hibernate实践[Java编程]

hiberante是对数据库长期层拜候的一种机制,hibernate的利用可以使程序员将重点放到业务逻辑的实现上.hibernate的原理是将数据库构造封装,使程序员可以像利用普通对象一样调用数据库的相关接口,从实现数据库的相关操作.

下面就说一个例子,环境j2sdk1.4.2_04,tomcat4.1.27,eclipse3.0,hibernate2.1

数据库的后果以下:

create table Users (
LogonID VARCHAR(255) not null,
EmailAddress VARCHAR(255),
LastLogon DATE,
Password VARCHAR(255),
Name VARCHAR(255),
primary key (LogonID)
);
create table Address2 (
ID VARCHAR(255) not null,
City VARCHAR(255),
State VARCHAR(255),
Zip VARCHAR(255),
primary key (ID)
);
create table Contacts (
ID BIGINT not null,
EmailAddress VARCHAR(255),
Name VARCHAR(255),
User_ID VARCHAR(255),
primary key (ID)
);
alter table Contacts add constraint FKE207C4735A7381EF foreign key (User_ID) references Users;
create index IXE207C4735A7381EF on Contacts (User_ID);

eclipse安装好hibernate插件后,很多对比烦琐,简单出错的配置文件,eclipse都可以帮您很好的自动生成,您的主要任务就是实现Dao,也就是eclipse针对每个表生成的数据拜候对象.比方本例的BaseAddress2DAO,ContactsDAO,UsersDAO,你可以改正这三个对象实现对Contacts,Users,Address2的相关操作.该例子的构造以下:

此中Address2,Contacts,Users相当于实体bean,实现对数据表的映射.由于表Users和Contacts存在one-to-many关系,所以在Users.java的实现中将Contacts也作为一个对象属性.

private java.util.Set _contactsSet;
/**
* Return the value associated with the column: ContactsSet
*/
public java.util.Set getContactsSet () {
return this._contactsSet;
}
/**
* Set the value related to the column: ContactsSet
* @param _contactsSet the ContactsSet value
*/
public void setContactsSet (java.util.Set _contactsSet) {
this._contactsSet = _contactsSet;
}
public void addToContactsSet (Object obj) {
if (null == this._contactsSet) this._contactsSet = new java.util.HashSet();
this._contactsSet.add(obj);
}

普通情形下,hibernate实现数据库的衔接有两种方法,一种是借助web服务器的衔接池,一种是自己配置衔接参数文件.这里只介绍第二种方法:

<hibernate-configuration>
<session-factory>
<!-- local connection properties -->
<!--数据库途径-->
<property name="hibernate.connection.url">
jdbc:jtds:sqlserver://192.198.64.168:1433;databasename=test;SelectMethod=Cursor
</property>
<!--衔接驱动-->
<property name="hibernate.connection.driver_class">
net.sourceforge.jtds.jdbc.Driver
</property>
<property name="hibernate.connection.username">sa</property>
<property name="hibernate.connection.password">sasa</property>
<!-- property name="hibernate.connection.pool_size"></property -->
<!-- 数据库方言 -->
<property name="dialect">
net.sf.hibernate.dialect.SQLServerDialect
</property>
<property name="hibernate.show_sql">false</property>
<property name="hibernate.use_outer_join">true</property>
<!-- mapping 文件-->
<mapping resource="com/head/multi/Contacts.hbm" />
<mapping resource="com/head/multi/Users.hbm" />
<mapping resource="com/head/multi/Address2.hbm" />
</session-factory>
</hibernate-configuration>