【文章內(nèi)容簡介】 o include a resource that does not change very much (such as a page fragment that represents a header or footer) in a JSP. Use the include directive in the including JSP page, and give the included JSP segment a .jspf extension. You want to include content in a JSP each time it receives a request, rather than when the JSP is converted to a servlet. Use the jsp:include standard action. You want to include a file dynamically in a JSP, based on a value derived from a configuration file. Use the jsp:include standard action. Provide the value in an external properties file or as a configuration parameter in the deployment descriptor. You want to include a fragment of an XML file inside of a JSP document, or include a JSP page in XML syntax. Use the jsp:include standard action for the includes that you want to occur with each request of the JSP. Use the jsp: element if the include action should occur during the translation phase. You want to include a JSP segment from outside the including file39。s context. Use the c:import The operation principle and the advantages of JSP tags In this section of the operating principle of simple introduction JSP and strengths. For the first time in a JSP documents requested by the engine, JSP Servlet is transformed into a document JSP. This engine is itself a Servlet. The operating process of the JSP shown below: (1) the JSP engine put the JSP files converting a Java source files (Servlet), if you find the files have any grammar mistake JSP, conversion process will interrupt, and to the server and client output error messages. (2) if converted, with the engine JSP javac Java source file piler into a corresponding scaleup files. (3) to create a the Servlet (JSP page), the transformation of the Servlet jspInit () method was executed, jspInit () method in the life cycle of Servlet executed only once. (4) jspService () method invocation to the client requests. For each request, JSP engine to create a new thread for processing the request. If you have multiple clients and request the JSP files, JSP engine will create multiple threads. Each client requests a thread. To execute multithread can greatly reduce the requirement of system resources, improving the concurrency value and response time. But also should notice the multithread programming, due to the limited Servlet always in response to memory, so is very fast. (5) if the file has been modified. The JSP, server will be set according to the document to decide whether to repile, if need to repile, will replace the Servlet pile the memory and continue the process. (6) although the JSP efficiency is high, but at first when the need to convert and pile and some slight delay. In addition, if at any time due to reasons of system resources, JSP engine will in some way of uncertain Servlet will remove from memory. When this happens jspDestroy () method was first call. (7) and then Servlet examples were marked with add garbage collection. But in jspInit () some initialization work, if establish connection with database, or to establish a work connection, from a configuration file take some parameters, such as, in jspDestory () release of the corresponding resources. Based on a Java language has many other techniques JSP page dynamic characteristics, technical have embodied in the following aspects: One simplicity and effectiveness The JSP dynamic web pages with the pilation of the static HTML pages of writing is very similar. Just in the original HTML page add JSP tags, or some of the proprietary scripting (this is not necessary). So, a familiar with HTML page write design personnel may be easily performed JSP page development. And the developers can not only, and write script by JSP tags used exclusively others have written parts to realize dynamic pages. So, an unfamiliar with the web developers scripting language, can use the JSP make beautiful dynamic pages. And this in other dynamic web development is impossible. Tow the independence of the program The JSP are part of the family of the API Java, it has the general characteristics of the crossplatform Java program. In other words, is to have the procedure, namely the independence of the platform, 6 Write bided anywhere! . Three procedures patibility The dynamic content can various JSP form, so it can show for all kinds of customers, namely from using HTML/DHTML browser to use various handheld wireless equipment WML (for example, mobile phones and pdas), personal digital equipment to use XML applications, all can use B2B JSP dynamic pages. Four program reusability In the JSP page can not directly, but embedded scripting dynamic interaction will be cited as a ponent part. So, once such a ponent to write, it can be repeated several procedures, the program of the reusability. Now, a lot of standard JavaBeans library is a good example. JSP 技術(shù)簡介及特點 JSP（ Java Server Pages）技術(shù)是由 Sun公司發(fā)布的用于開發(fā)動態(tài) Web應(yīng)用的一項技術(shù)。它以其簡單易學、跨平臺的特性，在眾多動態(tài) Web應(yīng)用程序設(shè)計語言中異軍突起，在短短幾年中已經(jīng)形成了一套完整的規(guī)范，并廣泛地應(yīng)用于電子商務(wù)等各個領(lǐng)域中。在國內(nèi)， JSP 現(xiàn)在也得到了比較廣泛的重視，得到了很 好的發(fā)展，越來越多的動態(tài)網(wǎng)站開始采用 JSP技術(shù)。下面就對 JSP 及其相關(guān)技術(shù)進行簡單的介紹。 JSP 技術(shù)可以以一種簡捷而快速的方法生成 Web頁面。使用 JSP技術(shù)的 Web頁面可以很容易地顯示動態(tài)內(nèi)容。 JSP技術(shù)的設(shè)計目的是使得構(gòu)造基于 Web的應(yīng)用程序更加容易和快捷，而這些應(yīng)用程序能夠與各種 Web服務(wù)器、應(yīng)用服務(wù)器、瀏覽器和開發(fā)工具共同工作。 JSP 技術(shù)不是惟一的動態(tài)網(wǎng)頁技術(shù)，也不是第一個，在 JSP技術(shù)出現(xiàn)之前就已經(jīng)存在幾種優(yōu)秀的動態(tài)網(wǎng)頁技術(shù)，如 CGI、 ASP等。下面結(jié)合這些技術(shù)的介紹，講述動態(tài)網(wǎng)頁技術(shù)的發(fā)展和 JSP技術(shù)的誕生。 JSP的開發(fā)背景及發(fā)展歷史 在萬維網(wǎng)短暫的歷史中，萬維網(wǎng)已經(jīng)從一個大部分顯示靜態(tài)信息的網(wǎng)絡(luò)演化到對股票進行交易和進行購書操作的一個基礎(chǔ)設(shè)施。在各種各樣的應(yīng)用程序中，對于可能使用的基 于 Web的客戶端，看上去沒有任何限制。 基于瀏覽器客戶端的應(yīng)用程序比傳統(tǒng)的基于客戶機 /服務(wù)器的應(yīng)用程序有幾個好處。這些好處包括幾乎沒有限制的客戶端訪問和極其簡化的應(yīng)用程序部署和管理（要更新一個應(yīng)用程序，管理人員只需要更改一個基于服務(wù)器的程序，而不是成千上萬的安裝在客戶端的應(yīng)用程序）。這樣，軟件工業(yè)正迅速地向建造基于瀏覽器客戶端的多層次應(yīng)用程序邁進。 這些快速增長的精巧的基于 Web 的應(yīng)用程序要求開發(fā)技術(shù)上的改進。靜態(tài) HTML 對于顯示相對靜態(tài)的內(nèi)容是不錯的選擇；新的挑戰(zhàn)在于創(chuàng)建交互的基于 Web的應(yīng)用程序，在這些 程序中，頁面的內(nèi)容是基于用戶的請求或者系統(tǒng)的狀態(tài)，而不是預先定義的文字。 對于這個問題的一個早期解決方案是使用 CGIBIN接口。開發(fā)人員編寫與接口相關(guān)的單獨的程序，以及基于 Web的應(yīng)用程序，后者通過 Web服務(wù)器來調(diào)用前者。這個方案有著嚴重的擴展性問題 —— 每個新的CGI 要求在服務(wù)器上新增