使用XML的Hibernate一对一示例

有两种方法可以在Hibernate模式下执行一对一的映射：

• 通过多对一元素（使用unique =“ true”属性）
• 一对一要素

在这里, 我们将通过一对一元素执行一对一映射。在这种情况下, 不会在主表中创建任何外键。

在此示例中, 一个雇员可以有一个地址, 而一个地址仅属于一个雇员。在这里, 我们使用双向关联。让我们看一下持久化类。

1）一对一映射的持久类

有两个持久性类Employee.java和Address.java。雇员类包含地址类引用, 反之亦然。

Employee.java

package com.srcmini; public class Employee { private int employeeId; private String name, email; private Address address; //setters and getters }

Address.java

package com.srcmini; public class Address { private int addressId; private String addressLine1, city, state, country; private int pincode; private Employee employee; //setters and getters }

2）持久类的映射文件

这两个映射文件是employee.hbm.xml和address.hbm.xml。

employee.hbm.xml

在此映射文件中, 我们在两个映射文件中都使用了一对一元素来进行一对一映射。

<?xml version='1.0' encoding='UTF-8'?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 5.3//EN" "http://hibernate.sourceforge.net/hibernate-mapping-5.3.dtd"> <hibernate-mapping> <class name="com.srcmini.Employee" table="emp212"> <id name="employeeId"> <generator class="increment"></generator> </id> <property name="name"></property> <property name="email"></property> <one-to-one name="address" cascade="all"></one-to-one> </class> </hibernate-mapping>

address.hbm.xml

这是Address类的简单映射文件。但是重要的是生成器类。在这里, 我们使用依赖于Employee类主键的外部生成器类。

<?xml version='1.0' encoding='UTF-8'?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 5.3//EN" "http://hibernate.sourceforge.net/hibernate-mapping-5.3.dtd"> <hibernate-mapping> <class name="com.srcmini.Address" table="address212"> <id name="addressId"> <generator class="foreign"> <param name="property">employee</param> </generator> </id> <property name="addressLine1"></property> <property name="city"></property> <property name="state"></property> <property name="country"></property> <property name="pincode"></property> <one-to-one name="employee"></one-to-one> </class> </hibernate-mapping>

3）配置文件

该文件包含有关数据库和映射文件的信息。

hibernate.cfg.xml

<?xml version='1.0' encoding='UTF-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 5.3//EN" "http://hibernate.sourceforge.net/hibernate-configuration-5.3.dtd"> <hibernate-configuration> <session-factory> <property name="hbm2ddl.auto">update</property> <property name="dialect">org.hibernate.dialect.Oracle9Dialect</property> <property name="connection.url">jdbc:oracle:thin:@localhost:1521:xe</property> <property name="connection.username">system</property> <property name="connection.password">jtp</property> <property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property> <mapping resource="employee.hbm.xml"/> <mapping resource="address.hbm.xml"/> </session-factory> </hibernate-configuration>

4）用于存储和获取数据的用户类

Store.java

package com.srcmini; import org.hibernate.*; import org.hibernate.boot.Metadata; import org.hibernate.boot.MetadataSources; import org.hibernate.boot.registry.StandardServiceRegistry; import org.hibernate.boot.registry.StandardServiceRegistryBuilder; public class Store { public static void main(String[] args) {	StandardServiceRegistry ssr=new StandardServiceRegistryBuilder().configure("hibernate.cfg.xml").build();	Metadata meta=new MetadataSources(ssr).getMetadataBuilder().build();	SessionFactory factory=meta.getSessionFactoryBuilder().build();	Session session=factory.openSession(); Transaction t=session.beginTransaction(); Employee e1=new Employee(); e1.setName("Ravi Malik"); e1.setEmail("ravi@gmail.com"); Address address1=new Address(); address1.setAddressLine1("G-21, Lohia nagar"); address1.setCity("Ghaziabad"); address1.setState("UP"); address1.setCountry("India"); address1.setPincode(201301); e1.setAddress(address1); address1.setEmployee(e1); session.persist(e1); t.commit(); session.close(); System.out.println("success"); } }

输出量

Fetch.java

package com.srcmini; import java.util.*; import javax.persistence.TypedQuery; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.boot.Metadata; import org.hibernate.boot.MetadataSources; import org.hibernate.boot.registry.StandardServiceRegistry; import org.hibernate.boot.registry.StandardServiceRegistryBuilder; public class Fetch { public static void main(String[] args) {	StandardServiceRegistry ssr=new StandardServiceRegistryBuilder().configure("hibernate.cfg.xml").build();	Metadata meta=new MetadataSources(ssr).getMetadataBuilder().build();	SessionFactory factory=meta.getSessionFactoryBuilder().build();	Session session=factory.openSession(); TypedQuery query=session.createQuery("from Employee e"); List<Employee> list=query.getResultList(); Iterator<Employee> itr=list.iterator(); while(itr.hasNext()){ Employee emp=itr.next(); System.out.println(emp.getEmployeeId()+" "+emp.getName()+" "+emp.getEmail()); Address address=emp.getAddress(); System.out.println(address.getAddressLine1()+" "+address.getCity()+" "+ address.getState()+" "+address.getCountry()+" "+address.getPincode()); } session.close(); System.out.println("success"); } }

输出量

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