Hibernate 一对一映射之主键关联 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

drop table if exists idcard;
drop table if exists student;
create table idcard 
(
	iid integer not null, 
	num integer, 
	primary key (iid)
);
create table student 
(	
	sid integer not null auto_increment, 
	name varchar(255), 
	primary key (sid)
);

表结构如下图所示

 

 

2.hibernate.cfg.xml

<?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>

		<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
		<property name="connection.url">jdbc:mysql://localhost:3306/test</property>
		<property name="connection.username">root</property>
		<property name="connection.password">123456</property>

		<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
		<property name="show_sql">true</property>
		<property name="format_sql">false</property>

	<!-- <mapping resource="org/fool/model/Student.hbm.xml" /> -->
	<!-- <mapping resource="org/fool/model/IdCard.hbm.xml" /> -->
		<mapping class="org.fool.model.Student" />
		<mapping class="org.fool.model.IdCard" />

	</session-factory>

</hibernate-configuration>

 这里使用Student表和IdCard表进行一对一关联

 

3.Student.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.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;

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

@Entity
@Table(name = "student")
public class Student {
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	@Column(name = "sid")
	private int id;

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

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

	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 IdCard getIdCard() {
		return idCard;
	}

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

}

 以上的annotation就相当于以下的Student.hbm.xml文件，可以进行对比一下

<?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.Student" table="student">

		<id name="id" column="sid" type="integer">
			<generator class="identity">
			</generator>
		</id>

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

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

	</class>

</hibernate-mapping>

 

4.IdCard.java

package org.fool.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.Fetch;
import org.hibernate.annotations.FetchMode;
import org.hibernate.annotations.GenericGenerator;
import org.hibernate.annotations.Parameter;

@Entity
@Table(name = "idcard")
public class IdCard {
	@Id
	@GenericGenerator(name = "generator", strategy = "foreign", 
		parameters = @Parameter(name = "property", value = "student"))
	@GeneratedValue(generator = "generator")
	@Column(name = "iid")
	private int id;

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

	@OneToOne(fetch = FetchType.LAZY)
	@PrimaryKeyJoinColumn
	@Fetch(FetchMode.SELECT)
	private Student student;

	public int getId() {
		return id;
	}

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

	public int getNum() {
		return num;
	}

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

	public Student getStudent() {
		return student;
	}

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

}

 以上的annotation就相当于以下的IdCard.hbm.xml文件，可以进行对比一下

<?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.IdCard" table="idcard">

		<id name="id" column="iid" type="integer">
			<generator class="foreign">
				<param name="property">student</param>
			</generator>
		</id>

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

		<one-to-one name="student" class="org.fool.model.Student"
			fetch="select"></one-to-one>

	</class>

</hibernate-mapping>

 

5.HibernateUtil.java

package org.fool.util;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtil {

	private static SessionFactory sessionFactory;

	static {
		try {
			sessionFactory = new Configuration().configure()
					.buildSessionFactory();
		} catch (Exception ex) {
			System.err.println("构造SessionFactory异常发生： " + ex.getMessage());
		}

	}

	public static Session openSession() {
		Session session = sessionFactory.openSession();
		return session;
	}

	public static void closeSession(Session session) {
		if (null != session) {
			session.close();
		}
	}

}

 

6.HibernateTest.java

package org.fool.test;

import org.fool.model.IdCard;
import org.fool.model.Student;
import org.fool.util.HibernateUtil;
import org.hibernate.Session;
import org.hibernate.Transaction;

public class HibernateTest {
	public static void main(String[] args) throws Exception {
		// insert();
		// selectStudent();
		// updateStudent();
	    // delete();
	}

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

		try {
			tx = session.beginTransaction();
			
			Student student = new Student();
			student.setName("zhangsan");
			
			IdCard idCard = new IdCard();
			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;
		
		Student student = null;

		try {
			tx = session.beginTransaction();

			student = (Student) session.get(Student.class, 1);
			
			tx.commit();
		} catch (Exception e) {
			e.printStackTrace();
			if (null != tx) {
				tx.rollback();
			}
		} finally {
			HibernateUtil.closeSession(session);
		}
		
		System.out.println(student.getName());
		System.out.println(student.getIdCard().getNum());
	}

	/**
	 * 更新学生信息
	 */
	public static void updateStudent() {
		Session session = HibernateUtil.openSession();
		Transaction tx = null;
		
		Student student = null;

		try {
			tx = session.beginTransaction();
			
			student = (Student) session.get(Student.class, 1);
			
			student.setName("lisi");

			tx.commit();
		} catch (Exception e) {
			e.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;
		
		Student student = null;

		try {
			tx = session.beginTransaction();
			
			student = (Student) session.get(Student.class, 1);
			
			session.delete(student);

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

}

 

7.总结

主键关联：一对一默认使用的是立即加载，如果需要使用延迟加载，那么需要在one-to-one元素中将constrained属性设为true，并且将待加载的一方的class元素中lazy属性设为true（或者不去设置，因为该属性默认值是true）；一对一加载时默认 使用左外连接，可以通过修改fetch属性为select，修改成每次发送一条select语句的形式。