一個簡單的Hibernate例子的心得

今天看了一下12*給我的那個Hibernate的簡單實例,結果弄了一個下午才搞定.有點感想和大家分享一下下. 稍後會把程序貼出來給大家展示一下出錯地方.
1.開發環境eclipse3.2.1,mysql5.0
2, 首先是開發環境配置上,我最開始的時候是把Hibernate所需的jar導入到window--refrences-java-installed jar中,結果編譯好多次也不行,後來我就把jar全部刪除了,在我建的項目上單擊右鍵,選擇Properties-java build path中,選擇add external jars,將需要的jar加入即可
3,上面完成後我執行程序發現數據不能插入到數據庫,但是能夠顯示插入的sql語句,並且可以從數據庫取出數據,試了一下才發現原因是建表的時候沒有把主鍵ID設置爲自動增加,致使無法插入,原因是我在xml文件中配置的主鍵的時候使用了這個<generator class="identity"/>,而他所對應的數據庫主鍵必須是自動增加的,這只是我理解的,因爲實在找不出其他原因了^_^.
收穫就這麼點,還是給大家看看代碼吧:
所需jar文件:
antlr.jar
cglib.jar
asm.jar
asm-attrs.jar
common-collections.jar
common-logging.jar
ehcache.jar
hibernate3.jar
jta.jar
dom4j.jar
log4j.jar
mysql初始化語句:
# MySQL-Front 3.1  (Build 9.0)


# Host: localhost    Database: demo
# ------------------------------------------------------
# Server version 5.0.22-community-nt

#
# Table structure for table user
#

CREATE TABLE `user` (
  `id` int(6) NOT NULL auto_increment,
  `name` varchar(255) NOT NULL,
  `age` int(6) NOT NULL default '0',
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=gbk;

#
# Dumping data for table user
#

INSERT INTO `user` VALUES (1,'david',23);
INSERT INTO `user` VALUES (2,'caterpillar',30);
INSERT INTO `user` VALUES (3,'caterpillar',30);
 # MySQL-Front 3.1  (Build 9.0)


# Host: localhost    Database: demo
# ------------------------------------------------------
# Server version 5.0.22-community-nt

#
# Table structure for table user
#

CREATE TABLE `user` (
  `id` int(6) NOT NULL auto_increment,
  `name` varchar(255) NOT NULL,
  `age` int(6) NOT NULL default '0',
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=gbk;

#
# Dumping data for table user
#

INSERT INTO `user` VALUES (1,'david',23);
INSERT INTO `user` VALUES (2,'caterpillar',30);
INSERT INTO `user` VALUES (3,'caterpillar',30);
# MySQL-Front 3.1  (Build 9.0)


# Host: localhost    Database: demo
# ------------------------------------------------------
# Server version 5.0.22-community-nt

#
# Table structure for table user
#

CREATE TABLE `user` (
  `id` int(6) NOT NULL auto_increment,
  `name` varchar(255) NOT NULL,
  `age` int(6) NOT NULL default '0',
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=gbk;

#
# Dumping data for table user
#

INSERT INTO `user` VALUES (1,'david',23);
INSERT INTO `user` VALUES (2,'caterpillar',30);
INSERT INTO `user` VALUES (3,'caterpillar',30);


# MySQL-Front 3.1  (Build 9.0)


# Host: localhost    Database: demo
# ------------------------------------------------------
# Server version 5.0.22-community-nt

#
# Table structure for table user
#

CREATE TABLE `user` (
  `id` int(6) NOT NULL auto_increment,
  `name` varchar(255) NOT NULL,
  `age` int(6) NOT NULL default '0',
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=gbk;

#
# Dumping data for table user
#

INSERT INTO `user` VALUES (1,'david',23);
INSERT INTO `user` VALUES (2,'caterpillar',30);
INSERT INTO `user` VALUES (3,'caterpillar',30);

數據庫配置文件:用戶名和密碼根據自己數據庫設置的進行修改
hibernate.cfg.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
    "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
   
<hibernate-configuration>
    <session-factory>
        <property name="show_sql">
            true
        </property>

        <property name="dialect">
            org.hibernate.dialect.MySQLDialect
        </property>

        <property name="connection.driver_class">
            com.mysql.jdbc.Driver
        </property>

        <property name="connection.url">
            jdbc:mysql://localhost:3306/demo
        </property>

        <property name="connection.username">
            root
        </property>

        <property name="connection.password">
            851120
        </property>

        <!-- 以下設置物件與資料庫表格映射文件 -->
        <mapping resource="onlyfun/caterpillar/User.hbm.xml"/>
        <mapping resource="events/Event.hbm.xml"/>
    </session-factory>
</hibernate-configuration>
user表對應的類:
package onlyfun.caterpillar;

public class User {
    private Integer id;
    private String name;
    private Integer age;
   
    public Integer getId() {
        return id;
    }
   
    public void setId(Integer id) {
        this.id = id;
    }
   
    public String getName() {
        return name;
    }
   
    public void setName(String name) {
        this.name = name;
    }
   
    public Integer getAge() {
        return age;
    }
   
    public void setAge(Integer age) {
        this.age = age;
    }
}
user對應的xml文件
User.hbm.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping
    PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

    <class name="onlyfun.caterpillar.User"
           table="user">

        <id name="id" column="id">
            <generator class="identity"/>
        </id>

        <property name="name" column="name"/>

        <property name="age" column="age"/>

    </class>

</hibernate-mapping>
控制操作的接口:
package onlyfun.caterpillar;

public interface IUserDAO {
    public void insert(User user);
    public User find(Integer id);
}
接口實現
package onlyfun.caterpillar;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;

public class UserDAO implements IUserDAO {
    private SessionFactory sessionFactory;
   
    public UserDAO() {
    }
   
    public UserDAO(SessionFactory sessionFactory) {
        this.setSessionFactory(sessionFactory);
    }
   
    public void setSessionFactory(SessionFactory sessionFactory) {
        this.sessionFactory = sessionFactory;
    }
   
    public void insert(User user) {
        // 取得Session
        Session session = sessionFactory.openSession();
        // 開啓事務
        Transaction tx= session.beginTransaction();
        // 直接儲存對象
        session.save(user);
        // 送出事務
        tx.commit();
        session.close();
    }

    public User find(Integer id) {
        Session session = sessionFactory.openSession();
       
        User user = (User) session.get(User.class, id);
       
        session.close();
       
        return user;
    }
}
測試類:
package onlyfun.caterpillar;

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateDemo {
    public static void main(String[] args) {
        // Configuration 負責管理 Hibernate 配置訊息
        Configuration config =
            new Configuration().configure();
        // 根據 config 建立 SessionFactory
        // SessionFactory 將用於建立 Session
        SessionFactory sessionFactory =
            config.buildSessionFactory();
       
        // 建立DAO對象
        IUserDAO userDAO = new UserDAO(sessionFactory);
        User user = new User();
      
        user.setName("caterpillar");
        user.setAge(30);
      
        userDAO.insert(user);
       
       
        user = userDAO.find(new Integer(1));
       
        System.out.println("name: " + user.getName()+"----"+user.getAge()+"----"+user.getId());
    }
}
到此爲止,如有不正確的地方,還請高手賜教,再次謝過!!!