Hibernate 使用 Annotation 4（一对多单向关联）-优快云博客

本文链接：https://blog.youkuaiyun.com/iteye_3779/article/details/82005594

本文介绍了一个使用Hibernate框架实现的简单一对多关系映射示例。通过Group和User两个实体类展示了如何定义实体间的关系，并提供了测试用例及Hibernate配置文件。

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Group.java代码：

package com.jlee04.one2moneydanxiang;

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

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.OneToMany;
import javax.persistence.Table;

@Entity
@Table(name="T_GROUP")
public class Group {

	private int id ;
	private String name ;
	private Set<User> user = new HashSet<User>() ;

	@OneToMany(fetch=FetchType.LAZY , cascade={CascadeType.ALL})
	@JoinColumn(name="groupId")
	public Set<User> getUser() {
		return user;
	}
	public void setUser(Set<User> user) {
		this.user = user;
	}
	@Id
	@GeneratedValue(strategy=GenerationType.AUTO)
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	
	@Column(name="name" , length=32)
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	
}

User.java代码：

package com.jlee04.one2moneydanxiang;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="T_USER")
public class User {

	private int id ;
	private String name ;
	
	@Id
	@GeneratedValue(strategy=GenerationType.AUTO)
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	
	@Column(name="name" , length=32)
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	
}

RelationsTest.java代码：

package com.jlee04.one2moneydanxiang;

import junit.framework.TestCase;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;

public class RelationsTest extends TestCase {

	public void testRelation(){
		SessionFactory sf = new AnnotationConfiguration()
														.configure().buildSessionFactory();
		Session session = sf.getCurrentSession() ;
		session.getTransaction().begin() ;
		
		
		
		session.getTransaction().commit() ;
	}
}

hibernate.cfg.xml配置文件：

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <!-- Database connection settings -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost/hibernate</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>

        <!-- JDBC connection pool (use the built-in) -->
        <property name="connection.pool_size">100</property>

        <!-- SQL dialect -->
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

        <!-- Enable Hibernate's automatic session context management -->
        <property name="current_session_context_class">thread</property>

        <!-- Disable the second-level cache  -->
        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
		
		 
        <!-- Echo all executed SQL to stdout -->
        <property name="show_sql">true</property>

         <property name="format_sql">true</property>
		
        <!-- Drop and re-create the database schema on startup -->
        <!--<property name="hbm2ddl.auto">create</property>-->

		<mapping class="com.jlee04.one2moneydanxiang.User"/>
		<mapping class="com.jlee04.one2moneydanxiang.Group"/>

    </session-factory>

</hibernate-configuration>