Hibernate 一对一映射示例注释
时间：2020-02-23 14:41:25 来源:igfitidea点击:
今天，我们将研究Hibernate中的一对一映射。
我们将研究使用注释和XML配置的Hibernate一对一映射示例。
Hibernate 中的一对一映射
在大多数情况下，数据库表是相互关联的。
关联的形式多种多样-一对一，一对多和多对多是广泛的关联。
这些可以进一步分为单向和双向映射。
今天，我们将研究使用XML配置以及注释配置实现Hibernate一对一映射。
Hibernate 一对一映射示例数据库设置
首先，我们需要在数据库表中设置一对一映射。
我们将为示例创建两个表-交易和客户。
这两个表将具有一对一的映射。
交易将是主表，我们将使用客户表中的外键进行一对一映射。
我正在提供MySQL脚本，也就是我用于本教程的数据库。
如果使用任何其他数据库，请确保相应地更改脚本。
-- Create Transaction Table CREATE TABLE `Transaction` ( `txn_id` int(11) unsigned NOT NULL AUTO_INCREMENT, `txn_date` date NOT NULL, `txn_total` decimal(10,0) NOT NULL, PRIMARY KEY (`txn_id`) ) ENGINE=InnoDB AUTO_INCREMENT=16 DEFAULT CHARSET=utf8; -- Create Customer table CREATE TABLE `Customer` ( `txn_id` int(11) unsigned NOT NULL, `cust_name` varchar(20) NOT NULL DEFAULT '', `cust_email` varchar(20) DEFAULT NULL, `cust_address` varchar(50) NOT NULL DEFAULT '', PRIMARY KEY (`txn_id`), CONSTRAINT `customer_ibfk_1` FOREIGN KEY (`txn_id`) REFERENCES `Transaction` (`txn_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
表之间一对一映射的实体关系图(ERD)如下图所示。
我们的数据库设置已准备就绪，现在让我们继续进行Hibernate一对一示例项目。
Hibernate 一对一映射示例项目结构
我正在使用Eclipse在Java IDE中创建一个简单的Maven项目。
我们的最终项目结构将如下图所示。
首先，我们将研究基于XML的Hibernate一对一映射示例，然后我们将使用批注实现相同的事情。
Hibernate Maven依赖关系
我们最终的pom.xml文件如下所示。
<project xmlns="https://maven.apache.org/POM/4.0.0" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.theitroad.hibernate</groupId> <artifactId>HibernateOneToOneMapping</artifactId> <version>0.0.1-SNAPSHOT</version> <dependencies> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>4.3.5.Final</version> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.0.5</version> </dependency> </dependencies> </project>
依赖关系仅适用于Hibernate 和mysql Java驱动程序。
请注意，我正在使用基于我的MySQL数据库服务器版本(5.0.5)的Hibernate最新版本4.3.5.Final和MySQL Java驱动程序。
Hibernate 4使用JBoss日志记录，并自动将其作为传递依赖项导入。
您可以在项目的Maven依赖项中进行确认。
如果您使用的是较早版本的Hibernate，则可能必须添加slf4j依赖项。
Hibernate 一对一映射模型类
Hibernate一对一映射以反映数据库表的模型类如下所示。
package com.theitroad.hibernate.model;
import java.util.Date;
public class Txn {
private long id;
private Date date;
private double total;
private Customer customer;
@Override
public String toString(){
return id+", "+total+", "+customer.getName()+", "+customer.getEmail()+", "+customer.getAddress();
}
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
public double getTotal() {
return total;
}
public void setTotal(double total) {
this.total = total;
}
public Customer getCustomer() {
return customer;
}
public void setCustomer(Customer customer) {
this.customer = customer;
}
}
package com.theitroad.hibernate.model;
public class Customer {
private long id;
private String name;
private String email;
private String address;
private Txn txn;
public long getId() {
return id;
}
public void setId(long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public Txn getTxn() {
return txn;
}
public void setTxn(Txn txn) {
this.txn = txn;
}
}
由于我们使用基于XML的配置进行映射，因此上述模型类是简单的POJO类或者具有getter-setter方法的Java Bean。
我将类名用作" Txn"以避免混淆，因为Hibernate API的类名为" Transaction"。
Hibernate 一对一映射配置
让我们为Txn和Customer表创建Hibernate 的一对一映射配置文件。
txn.hbm.xml
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "https://hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="com.theitroad.hibernate.model.Txn" table="TRANSACTION" > <id name="id" type="long"> <column name="txn_id" <generator class="identity" </id> <property name="date" type="date"> <column name="txn_date" </property> <property name="total" type="double"> <column name="txn_total" </property> <one-to-one name="customer" class="com.theitroad.hibernate.model.Customer" cascade="save-update" </class> </hibernate-mapping>
上面要注意的重要点是客户属性的Hibernate "一对一"元素。
customer.hbm.xml
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "https://hibernate.org/dtd/hibernate-mapping-3.0.dtd" > <hibernate-mapping> <class name="com.theitroad.hibernate.model.Customer" table="CUSTOMER"> <id name="id" type="long"> <column name="txn_id" <generator class="foreign"> <param name="property">txn</param> </generator> </id> <one-to-one name="txn" class="com.theitroad.hibernate.model.Txn" constrained="true"></one-to-one> <property name="name" type="string"> <column name="cust_name"></column> </property> <property name="email" type="string"> <column name="cust_email"></column> </property> <property name="address" type="string"> <column name="cust_address"></column> </property> </class> </hibernate-mapping>
generator class =" foreign"是用于Hibernate 外键实现的重要部分。
Hibernate 配置文件
这是基于XML的Hibernate 映射配置的Hibernate 配置文件。
hibernate.cfg.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"https://hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.password">hyman123</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost/TestDB</property>
<property name="hibernate.connection.username">hyman</property>
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="hibernate.current_session_context_class">thread</property>
<property name="hibernate.show_sql">true</property>
<mapping resource="txn.hbm.xml"
<mapping resource="customer.hbm.xml"
</session-factory>
</hibernate-configuration>
Hibernate配置文件很简单，它具有数据库连接属性和hibernate映射资源。
Hibernate SessionFactory实用程序
这是用于创建Hibernate SessionFactory实例的实用程序类。
package com.theitroad.hibernate.util;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
public class HibernateUtil {
private static SessionFactory sessionFactory;
private static SessionFactory buildSessionFactory() {
try {
//Create the SessionFactory from hibernate.cfg.xml
Configuration configuration = new Configuration();
configuration.configure("hibernate.cfg.xml");
System.out.println("Hibernate Configuration loaded");
ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
System.out.println("Hibernate serviceRegistry created");
SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
return sessionFactory;
}
catch (Throwable ex) {
System.err.println("Initial SessionFactory creation failed." + ex);
ex.printStackTrace();
throw new ExceptionInInitializerError(ex);
}
}
public static SessionFactory getSessionFactory() {
if(sessionFactory == null) sessionFactory = buildSessionFactory();
return sessionFactory;
}
}
就是这样，让我们编写一个测试程序来测试Hibernate 的一对一基于xml的映射配置。
Hibernate 一对一映射XML配置测试程序
在Hibernate 的一对一映射示例测试程序中，首先我们将创建Txn对象并将其保存。
将其保存到数据库后，我们将使用生成的ID来检索Txn对象并进行打印。
package com.theitroad.hibernate.main;
import java.util.Date;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import com.theitroad.hibernate.model.Customer;
import com.theitroad.hibernate.model.Txn;
import com.theitroad.hibernate.util.HibernateUtil;
public class HibernateOneToOneMain {
public static void main(String[] args) {
Txn txn = buildDemoTransaction();
SessionFactory sessionFactory = null;
Session session = null;
Transaction tx = null;
try{
//Get Session
sessionFactory = HibernateUtil.getSessionFactory();
session = sessionFactory.getCurrentSession();
System.out.println("Session created");
//start transaction
tx = session.beginTransaction();
//Save the Model object
session.save(txn);
//Commit transaction
tx.commit();
System.out.println("Transaction ID="+txn.getId());
//Get Saved Trasaction Data
printTransactionData(txn.getId(), sessionFactory);
}catch(Exception e){
System.out.println("Exception occured. "+e.getMessage());
e.printStackTrace();
}finally{
if(!sessionFactory.isClosed()){
System.out.println("Closing SessionFactory");
sessionFactory.close();
}
}
}
private static void printTransactionData(long id, SessionFactory sessionFactory) {
Session session = null;
Transaction tx = null;
try{
//Get Session
sessionFactory = HibernateUtil.getSessionFactory();
session = sessionFactory.getCurrentSession();
//start transaction
tx = session.beginTransaction();
//Save the Model object
Txn txn = (Txn) session.get(Txn.class, id);
//Commit transaction
tx.commit();
System.out.println("Transaction Details=\n"+txn);
}catch(Exception e){
System.out.println("Exception occured. "+e.getMessage());
e.printStackTrace();
}
}
private static Txn buildDemoTransaction() {
Txn txn = new Txn();
txn.setDate(new Date());
txn.setTotal(100);
Customer cust = new Customer();
cust.setAddress("Bangalore, San Franceco");
cust.setEmail("[email protected]");
cust.setName("hyman Kumar");
txn.setCustomer(cust);
cust.setTxn(txn);
return txn;
}
}
现在，当我们在Hibernate 测试程序中运行一对一映射时，将得到以下输出。
Hibernate Configuration loaded Hibernate serviceRegistry created Session created Hibernate: insert into TRANSACTION (txn_date, txn_total) values (?, ?) Hibernate: insert into CUSTOMER (cust_name, cust_email, cust_address, txn_id) values (?, ?, ?, ?) Transaction ID=19 Hibernate: select txn0_.txn_id as txn_id1_1_0_, txn0_.txn_date as txn_date2_1_0_, txn0_.txn_total as txn_tota3_1_0_, customer1_.txn_id as txn_id1_0_1_, customer1_.cust_name as cust_nam2_0_1_, customer1_.cust_email as cust_ema3_0_1_, customer1_.cust_address as cust_add4_0_1_ from TRANSACTION txn0_ left outer join CUSTOMER customer1_ on txn0_.txn_id=customer1_.txn_id where txn0_.txn_id=? Transaction Details= 19, 100.0, hyman Kumar, [email protected], Bangalore, San Franceco Closing SessionFactory
如您所见，它工作正常，我们能够使用交易ID从两个表中检索数据。
在内部检查Hibernate使用的SQL来获取数据，使用Hibernate的联接从两个表中获取数据。
Hibernate 一对一映射注释
在上一节中，我们了解了如何将基于XML的配置用于Hibernate 一对一映射，现在让我们看看如何使用JPA和Hibernate批注实现相同的目的。
Hibernate 配置文件
hibernate-annotation.cfg.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"https://hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.password">hyman123</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost/TestDB</property>
<property name="hibernate.connection.username">hyman</property>
<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="hibernate.current_session_context_class">thread</property>
<property name="hibernate.show_sql">true</property>
<mapping class="com.theitroad.hibernate.model.Txn1"
<mapping class="com.theitroad.hibernate.model.Customer1"
</session-factory>
</hibernate-configuration>
Hibernate 配置很简单，您可以看到我有两个模型类将与注释一起使用-Txn1和Customer1。
Hibernate 一对一映射注释示例模型类
对于Hibernate 的一对一映射注释配置，模型类是最重要的部分。
让我们看看我们的模型类的外观。
package com.theitroad.hibernate.model;
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.Table;
import org.hibernate.annotations.Cascade;
@Entity
@Table(name="TRANSACTION")
public class Txn1 {
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="txn_id")
private long id;
@Column(name="txn_date")
private Date date;
@Column(name="txn_total")
private double total;
@OneToOne(mappedBy="txn")
@Cascade(value=org.hibernate.annotations.CascadeType.SAVE_UPDATE)
private Customer1 customer;
@Override
public String toString(){
return id+", "+total+", "+customer.getName()+", "+customer.getEmail()+", "+customer.getAddress();
}
//Getter-Setter methods, omitted for clarity
}
请注意，大多数注释来自Java Persistence API，因为Hibernate提供了它的实现。
但是，对于级联，我们将需要使用Hibernate注释org.hibernate.annotations.Cascade和枚举org.hibernate.annotations.CascadeType。
package com.theitroad.hibernate.model;
import javax.persistence.Column;
import javax.persistence.Entity;
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="CUSTOMER")
public class Customer1 {
@Id
@Column(name="txn_id", unique=true, nullable=false)
@GeneratedValue(generator="gen")
@GenericGenerator(name="gen", strategy="foreign", parameters={@Parameter(name="property", value="txn")})
private long id;
@Column(name="cust_name")
private String name;
@Column(name="cust_email")
private String email;
@Column(name="cust_address")
private String address;
@OneToOne
@PrimaryKeyJoinColumn
private Txn1 txn;
//Getter-Setter methods
}
注意，我们需要使用@GenericGenerator，以便从txn使用id而不是生成它。
Hibernate SessionFactory Utility类
创建SessionFactory独立于我们提供Hibernate 映射的方式。
我们用于创建SessionFactory的实用程序类如下所示。
package com.theitroad.hibernate.util;
import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
public class HibernateAnnotationUtil {
private static SessionFactory sessionFactory;
private static SessionFactory buildSessionFactory() {
try {
//Create the SessionFactory from hibernate-annotation.cfg.xml
Configuration configuration = new Configuration();
configuration.configure("hibernate-annotation.cfg.xml");
System.out.println("Hibernate Annotation Configuration loaded");
ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
System.out.println("Hibernate Annotation serviceRegistry created");
SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
return sessionFactory;
}
catch (Throwable ex) {
System.err.println("Initial SessionFactory creation failed." + ex);
ex.printStackTrace();
throw new ExceptionInInitializerError(ex);
}
}
public static SessionFactory getSessionFactory() {
if(sessionFactory == null) sessionFactory = buildSessionFactory();
return sessionFactory;
}
}
Hibernate 一对一映射注释示例测试程序
这是Hibernate 的一对一映射注释示例的简单测试程序。
package com.theitroad.hibernate.main;
import java.util.Date;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import com.theitroad.hibernate.model.Customer1;
import com.theitroad.hibernate.model.Txn1;
import com.theitroad.hibernate.util.HibernateAnnotationUtil;
public class HibernateOneToOneAnnotationMain {
public static void main(String[] args) {
Txn1 txn = buildDemoTransaction();
SessionFactory sessionFactory = null;
Session session = null;
Transaction tx = null;
try{
//Get Session
sessionFactory = HibernateAnnotationUtil.getSessionFactory();
session = sessionFactory.getCurrentSession();
System.out.println("Session created using annotations configuration");
//start transaction
tx = session.beginTransaction();
//Save the Model object
session.save(txn);
//Commit transaction
tx.commit();
System.out.println("Annotation Example. Transaction ID="+txn.getId());
//Get Saved Trasaction Data
printTransactionData(txn.getId(), sessionFactory);
}catch(Exception e){
System.out.println("Exception occured. "+e.getMessage());
e.printStackTrace();
}finally{
if(sessionFactory != null && !sessionFactory.isClosed()){
System.out.println("Closing SessionFactory");
sessionFactory.close();
}
}
}
private static void printTransactionData(long id, SessionFactory sessionFactory) {
Session session = null;
Transaction tx = null;
try{
//Get Session
sessionFactory = HibernateAnnotationUtil.getSessionFactory();
session = sessionFactory.getCurrentSession();
//start transaction
tx = session.beginTransaction();
//Save the Model object
Txn1 txn = (Txn1) session.get(Txn1.class, id);
//Commit transaction
tx.commit();
System.out.println("Annotation Example. Transaction Details=\n"+txn);
}catch(Exception e){
System.out.println("Exception occured. "+e.getMessage());
e.printStackTrace();
}
}
private static Txn1 buildDemoTransaction() {
Txn1 txn = new Txn1();
txn.setDate(new Date());
txn.setTotal(100);
Customer1 cust = new Customer1();
cust.setAddress("San Jose, USA");
cust.setEmail("[email protected]");
cust.setName("hyman Kr");
txn.setCustomer(cust);
cust.setTxn(txn);
return txn;
}
}
这是我们执行上述程序时的输出片段。
Hibernate Annotation Configuration loaded Hibernate Annotation serviceRegistry created Session created using annotations configuration Hibernate: insert into TRANSACTION (txn_date, txn_total) values (?, ?) Hibernate: insert into CUSTOMER (cust_address, cust_email, cust_name, txn_id) values (?, ?, ?, ?) Annotation Example. Transaction ID=20 Hibernate: select txn1x0_.txn_id as txn_id1_1_0_, txn1x0_.txn_date as txn_date2_1_0_, txn1x0_.txn_total as txn_tota3_1_0_, customer1x1_.txn_id as txn_id1_0_1_, customer1x1_.cust_address as cust_add2_0_1_, customer1x1_.cust_email as cust_ema3_0_1_, customer1x1_.cust_name as cust_nam4_0_1_ from TRANSACTION txn1x0_ left outer join CUSTOMER customer1x1_ on txn1x0_.txn_id=customer1x1_.txn_id where txn1x0_.txn_id=? Annotation Example. Transaction Details= 20, 100.0, hyman Kr, [email protected], San Jose, USA Closing SessionFactory
请注意，输出类似于Hibernate 一对一基于XML的配置。
