Hibernate教程-Hibernate 多对一关系示例（使用 XML）

在多对一映射中，多个属性可以引用同一个属性。

在这个示例中，每个员工只有一个公司地址，一个地址可以属于多个员工。这里我们将使用 XML 来执行多对一映射。

1) 一对一映射的持久类

这里有两个持久类 Employee.java 和 Address.java。Employee 类包含 Address 类的引用，反之亦然。

Employee.java

package cn.javatiku;

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

Address.java

package cn.javatiku;

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

两个映射文件分别是 employee.hbm.xml 和 address.hbm.xml。

employee.hbm.xml

<?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="cn.javatiku.Employee" table="emp22">
        <id name="employeeId">
            <generator class="increment"></generator>
        </id>
        <property name="name"></property>
        <property name="email"></property>
        <many-to-one name="address" cascade="all"></many-to-one>
    </class>
</hibernate-mapping>

address.hbm.xml

<?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="cn.javatiku.Address" table="address22">
        <id name="addressId">
            <generator class="increment"></generator>
        </id>
        <property name="addressLine1"></property>
        <property name="city"></property>
        <property name="state"></property>
        <property name="country"></property>
        <property name="pincode"></property>
    </class>
</hibernate-mapping>

3) 配置文件

此文件包含有关数据库和映射文件的信息。

<?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) 存储和获取数据的用户类

Store.java

package cn.javatiku;

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");

        Employee e2 = new Employee();
        e2.setName("Anuj Verma");
        e2.setEmail("anuj@gmail.com");

        Address address1 = new Address();
        address1.setAddressLine1("G-13,Sector 3");
        address1.setCity("Noida");
        address1.setState("UP");
        address1.setCountry("India");
        address1.setPincode(201301);

        e1.setAddress(address1);
        e2.setAddress(address1);

        session.persist(e1);
        session.persist(e2);
        t.commit();

        session.close();
        System.out.println("success");
    }
}

输出

Fetch.java

package cn.javatiku;

import java.util.Iterator;
import java.util.List;

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