Jpetstore分层结构如何?
虽然对Spring不熟悉,又不懂iBatis,而且对模式的概念还没有弄清楚,但也硬着头皮去读Spring包自带的Jpetstore经典J2EE例子。
可以肯定,Jpetstore是按照MVC模式设计的。持久化层用iBatis(这个我不懂,我希望是用Hibernate),web层控制器的servlet有两个选择,一个是用Struts,另一个是Spring的MVC。
以下是自己的阅读体会,也许分析不当或描述不清,但也算初步尝试,所以记下来了。
一,分层结构
Jpetstore使用了门面模式、单例模式,DAO模式。
1.门面模式
门面接口的实现类: PetStoreImpl
public class PetStoreImpl implements PetStoreFacade, OrderService
{
private AccountDao accountDao;
private CategoryDao categoryDao;
private ProductDao productDao;
private ItemDao itemDao;
private OrderDao orderDao;
// ----------------------------------------------------------------
// Setter methods for dependency injection
// ----------------------------------------------------------------
public void setAccountDao(AccountDao accountDao)
{
this.accountDao = accountDao;
}
//省略余下的四个setter
// -------------------------------------------------------------------------
// Operation methods, implementing the PetStoreFacade interface
// -------------------------------------------------------------------------
public Account getAccount(String username)
{
return this.accountDao.getAccount(username);
}
public Account getAccount(String username, String password)
{
return this.accountDao.getAccount(username, password);
}
public void insertAccount(Account account)
{
this.accountDao.insertAccount(account);
}
public void updateAccount(Account account)
{
this.accountDao.updateAccount(account);
}
//省略其它的crud方法
}
暂时先不管 OrderService 这个接口。
PetStoreImpl的那些setter方法正是spring的注入方法。
在配置文件中:
<bean id="petStore" class="org.springframework.samples.jpetstore.domain.logic.PetStoreImpl">
<property name="accountDao" ref="accountDao" />
<property name="categoryDao" ref="categoryDao" />
<property name="productDao" ref="productDao" />
<property name="itemDao" ref="itemDao" />
<property name="orderDao" ref="orderDao" />
</bean>
2. 单例模式
单例模式中,我们一般把类的构造方法设置为private,提供静态工厂方法给外界返回唯一的实例,但在这里,它不是这样做的,因为有了Spring。有了Spring的BeanFactory管理,可以轻易配置实现单例。看看作者的注释。
There is one instance of this class in the JPetStore application. In Spring terminology, it is a "singleton". This means a per-Application Context singleton. The factory creates a single instance; there is no need for a private constructor, static factory method etc as in the traditional implementation of the Singleton Design Pattern.
单例的PetStoreImpl
在Struts当控制器时,它这样做:为整个应用程序编写一个继承自Action的BaseAction基础类。
public abstract class BaseAction extends Action
{
private PetStoreFacade petStore;
public void setServlet(ActionServlet actionServlet)
{
super.setServlet(actionServlet);
if (actionServlet != null)
{
ServletContext servletContext = actionServlet.getServletContext();
WebApplicationContext wac = WebApplicationContextUtils
.getRequiredWebApplicationContext(servletContext);
this.petStore = (PetStoreFacade) wac.getBean("petStore");
}
}
protected PetStoreFacade getPetStore()
{
return petStore;
}
}
3.DAO模式
ORM工具用iBatis,在领域模式层使用了粗粒度对象。下面是AccountDao 的配置。
<select id="getAccountByUsername" resultMap="result">
select
signon.username as userid,
account.email,
account.firstname,
account.lastname,
account.status,
account.addr1,
account.addr2,
account.city,
account.state,
account.zip,
account.country,
account.phone,
profile.langpref,
profile.favcategory,
profile.mylistopt,
profile.banneropt,
bannerdata.bannername
from account, profile, signon, bannerdata
where account.userid = #value#
and signon.username = account.userid
and profile.userid = account.userid
and profile.favcategory = bannerdata.favcategory
</select>
本文地址:http://www.45fan.com/a/question/66969.html