使用注解Hibernate多对一映射

本文概述

• 1）一对一映射的持久类
• 2）在pom.xml文件中添加项目信息和配置。
• 3）配置文件
• 4）用于存储和获取数据的用户类

在多对一映射中, 各种属性只能称为一个属性。

在此示例中, 每个员工只有一个公司地址, 而一个地址属于许多员工。在这里, 我们将使用注释执行多对一映射。

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;
import javax.persistence.*;

@Entity
@Table(name="emp107")
public class Employee {  
	 @Id
	 @GeneratedValue(strategy=GenerationType.AUTO)	
private int employeeId;  
private String name, email;  
@ManyToOne(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 com.srcmini;

import javax.persistence.*;

@Entity
@Table(name="address107")
public class Address {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
	private int addressId;  
	private String addressLine1, city, state, country;  
	private int pincode;  
   @OneToOne(cascade=CascadeType.ALL)
	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, 然后单击源。现在, 在<dependencies> …. </ dependencies>标记之间添加以下依赖关系。这些依赖关系用于在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

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">create</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="com.srcmini.Address"/>  
    <mapping class="com.srcmini.Employee"/>  
    </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");  
    
    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");  
}  
}

输出值

Fetch.java

package com.srcmini;  
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");  
}  
}

输出量

输出量