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1、一种基于Hibernate、Struts和Spring的J2EE应用开发框架随着Java技术的逐渐成熟与完善,作为建立企业级应用的标准平台,J2EE平台得到了长足的发展。借助于J2EE规范中包含的多项技术：Enterprise JavaBean(EJB)、Java Servlets(Servlet)、Java Server Pages(JSP)、Java Message Service(JMS)等，开发出了许多应用系统。但是，在传统J2EE应用的开发过程中也出现了一些问题：(1)数据模型和逻辑模型之间的矛盾。目前使用的数据库基本上都是关系型数据库，而Java本质上是一种面向对象的语言，对象在存
2、储和读取时使用SQL和JDBC进行数据库操作，降低了编程的效率以及系统的可维护性；(2)传统的J2EE应用多采用基于EJB的重量级框架，这种框架适合于开发大型企业应用，但是使用EJB容器进行开发和调试需要耗费大量时间。为了降低代码的耦合性，提高系统的开发效率，本文提出了一种基于Struts框架、Hibernate框架和Spring框架的J2EE应用开发策略。Hibernate 框架Hibernate是一个数据持久层框架，是一种实现对象和关系之间映射（O/R Mapping）的工具，它对JDBC进行了轻量级的对象封装，使程序员可以使用对象编程思想来操作数据库。它不仅提供了从Java类到数据表的映
3、射，也提供了数据查询和恢复机制。相对于使用JDBC和SQL来操作数据库，使用Hibernate能大大的提高实现的效率。Hibernate框架用配置文件的形式来定义Java对象和数据表之间的映射关系，同时在更深的层面将数据表之间的关系解释为Java对象之间的继承及包含等关系。通过使用HQL语句将复杂的关系算法用对象的方式描述，在很大程度上简化了对数据的查询，加快了开发的效率。在Hibernate中有一个简单而直观的API，用于对数据库所表示的对象执行查询。要创建或修改这些对象，只需在程序中与它们进行交互，然后告诉Hibernate保存即可。这样，大量封装持久化操作的业务逻辑不再需要编写烦琐的JD
4、BC语句，从而使数据持久层得到了极大的简化。 用Struts实现MVC架构 MVC（Model-View-Controller）由Trygve Reenskaug提出，首先被应用在SmallTalk-80环境中，是许多交互和界面系统的构成基础。根据界面设计可变性的需求，MVC把交互系统的组成分解成模型、视图、控制器三部分。模型（Model）是软件所处理问题逻辑在独立于外在显示内容和形式情况下的内在抽象，封装了问题的核心数据、逻辑和功能的计算关系，独立于具体的界面表达和I/O操作。视图（View）把表示模型数据及逻辑关系和状态的信息及特定形式展示给用户。它从模型获得显示信息，对于相同的信息可以有
5、多个不同的显示形式或视图。控制器（Controller）是处理用户与软件的交互操作的，其职责是控制提供模型中任何变化的传播，确保用户界面于模型间的对应联系；它接受用户的输入，将输入反馈给模型，进而实现对模型的计算控制，是使模型和视图协调工作的部件。通常一个视图对应一个控制器。模型、视图与控制器的分离，使得一个模型可以具有多个显示视图。如果用户通过某个视图的控制器改变了模型的数据，所有其它依赖于这些数据的视图都应反映到这些变化。因此，无论何时发生了何种数据变化，控制器都会将变化通知所有的视图，导致显示的更新。这实际上是一种模型的变化-传播机制。 Struts框架Struts框架最早是作为Apac
6、he Jakarta项目的组成部分问世运做，它继承了MVC的各项特性，并根据J2EE的特点，做了相应的变化与扩展。Struts框架很好的结合了Jsp，Java Servlet，Java Bean，Taglib等技术。在Struts中，承担MVC中控制器角色的是ActionServlet。ActionServlet是一个通用的控制组件。这个控制组件提供了处理所有发送到Struts的HTTP请求的入口点，它截取和分发这些请求到相应的动作类（这些动作类都是Action类的子类）。另外控制组件也负责用相应的请求参数填充Action Form（FromBean），并传给动作类（ActionBean）。动
7、作类访问核心商业逻辑，即访问Java Bean或调用EJB。最后动作类把控制权传给后续的JSP文件，由JSP文件生成视图。所有这些控制逻辑利用Struts-config.xml文件来配置。在Struts框架中，视图主要由JSP生成页面完成，Struts提供丰富的JSP标签库，这有利于分开表现逻辑和程序逻辑。模型以一个或多个Java Bean的形式存在。在Struts中，主要存在三种Bean，分别是：Action，ActionForm，EJB或者Java Bean。 Struts框架没有具体定义模型层的实现，在实际开发中，模型层通常是和业务逻辑紧密相连的，并且要对底层数据进行操作。下面介绍一种开
8、发策略，将Hibernate引入到Struts框架的模型层中，使用它来进行数据封装和映射，提供持久化的支持。Spring 框架Spring明显区别于其他轻量级application framework, 它将专注于web的支持，与struts 和 webwork有着明显的区别。 在与struts、webwork的对比上,Spring是一个服务于所有层面的application framework:提供了bean的配置基础，AOP的支持，JDBC的提取框架，抽象事务支持等等。它有一个非常显著的特点：在某个层面上如果你不需要Spring的支持，你就可以不使用Spring的class，只使用它的某一
9、部分的功能。 从它的设计理念，你可以看到Spring 帮助你实现了真正的逻辑层和web层的分离。例如：一个校验应用将不用依靠controllers就可以实现。这样的目标更好的重用和易测,过分依靠不必要的容器和框架将不能实现这一点。当然,Spring 有自己的web支持和通常框架模式细致完整。然而，Spring替换struts、webwork或者其他的web方案非常容易。对于Spring的web支持或者不同的地方，Spring 允许你在web容器里面建立一个中间层，在测试环境或者标准独立的应用里面来设置重用你的商务逻辑.还有在J2EE环境里面，你的商务逻辑不必依靠容器提供的服务，像JTA ,EJ
10、B的支持。良好的构架的web应用可以运行在任何容器上，如，Tomcat 或者 Resin。值得注意的是，Spring 不是和已经存在的解决方案进行竞争. 我们鼓励结合标准的技术，如，Servlet,JSP, JTA,JNDI,JDBCand JDO和非常匹配的工具，如，Hibernate, Velocity, Log4J, and Cauchos Hessian/Burlap。这个框架的的设计思想是在你的应用需要改良的时候，你将会做一些技术的选择，例如,如果你需要分布式事务处理，你可能需要用Spring的Jta TransactionManager 来实现JTA服务。或者用DataSource
11、 TransactionManager or HibernateTransactionManager 来实现的单个数据库交换。Spring 框架通过配置操作mappings,展示resolution,本地化和模版集成围绕着分派请求操作的servlet-DispatcherServlet设计的。缺省的操作是一个非常简单的控制接口, 他只提供了ModelAndView handleRequest (request, response)方法。这将用于一个应用的控制,但是,如果你想包含多个层次的控制，AbstractController,AbstractCommandController, Multi
12、ActionController,SimpleFormController,AbstractWizardFormController将帮助你完成.应用控制将代表那些子系统。注意，你可以选择一个适当的基类:如果你没有web form,你就不必用FormController，这就是和Struts最大的不同。你可以通过命令或者form对象来操作任何对象，这不需要接口工具或者一个基础类的驱动。Spring的数据绑定非常灵活。举例来说,它描述了具有在应用范围内的校验错误的输入机制,但不是系统错误，所以在你的form对象里面你不必复制你的业务对象的spring属性,只操作出错的子任务,或者适当地转换spr
13、ing。换句话说,它通常可以很好的直接绑定你的业务对象。 这也是和struts围绕请求基础类Action 和 ActionForm (每个action操作类型) 建立主要的不同之一。对比WebWork,Sping更多的区别在于对象角色:Spring支持控制器的感念,一个操作命令或者form对象和得到数据传递给视图的模式，这个模式通常包含命令和form对象,但有时也包含任意的参考数据。换句话说,一个WebWork Action联合所有这些角色到一个单独的对象。WebWork允许你用已经存在的业务对象作为你form的一部分,但是只生成各自Action 的bean属性。最后,操作请求的Action
14、实例在一个视图里面获得付值和form population。然而,参考数据也需要作为Action 的属性被模拟。关于视图:Spring的视图方案非常的灵活。一个控制器执行可以通过response 返回ModelAndView对象null就可以直接写到一个视图里，在一般情况下,一个ModelAndView实例结合了一个view和一个model Map,包含了bean name 和通讯对象(像命令或者form,参考数据等等)。View名称是非常高端的配置，不是通过bean name,一个properties 文件就是通过你自己的ViewResolver.这个抽象的model Map 允许你在视图层
15、面完成提取,没有任何的争辩JSP/Velocity或者其他,每一种都可以直接完整使用.这个model Map 还可以简单得得到适当的格式化数据的转换,像JSP 请求属性或者Velocity 模版模式. 如果你不想用Spring的 web MVC，但是想借用Spring嫁接其他的解决方案,你可以非常简单地通过Spring继承你自己的web 框架，你可以非常简单地通过ContextLoaderListener启动一个Spring root application context,并且,通过Struts 或者WebWork 的action 利用ServletContext 属性(或者Spring 的
16、helper方法)存取它。值得注意的是, 这里没有任何的plugins被调用,因此没有专门的集成:来自web层的视图, 你可以简单的将Spring作为一个管理application context 实例入口点的类库。所有你注册bean和Spring服务都可以在不需要Spring的web MVC的情况下都可以轻松掌握。Spring不是和Struts 、WebWork这些应用进行竞争,它将作为一个纯web框架应用于很多领域,因为它不需要配置数据存储和事务操作，所以，你可以利用Spring提供的中间层和数据存储层来丰富你的应用,甚至用JDBC或者Hibernate进行事务抽象。如果仅仅聚焦于web支
17、持,Spring的一些显著特点是清楚分离:controller,validator,command object,form object,model object,和 DispatcherServlet,handler mapping vs view resolver等等强大而且直接的框架和作为JavaBeans的应用配置,包括简单的参照和应用内容,例如,从web控制器到业务对象和数据校验。适应性,无论什么样的控制器你都需要得到代替Action/ActionForm所做的每件事情的方案(简单,命令,form,范例,多重action,或者定制一个) 重用业务逻辑代码,不需要复制,你可以用已经有的
18、业务逻辑对象作为命令或则form对象代替反射特定的ActionForm子类。可订制的绑定和数据校验作为应用级的输入机制的错误校验,固定日期和数字绑定,例如,通过手动检查和转换业务对象来替换单个的string。可订制的操作,可订制的视图方案:通过name/value Map灵活的模型传送,用一个简单的方法从简单到复杂操作映射和视图方案策略。以在J2EE应用中非常普遍的用户登录过程为例来说明上述体系结构是如何具体运用的。登录的流程非常清晰：用户从登录页面login.jsp输入登录信息，系统对登录信息进行验证，如果正确则成功登录，否则提示相应错误信息。在开发过程中，使用Eclipse做为开发环境，同
19、时加载了对Struts、Spring及Hibernate提供更好的控制和支持的第三方插件MyEclipse，Web服务器使用Tomcat，数据库选用了Mysql。首先对Hibernate进行配置，只需要对系统自动生成的hibernate.cfg.xml进行修改，配置好数据库连接的各种参数以及定义数据映射文件。由于Hibernate所带的连接池主要用于测试，性能不是很好，可以通过JNDI将其修改为使用Tomcat的连接池。A Development Frame Application Based on the Hibernate、the Struts and the Spring J2EEOne
20、 preface along with the Java technique of gradual mature and perfect. Be establishment business enterprise class application of standard terrace,the J2 EE terrace got substantial of development .Several technique asked for help from to include in the J2 EE norm : Enterprise JavaBean (EJB), Java Serv
21、lets (Servlet), Java Server Pages(JSP), Java Message Service(JMS)etc., development many application system.But, also appeared some problem in the tradition J2 the EE the application of the development the process:1)the antinomy of of data model and logic model. Currently the database of usage basica
22、lly and all is relation type database, but the Java be essentially a kind of the language which face to object, object at saving with read usage SQL and JDBC carry on a database operation and lowered plait distance of efficiency and system of can maintenance;2)tradition of J2 EE application much the
23、 adoption is according to the EJB heavy weight frame, this kind of frame suitable for develop a large business enterprise application, but usage the EJB container carry on development and adjust to try to need to be waste a great deal of time.For lowering the Ou of code to match sex, exaltation syst
24、em of development efficiency, this text put forward one kind EE according to the J2 of the Struts frame 、the Hibernate frame and the Spring frame application development strategy. The Hibernate FrameDatas holding out for long time layer and Hibernate is one piece according to hold out for long time
25、layer frame, is a kind of realization object and relation of the tool which reflect to shoot(O/R Mapping), it carried on the object of the lightweight to pack to the JDBC and make procedure member can usage object plait distance thought to operation database. It not only provided to shoot from Java
26、to reflect of data form, but also provided a data a search and instauration mechanism. Opposite in usage JDBC and SQL to operation database, use Hibernate ability consumedly of exaltation realization of efficiency. The Hibernate frame use allocation document of the form come to the reflect of the de
27、finition Java object and data form to shoot relation, in the meantime at more deep of level of data form of relation explanation for the relations such as inherit of and containment etc. of Java object. Pass the usage HQL language sentence complications of relation the calculate way use the way of o
28、bject description, to a large extent simplification logarithms according to of search, speed development of efficiency. Have in the Hibernate a simple but keep the API of view, used for to the database mean of object performance search. Want to establish or the modification be these objects, need in
29、 the procedure carry on with them to hand over with each other, then tell Hibernate to keep. So, a great deal of pack hold out for long time turn operation of business logic no longer demand write a trivial JDBC language sentence, make data last long thus the layer got biggest of simplification. Use
30、 the Struts realization MVC structure MVC(Model-View-Controller) is put forward by the Trygve Reenskaug, first drive application in the environment SmallTalk-80, is many to hand over with each other with interface system of constitute foundation. According to the need of variable of the interface de
31、sign, MVC hand over with each other constitute of system to resolve into model and see diagram, controller three part. Model(Model) is software processing problem logic at independence in outside manifestation under contents and form circumstance of inside abstract, packed the core data, logic of pr
32、oblem and function of calculation relation, independence in concrete of interface expression and I/O operation. See diagram(View) mean information and particular form demonstration of model data and logic relation and appearance to the customer. It acquire a manifestation information from the model,
33、 there can be many for homology of information dissimilarity of manifestation form or see diagram. The controller(Controller) is a processing the customer hand over with software with each other operation of, its job is control provide model in any variety of dissemination, insure a customer interfa
34、ce among the model of rightness should contact; It accept a customer of importation, give the importation feedback model, then realization compute model control, is make model and see diagram to moderate work of parts. Usually 1 see a diagram rightness should a controller. Model, see separate of dia
35、gram and controller, make a model be able to have many manifestation to see diagram. If the customer pass a certain see the controller of diagram change the data of model, all other dependence in these see of data diagram all should reflection arrive these variety. When therefore and regardless occu
36、rrence what data variety, controller all would variety notice ally see diagram, cause manifestation of renewal. This is actually a kind of variety of model-dissemination mechanism. The Struts FrameThe Struts frame is to be the item of Apache Jakarta to constitute part to publish luck to do at the ea
37、rliest stage, it inherited MVC of each item characteristic, and did according to the characteristics of J2 EE correspond of variety with expand. The Struts frame was good to combine Jsp , Java Servlet , Java Bean, Talia etc. technique. In the Struts, what to undertake the controller role in the MVC
38、be an ActionServlet. The ActionServlet is an in general use control module. This control module provided a processing all HTTP claim which send out Struts of entrance point. Its interception with distribute these claim to arrive correspond of action type.(these action all of type is Action son type)
39、Moreover the control module is also responsible for using to correspond of claim the parameter fill Action Form(FromBean), and pass action type(ActionBean).Action type the business logic of the interview core, then interview Java Bean or adjust to use EJB. End action type control the power pass foll
40、ow-up of JSP document, from JSP document born see diagram. All these control logic make use of Struts-config.xml the document come to allocation. See diagram in the Struts frame main from JSP born page completion, the Struts provide abundant of JSP label database, this is advantageous to separating
41、performance logic and procedure logic.The model is with 1 or the form existence of several Java Bean. In the Struts, main existence three kinds of Bean, respectively BE: Action, ActionForm, EJB perhaps Java Bean. The Struts frame have no concrete definition model layer of realization, in actually th
42、e development, model layer usually is close with business logic connect with each other, and want to carry on operation to the first floor data. The underneaths introduction is a kind of development strategy, lead the Hibernate into the model layer of Struts frame, usage it to carry on a data to pac
43、k with reflect to shoot, provide hold out for long time turn of support. 4 usage Hibernate and the Struts development J2 EE application 4.1 system structure diagram 3 manifestation according to Hibernate and Struts development strategy of system structure diagram. the Spring FrameSpring isnt particu
44、larly a web framework but a generic lightweight application framework with dedicated web support, and show the architectural differences to Struts and WebWorkIn contrast to Struts or WebWork, Spring is an application framework for all layers: It offers a bean configuration foundation, AOP support, J
45、DBC abstraction framework, abstract transaction support etc. It is a very non-intrusive effort: Your application classes do not need to depend on any Spring classes if not necessary, and you can reuse every part on its own if you like to. From its very design, the framework encourages clean separati
46、on of tiers, most importantly web tier and business logic. e.g: the validation framework does not depend on web controllers. Major goals are reusability and testability: Unnecessary container or framework dependencies can be considered avoidable evils.Of course, Springs own web support is nicely int
47、egrated with the frameworks general patterns. Nevertheless, replacing the web solution with Struts, WebWork, or the like is easy. Both with Springs web support or a different one, Spring allows for building a true dedicated middle tier in the web container, with the option to reuse exactly the same
48、business logic in test environments or standalone applications. And within J2EE, your business logic will not unnecessarily depend on container services like JTA or EJB - allowing complex, well-architected web applications to run in a simple container like Tomcat or Resin.Note that Spring doesnt gen
49、erally aim to compete with existing solutions. It rather fosters seamless integration with standards like Servlet, JSP, JTA, JNDI, JDBC, and JDO, and well-suited tools like Hibernate, Velocity, Log4J, and Cauchos Hessian/Burlap. The framework is designed to grow with the needs of your applications, in terms of technology choice: For example, you will probably use JTA via Springs JtaTransactionManager if you need distributed transactions - but only then, as there are perfect replacements for single databases, like D