【正文】 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。 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。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(kù)連接共享和類似的資源共享優(yōu)化。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。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）。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。 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(kù)或應(yīng)用程序。 （ 4） 向客戶發(fā)送顯式數(shù)據(jù)（即文檔）。 頁(yè)面由頻繁改變的數(shù)據(jù)導(dǎo)出。如果 CGI 程序自身相對(duì)比較簡(jiǎn)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。所有主要的 Web 服務(wù)器。其次，這兩個(gè)國(guó)家的貨幣 5 對(duì)美元的匯率都極為不利。 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。t know what to display until you read the data that the user submits. Just remember that the user submits two kinds of data: explicit (., HTML form data) and implicit (., HTTP request headers). Either kind of input can be used to build the output page. In particular, it is quite mon to build a userspecific page based on a cookie value. 2． The Web page is derived from data that changes frequently. 8 If the page changes for every request, then you certainly need to build the response at request time. If it changes only periodically, however, you could do it two ways: you could periodically build a new Web page on the server (independently of client requests), or you could wait and only build the page when the user requests it. The right approach depends on the situation, but sometimes it is more convenient to do the latter: wait for the user request. For example, a weather report or news headlines site might build the pages dynamically, 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。 An Overview of Servlet and JSP Technology Abstract: Servlet program running in the serverside, dynamically generated Web page with the traditional CGI and many other similar pared to CGI technology, Java Servlet with a more efficient, easier to use, more powerful and has better portability, more savings to invest . Key words: JSP Technology, Servlet, HTTP server A Servlet39。他們還是不需要做出任何更改。印度接近列表的頂端，可能 僅次于美國(guó)。例如，與 Web 服務(wù)器的通信使得講相對(duì) URL 轉(zhuǎn)換成具體的路徑名變得更為容易。例如， servlet 能夠嵌入到 FTP 或郵件 服務(wù)器中，擴(kuò)展他們的功能。在沒有讀取到用戶提交的數(shù)據(jù)之前，我們不知道應(yīng)該顯示什么。該數(shù)據(jù)庫(kù)可能不理解 HTTP，或者不能返回 HTML 形式的結(jié)果， 所有 Web 瀏覽器不能直接與數(shù)據(jù)庫(kù)進(jìn)行會(huì)話。Servlet 的工作是執(zhí)行西門的任務(wù)，如圖 所示 。 這個(gè)文檔可以用各種格式發(fā)送，包括文本（ HTML 或 XML），二進(jìn)制（ GIF圖），甚至可以式建立在其他底層格式之上的壓縮格式，如 gzip。 如果頁(yè)面需要根據(jù)每個(gè)具體的請(qǐng)求做出相應(yīng)的改變，當(dāng)然需要在請(qǐng)求發(fā)生時(shí)構(gòu)建響應(yīng)。而使用 servelt， Java 虛擬機(jī)會(huì)一直運(yùn)行，并用輕量級(jí)的 Java 線程處理每個(gè)請(qǐng)求，而非重量級(jí)的操作系統(tǒng)進(jìn)程。實(shí)際上都直接或通過插件支持 servlet。因此，從美國(guó)公司那里購(gòu)買專用 Web 服務(wù)器會(huì)消耗掉項(xiàng)目的大部分前期資金。例如，在 C和 C＋＋中，可以分配一 個(gè) 100 個(gè)元素的數(shù)組，然后向第 999 個(gè) “ 元素“ 寫入數(shù)據(jù) —— 實(shí)際上是程序內(nèi)存的隨機(jī)部分，這完全合法。 you need to talk to the database. Going from the client to the Web tier to the database (a threetier approach) instead of from an applet directly to a database (a twotier approach) provides increased flexibility and security with little or no performance penalty. After all, the database call is usually the ratelimiting step, so going through the Web server does not slow things down. In fact, a threetier approach is often faster because the middle tier can perform caching and connection pooling. In principle, servlets are not restricted to Web or application servers that handle HTTP requests but can be used for other types of servers as well. For example, servlets could be embedded in FTP or mail servers to extend their functionality. And, a servlet API for SIP (Session Initiation Protocol) servers was recently standardized (see In practice, h