Hibernate 零配置之Annotation注解

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Hibernate 零配置之Annotation注解

2024-08-11 02:37:53 223人阅读

　　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 XML 映射文件），将映射信息（写在Annotation中）与实体类集中在一起。

　　以下我将使用eclipse来构建一个简单使用注解取代*.hbm.xml的查询小例子。（p.s 建议不要使用Myeclipse，他很方便但是对于初学者来说没有eclipse学得牢靠）

1.在数据库中构建一张表

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2.生成相应的hibernate.cfg.xml文件

<?xml version="1.0" encoding="UTF-8"?><!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>        <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.xml文件时，要create Hibernate Console Configuration

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3.生成hibernate.reveng.xml逆向工程

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-reverse-engineering PUBLIC "-//Hibernate/Hibernate Reverse Engineering DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-reverse-engineering-3.0.dtd" ><hibernate-reverse-engineering>  <table-filter match-catalog="zzh" match-name="commodity"/></hibernate-reverse-engineering>

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在Eclipse界面工具栏，择Hibernate code generation Configuration，new 一个新的配置。

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4.选择Exporters的选项，接下来是重点！！！

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选择勾选的两项，不再选.hbm.xml.

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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.xml,打开实体类

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.xml中配置映射信息

一定要注意mapping后面是class，如果是配置*.hbm.xml就是resource。

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.xml文件，完成初始化        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());        }    }}