本例以Windows, JDK1.8, MySQL5 为基础，演示使用Hibernate5以注解的方式完成多对一的双向关系映射。

如果是双向关系关联，在多对一和一对多，存在相互的转换的过程，在一对多种，一方持有多方的集合，而多方持有一方的集合，而在多对一当中，多方持有一方的外键，一方持有多方的集合，也就是看站在那一方的角度，关于一对多的关系映射：Hibernate5 One-To-Many 一对多 Demo (Annotation)

使用的工具及技术

1.Hibernate 5.2.10.Final
2.MySQL 5
3.Eclipse
4.Maven 3

多对一的表的关系

Model

分别创建Employee和Company两个Model对象，在映射关系上，多个Employee对应一个Company。

File ： Employee.java

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package com.devnp.hibernate.association.mto.model;

import javax.persistence.Basic;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Entity
@Table(name = "Employee")
public class Employee {

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	@Basic(optional = false)
	@Column(name = "E_ID")
	private Long eId ;
	
	@Column(name = "E_NAME")
	private String eName ;
	
	@Column(name = "E_AGE")
	private Integer eAge ;
	
	@ManyToOne(fetch = FetchType.LAZY, cascade=CascadeType.ALL)
	@JoinColumn(name="CID", referencedColumnName="C_ID")
	private Company company ;
	
	public Employee() {
		super();
	}

	public Employee(String eName, Integer eAge) {
		super();
		this.eName = eName;
		this.eAge = eAge;
	}

	public Long geteId() {
		return eId;
	}

	public void seteId(Long eId) {
		this.eId = eId;
	}

	public String geteName() {
		return eName;
	}

	public void seteName(String eName) {
		this.eName = eName;
	}

	public Integer geteAge() {
		return eAge;
	}

	public void seteAge(Integer eAge) {
		this.eAge = eAge;
	}

	public Company getCompany() {
		return company;
	}

	public void setCompany(Company company) {
		this.company = company;
	}
	
}

File : Company.java

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package com.devnp.hibernate.association.mto.model;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.Basic;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Entity
@Table(name = "Company")
public class Company {

	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	@Basic(optional = false)
	@Column(name = "C_ID")
	private Long cId ;
	
	@Column(name = "C_NAME")
	private String cName ;
	
	@OneToMany(fetch = FetchType.LAZY, cascade=CascadeType.ALL, mappedBy="company")
	private Set<Employee> employees = new HashSet<Employee>() ;

	public Company() {
		super();
	}

	public Company(String cName) {
		super();
		this.cName = cName;
	}

	public Long getcId() {
		return cId;
	}

	public void setcId(Long cId) {
		this.cId = cId;
	}

	public String getcName() {
		return cName;
	}

	public void setcName(String cName) {
		this.cName = cName;
	}

	public Set<Employee> getEmployees() {
		return employees;
	}

	public void setEmployees(Set<Employee> employees) {
		this.employees = employees;
	}
	
	
	
}

Hibernate SessionFactory

本例以属性配置的加载，更多获取SessionFactory的方式:Hibernate5 SessionFactory 的获取

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package com.devnp.hibernate.util;

import java.util.Properties;

import org.hibernate.SessionFactory;
import org.hibernate.boot.Metadata;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.model.naming.ImplicitNamingStrategyJpaCompliantImpl;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;

import com.devnp.hibernate.association.mto.model.Company;
import com.devnp.hibernate.association.mto.model.Employee;
import com.devnp.hibernate.association.otm.model.Book;
import com.devnp.hibernate.association.otm.model.Person;
import com.devnp.hibernate.association.oto.model.Student;
import com.devnp.hibernate.association.oto.model.Transcripts;

public class HibernateProUtil {

	private static SessionFactory sessionFactory = buildSessionFactory();

	private static SessionFactory buildSessionFactory() {
		Properties properties = new Properties();
	    properties.put("hibernate.dialect","org.hibernate.dialect.MySQL5InnoDBDialect"); //数据库方言
	    properties.put("hibernate.show_sql", "true");	//是否打印SQL
	    properties.put("hibernate.hbm2ddl.auto","update"); //执行跟新，及如果表不存在则会自动创建表
	    
	    properties.put("hibernate.format_sql", "true"); //格式化
	    
	    properties.put("hibernate.connection.driver_class", "com.mysql.jdbc.Driver");
	    properties.put("hibernate.connection.password", "!qaz2wsx");
	    properties.put("hibernate.connection.url", "jdbc:mysql://localhost:3306/test");
	    properties.put("hibernate.connection.username", "root");

	    /*StandardServiceRegistryBuilder standardServiceRegistryBuilder = new StandardServiceRegistryBuilder();
	    standardServiceRegistryBuilder.applySettings(properties);

	    MetadataSources metadataSources = new MetadataSources(standardServiceRegistryBuilder.build());
	    metadataSources.addAnnotatedClass(Student.class);*/
	    
	    StandardServiceRegistry serviceRegistry= new StandardServiceRegistryBuilder().applySettings(properties).build();
	    
	    MetadataSources metadataSources = new MetadataSources(serviceRegistry);
	    metadataSources.addAnnotatedClass(Student.class).addAnnotatedClass(Transcripts.class);
	    
	    metadataSources.addAnnotatedClass(Person.class).addAnnotatedClass(Book.class);
	    
	    metadataSources.addAnnotatedClass(Employee.class).addAnnotatedClass(Company.class);
	    
	    Metadata metadata = metadataSources.getMetadataBuilder().applyImplicitNamingStrategy(
	    		ImplicitNamingStrategyJpaCompliantImpl.INSTANCE).build();
	    
	    sessionFactory = metadata.getSessionFactoryBuilder().build();  
	    
	    return sessionFactory;
	}

	public static SessionFactory getSessionFactory() {
		return sessionFactory;
	}

	public static void shutdown() {
		// Close caches and connection pools
		getSessionFactory().close();
	}
}

测试

以添加两个员工和一个公司为例：

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/**
 * 创建多个员工信息并保存
 */
public static void save(){
	SessionFactory sessionFactory = HibernateProUtil.getSessionFactory();

	Session session = sessionFactory.openSession();

	session.getTransaction().begin();
	
	
	Company company = new Company("devnp.com");
	
	Employee employee1 = new Employee("JACK", 22);
	Employee employee2 = new Employee("Alen", 25);
	
	employee1.setCompany(company);
	employee2.setCompany(company);
	
	session.save(employee1);
	session.save(employee2);
	
	session.getTransaction().commit();
	
	HibernateProUtil.shutdown();
	
}

运行结果：

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--Hibernate: 
    
    create table Company (
       C_ID bigint not null auto_increment,
        C_NAME varchar(255),
        primary key (C_ID)
    ) engine=InnoDB
--Hibernate: 
    
    create table Employee (
       E_ID bigint not null auto_increment,
        E_AGE integer,
        E_NAME varchar(255),
        CID bigint,
        primary key (E_ID)
    ) engine=InnoDB
--Hibernate: 
    
    alter table Employee 
       add constraint FKq3wcxuroflbk632vkfs6c87ht 
       foreign key (CID) 
       references Company (C_ID)
--Hibernate: 
    insert 
    into
        Company
        (C_NAME) 
    values
        (?)
--Hibernate: 
    insert 
    into
        Employee
        (CID, E_AGE, E_NAME) 
    values
        (?, ?, ?)
--Hibernate: 
    insert 
    into
        Employee
        (CID, E_AGE, E_NAME) 
    values
        (?, ?, ?)

更多测试

查询信息：

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public static void select(){
	SessionFactory sessionFactory = HibernateProUtil.getSessionFactory();

	Session session = sessionFactory.openSession();

	session.getTransaction().begin();
	
	Employee employee = session.get(Employee.class, 1L);
	
	System.out.println("Company ID : " + employee.getCompany().getcId() + " Name : " + employee.getCompany().getcName());
	
	session.getTransaction().commit();
	
	HibernateProUtil.shutdown();
}

查询信息：

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public static void select(){
	SessionFactory sessionFactory = HibernateProUtil.getSessionFactory();

	Session session = sessionFactory.openSession();

	session.getTransaction().begin();
	
	Employee employee = session.get(Employee.class, 1L);
	
	System.out.println("Company ID : " + employee.getCompany().getcId() + " Name : " + employee.getCompany().getcName());
	
	session.getTransaction().commit();
	
	HibernateProUtil.shutdown();
}

更新信息：

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public static void update(){
	SessionFactory sessionFactory = HibernateProUtil.getSessionFactory();

	Session session = sessionFactory.openSession();

	session.getTransaction().begin();
	
	Employee employee = session.get(Employee.class, 1L);
	
	employee.getCompany().setcName("www.devnp.com");
	
	session.update(employee);
	
	session.getTransaction().commit();
	
	HibernateProUtil.shutdown();
}

删除信息：

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public static void delete(){
	SessionFactory sessionFactory = HibernateProUtil.getSessionFactory();

	Session session = sessionFactory.openSession();

	session.getTransaction().begin();
	
	Employee employee = session.get(Employee.class, 1L);
	
	session.delete(employee);
	
	session.getTransaction().commit();
	
	HibernateProUtil.shutdown();
}

代码下载

java-hibernate-association-demo.zip