【正文】 交互的應(yīng)用程序的服務(wù)器端的代碼變得容易。開(kāi)發(fā)人員能夠編寫(xiě)出這樣的Servlet，以接收來(lái)自Web瀏覽器的HTTP請(qǐng)求，動(dòng)態(tài)地生成響應(yīng)（可能要查詢數(shù)據(jù)庫(kù)來(lái)完成這項(xiàng)請(qǐng)求），然后發(fā)送包含HTML或XML文檔的響應(yīng)到瀏覽器。注意：一個(gè)Java Servlet就是一個(gè)基于Java技術(shù)的運(yùn)行在服務(wù)器端的程序（與Applet不同，后者運(yùn)行在瀏覽器端）。Servlet會(huì)在本書(shū)第4章介紹。采用這種方法，整個(gè)網(wǎng)頁(yè)必須都在Java Servlet中制作。如果開(kāi)發(fā)人員或者Web管理人員想要調(diào)整頁(yè)面顯示，就不得不編輯并重新編譯該Java Servlet，即使在邏輯上已經(jīng)能夠運(yùn)行了。采用這種方法，生成帶有動(dòng)態(tài)內(nèi)容的頁(yè)面仍然需要應(yīng)用程序的開(kāi)發(fā)技巧。很顯然，目前所需要的是一個(gè)業(yè)界范圍內(nèi)的創(chuàng)建動(dòng)態(tài)內(nèi)容頁(yè)面的解決方案。這個(gè)方案將解決當(dāng)前方案所受到的限制。如下：。JSP技術(shù)就是被設(shè)計(jì)用來(lái)滿足這樣的要求的。JSP規(guī)范是Web服務(wù)器、應(yīng)用服務(wù)器、交易系統(tǒng)以及開(kāi)發(fā)工具供應(yīng)商間廣泛合作的結(jié)果。Sun開(kāi)發(fā)出這個(gè)規(guī)范來(lái)整合和平衡已經(jīng)存在的對(duì)Java編程環(huán)境（例如，Java Servlet和JavaBeans）進(jìn)行支持的技術(shù)和工具。其結(jié)果是產(chǎn)生了一種新的、開(kāi)發(fā)基于Web應(yīng)用程序的方法，給予使用基于組件應(yīng)用邏輯的頁(yè)面設(shè)計(jì)者以強(qiáng)大的功能。JavaScript是用于瀏覽器的第一種具有通用目的、動(dòng)態(tài)的客戶端腳本語(yǔ)言。Netscape于1995年首先提出了JavaScript，但當(dāng)時(shí)將其稱為L(zhǎng)iveScript。后來(lái)Netscape迅速地將LiveScript改名為JavaScript，Java的開(kāi)發(fā)商Sun與他們?cè)谕荒臧l(fā)表了一項(xiàng)聲明。聲明中指出Java和JavaScript將互相補(bǔ)充，但它們是截然不同的技術(shù)，這樣才打消了很多人對(duì)這兩項(xiàng)技術(shù)的錯(cuò)誤理解。JavaScript為創(chuàng)建用戶界面控件提供了一種腳本語(yǔ)言。事實(shí)上，JavaScript在瀏覽器中插入了代碼邏輯。它可以支持這樣的效果：當(dāng)光標(biāo)在Web頁(yè)的某個(gè)位置移動(dòng)時(shí)驗(yàn)證用戶輸入或者變換圖像。Microsoft也編寫(xiě)出了自己的JavaScript版本并將其稱為JScript。Microsoft和Netscape都支持一種圍繞JavaScript和JScript的核心特性并由（European Computer Manufacturers Association，ECMA）標(biāo)準(zhǔn)組織控制的腳本語(yǔ)言標(biāo)準(zhǔn)。ECMA將其腳本語(yǔ)言命名為ECMAScript。servlet和JSP經(jīng)常包括一些組織中常見(jiàn)的信息，如logo、版本、商標(biāo)或?qū)Ш綏l。Web應(yīng)用程序使用導(dǎo)入機(jī)制在任何所需的位置導(dǎo)入這些信息，因?yàn)檫@樣可以很容易地在一個(gè)地方改變內(nèi)容，然后維持在所有使用它的代碼中。有些信息是靜態(tài)的，永遠(yuǎn)不會(huì)或很少會(huì)改變，如組織的logo。在其他情況下，信息是動(dòng)態(tài)的，經(jīng)常在不可預(yù)見(jiàn)的時(shí)候改變，如必須針對(duì)每個(gè)用戶的文本歡迎語(yǔ)。在這兩種情況下，你可能都希望保證servlet或JSP可以獨(dú)立于所導(dǎo)入的內(nèi)容進(jìn)行開(kāi)發(fā)，servlet或JSP的實(shí)現(xiàn)在必要時(shí)正確地更新其導(dǎo)入的內(nèi)容。希望在JSP中導(dǎo)入不經(jīng)常改變的資源。在導(dǎo)入JSP頁(yè)面中使用include指令。希望在JSP每次接收請(qǐng)求時(shí)，而不是在JSP轉(zhuǎn)換為servlet時(shí)導(dǎo)入內(nèi)容。使用jsp:include標(biāo)準(zhǔn)動(dòng)作。希望在JSP中根據(jù)從配置文件取得的值，動(dòng)態(tài)地導(dǎo)入文件。使用jsp:include標(biāo)準(zhǔn)動(dòng)作。在外部特性文件中提供它的值，或作為部署描述文件中的配置參數(shù)來(lái)提供。希望在JSP文檔中導(dǎo)入一段XML文件，或?qū)隭ML語(yǔ)法的JSP頁(yè)面。要在每次請(qǐng)求時(shí)進(jìn)行導(dǎo)入，使用jsp:include標(biāo)準(zhǔn)動(dòng)作。如果要在翻譯階段進(jìn)行導(dǎo)入，使用jsp:directive。include元素。JSP的運(yùn)行原理與優(yōu)點(diǎn)基于Java語(yǔ)言的JSP技術(shù)具有很多其他動(dòng)態(tài)網(wǎng)頁(yè)技術(shù)所沒(méi)有的特點(diǎn)，具體表現(xiàn)在如下方面：1．簡(jiǎn)便性和有效性 JSP動(dòng)態(tài)網(wǎng)頁(yè)的編寫(xiě)與一般的靜態(tài)HTML的網(wǎng)頁(yè)編寫(xiě)是十分相似的。只是在原來(lái)的HTML網(wǎng)頁(yè)中加入一些JSP專有的標(biāo)簽，或是一些腳本程序（此項(xiàng)不是必需的）。這樣，一個(gè)熟悉HTML網(wǎng)頁(yè)編寫(xiě)的設(shè)計(jì)人員可以很容易進(jìn)行JSP網(wǎng)頁(yè)的開(kāi)發(fā)。而且開(kāi)發(fā)人員完全可以不自己編寫(xiě)腳本程序，而只是通過(guò)JSP獨(dú)有的標(biāo)簽使用別人已寫(xiě)好的部件來(lái)實(shí)現(xiàn)動(dòng)態(tài)網(wǎng)頁(yè)的編寫(xiě)。這樣，一個(gè)不熟悉腳本語(yǔ)言的網(wǎng)頁(yè)開(kāi)發(fā)者，完全可以利用JSP做出漂亮的動(dòng)態(tài)網(wǎng)頁(yè)。而這在其他的動(dòng)態(tài)網(wǎng)頁(yè)開(kāi)發(fā)中是不可實(shí)現(xiàn)的。2．程序的獨(dú)立性JSP是Java API家族的一部分，它擁有一般的Java程序的跨平臺(tái)的特性。換句話說(shuō)，就是擁有程序的對(duì)平臺(tái)的獨(dú)立性，即Write once，Run anywhere!。3．程序的兼容性 JSP中的動(dòng)態(tài)內(nèi)容可以各種形式進(jìn)行顯示，所以它可以為各種客戶提供服務(wù)，即從使用HTML/DHTML的瀏覽器，到使用WML的各種手提無(wú)線設(shè)備（例如，移動(dòng)電話和個(gè)人數(shù)字設(shè)備PDA），再到使用XML的B2B應(yīng)用，都可以使用JSP的動(dòng)態(tài)頁(yè)面。4．程序的可重用性 在JSP頁(yè)面中可以不直接將腳本程序嵌入，而只是將動(dòng)態(tài)的交互部分作為一個(gè)部件加以引用。這樣，一旦這樣的一個(gè)部件寫(xiě)好，它可以為多個(gè)程序重復(fù)引用，實(shí)現(xiàn)了程序的可重用性?，F(xiàn)在，大量的標(biāo)準(zhǔn)JavaBeans程序庫(kù)就是一個(gè)很好的例證。附錄B外文文獻(xiàn)原文JSP technology introduction and characteristicsJSP (Java Server Pages) technology is published by Sun pany to develop a technique of dynamic Web applications. It with its easy to learn, crossplatform features, emerged in many dynamic Web application design language, in a few short years, has formed a plete set of specifications, and widely used in emerce and other fields. At home, the JSP now also got more extensive attention and got very good development, more and more dynamic website started using JSP technology. The following on the JSP and related technologies were introduced simply. JSP technology can be in a simple and quick way to generate a Web page. Use the JSP technology Web page can be easily display dynamic content. JSP technology is designed to make structure based on Web application more easily and quickly, and these applications and various Web server, application server, the browser and development tools work together. JSP technology is not only the dynamic web page technology, also is not the first, in the JSP technology existed before the emergence of several excellent dynamic web technologies, such as CGI, ASP, etc. Under the bination of these technologies is introduced, the development of dynamic web page technology and the birth of JSP technology. The JSP development background and development history In the short history of the world wide web, the world wide web has most display from a static information network evolution to the stock trading and an infrastructure of acquisition operations). In a wide variety of applications, for Web based client might use, appears not to have any limits. Based on the browser on the client side application than the traditional client/server based application has several advantages. These benefits including almost no limit to the client access and extremely simplified application deployment and management (to update an application, management personnel only need to change the program, a server based rather than tens of thousands of installed in the client application). In this way, the software industry is rapidly to build browserbased client multilevel application. The rapid growth of sophisticated technologies to develop a webbased application requirements on improvement. Static HTML for display relatively static content is a good choice。 New challenge is to create interactive webbased applications, in these applications, the content of the page is based on the user39。s request or system of the state, instead of predefined characters. An early solution to this problem is to use the CGI interface BIN. Developers to write separate programs related to the interface, and webbased applications, the latter by the Web server to invoke the former. This scheme has serious scalability problems each new CGI requires a new process on the server. If multiple users to concurrently accessing the program, the process will consume the Web server of all available resources, and the system performance will be reduced to very low levels. Some Web server vendors have been trying to through the plugin for their servers and the API to simplify the development of Web applications. These solutions are associated with a particular Web server, can39。t solve the problem of solutions across multiple suppliers. For example, Microsoft39。s Active Server Pages (ASP) technology easier to create dynamic content on the Web page, but also can work in Microsoft IIS and Personal Web Server. There are other solutions, but can39。t make a normal page designers can easily master. For example, like Java Servlet technology can make interactive applications that are written in the Java language on the serv