Hibernate教程-Hibernate 一对一关系示例（使用注解）

在这里，我们将通过 one-to-one 元素使用注解来实现一对一的映射。在这种情况下，主表中不会创建外键。

在这个示例中，一个员工可以有一个地址，一个地址也只属于一个员工。这里我们使用双向关联。让我们来看看持久类。

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;

import javax.persistence.*;

@Entity
@Table(name="emp220")
public class Employee {  
   
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    @PrimaryKeyJoinColumn
    private int employeeId;  
    private String name, email;  

    @OneToOne(targetEntity=Address.class, cascade=CascadeType.ALL)
    private Address address; 

    public int getEmployeeId() {
        return employeeId; 
    } 

    public void setEmployeeId(int employeeId) { 
        this.employeeId = employeeId; 
    } 

    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 Address getAddress() { 
        return address; 
    } 

    public void setAddress(Address address) { 
        this.address = address; 
    }  
}

Address.java

package cn.javatiku;

import javax.persistence.*;

@Entity
@Table(name="address220")
public class Address {  
   
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int addressId;  
    private String addressLine1, city, state, country;  
    private int pincode;  

    @OneToOne(targetEntity=Employee.class)
    private Employee employee; 

    public int getAddressId() { 
        return addressId; 
    } 

    public void setAddressId(int addressId) { 
        this.addressId = addressId; 
    } 

    public String getAddressLine1() { 
        return addressLine1; 
    } 

    public void setAddressLine1(String addressLine1) { 
        this.addressLine1 = addressLine1; 
    } 

    public String getCity() { 
        return city; 
    } 

    public void setCity(String city) { 
        this.city = city; 
    } 

    public String getState() { 
        return state; 
    } 

    public void setState(String state) { 
        this.state = state; 
    } 

    public String getCountry() { 
        return country; 
    } 

    public void setCountry(String country) { 
        this.country = country; 
    } 

    public int getPincode() { 
        return pincode; 
    } 

    public void setPincode(int pincode) { 
        this.pincode = pincode; 
    } 

    public Employee getEmployee() { 
        return employee; 
    } 

    public void setEmployee(Employee employee) { 
        this.employee = employee; 
    }  
}

2) 在 pom.xml 文件中添加项目信息和配置

打开 pom.xml 文件并点击源代码。现在，在 <dependencies>....</dependencies> 标签之间添加以下依赖项。这些依赖项用于在 Maven 项目中添加 jar 文件。

<dependency>  
    <groupId>org.hibernate</groupId>  
    <artifactId>hibernate-core</artifactId>  
    <version>5.3.1.Final</version>  
</dependency>  

<dependency>  
    <groupId>com.oracle</groupId>  
    <artifactId>ojdbc14</artifactId>  
    <version>10.2.0.4.0</version>  
</dependency>  

3) 配置文件

此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 class="cn.javatiku.Address"/>  
        <mapping class="cn.javatiku.Employee"/>  
    </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");  

        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

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");  
        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