【8.2】注解方式：双向多对一-优快云博客

本文介绍了一个使用Hibernate框架实现的书籍与类别关联映射的示例，包括实体类定义、配置文件设置及简单的测试代码。

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1.Book类和Category类

package cn.siggy.pojo;

import java.util.Date;

import javax.persistence.CascadeType;
import javax.persistence.Entity;
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表示需要持久化的实体类
@Entity
//实体类 所对应的表
@Table
public class Book {
	//id主键
	@Id
	//指定 主键生成策略
	@GeneratedValue(strategy=GenerationType.AUTO)
	private int id;
	private String name;
	private double price;
	private String author;
	private Date pubDate;
	@ManyToOne(cascade=CascadeType.ALL)
	@JoinColumn(name="category_id")
	private Category category;
	/*get/set*/
}

===========================

package cn.siggy.pojo;

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

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

@Entity
@Table
public class Category {
	@Id
	@GeneratedValue(strategy=GenerationType.AUTO)
	private int id;
	private String name;
	@OneToMany(mappedBy="category")
	private Set<Book> books = new HashSet<Book>();
	/*get/set*/
}

2.Hibernate.cfg.xml

<!DOCTYPE hibernate-configuration PUBLIC
	"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
	"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
<session-factory>
	<!--数据库信息  -->
	<property name="connection.driver_class">
		com.mysql.jdbc.Driver
	</property>
	<property name="connection.url">jdbc:mysql:///hibernate4</property>
	<property name="connection.username">root</property>
	<property name="connection.password">root</property>
	<!--hibernate可选项 -->
	<property name="dialect">
		org.hibernate.dialect.MySQLDialect
	</property>
	<property name="show_sql">true</property>
	<property name="format_sql">true</property>
	<property name="hbm2ddl.auto">update</property>
	<!-- hbm文件 -->
	<mapping class="cn.siggy.pojo.Book" />
	<mapping class="cn.siggy.pojo.Category" />
</session-factory>
</hibernate-configuration>

3.测试代码

package cn.siggy.test;

import java.util.Date;

import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.junit.Test;

import cn.siggy.pojo.Book;
import cn.siggy.pojo.Category;
import cn.siggy.util.HibernateUtil;

public class HibernateTest {
	@Test
	public void testCreateDB(){
		//3.x
		//Configuration cfg = new AnnotationConfiguration().configure();
		Configuration cfg = new Configuration().configure();
		SchemaExport se = new SchemaExport(cfg);
		se.create(true, true);
	}
	@Test
	public void testSave(){
		Session session = HibernateUtil.getSession();
		Book book = new Book();
		book.setName("丰乳肥臀");
		book.setPrice(60.5);
		book.setAuthor("莫言");
		book.setPubDate(new Date());
		
		Category category = new Category();
		category.setName("文学");
		book.setCategory(category);
		Transaction tx = session.beginTransaction();
		session.save(book);
		tx.commit();
		HibernateUtil.closeSession();
	}
	@Test
	public void testGet(){
		Session session = HibernateUtil.getSession();
		Transaction tx = session.beginTransaction();
		Book book = (Book)session.get(Book.class, 1);
		System.out.println(book.getName()+"---"+book.getCategory().getName());
		
		tx.commit();
		HibernateUtil.closeSession();
	}
}

转载于:https://www.cnblogs.com/chxbar/p/6686677.html