Hibernate_01_初体验

hibernate开发的基本步骤：

1. 编写配置文档hibernate.cfg.xml；
2. 编写实体类；
3. 生成对应实体类的映射文件并添加到配置文档中；
4. 调用hibernate API进行测试。

Hibernate的一个小例子（慕课网教程整理的代码）：

首先在eclipse--help--Eclipse MarketPlace中搜索“jboss Tool”

导入hibernate核心jar包、Junit包。

创建一个java类：

 1 package com.imooc.hibernate;
 2 
 3 import java.util.Date;
 4 
 5 public class Students {
 6 
 7     private int sid;
 8     private String sname;
 9     private String gender;
10     private Date birthday;
11     private String address;
12 
13     public Students(int sid, String sname, String gender, Date birthday, String address) {
14         super();
15         this.sid = sid;
16         this.sname = sname;
17         this.gender = gender;
18         this.birthday = birthday;
19         this.address = address;
20     }
21 
22     @Override
23     public String toString() {
24         return "Students [sid=" + sid + ", sname=" + sname + ", gender=" + gender + ", birthday=" + birthday
25                 + ", address=" + address + "]";
26     }
27 
28     public int getSid() {
29         return sid;
30     }
31 
32     public void setSid(int sid) {
33         this.sid = sid;
34     }
35 
36     public String getSname() {
37         return sname;
38     }
39 
40     public void setSname(String sname) {
41         this.sname = sname;
42     }
43 
44     public String getGender() {
45         return gender;
46     }
47 
48     public void setGender(String gender) {
49         this.gender = gender;
50     }
51 
52     public Date getBirthday() {
53         return birthday;
54     }
55 
56     public void setBirthday(Date birthday) {
57         this.birthday = birthday;
58     }
59 
60     public String getAddress() {
61         return address;
62     }
63 
64     public void setAddress(String address) {
65         this.address = address;
66     }
67 }

 点击项目名，右键new--other--自动生成类的配置文件：

 

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2017-5-23 0:24:09 by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping>
    <class name="com.imooc.hibernate.Students" table="STUDENTS">
        <id name="sid" type="int">
            <column name="SID" />
            <generator class="assigned" />
        </id>
        <property name="sname" type="java.lang.String">
            <column name="SNAME" />
        </property>
        <property name="gender" type="java.lang.String">
            <column name="GENDER" />
        </property>
        <property name="birthday" type="java.util.Date">
            <column name="BIRTHDAY" />
        </property>
        <property name="address" type="java.lang.String">
            <column name="ADDRESS" />
        </property>
    </class>
</hibernate-mapping>

 生成hibernate配置文件：

<?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="connection.username">root</property>
        <property name="connection.password">root</property>
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/hibernate?useUnicode=true&amp;characterEncoding=UTF-8</property>
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
        <!-- 是否将sql语句打印到控制台，编码阶段便于测试，建议设为true -->
        <property name="show_sql">true</property>
        <!-- 是否将sql语句进行排版，建议设为true -->
        <property name="format_sql">true</property>
        <!-- 生成表结构的策略。create是如果之前有表结构，先删除表结构再重建；
            update：原有的基础上更新；
            create-drop：先删除表结构再重建
            validate：与原表进行验证，如果和原表表结构不同，则不进行创建。
            一般使用create和update
         -->
        <property name="hbm2ddl.auto">create</property>
        
        <mapping resource="com/imooc/hibernate/Students.hbm.xml"/>
    </session-factory>
</hibernate-configuration>

 写StudentsTest.java文件：

package com.icoom.test;
import static org.junit.Assert.fail;

import java.util.Date;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.imooc.hibernate.Students;

public class StudentsTest {
    
    private SessionFactory sessionFactory;
    private Session session;
    private Transaction transaction;

    @Before
    public void init() {
        // 1.创建配置对象
        Configuration config = new Configuration().configure();
        // 2.创建服务注册对象
        ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
        // 3.创建会话工厂对象
        sessionFactory = config.buildSessionFactory(serviceRegistry);
        // 会话对象
        session = sessionFactory.openSession();
        // 开启事务
        transaction = session.beginTransaction();
    }
    @After
    public void destory() {
        transaction.commit();
        session.close();
        sessionFactory.close();
    }
    @Test
    public void testSaveStudents() {
        // 生成学生对象
        Students s = new Students(1, "老张", "男", new Date(), "山东");
        session.save(s);//保存对象进入数据库
    }

}

使用Junit执行，然后在数据库中就会看到新建的表结构和插入的数据。

hibernate.cfg.xml文件中的<property name="hbm2ddl.auto">create</property>指定由hibernate新建表。

-------------------------------------

以上是对hibernate的配置文件元素的作用和hibernate的用法做一个简单的了解，一开始学习新技术要保持不求甚解，先快速入门以避免从入门到放弃。等达到一定熟练度再深入了解其原理。因此强烈推荐慕课网的教程，先快速了解再深入学习。