JPA规范推荐使用Annotation来管理实体类与数据表之间的映射关系，从而避免同时维护两份文件（Java 实体类 和
以下我将使用eclipse来构建一个简单使用注解取代*.hbm.
1.在数据库中构建一张表
2.生成相应的hibernate.cfg.
<?configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><hibernate-configuration> <session-factory> <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property> <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property> <property name="hibernate.connection.password">root</property> <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/zzh</property> <property name="hibernate.connection.username">root</property> <property name="show_sql">true</property> <property name="hbm2ddl.auto">update</property> </session-factory></hibernate-configuration>
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注意，在生成cfg.
3.生成hibernate.reveng.
<?
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在Eclipse界面工具栏，择Hibernate code generation Configuration，new 一个新的配置。
4.选择Exporters的选项，接下来是重点！！！
选择勾选的两项，不再选.hbm.
点击Run。
5.只生成了与数据表对应的实体类Commodity.java，而没有生成与该实体类对应的映射文件Commodity.hbm.
package com.zzh;// Generated 2016-8-28 9:42:01 by Hibernate Tools 4.3.1.Finalimport javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import static javax.persistence.GenerationType.IDENTITY;import javax.persistence.Id;import javax.persistence.Table;/** * Commodity generated by hbm2java */@Entity@Table(name = "commodity", catalog = "zzh")public class Commodity implements java.io.Serializable { private Integer id; private String name; private Double price; private String unit; private String category; private String description; private Integer seller; public Commodity() { } public Commodity(String name, Double price, String unit, String category, String description, Integer seller) { this.name = name; this.price = price; this.unit = unit; this.category = category; this.description = description; this.seller = seller; } @Id @GeneratedValue(strategy = IDENTITY) @Column(name = "Id", unique = true, nullable = false) public Integer getId() { return this.id; } public void setId(Integer id) { this.id = id; } @Column(name = "name", length = 100) public String getName() { return this.name; } public void setName(String name) { this.name = name; } @Column(name = "price", precision = 11) public Double getPrice() { return this.price; } public void setPrice(Double price) { this.price = price; } @Column(name = "unit", length = 50) public String getUnit() { return this.unit; } public void setUnit(String unit) { this.unit = unit; } @Column(name = "category", length = 100) public String getCategory() { return this.category; } public void setCategory(String category) { this.category = category; } @Column(name = "description", length = 1000) public String getDescription() { return this.description; } public void setDescription(String description) { this.description = description; } @Column(name = "seller") public Integer getSeller() { return this.seller; } public void setSeller(Integer seller) { this.seller = seller; }}
使用@Entity注解，表示当前类为实体Bean，需要进行持久化，使用@Table注解实现数据表 commodity 与持久化类Commodity之间的映射，@Id注解指定当前持久化类的ID属性，使用@GeneratedValue注解指定ID表示生成器，使用@Column注解指定当前属性所对应的数据表中的字段，name指定字段名；unique指定是否为唯一，nullable指定是否可为null。
6.在hibernate.cfg.
<mapping />
一定要注意mapping后面是class，如果是配置*.hbm.。
7.添加会话工厂类HibernateUtil以获取Session
package com.zzh.utl;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.boot.registry.StandardServiceRegistry;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;import org.hibernate.cfg.Configuration;public class HibernateUtil { private static SessionFactory sessionFactory; private static Session session; static { // 创建Configuration对象，读取hibernate.cfg. Configuration config = new Configuration().configure(); StandardServiceRegistryBuilder ssrb = new StandardServiceRegistryBuilder() .applySettings(config.getProperties()); StandardServiceRegistry ssr=ssrb.build(); sessionFactory=config.buildSessionFactory(ssr); } //获取SessionFactory public static SessionFactory getSessionFactory(){ return sessionFactory; } //获取Session public static Session getSession(){ session=sessionFactory.openSession(); return session; } //关闭Session public static void closeSession(Session session){ if(session!=null){ session.close(); } }}
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8.用JUnit创建一个类ZhuShi.java用于测试
package anno;import static org.junit.Assert.*;import java.util.List;import org.hibernate.Query;import org.hibernate.Session;import org.junit.After;import org.junit.Before;import org.junit.Test;import org.hibernate.annotations.*;import com.zzh.Commodity;import com.zzh.utl.HibernateUtil;public class ZhuShi { Session session = null; @Before public void setUp() throws Exception { session = HibernateUtil.getSession(); } @After public void tearDown() throws Exception { session.close(); } @Test public void test() { String hql = " from Commodity "; Query query = session.createQuery(hql); List<Commodity> c = query.list(); for (Commodity commodity : c) { System.out.println("name"+commodity.getName()); } }}
9.整个文件已经形成
运行测试，得到结果
10.总结
原来大量的*.hbm.
11.个人想法
之前我有过不用注解后来因为路径调试半天的经历，那时自己也是笨，我就跟大家讲讲；我当时也是用反向工程生成实体类，还有*.hbm.
由于是工具帮我生成的我也没在意，然后高高兴兴去配置cfg.
全部文件如下所示：
以为一切顺利，便用JUnit进行测试：
实体类无法找到，坑爹呀，我都是按工具一步一步来的呀，为什么会这样，后来才发现*.hbm.
再进行测试：
总算成功了，这不代表*.hbm.
在这之后我会继续写一些关联映射的注释案例（比如双向一对多和双向多对多），如果你觉得还不错，请继续关注我或帮我点赞，谢谢观看！
---参考资料《Struts2+Spring3+Hibernate框架技术精讲与整合案例》
原标题：Hibernate 零配置之Annotation注解
关键词：Hibernate
我知道了 