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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