【正文】 ally, perhaps returning a previously built page if that page is still up to date. 3． The Web page uses information from corporate databases or other serverside sources. If the information is in a database, you need serverside processing even if the client is using dynamic Web content such as an applet. Imagine using an applet by itself for a search engine site: Downloading 50 terabyte applet, please wait! Obviously, that is silly。它們用在航空業(yè)、電子商務(wù)、在線銀行、 web 搜索引擎、門戶、大型金融網(wǎng)站、以及成百上千您日常光顧的其他網(wǎng)站。 問題的第二個(gè)來源是，一些 CGI 程序用不自動(dòng)檢查數(shù)組和字符串邊界的語言編寫而成。如果項(xiàng)目變得極為龐大，錯(cuò)綜復(fù)雜，他們或許希望使用 Enterprise JavaBeans 來封裝他們的商業(yè)邏輯。其次，這兩個(gè)國家的貨幣 5 對(duì)美元的匯率都極為不利。因此，通過使用 servelt 和 jsp，我們可以從免費(fèi)或廉價(jià)的服務(wù)器開始，在項(xiàng)目獲得初步成功后，在移植到更高性能或高級(jí)管理工具的昂貴的服務(wù)器上。所有主要的 Web 服務(wù)器。 便利 Servelt 提供大量的基礎(chǔ)構(gòu)造，可以自動(dòng)分析和解碼 HTML 的表單數(shù)據(jù)，讀取和設(shè)置 4 HTTP 報(bào)頭，處理 cookie，跟蹤會(huì)話，以及其他次類高級(jí)功能。如果 CGI 程序自身相對(duì)比較簡短，那么啟動(dòng)進(jìn)程的開銷會(huì)占用大部分執(zhí)行時(shí)間。顯然，這樣很愚蠢；這種情況下，我們需要與數(shù)據(jù)庫進(jìn)行會(huì)話。 頁面由頻繁改變的數(shù)據(jù)導(dǎo)出。 動(dòng)態(tài)構(gòu)建網(wǎng)頁的原因 預(yù)先建立的文檔可以滿足客戶的許多請(qǐng)求，服務(wù)器無需調(diào)用 servlet 就可以處理這些請(qǐng)求。 （ 4） 向客戶發(fā)送顯式數(shù)據(jù)（即文檔）。 HTTP 信息包括 cookie、瀏覽器所能識(shí)別的媒體類型和壓縮模式等。 關(guān)鍵字 ： JSP 技術(shù)， Servlet， HTTP 服務(wù) 的功能 Servlets 是運(yùn)行在 Web 或應(yīng)用服務(wù)器上的 Java 程序，它是一個(gè)中間層，負(fù)責(zé)連接來自 Web 瀏覽器或其他 HTTP 客戶程序的請(qǐng)求和 HTTP 服務(wù)器上的數(shù)據(jù)庫或應(yīng)用程序。 （ 2） 讀取由瀏覽器發(fā)送的隱式請(qǐng)求數(shù)據(jù)。即使它能夠做到這一點(diǎn)，為了安全上的考慮，我們也不希望讓它這么做。但是，實(shí)際發(fā)送的數(shù)據(jù)有兩種：文檔本身，以及后臺(tái)的 HTTP 信息。要記住，用戶提交兩種類型的數(shù)據(jù)：顯示（即 HTML 表單的數(shù)據(jù)）和隱式（即 HTTP 請(qǐng)求的報(bào)頭）。 3 頁面中使用了來自公司數(shù)據(jù)庫或其他數(shù)據(jù)庫斷數(shù)據(jù)源的信息。而且，用于會(huì)話啟動(dòng)協(xié)議服務(wù)器的 servlet API 最近已經(jīng)被標(biāo)準(zhǔn)化（參見 servelt 的這種用法尚不流行，在此，我們只論述 HTTP Servlet。最后，當(dāng) CGI 程序結(jié)束對(duì)請(qǐng)求的處理之后，程序結(jié)束。多個(gè) servelt 還可以共享數(shù)據(jù)，從而易于實(shí)現(xiàn)數(shù)據(jù)庫連接共享和類似的資源共享優(yōu)化。 Oracle9i AS 或者 StrNine WebStar 上運(yùn)行。 Marty 曾在馬尼拉講授過 jsp 和 servlet 培訓(xùn)課程，那兒對(duì) servelt 和 jsp 技術(shù)抱很大的興趣。如果他們的項(xiàng)目變得更龐大，他們或許希望轉(zhuǎn)移到分布式環(huán)境。 安全 傳統(tǒng) CGI 程序中主要的漏洞來源之一就是， CGI 程序常常由通過的操作系統(tǒng)外殼來執(zhí)行。當(dāng)然，數(shù)組邊界的檢查以及其他內(nèi)存包含特性是java 編程語言的核心部分。s Job Servlets are Java programs that run on Web or application servers, acting as a middle layer between requests ing from Web browsers or other HTTP clients and databases or applications on the HTTP server. Their job is to perform the following tasks, as illustrated in Figure 11. Figure 11 1． Read the explicit data sent by the client. The end user normally enters this data in an HTML form on a Web page. However, the data could also e from an applet or a custom HTTP client program. 2． Read the implicit HTTP request data sent by the browser. Figure 11 shows a single arrow going from the client to the Web server (the layer where servlets and JSP execute), but there are really two varieties of data: the explicit data that the end user enters in a form and the 7 behindthescenes HTTP information. Both varieties are critical. The HTTP information includes cookies, information about media types and pression schemes the browser understands, and so on. 3． Generate the results. This process may require talking to a database, executing an RMI or EJB call, invoking a Web service, or puting the response directly. Your real data may be in a relational database. Fine. But your database probably doesn39。t support them and developers don39。t talk directly to the database. Even if it could, for security reasons, you probably would not want it to. The same argument applies to most other need the Web middle layer to extract the results inside a document. 4． Send the explicit data (., the document) to the client. This document can be sent in a variety of formats, including text (HTML or XML), binary (GIF images), or even a pressed format like gzip that is layered on top of some other underlying format. But, HTML is by far the most mon format, so an important servlet/JSP task is to wrap the results inside of HTML. 5． Send the implicit HTTP response data. Figure 11 shows a single arrow going from the Web middle layer (the servlet or JSP page) to the client. But, there are really two varieties of data sent: the document itself and the behindthescenes HTTP information