GenerationType.AUTO)
   @Column(name = “id”, unique = true, nullable = false)
   public int getId() {
       return this.id;
   }

   public void setId(int id) {
       this.id = id;
   }

   @Column(name = “name”, length = 100)
   public String getName() {
       return this.name;
   }

   public void setName(String name) {
       this.name = name;
   }

   @Column(name = “sex”)
   public Integer getSex() {
       return this.sex;
   }

   public void setSex(Integer sex) {
       this.sex = sex;
   }

   @Column(name = “age”)
   public Integer getAge() {
       return this.age;
   }

   public void setAge(Integer age) {
       this.age = age;
   }

   @OneToOne(cascade = CascadeType.ALL,fetch = FetchType.LAZY, mappedBy = “student”)
   public Friend getFriend() {
       return this.friend;
   }

   public void setFriend(Friend friend) {
       this.friend = friend;
   }
}

22Friend.java

package test1.model;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;
import org.hibernate.annotations.GenericGenerator;
import org.hibernate.annotations.Parameter;

@Entity
@Table(name = “friend”, catalog = “t2”)
public class Friend implements java.io.Serializable {

   private Integer id;
   private Student student;
   private Integer friendId;
   private String name;
   private Integer sex;

public Friend() {
}

   public Friend(Student student) {
       this.student = student;
   }

   public Friend(Student student, Integer friendId, String name, Integer sex) {
       this.student = student;
       this.friendId = friendId;
       this.name = name;
       this.sex = sex;
   }

   @GenericGenerator(name = “generator”, strategy = “foreign”, parameters = @Parameter(name = “property”, value = “student”))
   @Id
   @GeneratedValue(generator = “generator”)

   @Column(name = “id”, unique = true, nullable = false)
   public Integer getId() {
       return this.id;
   }

   public void setId(Integer id) {
       this.id = id;
   }

   @OneToOne(fetch = FetchType.LAZY)
   @PrimaryKeyJoinColumn
   public Student getStudent() {
       return this.student;
   }

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

   @Column(name = “friend_id”)
   public Integer getFriendId() {
       return this.friendId;
   }

   public void setFriendId(Integer friendId) {
       this.friendId = friendId;
   }

   @Column(name = “name”, length = 100)
   public String getName() {
       return this.name;
   }

   public void setName(String name) {
       this.name = name;
   }

   @Column(name = “sex”)
   public Integer getSex() {
       return this.sex;
   }

   public void setSex(Integer sex) {
       this.sex = sex;
   }
}

3.测试
package test1.r1;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import test1.model.Friend;
import test1.model.Student;

public class HibernateOne2One1 {
   public static void main(String[] args) {
               System.out.println(“开始事务”);
               Configuration config = new Configuration().configure();
               SessionFactory sessionFactory = config.buildSessionFactory();
               Session session = sessionFactory.openSession();
               try {
                   Transaction tx = session.beginTransaction();

                   Student stu1 = new Student();
                   stu1.setName(“bkd2”);
               //   session.save(stu1);
                   Friend fr1 = new Friend(stu1);
                   fr1.setName(“bkd1”);
                    session.save(fr1);
                    tx.commit();
               } catch (HibernateException e) {
                   e.printStackTrace();
                   session.getTransaction().rollback();
               } finally {
                   session.close();
                   sessionFactory.close();
               }
               System.out.println(“事务结束”);
   }
}

二、外键一对一
1.建表
drop table student;
drop table friend;
CREATE TABLE student (
   id INT NOT NULL auto_increment,
   name VARCHAR(100),
   sex INT,
   age INT,
   CONSTRAINT `PRIMARY` PRIMARY KEY (id)
);
CREATE TABLE friend (
   id INT NOT NULL auto_increment,
   friendId INT unique,
   name VARCHAR(100),
   sex INT,
   CONSTRAINT `PRIMARY` PRIMARY KEY (id),
   CONSTRAINT friend_ibfk_1 FOREIGN KEY (friendId) REFERENCES student(id)
);

2.建model。
2.1Student.java
package test1.model;

import static javax.persistence.GenerationType.IDENTITY;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name = “student”, catalog = “t2”)
public class Student implements java.io.Serializable {

   private Integer id;
   private String name;
   private Integer sex;
   private Integer age;
   private Friend friend;

public Student() {
}

@Id
@GeneratedValue(strategy = IDENTITY)