有关jsp的简单介绍外文翻译

专业外文翻译

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Brief Related JSP

信息工程系 计算机科学与技术 2013级2班 郑慧平 1312110226 孙强强 讲师

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二〇一五年五月五日

滨州学院毕业设计(专业外文翻译)

Brief Related JSP

The Java Server Pages (JSP) is a kind of according to web of the script plait distance technique, similar carries the script language of Java in the server of the Netscape company of server- side JavaScript (SSJS) and the Active Server Pages (ASP) of the Microsoft.JSP compares the SSJS and ASP to have better can expand sex, and it is no more exclusive than any factory or some one particular server of Web. Though the norm of JSP is to be draw up by the Sun company of, any factory can carry out the JSP on own system.

The After Sun release the JSP( the Java Server Pages) formally, the this kind of new Web application development technique very quickly caused the people's concern.JSP provided a special development environment for the Web application that establishes the high dynamic state. According to the Sun parlance, the JSP can adapt to include the Apache WebServer, IIS4.0 on the market at inside of 85% server product.

This chapter will introduce the related knowledge of JSP and Databases, and JavaBean related contents, is all certainly rougher introduction among them basic contents, say perhaps to is a Guide only, if the reader needs the more detailed information, pleasing the book of consult the homologous JSP.

1.1 JSP the development background and development histoty

In web brief history, from a world wide web that most of the network information static on stock transactions evolution to acquisition of an operation and infrastructure. In a variety of applications, may be used for based on Web client, look no restrictions.

Based on the browser client applications than traditional based on client/server applications has several advantages. These benefits include almost no limit client access and extremely simplified application deployment and management (to update an application, management personnel only need to change the program on a server, not thousands of installation in client applications). So, the software industry is rapidly to build on the client browser multi-layer application.

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The rapid growth of exquisite based Web application requirements development of technical improvements. Static HTML to show relatively static content is right choice, The new challenge is to create the interaction based on Web applications, in these procedures, the content of a Web page is based on the user's request or the state of the system, and are not predefined characters.

For the problem of an early solution is to use a CGI - BIN interface. Developers write to interface with the relevant procedures and separate based on Web applications, the latter through the Web server to invoke the former. This plan has serious problem -- each new extensible CGI requirements in a new process on the server. If multiple concurrent users access to this procedure, these processes will use the Web server of all available resources, and the performance of the system will be reduced to extremely low.

Some Web server providers have to provide for their server by plugins \to simplify the Web application development. These solutions are associated with certain Web server, cannot solve the span multiple suppliers solutions. For example, Microsoft's Active Server mix (ASP) technology in the Web page to create dynamic content more easily, but also can work in Microsoft on Personal Web Server and IIS.

There are other solutions, but cannot make an ordinary page designers can easily master. For example, such as the Servlet Java technologies can use Java language interaction application server code easier. Developers to write such Servlet to receive signals from the Web browser to generate an HTTP request, a dynamic response (may be inquires the database to finish the request), then send contain HTML or XML documents to the response of the browser.

? note: one is based on a Java Servlet Java technical operation in the server program (with different, the latter operating in the Applet browser end). In this book the Servlet chapter 4.

Using this method, the entire page must have made in Java Servlet. If developersor Web managers want to adjust page, you'll have to edit and recompile the Servlet Java, even in logic has been able to run. Using this method, the dynamic content with the application of the page still need to develop skills.

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Obviously, what is needed is a industry to create dynamic content within the scope of the pages of the solution. This program will solve the current scheme are limited. As follows:

can on any Web server or applications. will application page displays and separation. can rapidly developing and testing.

simplify the interactive development based on Web application process.

The JSP technology is designed to meet such requirements. The JSP specification is a Web server, application server, trading system and develop extensive cooperation between the tool suppliers. From this standard to develop the existing integration and balance of Java programming environment (for example, Java Servlet and JavaBeans) support techniques and tools. The result is a kind of new and developing method based on Web applications, using component-based application logic page designers with powerful functions.

1.2 SOURCE OF JSP

The technique of JSP of the company of Sun, making the page of Web develop the personnel can use the HTML perhaps marking of XML to design to turn the end page with format. Use the perhaps small script future life of marking of JSP becomes the dynamic state on the page contents.( the contents changes according to the claim of)

The Java Servlet is a technical foundation of JSP, and the large Web applies the development of the procedure to need the Java Servlet to match with with the JSP and then can complete, this name of Servlet comes from the Applet, the local translation method of now is a lot of, this book in order not to misconstruction, decide the direct adoption Servlet but don't do any translation, if reader would like to, can call it as\service procedure\The Servlet is similar to traditional CGI, ISAPI, NSAPI etc. Web procedure development the function of the tool in fact, at use the Java Servlet hereafter, the customer need not use again the lowly method of CGI of efficiency, also need not use only the ability come to born page of Web of dynamic state in the method of API that a

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certain fixed Web server terrace circulate. Many servers of Web all support the Servlet, even not support the Servlet server of Web directly and can also pass the additional applied server and the mold pieces to support the Servlet. Receive benefit in the characteristic of the Java cross-platform, the Servlet is also a terrace irrelevant, actually, as long as match the norm of Java Servlet, the Servlet is complete to have nothing to do with terrace and is to have nothing to do with server of Web. Because the Java Servlet is internal to provide the service by the line distance, need not start a progress to the each claimses, and make use of the multi-threading mechanism can at the same time for several claim service, therefore the efficiency of Java Servlet is very high.

But the Java Servlet also is not to has no weakness, similar to traditional CGI, ISAPI, the NSAPI method, the Java Servlet is to make use of to output the HTML language sentence to carry out the dynamic state web page of, if develop the whole website with the Java Servlet, the integration process of the dynamic state part and the static state page is an evil-foreboding dream simply. For solving this kind of weakness of the Java Servlet, the SUN released the JSP.

A number of years ago, Marty was invited to attend a small 20-person industry roundtable discussion on software technology. Sitting in the seat next to Marty was James Gosling, inventor of the Java programming language. Sitting several seats away was a high-level manager from a very large software company in Redmond, Washington. During the discussion, the moderator brought up the subject of Jini, which at that time was a new Java technology. The moderator asked the manager what he thought of it, and the manager responded that it was too early to tell, but that it seemed to be an excellent idea. He went on to say that they would keep an eye on it, and if it seemed to be catching on, they would follow his company's usual \Gosling lightheartedly interjected \

Now, the grievance that Gosling was airing was that he felt that this company would take technology from other companies and suborn it for their own purposes. But guess what? The shoe is on the other foot here. The Java community did not invent the idea of designing pages as a mixture of static HTML and dynamic code marked with

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special tags. For example, Cold Fusion did it years earlier. Even ASP (a product from the very software company of the aforementioned manager) popularized this approach before JSP came along and decided to jump on the bandwagon. In fact, JSP not only adopted the general idea, it even used many of the same special tags as ASP did.

The JSP is an establishment at the model of Java servlets on of the expression layer technique, it makes the plait write the HTML to become more simple.Be like the SSJS, it also allows you carry the static state HTML contents and servers the script mix to put together the born dynamic state exportation. JSP the script language that the Java is the tacit approval, however, be like the ASP and can use other languages( such as JavaScript and VBScript), the norm of JSP also allows to use other languages.

1.3 JSP CHARACTERISTICS

Is a service according to the script language in some one language of the statures system this kind of discuss, the JSP should be see make is a kind of script language. However, be a kind of script language, the JSP seemed to be too strong again, almost can use all Javas in the JSP.

Be a kind of according to text originally of, take manifestation as the central development technique, the JSP provided all advantages of the Java Servlet, and, when combine with a JavaBeans together, providing a kind of make contents and manifestation that simple way that logic separate. Separate the contents and advantage of logical manifestations is, the personnel who renews the page external appearance need not know the code of Java, and renew the JavaBeans personnel also need not be design the web page of expert in hand, can use to take the page of JavaBeans JSP to define the template of Web, to build up a from have the alike external appearance of the website that page constitute. JavaBeans completes the data to provide, having no code of Java in the template thus, this means that these templates can be written the personnel by a HTML plait to support. Certainly, can also make use of the Java Servlet to control the logic of the website, adjust through the Java Servlet to use the way of the document of JSP to separate website of logic and contents.

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Generally speaking, in actual engine of JSP, the page of JSP is the edit and translate type while carry out, not explain the type of. Explain the dynamic state web page development tool of the type, such as ASP, PHP3 etc., because speed etc. reason, have already can't satisfy current the large electronic commerce needs appliedly, traditional development techniques are all at to edit and translate the executive way change, such as the ASP → ASP+;PHP3 → PHP4.

In the JSP norm book, did not request the procedure in the JSP code part( be called the Scriptlet) and must write with the Java definitely. Actually, have some engines of JSP are adoptive other script languages such as the EMAC- Script, etc., but actually this a few script languages also are to set up on the Java, edit and translate for the Servlet to carry out of. Write according to the norm of JSP, have no Scriptlet of relation with Java also is can of, however, mainly lie in the ability and JavaBeans, the Enterprise JavaBeanses because of the JSP strong function to work together, so even is the Scriptlet part not to use the Java, edit and translate of performance code also should is related with Java.

1.4 JSP MECHANISM

To comprehend the JSP how unite the technical advantage that above various speak of, come to carry out various result easily, the customer must understand the differentiation of\the module develops for the web page of the center\and\the page develops for the web page of the center\

The SSJS and ASP are all in several year ago to release, the network of that time is still very young, no one knows to still have in addition to making all business, datas and the expression logic enter the original web page entirely heap what better solve the method. This kind of model that take page as the center studies and gets the very fast development easily. However, along with change of time, the people know that this kind of method is unwell in set up large, the Web that can upgrade applies the procedure. The expression logic write in the script environment was lock in the page, only passing to shear to slice and glue to stick then can drive heavy use. Express the logic to usually mix together with business and the data logics, when this makes be the procedure member to

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try to change an external appearance that applies the procedure but do not want to break with its llied business logic, apply the procedure of maintenance be like to walk the similar difficulty on the eggshell. In fact in the business enterprise, heavy use the application of the module already through very mature, no one would like to rewrite those logics for their applied procedure.HTML and sketch the designer handed over to the implement work of their design the Web plait the one who write, make they have to double work- Usually is the handicraft plait to write, because have no fit tool and can carry the script and the HTML contents knot to the server to put together. Chien but speech, apply the complexity of the procedure along with the Web to promote continuously, the development method that take page as the center limits sex to become to get up obviously.

At the same time, the people always at look for the better method of build up the Web application procedure, the module spreads in customer's machine/ server the realm. JavaBeans and ActiveX were published the company to expand to apply the procedure developer for Java and Windows to use to come to develop the complicated procedure quickly by\the fast application procedure development\RAD) tool. These techniques make the expert in the some realm be able to write the module for the perpendicular application plait in the skill area, but the developer can go fetch the usage directly but need not control the expertise of this realm.

Be a kind of take module as the central development terrace, the JSP appeared. It with the JavaBeans and Enterprise JavaBeans( EJB) module includes the model of the business and the data logic for foundation, provide a great deal of label and a script terraces to use to come to show in the HTML page from the contents of JavaBeans creation or send a present in return. Because of the property that regards the module as the center of the JSP, it can drive Java and not the developer of Java uses equally. Not the developer of Java can pass the JSP label( Tags) to use the JavaBeans that the deluxe developer of Java establish. The developer of Java not only can establish and use the JavaBeans, but also can use the language of Java to come to control more accurately in the JSP page according to the expression logic of the first floor JavaBeans.

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See now how JSP is handle claim of HTTP. In basic claim model, a claim directly was send to JSP page in. The code of JSP controls to carry on hour of the logic processing and module of JavaBeanses' hand over with each other, and the manifestation result in dynamic state bornly, mixing with the HTML page of the static state HTML code. The Beans can be JavaBeans or module of EJBs. Moreover, the more complicated claim model can see make from is request other JSP pages of the page call sign or Java Servlets.

The engine of JSP wants to chase the code of Java that the label of JSP, code of Java in the JSP page even all converts into the big piece together with the static state HTML contents actually. These codes piece was organized the Java Servlet that customer can not see to go to by the engine of JSP, then the Servlet edits and translate them automatically byte code of Java.

Thus, the visitant that is the website requests a JSP page, under the condition of it is not knowing, an already born, the Servlet actual full general that prepared to edit and translate completes all works, very concealment but again and efficiently. The Servlet is to edit and translate of, so the code of JSP in the web page does not need when the every time requests that page is explain. The engine of JSP need to be edit and translate after Servlet the code end is modify only once, then this Servlet that editted and translate can be carry out. The in view of the fact JSP engine auto is born to edit and translate the Servlet also, need not procedure member begins to edit and translate the code, so the JSP can bring vivid sex that function and fast developments need that you are efficiently.

Compared with the traditional CGI, the JSP has the equal advantage. First, on the speed, the traditional procedure of CGI needs to use the standard importation of the system to output the equipments to carry out the dynamic state web page born, but the JSP is direct is mutually the connection with server. And say for the CGI, each interview needs to add to add a progress to handle, the progress build up and destroy by burning constantly and will be a not small burden for calculator of be the server of Web. The next in order, the JSP is specialized to develop but design for the Web of, its purpose is for building up according to the Web applied procedure, included the norm and the tool of a

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the whole set. Use the technique of JSP can combine a lot of JSP pages to become a Web application procedure very expediently.

1.5 JSP application frameworks

What are application frameworks:

A framework is a reusable, semi-complete application that can be specialized to produce custom applications [Johnson]. Like people, software applications are more alike than they are different. They run on the same computers, expect input from the same devices, output to the same displays, and save data to the same hard disks. Developers working on conventional desktop applications are accustomed to toolkits and development environments that leverage the sameness between applications. Application frameworks build on this common ground to provide developers with a reusable structure that can serve as the foundation for their own products.

A framework provides developers with a set of backbone components that have the following characteristics:

1.They are known to work well in other applications. 2. They are ready to use with the next project.

3. They can also be used by other teams in the organization.

Frameworks are the classic build-versus-buy proposition. If you build it, you will understand it when you are done—but how long will it be before you can roll your own? If you buy it, you will have to climb the learning curve—and how long is that going to take? There is no right answer here, but most observers would agree that frameworks such as Struts provide a significant return on investment compared to starting from scratch, especially for larger projects. Other types of frameworks:

The idea of a framework applies not only to applications but to application componentsas well. Throughout this article, we introduce other types of frameworks that you can use with Struts. These include the Lucene search engine, the Scaffold toolkit, the Struts validator, and the Tiles tag library. Like application frameworks, these tools provide

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semi-complete versions of a subsystem that can be specialized to provide a custom component.

Some frameworks have been linked to a proprietary development environment. This is not the case with Struts or any of the other frameworks shown in this book. You can use any development environment with Struts: Visual Age for Java, JBuilder, Eclipse, Emacs, and Textpad are all popular choices among Struts developers. If you can use it with Java, you can use it with Struts. Enabling technologies:

Applications developed with Struts are based on a number of enabling technologies.These components are not specific to Struts and underlie every Java web application. A reason that developers use frameworks like Struts is to hide the nasty details behind acronyms like HTTP, CGI, and JSP. As a Struts developer, you don’t need to be an alphabet soup guru, but a working knowledge of these base technologies can help you devise creative solutions to tricky problems.

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有关JSP的简单介绍

Java Server Pages(JSP)是一种基于web的脚本编程技术，类似于网景公司的服务器端Java脚本语言—— server-side JavaScript(SSJS)和微软的Active Server Pages(ASP)。与SSJS和ASP相比，JSP具有更好的可扩展性，并且它不专属于任何一家厂商或某一特定的Web服务器。尽管JSP规范是由Sun公司制定的，但任何厂商都可以在自己的系统上实现JSP。

在Sun正式发布JSP(Java Server Pages)之后，这种新的Web应用开发技术很快引起了人们的关注。JSP为创建高度动态的Web应用提供了一个独特的开发环境。按照Sun的说法，JSP能够适应市场上包括Apache WebServer、IIS4.0在内的85%的服务器产品。

本文将介绍JSP相关的知识，当然都是比较粗略的介绍其中的基本内容，仅仅起到抛砖引玉的作用，如果读者需要更详细的信息，请参考相应的JSP的书籍。

1.1 JSP的开发背景及发展历史

在万维网短暂的历史中，万维网已经从一个大部分显示静态信息的网络演化到对股票进行交易和进行购书操作的一个基础设施。在各种各样的应用程序中，对于可能使用的基于Web的客户端，看上去没有任何限制。

基于浏览器客户端的应用程序比传统的基于客户机/服务器的应用程序有几个好处。这些好处包括几乎没有限制的客户端访问和极其简化的应用程序部署和管理（要更新一个应用程序，管理人员只需要更改一个基于服务器的程序，而不是成千上万的安装在客户端的应用程序）。这样，软件工业正迅速地向建造基于浏览器客户端的多层次应用程序迈进。

这些快速增长的精巧的基于Web的应用程序要求开发技术上的改进。静态HTML对于显示相对静态的内容是不错的选择；新的挑战在于创建交互的基于Web的应用程序，在这些程序中，页面的内容是基于用户的请求或者系统的状态，而不是预先定义的文字。对于这个问题的一个早期解决方案是使用CGI-BIN接口。开发人员编写与接口相关的单独的程序，以及基于Web的应用程序，后者通过Web服务器来调用前者。这个方案有着严重的扩展性问题——每个新的CGI要求在服务器上

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新增一个进程。如果多个用户并发地访问该程序，这些进程将消耗该Web服务器所有的可用资源，并且系统性能会降低到极其低下的地步。

某些Web服务器供应商已经尝试通过为他们的服务器提供“插件”和API来简化Web应用程序的开发。这些解决方案是与特定的Web服务器相关的，不能解决跨多个供应商的解决方案的问题。例如，微软的Active Server Pages（ASP）技术使得在Web页面上创建动态内容更加容易，但也只能工作在微软的IIS和Personal Web Server上。

还存在其他的解决方案，但都不能使一个普通的页面设计者能够轻易地掌握。例如，像Java Servlet这样的技术就可以使得用Java语言编写交互的应用程序的服务器端的代码变得容易。开发人员能够编写出这样的Servlet，以接收来自Web浏览器的HTTP请求，动态地生成响应(可能要查询数据库来完成这项请求)，然后发送包含HTML或XML文档的响应到浏览器。

?注意：一个Java Servlet就是一个基于Java技术的运行在服务器端的程序(与Applet不同，后者运行在浏览器端)。Servlet会在本书第4章介绍。

采用这种方法，整个网页必须都在Java Servlet中制作。如果开发人员或者Web管理人员想要调整页面显示，就不得不编辑并重新编译该Java Servlet，即使在逻辑上已经能够运行了。采用这种方法，生成带有动态内容的页面仍然需要应用程序的开发技巧。

很显然，目前所需要的是一个业界范围内的创建动态内容页面的解决方案。这个方案将解决当前方案所受到的限制。如下：

能够在任何Web或应用程序服务器上运行。 将应用程序逻辑和页面显示分离。 能够快速地开发和测试。

简化开发基于Web的交互式应用程序的过程。

JSP技术就是被设计用来满足这样的要求的。JSP规范是Web服务器、应用服务器、交易系统以及开发工具供应商间广泛合作的结果。Sun开发出这个规范来整合和平衡已经存在的对Java编程环境(例如，Java Servlet和JavaBeans)进行支持的技术和工具。其结果是产生了一种新的、开发基于Web应用程序的方法，给予使用基于组件应用逻辑的页面设计者以强大的功能。

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1.2 JSP的由来

Sun公司的JSP技术，使Web页面开发人员可以使用HTML或者XML标识来设计和格式化最终页面。使用JSP标识或者小脚本来生成页面上的动态内容(内容是根据请求来变化的)。

Java Servlet是JSP技术的基础，而且大型的Web应用程序的开发需要Java Servlet和JSP配合才能完成，Servlet这个名称源于Applet，现在国内的翻译方式很多，本书为了避免误会，决定直接采用Servlet而不做任何翻译，读者如果愿意，可以称之为“小服务程序”。Servlet其实和传统的CGI、ISAPI、NSAPI等Web程序开发工具的作用是相似的，在使用Java Servlet以后，用户不必再使用效率低下的CGI方式，也不必使用只能在某个固定Web服务器平台运行的API方式来动态生成Web页面。许多Web服务器都支持Servlet，即使不直接支持Servlet的Web服务器也可以通过附加的应用服务器和模块来支持Servlet。得益于Java的跨平台的特性，Servlet也是平台无关的，实际上，只要符合Java Servlet规范，Servlet是完全与平台无关且是与Web服务器无关的。由于Java Servlet内部是以线程方式提供服务，不必对于每个请求都启动一个进程，并且利用多线程机制可以同时为多个请求服务，因此Java Servlet效率非常高。

但Java Servlet也不是没有缺点，和传统的CGI、ISAPI、NSAPI方式相同，Java Servlet是利用输出HTML语句来实现动态网页的，如果用Java Servlet来开发整个网站，动态部分和静态页面的整合过程会非常难以实现。为了解决Java Servlet的这种缺点，SUN推出了JSP。

许多年前，Marty受到邀请,参加一个有关软件技术的小型研讨会.坐在Marty旁边的人是James Gosling--- Java编程语言的发明者。隔几个位置,是来自华盛顿一家大型软件公司的高级经理。在讨论过程中,研讨会的主席提出了Jini的议题,这在当时是一项新的Java技术。主席向该经理询问他的想法.他回答说,虽然现在言之过早，但这看起来会是非常有前途的一项技术。他们会持续关注这项技术,如果这项技术变得流行起来,他们会遵循公司的“接受并扩充(embrace and extend)”的策略.此时, Gosling随意地插话说“你的意思其实就是不接受且不扩充(disgrace and distend)。”

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在此, Gosling的抱怨显示出，他感到这个公司会从其他公司那里拿走技术,用于他们自己的目的.出人意料的是，形势已经完全不同。Java团队并没有发明这一思想----将页面设计成由静态HTML和用特殊标签标记的动态代码混合组成.。ColdFusion多年前就已经这样做了。甚至ASP(来自于前述经理所在公司的一项产品)都在JSP出现之前推广了这种方式。实际上,JSP不只采用了这种通用概念,它甚至使用许多和ASP相同的特殊标签。

JSP是建立在Java servlets模型之上的表达层技术，它使编写HTML变得更简单。像SSJS一样，它也允许你将静态HTML内容与服务器端脚本混合起来生成动态输出。JSP把Java作为默认的脚本语言，然而，就像ASP可以使用其他语言(如JavaScript和VBScript)一样，JSP规范也允许使用其他语言。

1.3 JSP特点

按照脚本语言是服务于某一个子系统的语言这种论述，JSP应当被看作是一种脚本语言。然而，作为一种脚本语言，JSP又显得过于强大了，在JSP中几乎可以使用全部的Java类。

作为一种基于文本的、以显示为中心的开发技术，JSP提供了Java Servlet的所有好处，并且，当与一个JavaBeans类结合在一起时，提供了一种使内容和显示逻辑分开的简单方式。分开内容和显示逻辑的好处是，更新页面外观的人员不必懂得Java代码，而更新JavaBeans类的人员也不必是设计网页的行家里手，就可以用带JavaBeans类的JSP页面来定义Web模板，以建立一个由具有相似的外观的页面组成的网站。JavaBeans类完成数据提供，这样在模板中就没有Java代码，这意味着这些模板可以由一个HTML编写人员来维护。当然，也可以利用Java Servlet来控制网站的逻辑，通过Java Servlet调用JSP文件的方式来将网站的逻辑和内容分离。

一般来说，在实际的JSP引擎中，JSP页面在执行时是编译式，而不是解释式的。解释式的动态网页开发工具如ASP、PHP3等由于速度等原因已经满足不了当前大型电子商务应用的需要了，传统的开发技术都在向编译执行的方式改变，如ASP→ASP+；PHP3→PHP4。

在JSP规范书中，并没有明确要求JSP中的程序代码部分(称为Scriptlet)一定要用Java来写。实际上，有一些JSP引擎就是采用的其他脚本语言，如EMAC-Script

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滨州学院毕业设计(专业外文翻译)

等，但实际上这几种脚本语言也是构建在Java上面，编译为Servlet来实现的。按照JSP规范书写，和Java没有任何关系的Scriptlet也是可以的，不过，由于JSP的强大功能主要在于能和JavaBeans、Enterprise JavaBeans一起工作，所以即使是Scriptlet部分不使用Java，编译成的执行代码也应该是与Java相关的。

1.4 JSP的机制

要理解JSP怎样联合以上各种所提到的技术的优点，从而轻而易举地实现各种效果，用户必须首先了解“组件为中心的网页开发”和“页面为中心的网页开发”的区别。

SSJS和ASP都是在几年前推出的，那时网络还很年轻，没有人知道除了把所有的商务、数据和表达逻辑统统堆进原始网页中之外还有什么更好的解决方法。这种以页面为中心的模型容易学习并且得到相当快速的发展。然而，随着时间的推移，人们认识到这种方法不适于构建大型的、可升级的Web应用程序。在脚本环境中书写的表达逻辑被锁在页面内，只有通过剪切和粘贴才能被重用。表达逻辑通常和商务及数据逻辑混在一起，这使得当程序员试图改变一个应用程序的外观而不想破坏与之紧密结合的商务逻辑时，应用程序的维护就变得十分艰难。其事实上，企业中可重用组件的应用早已经很成熟，没有人愿意为它们的应用程序重写那些逻辑。HTML和图形设计师把它们的设计的实施工作交给了Web编写者，使他们不得不加倍工作—— 常常是手工编写，因为没有合适的工具可以把服务器端脚本与HTML内容结合起来。简而言之，随着Web应用程序的复杂性不断提升，以页面为中心的开发方式的局限性变得明显起来。

与此同时，人们一直在寻找建立Web应用程序的更好方法，组件在客户机/服务器领域流行起来。JavaBeans和ActiveX被“快速应用程序开发”(RAD)工具发行商推广给Java和Windows应用程序开发者用来快速开发复杂的程序。这些技术使某领域内的专家可以为本领域内的垂直应用编写组件，而开发者可以直接拿来使用而不必掌握这一领域的专门技术。

作为一种以组件为中心的开发平台，JSP出现了。它以JavaBeans和Enterprise JavaBeans(EJB)组件包含商务和数据逻辑的模型为基础，提供大量标签和一个脚本平台用来在HTML页中显示由JavaBeans产生或回送的内容。由于JSP的以组件为中

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滨州学院毕业设计(专业外文翻译)

心的性质，它可以被Java和非Java开发者同样使用。非Java开发者可以通过JSP的标签(Tags)来使用高级Java开发者创建的JavaBeans。Java开发者不仅可以创建和使用JavaBeans，还能在JSP页中使用Java语言来更精密地控制基于底层JavaBeans的表达逻辑。

现在来看看JSP是如何处理HTTP请求的。在基本请求模型中，一个请求直接被送到JSP页中。JSP代码控制着进行逻辑处理时与JavaBeans组件的交互，并在动态生成的、混合了静态HTML代码的HTML页中显示结果。Beans 可以是JavaBeans 或EJB组件。另外，更加复杂的请求模型可看作从被请求页呼叫其他JSP页或Java Servlets。

JSP引擎实际上要把JSP标签、JSP页中的Java代码甚至连同静态HTML内容都转换为大块的Java代码。这些代码块被JSP引擎组织到用户看不到的Java Servlet中去，然后Servlet自动把它们编译成Java字节码。这样，当网站的访问者请求一个JSP页时，在它不知道的情况下，一个已经生成的、预编译过的Servlet实际上将完成所有的工作，非常隐蔽而又高效。因为Servlet是编译过的，所以网页中的JSP代码不需要在每次请求该页时被解释一遍。JSP引擎只需在Servlet代码最后被修改后编译一次，然后这个编译过的Servlet就可以被执行了。由于是JSP引擎自动生成并编译Servlet，不用程序员动手编译代码，所以JSP能带给你高效的性能和快速开发所需的灵活性。

和传统的CGI相比较，JSP有相当的优势。首先，在速度上，传统的CGI程序需要使用系统的标准输入输出设备来实现动态网页的生成，而JSP是直接和服务器相关联的。而且对于CGI来说，每一个访问就需要新增加一个进程来处理，进程不断地建立和销毁对于作为Web服务器的计算机将是不小的负担。其次，JSP是专门为Web开发而设计的，其目的是为了建立基于Web的应用程序，其中包含了一整套的规范和工具。使用JSP技术可以很方便地将一大堆JSP页面组合成为一个Web应用程序。

1.5 JSP的应用框架

什么是应用框架：

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滨州学院毕业设计(专业外文翻译)

框架(framework)是可重用的，半成品的应用程序，可以用来产生专门的定制程序。象人一样，软件应用的相似性比不同点要多。它们运行在相似的机器上，期望从相同的设备输入信息，输出到相同的显示设备，并且将数据存储到相同的硬盘设备。开发传统桌面应用的开发人员更习惯于那些可以涵盖应用开发同一性的工具包和开发环境。构架在这些公共基础上的应用框架可以为开发人员提供可以为他们的产品提供可重用服务的基础架构。

框架向开发人员提供一系列具有以下特征的骨架组件： 1．已经知道它们在其它程序上工作得很好； 2．它们随时可以在下一个项目中使用； 3．它们可以被组织的其它团队使用；

对于框架是典型的构建还是购买命题。如果你自己构建它，在你完成时你就会理解它，但是在你被融入之前又将花费多长时间呢？如果要购买，你必须得克服学习曲线，同样，在你可以用它进行工作之前又得花多长时间？这里没有所谓正确答案，但许多观察者都会同意，象Struts这样的框架能提供比从头开始开发更显著的投资回报，特别是对于大型项目来说。

其它类型的框架：

框架的概念不仅用于应用程序也可用于组件。在其它的资料里面，我们也介绍了一些可以和Struts一起使用的框架。这些包括Lucene搜索引擎，Scaffold工具包，Struts验证器，以及Tiles标签库。与应用框架一样，这些工具也提供了一些半完成的版本，可以用在用户的定制组件之中。某些框架被限制于专门的开发环境中。Struts以及本文中涉及的组件却不是这样。你可以在很多环境中来开发Struts： Visual Age for Java, JBuilder, Eclipse, Emacs, 甚至使用Textpad。对于你的工具，如果你可以用来开发Java, 你就可以用它来开发Struts。

使用的技术：

使用Struts的应用开发使用了大量的其他基础技术。这些技术并不是专门针对Struts，而是所有Java web 应用都可以使用的。开发者使用Struts之类的框架是为了隐藏在诸如HTTP，CGI，以及JSP之类技术后面的繁琐的细节。作为一个Struts开

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滨州学院毕业设计(专业外文翻译)

发者，你并不需要知晓所有的相关知识，但是这些基本技术的工作原理可能有助于你针对棘手问题设计出创造性的方案。

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