Hibernate 零配置之Annotation註解

JPA規範推薦使用Annotation來管理實體類與數據表之間的映射關係，從而避免同時維護兩份文件（Java 實體類和 XML 映射文件），將映射信息（寫在Annotation中）與實體類集中在一起。以下我將使用eclipse來構建一個簡單使用註解取代*.hbm.xml的查詢小例子。（p.s 建 ...

　　JPA規範推薦使用Annotation來管理實體類與數據表之間的映射關係，從而避免同時維護兩份文件（Java 實體類和 XML 映射文件），將映射信息（寫在Annotation中）與實體類集中在一起。

　　以下我將使用eclipse來構建一個簡單使用註解取代*.hbm.xml的查詢小例子。（p.s 建議不要使用Myeclipse，他很方便但是對於初學者來說沒有eclipse學得牢靠）

1.在資料庫中構建一張表

2.生成相應的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>

View Code

註意，在生成cfg.xml文件時，要create Hibernate Console Configuration

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>

View Code

在Eclipse界面工具欄，擇Hibernate code generation Configuration，new 一個新的配置。

4.選擇Exporters的選項，接下來是重點！！！

選擇勾選的兩項，不再選.hbm.xml.

點擊Run。

5.只生成了與數據表對應的實體類Commodity.java，而沒有生成與該實體類對應的映射文件Commodity.hbm.xml,打開實體類

package com.zzh;
// Generated 2016-8-28 9:42:01 by Hibernate Tools 4.3.1.Final

import 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註解，表示當前類為實體Bean，需要進行持久化，使用@Table註解實現數據表 commodity 與持久化類Commodity之間的映射，@Id註解指定當前持久化類的ID屬性，使用@GeneratedValue註解指定ID表示生成器，使用@Column註解指定當前屬性所對應的數據表中的欄位，name指定欄位名；unique指定是否為唯一，nullable指定是否可為null。

6.在hibernate.cfg.xml中配置映射信息

一定要註意mapping後面是class，如果是配置*.hbm.xml就是resource。

7.添加會話工廠類HibernateUtil以獲取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 {
        // 創建Configuration對象，讀取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);
    }
    
    //獲取SessionFactory
    public static SessionFactory getSessionFactory(){
        return sessionFactory;
    }
    
    //獲取Session
    public static Session getSession(){
        session=sessionFactory.openSession();
        return session;
    }
    
    //關閉Session
    public static void closeSession(Session session){
        if(session!=null){
            session.close();
        }
    }
}

View Code

8.用JUnit創建一個類ZhuShi.java用於測試

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());
        }
    }

}