Hibernate学习笔记

时间：2015-06-28 15:29:38 阅读：145 评论：0 收藏：0 [点我收藏+]

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（一）第一个例子

零、说明

　　这个例子参考了<Hibernate Reference Documentation 3.6.10.Final>1.1. 第一部分 - 第一个Hibernate应用程序.

一、Hibernate介绍

　　Hibernate项目主页：http://hibernate.org/orm/

二、环境搭建

（1）新建项目HibernateDemo，如下图所示

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（2）导入相关jar包，如下图所示

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（3）创建数据库和表

 1 create database hibernatedemo character set gbk;
 2 use hibernatedemo;
 3 create table department (
 4     id int primary key,
 5     parentid int,
 6     name varchar(20)
 7 );
 8 -- 一级部门
 9 insert into department(id,parentid,name) values(1,-1,"销售部");
10 insert into department(id,parentid,name) values(2,-1,"生产部");
11 insert into department(id,parentid,name) values(3,-1,"质检部");
12 insert into department(id,parentid,name) values(4,-1,"行政部");
13 insert into department(id,parentid,name) values(5,-1,"仓库部");
14 insert into department(id,parentid,name) values(6,-1,"配套部");
15 insert into department(id,parentid,name) values(7,-1,"财务部");

三、使用Hibernate完成数据库查询

（1）定义数据库表对应的实体类

 1 package com.cattom.domain;
 2 
 3 /**
 4  * 持久化类. 用来代表我们希望储存在数据库的对象.
 5  */
 6 public class Department {
 7 
 8     private Long id;
 9     private Long parentId;
10     private String name;
11     
12     // 所有的持久化类都要求有无参的构造器. 因为Hibernate必须使用Java反射机制来创建对象.
13     public Department() {
14         
15     }
16 
17     public Long getId() {
18         return id;
19     }
20 
21     public void setId(Long id) {
22         this.id = id;
23     }
24 
25     public Long getParentId() {
26         return parentId;
27     }
28 
29     public void setParentId(Long parentId) {
30         this.parentId = parentId;
31     }
32 
33     public String getName() {
34         return name;
35     }
36 
37     public void setName(String name) {
38         this.name = name;
39     }
40 
41 }

（2）定义Hibernate映射文件

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
 3 <!-- 
 4     告诉Hibernate怎样加载和存储持久化类的对象.
 5     映射文件告诉 Hibernate它应该访问数据库里面的哪个表及应该使用表里面的哪些字段.
 6 -->
 7 <hibernate-mapping package="com.cattom.domain">
 8 
 9     <!-- class元素的name属性告诉Hibernate用那个持久化类, table属性告诉Hibernate用数据库中那个表 -->
10     <class name="Department" table="DEPARTMENT">
11         <!-- property元素的name属性告诉Hibernate使用哪个getter和setter方法, column属性告诉Hibernate对应数据库表的那个字段 -->
12         <id name="id" column="ID" /> <!-- id元素是对identifier属性的声明，对应数据库的primary key列 -->
13         <property name="parentId" column="PARENTID" />
14         <property name="name" column="NAME" />
15     </class>
16 
17 </hibernate-mapping>

（3）定义Hibernate配置文件

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
 3 <!-- 告诉Hibernate如何获取数据库连接 -->
 4 <hibernate-configuration>
 5 
 6     <session-factory>
 7         <!-- Database connection settings -->
 8         <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
 9         <property name="connection.url">jdbc:mysql://localhost:3306/hibernatedemo</property>
10         <property name="connection.username">root</property>
11         <property name="connection.password">root</property>
12         
13         <!-- JDBC connection pool (use the built-in) -->
14         <property name="connection.pool_size">1</property>
15         
16         <!-- SQL dialect -->
17         <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
18         
19         <!-- Enable Hibernate‘s automatic session context management -->
20         <property name="current_session_context_class">thread</property>
21         
22         <!-- Echo all executed SQL to stdout -->
23         <property name="show_sql">true</property>
24         
25         <mapping resource="com/cattom/domain/Department.hbm.xml" />
26     </session-factory>
27 
28 </hibernate-configuration>

（4）启动和辅助类

 1 package com.cattom.util;
 2 
 3 import org.hibernate.SessionFactory;
 4 import org.hibernate.cfg.Configuration;
 5 
 6 /**
 7  * 启动和辅助类. 创建一个全局的SessionFactory. 这个类来自<Hibernate Reference Documentation 3.6.10.Final> 
 8  */
 9 public class HibernateUtil {
10     
11     private static final SessionFactory sessionFactory = buildSessionFactory();
12     
13     private static SessionFactory buildSessionFactory() {
14         try {
15             return new Configuration().configure().buildSessionFactory();
16         } catch (Throwable ex) {
17             System.err.println("Initial SessionFactory creation failed." + ex);
18             throw new ExceptionInInitializerError();
19         }
20     }
21     
22     public static SessionFactory getSessionFactory() {
23         return sessionFactory;
24     }
25 
26 }

（5）编写测试代码

 1 package com.cattom;
 2 
 3 import java.util.List;
 4 
 5 import org.hibernate.Session;
 6 
 7 import com.cattom.domain.Department;
 8 import com.cattom.util.HibernateUtil;
 9 
10 public class DepartmentManager {
11 
12     public static void main(String[] args) {
13         DepartmentManager mgr = new DepartmentManager();
14         
15         List departments = mgr.listDepartments();
16         for (int i = 0; i < departments.size(); i++) {
17             Department department = (Department) departments.get(i);
18             System.out.println("Id:" + department.getId() + " ParentId:" + department.getParentId() + " Name:" + department.getName());
19         }
20         
21         HibernateUtil.getSessionFactory().close();
22     }
23     
24     public List listDepartments() {
25         // SessionFactory创建并打开新的Session. 一个Session代表一个单线程的单元操作.
26         Session session = HibernateUtil.getSessionFactory().getCurrentSession();
27         session.beginTransaction();
28         // 用Hibernate查询语言(HQL)查询数据库
29         List result = session.createQuery("from Department").list();
30         session.getTransaction().commit();
31         return result;
32     }
33 
34 }

（6）添加log4j的配置信息log4j.properties，这个文件来自Hibernate项目下etc目录中的log4j.properties，去掉了无关的注释行

 1 ### direct log messages to stdout ###
 2 log4j.appender.stdout=org.apache.log4j.ConsoleAppender
 3 log4j.appender.stdout.Target=System.out
 4 log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
 5 log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %c{1}:%L - %m%n
 6 
 7 ### set log levels - for more verbose logging change ‘info‘ to ‘debug‘ ###
 8 
 9 log4j.rootLogger=warn, stdout
10 
11 log4j.logger.org.hibernate=debug
12 
13 ### log JDBC bind parameters ###
14 log4j.logger.org.hibernate.type=info
15 
16 ### log schema export/update ###
17 log4j.logger.org.hibernate.tool.hbm2ddl=debug