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>