Hibernate 一对一映射之外键关联 Annotation Example

0.pom.xml

......
	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<hibernate-version>3.6.10.Final</hibernate-version>
		<javassist-version>3.12.1.GA</javassist-version>
		<slf4j-nop-version>1.6.6</slf4j-nop-version>
		<mysql-connector-version>5.1.21</mysql-connector-version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.hibernate</groupId>
			<artifactId>hibernate-core</artifactId>
			<version>${hibernate-version}</version>
		</dependency>

		<dependency>
			<groupId>javassist</groupId>
			<artifactId>javassist</artifactId>
			<version>${javassist-version}</version>
		</dependency>

		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-nop</artifactId>
			<version>${slf4j-nop-version}</version>
		</dependency>

		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>${mysql-connector-version}</version>
		</dependency>
	</dependencies>
......	

 

1.schema.sql

alter table idcard2 drop foreign key FK62B3D2E778B7ECB9;
drop table if exists idcard2;
drop table if exists student2;
create table idcard2 
(
	iid varchar(255) not null, 
	num integer, 
	student_id varchar(255) unique, 
	primary key (iid)
);
create table student2 
(
	sid varchar(255) not null, 
	name varchar(255), primary key (sid)
);
alter table idcard2 add index FK62B3D2E778B7ECB9 (student_id), 
add constraint FK62B3D2E778B7ECB9 foreign key (student_id) references student2 (sid); 

表结构如下图所示

 

 

2.Student2.java

package org.fool.model;

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;

import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;
import org.hibernate.annotations.GenericGenerator;

@Entity
@Table(name = "student2")
public class Student2 {

	@Id
	@GenericGenerator(name = "uuid", strategy = "uuid")
	@GeneratedValue(generator = "uuid")
	@Column(name = "sid")
	private String id;

	@Column(name = "name")
	private String name;

	@OneToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "student")
	@Fetch(FetchMode.SELECT)
	private IdCard2 idCard;

	public String getId() {
		return id;
	}

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

	public String getName() {
		return name;
	}

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

	public IdCard2 getIdCard() {
		return idCard;
	}

	public void setIdCard(IdCard2 idCard) {
		this.idCard = idCard;
	}

}

 以上的Annotation的就相当于以下的Student2.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

	<class name="org.fool.model.Student2" table="student2">

		<id name="id" column="sid" type="string">
			<generator class="uuid">
			</generator>
		</id>

		<property name="name" column="name" type="string" />

		<one-to-one name="idCard" class="org.fool.model.IdCard2"
			cascade="all" fetch="select"></one-to-one>

	</class>

</hibernate-mapping>

 

3.IdCard2.java

package org.fool.model;

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.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

import org.hibernate.annotations.GenericGenerator;

@Entity
@Table(name = "idcard2")
public class IdCard2 {

	@Id
	@GenericGenerator(name = "uuid", strategy = "uuid")
	@GeneratedValue(generator = "uuid")
	@Column(name = "iid")
	private String id;

	@Column(name = "num")
	private int num;

	@ManyToOne(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
	@JoinColumn(name = "student_id", unique = true)
	private Student2 student;

	public String getId() {
		return id;
	}

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

	public int getNum() {
		return num;
	}

	public void setNum(int num) {
		this.num = num;
	}

	public Student2 getStudent() {
		return student;
	}

	public void setStudent(Student2 student) {
		this.student = student;
	}

}

 以上的Annotation的就相当于以下的IdCard2.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

	<class name="org.fool.model.IdCard2" table="idcard2">

		<id name="id" column="iid" type="string">
			<generator class="uuid">
			</generator>
		</id>

		<property name="num" column="num" type="integer" />

		<many-to-one name="student" class="org.fool.model.Student2"
			column="student_id" cascade="all" unique="true" lazy="false"></many-to-one>

	</class>

</hibernate-mapping>

 4.HibernateTest2.java

 

package org.fool.test;

import org.fool.model.IdCard2;
import org.fool.model.Student2;
import org.fool.util.HibernateUtil;
import org.hibernate.Session;
import org.hibernate.Transaction;

public class HibernateTest2 {
	public static void main(String[] args) {
		// insert();
		// selectStudent();
		// selectIdCard();
		// updateStudent();
		// delete();
	}

	/**
	 * 添加信息
	 */
	public static void insert() {
		Session session = HibernateUtil.openSession();
		Transaction tx = null;

		try {
			tx = session.beginTransaction();

			Student2 student = new Student2();
			student.setName("zhangsan");

			IdCard2 idCard = new IdCard2();
			idCard.setNum(123456);

			student.setIdCard(idCard);
			idCard.setStudent(student);

			session.save(student);

			tx.commit();
		} catch (Exception e) {
			e.printStackTrace();
			if (null != tx) {
				tx.rollback();
			}
		} finally {
			HibernateUtil.closeSession(session);
		}
	}

	/**
	 * 查询学生信息
	 */
	public static void selectStudent() {
		Session session = HibernateUtil.openSession();
		Transaction tx = null;

		Student2 student = null;

		try {
			tx = session.beginTransaction();

			student = (Student2) session.get(Student2.class,
					"8aea139d397170d801397170d9480000");

			tx.commit();
		} catch (Exception e) {
			e.printStackTrace();
			if (null != tx) {
				tx.rollback();
			}
		} finally {
			HibernateUtil.closeSession(session);
		}

		System.out.println(student.getName());
	}

	/**
	 * 查询IdCard信息
	 */
	public static void selectIdCard() {
		Session session = HibernateUtil.openSession();
		Transaction tx = null;

		IdCard2 idCard = null;

		try {
			tx = session.beginTransaction();

			idCard = (IdCard2) session.get(IdCard2.class,
					"8aea139d397170d801397170d9570001");

			tx.commit();
		} catch (Exception ex) {
			ex.printStackTrace();
			if (null != tx) {
				tx.rollback();
			}
		} finally {
			HibernateUtil.closeSession(session);
		}

		System.out.println(idCard.getNum());
		System.out.println(idCard.getStudent().getName());
	}
	
	/**
	 * 更新学生信息
	 */
	public static void updateStudent() {
		Session session = HibernateUtil.openSession();
		Transaction tx = null;
		
		Student2 student = null;
		
		try {
			tx = session.beginTransaction();
			
			student = (Student2) session.get(Student2.class, "8aea139d397170d801397170d9480000");
		
			student.setName("lisi");
			
			tx.commit();
		} catch(Exception ex) {
			ex.printStackTrace();
			if (null != tx) {
				tx.rollback();
			}
		} finally {
			HibernateUtil.closeSession(session);
		}
		
		System.out.println(student.getName());
	}
	
	/**
	 * 级联删除
	 */
	public static void delete() {
		Session session = HibernateUtil.openSession();
		Transaction tx = null;
		
		IdCard2 idCard = null;
		
		try {
			tx = session.beginTransaction();
			
			idCard = (IdCard2) session.get(IdCard2.class, "8aea139d397170d801397170d9570001");
		
			session.delete(idCard);
			
			tx.commit();
		} catch(Exception ex) {
			ex.printStackTrace();
			if (null != tx) {
				tx.rollback();
			}
		} finally {
			HibernateUtil.closeSession(session);
		}
	}
}

 

5.插入一条数据后的结果

 

6.小结

外键关联：本质上是一对多的蜕化形式。将many-to-one元素中增加unique="true"属性，就变成了一对一。