Hibernate的开发全步骤过程

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开发顺序

1 下载并安装Hibernate

2 Hibernate配置文件详解配置与MySQL数据库的链接与映射文件User.hbm.xml

3 生成映射文件User.hbm.xml

4 编写持久化类User.java

5 编写辅助类HibernateSessionFactory.java 负责取得和关闭Hibernate的Session对象

6 编写DAO类UserDAO.java 编写根据用户名取得用户对象的getUser()

7 编写Service类UserService.java 编写valid()函数调用UserDAO.java的getUser()函数执行函数验证

1 下载并安装Hibernate

下载hibernate-3.0.zip 将hibernate3.zip文件和lib下的所有文件都复制到新建的HibernateTest项目的lib子目录下

MySQL数据库的驱动文件复制到lib子目录下

2 hibernate.cfg.xml配置文件

<?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">

<!-- Generated by MyEclipse Hibernate Tools. -->
<hibernate-configuration>

    <session-factory>
        <property name="myeclipse.connection.profile">
            JDBC for MySQL
        </property>
        <property name="connection.url">
            jdbc:mysql://localhost:3306/demo
        </property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>
        <property name="connection.driver_class">
            org.gjt.mm.mysql.Driver
        </property>
        <property name="dialect">
            org.hibernate.dialect.MySQLDialect
        </property>
        <mapping resource="com/demo/hibernate/beans/User.hbm.xml" />


    </session-factory>

</hibernate-configuration>

使用XML文件进行配置时指定Java类与数据库表格的映射文件位置 XML配置文件的位置必须在CLASSPATH的设定中 Web程式的WEB-INF/classes中我们使用下面的方式读入XML文件以配置Hibernate

SessionFactory sf = new Configuration().configure().buildSessionFactory();

Configuration表示Java类与数据库表格映射的集合用于之后建立SessionFactory 之后Configuration就不再起作用了预设的XML文件名称是hibernate.cfg.xml你也可以指定文件的名称

压缩包Hibernate-3.0.zip压缩包的etc子目录下提供默认的Hibernate配置文件hibernate.cfg.xml 我们要在HibernateTest中使用XML的配置文件因此请复制该文件到HibernateTest项目的src目录下并添加MySQL的相关配置项这样 HibernateTest就支持Hibernate了

3 编写映射文件 User.hbm.xml

Hibernate映射文件包含了对象/关系映射所需的元数据元数据包含持久化类的声明和属性到数据库的映射

映射文件是XML格式的文件它负责持久化类与数据库表之间的映射其根目录是hibernate-mapping 并通过属性package指定类所在的包每一个表使用一个class定义那么表示类的名称 table表示关联的表明通过property子元素来映射类的变量名与数据库表字段名之间的映射关系

在这个HibernateTest项目中我们建立一个映射文件User.hbm.xml来映射到数据表user 映射的类名为User 所在的包为com.demo.hibernate.beans

<?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" >

<!-- DO NOT EDIT: This is a generated file that is synchronized -->
<!-- by MyEclipse Hibernate tool integration. -->
<!-- Created Tue Aug 14 18:57:22 CST 2007 -->
<hibernate-mapping package="com.demo.hibernate.beans">

    <class name="User" table="user">
        <id name="id" column="ID" type="integer">
            <generator class="native"/>
        </id>

        <property name="username" column="username" type="string" />
        <property name="password" column="password" type="string" />
        <property name="email" column="email" type="string" />
    </class>
    
</hibernate-mapping>

4 编写持久化类User.java

持久化类是指其实例需要被Hibernate持久化到数据库中的类持久化通常是与模型中的实体域类一般都是一张数据表对应一个持久化类不能认为所有的持久化类的实例都是持久的状态一个实例的状态也可能是瞬时的或脱管的。

在HibernateTest示例程序中包含了一个持久化类User.java 该类包含表User的4个字段对应的变量这些变量都申明为private类型的

package com.demo.hibernate.beans;

public class User {
    private java.lang.Integer id;

    private java.lang.String username;

    private java.lang.String password;

    private java.lang.String email;

    public java.lang.String getEmail() {
        return email;
    }

    public void setEmail(java.lang.String email) {
        this.email = email;
    }

    public java.lang.Integer getId() {
        return id;
    }

    public void setId(java.lang.Integer id) {
        this.id = id;
    }

    public java.lang.String getPassword() {
        return password;
    }

    public void setPassword(java.lang.String password) {
        this.password = password;
    }

    public java.lang.String getUsername() {
        return username;
    }

    public void setUsername(java.lang.String username) {
        this.username = username;
    }

}

5 编写辅助类 HibernateSessionFactory.java

Hibernate的Session 这是一个持久化管理器通过它从数据库中存取User

首先我们要从SessionFactory中获取一个Session

SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();

通过对configure()的调用来转载hibernate.cfg.xml配置文件并初始化成一个Configuration实例在创建SessionFactory之前可以访问Configuration来设置其他属性

SessionFactory应该设置成单例模式这样才能在程序中容易地访问SessionFactory

程序代码如下

package com.demo.hibernate.util;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.cfg.Configuration;

/**
 * Configures and provides access to Hibernate sessions, tied to the
 * current thread of execution. Follows the Thread Local Session
 * pattern, see {@link http://hibernate.org/42.html}.
 */
public class HibernateSessionFactory {

    /** 
     * Location of hibernate.cfg.xml file.
     * NOTICE: Location should be on the classpath as Hibernate uses
     * #resourceAsStream style lookup for its configuration file. That
     * is place the config file in a Java package - the default location
     * is the default Java package.


     * Examples: 

     * CONFIG_FILE_LOCATION = "/hibernate.conf.xml". 
     * CONFIG_FILE_LOCATION = "/com/foo/bar/myhiberstuff.conf.xml". 
     */
    private static String CONFIG_FILE_LOCATION = "/hibernate.cfg.xml";

    /** Holds a single instance of Session */
    private static final ThreadLocal threadLocal = new ThreadLocal();

    /** The single instance of hibernate configuration */
    private static final Configuration cfg = new Configuration();

    /** The single instance of hibernate SessionFactory */
    private static org.hibernate.SessionFactory sessionFactory;

    /**
     * Returns the ThreadLocal Session instance. Lazy initialize
     * the SessionFactory if needed.
     *
     * @return Session
     * @throws HibernateException
     */
    public static Session currentSession() throws HibernateException {
        Session session = (Session) threadLocal.get();

        if (session == null) {
            if (sessionFactory == null) {
                try {
                    cfg.configure(CONFIG_FILE_LOCATION);
                    sessionFactory = cfg.buildSessionFactory();
                }
                catch (Exception e) {
                    System.err.println("%%%% Error Creating SessionFactory %%%%");
                    e.printStackTrace();
                }
            }
            session = sessionFactory.openSession();
            threadLocal.set(session);
        }

        return session;
    }

    /**
     * Close the single hibernate session instance.
     *
     * @throws HibernateException
     */
    public static void closeSession() throws HibernateException {
        Session session = (Session) threadLocal.get();
        threadLocal.set(null);

        if (session != null) {
            session.close();
        }
    }

    /**
     * Default constructor.
     */
    private HibernateSessionFactory() {
    }

}

这个类不但在他的静态初始器中使用了SessionFactory 还使用了了一个ThreadLocal变量来保存Session作为当前工作线程

6 编写DAO类UserDAO.java

所谓的DAO层就是数据访问接口为了基于Hibernate的开发中将业务层与数据层分开 DAO层只负责处理调用Hibernate API实现CRUD操作 Service层面向用户负责调用DAO层的代码这样做的好处是数据层的代码不用关心业务服务可以更好的实现移植

package com.demo.hibernate.dao;

import org.hibernate.HibernateException;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;

import com.demo.hibernate.beans.User;
import com.demo.hibernate.util.HibernateSessionFactory;

public class UserDAO {

    public User getUser(String username) throws HibernateException {
        Session session = null;
        Transaction tx = null;
        User user = null;
        try {
            session = HibernateSessionFactory.currentSession();
            tx = session.beginTransaction();
            Query query = session.createQuery("from User where username=?");
            query.setString(0, username.trim());
            user = (User)query.uniqueResult();
            query = null;
            tx.commit ();
        }catch(HibernateException e){
            throw e;
        }finally{
            if (tx!=null) {
                tx.rollback();
            }
            HibernateSessionFactory.closeSession();
        }
        return user;
    }
}

该类实现了一个getUser()函数根据用户名username查询一个用户对象在该函数中使用HibernateSessionFactory取得Session对象然后通过session执行事务创建查询对象返回查询的用户对象，操作Session的代码都是Hibernate提供的API

7 编写Service类并运行

Service类即服务层就是面向用户服务它定义的方法都是与实际的业务相关的

此例子中定义一个Service类UserService 他有一个函数valid() 根据用户名和密码来判断用户是否存在改函数调用DAO层的UserDAO类来取得一个用户对象并比较该对象的密码与输入的密码是否相等如果相等就返回true 否则返回false 然后编写一个main()入口函数用户调用valid()函数来执行业务的调用并输出返回的结果

package com.demo.hibernate.service;

import com.demo.hibernate.beans.User;
import com.demo.hibernate.dao.UserDAO;

public class UserService {
    
    public boolean valid(String username, String password) {
        UserDAO test = new UserDAO();
        User user = test.getUser("admin");
        if(user.getPassword().equals(password)) {
            return true;
        } else {
            return false;
        }
    }
    
    public static void main(String[] args) {
        UserService service = new UserService();
        boolean login = service.valid("admin", "admin");
        System.out.println("验证结果："+login);
    }
}

接下来运行 UserService.java 运行方式 Java应用程序即可运行main()函数

此处记住还要添加日志属性文件三个日志属性文件复制到Hibernate的src子目录下即可

运行程序出现错误

Communication failure during handshake. Is there a server running on localhost:3306?

原因：

结果在Mysql.com的官方网站上看到这个解释，是因为新的Mysql的认证机制发生了一些变化造成的，解决方法如下

解决方法：

I'd to change the authentication method at the mysql server:
set password for @ = old_password('');

将红色那部分在cmd-mysql登录之后敲进去就解决了

假如你的用户名密码是root root 那么红色部分就是

set password for root@localhost=old_password('root');

最后正确运行的输出信息

INFO - Hibernate 3.0.5
INFO - hibernate.properties not found
INFO - using CGLIB reflection optimizer
INFO - using JDK 1.4 java.sql.Timestamp handling
INFO - configuring from resource: /hibernate.cfg.xml
INFO - Configuration resource: /hibernate.cfg.xml
INFO - Mapping resource: com/demo/hibernate/beans/User.hbm.xml
INFO - Mapping class: com.demo.hibernate.beans.User -> user
INFO - Configured SessionFactory: null
INFO - processing extends queue
INFO - processing collection mappings
INFO - processing association property references
INFO - processing foreign key constraints
INFO - Using Hibernate built-in connection pool (not for production use!)
INFO - Hibernate connection pool size: 20
INFO - autocommit mode: false
INFO - using driver: org.gjt.mm.mysql.Driver at URL: jdbc:mysql://localhost:3306/demo
INFO - connection properties: {user=root, password=****}
INFO - RDBMS: MySQL, version: 5.5.17
INFO - JDBC driver: Mark Matthews' MySQL Driver, version: 2.0.4
INFO - Using dialect: org.hibernate.dialect.MySQLDialect
INFO - Using default transaction strategy (direct JDBC transactions)
INFO - No TransactionManagerLookup configured (in JTA environment, use of read-write or transactional second-level cache is not recommended)
INFO - Automatic flush during beforeCompletion(): disabled
INFO - Automatic session close at end of transaction: disabled
INFO - Scrollable result sets: enabled
INFO - JDBC3 getGeneratedKeys(): disabled
INFO - Connection release mode: null
INFO - Maximum outer join fetch depth: 2
INFO - Default batch fetch size: 1
INFO - Generate SQL with comments: disabled
INFO - Order SQL updates by primary key: disabled
INFO - Query translator: org.hibernate.hql.ast.ASTQueryTranslatorFactory
INFO - Using ASTQueryTranslatorFactory
INFO - Query language substitutions: {}
INFO - Second-level cache: enabled
INFO - Query cache: disabled
INFO - Cache provider: org.hibernate.cache.EhCacheProvider
INFO - Optimize cache for minimal puts: disabled
INFO - Structured second-level cache entries: disabled
INFO - Statistics: disabled
INFO - Deleted entity synthetic identifier rollback: disabled
INFO - Default entity-mode: pojo
INFO - building session factory
WARN - No configuration found. Configuring ehcache from ehcache-failsafe.xml found in the classpath: jar:file:/F:/eeeeeee/HibernateTest/WebRoot/WEB-INF/lib/ehcache-1.1.jar!/ehcache-failsafe.xml
INFO - Not binding factory to JNDI, no JNDI name configured
INFO - Checking 0 named queries
验证结果：true

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