【正文】 9i AS. Again, none of their servlets or JSP pages have to be rewritten. Finally, if their project bees even bigger, they might move it off of their Linux box and onto an IBM mainframe running IBM WebSphere. But once again, none of their servlets or JSP pages have to be rewritten. 6． Secure One of the main sources of vulnerabilities in traditional CGI stems from the fact that the programs are often executed by generalpurpose operating system shells. So, the CGI programmer must be careful to filter out characters such as backquotes and semicolons that are treated specially by the shell. Implementing this precaution is harder than one might think, and weaknesses stemming from this problem are constantly being uncovered in widely used CGI libraries. A second source of problems is the fact that some CGI programs are processed by languages that do not automatically check array or string bounds. For example, in C and C++ it is perfectly legal to allocate a 100element array and then write into the 999th element, which is really some random part of program memory. So, programmers who fet to perform this check open up their system to deliberate or accidental buffer overflow attacks. Servlets suffer from neither of these problems. Even if a servlet executes a system call (., with or JNI) to invoke a program on the local operating system, it does not use a shell to do so. And, of course, array bounds checking and other memory protection features are a central part of the Java programming language. 7． Mainstream There are a lot of good technologies out there. But if vendors don39。An Overview of Servlet and JSP Technology Nagle and Wiegley， Aug. 2020， 953 – 958. 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。re already convinced that Java technology makes for more reliable and reusable code than does Visual Basic, VBScript, or C++. Why go back to those languages for serverside programming? 3． Powerful Servlets support several capabilities that are difficult or impossible to acplish with regular CGI. Servlets can talk directly to the Web server, whereas regular CGI programs cannot, at least not without using a serverspecific API. Communicating with the Web server makes it easier to translate relative URLs into concrete path names, for instance. Multiple servlets can also share data, making it easy to implement database connection pooling and similar resourcesharing optimizations. Servlets can also maintain information from request to request, simplifying techniques like session tracking and caching of previous putations. 4． Portable Servlets are written in the Java programming language and follow a standard API. Servlets are supported directly or by a plugin on virtually every major Web server. Consequently, servlets written for, say, Macromedia JRun can run virtually unchanged on Apache Tomcat, Microsoft Inter Information Server (with a separate plugin), IBM WebSphere, iPla Enterprise Server, Oracle9i AS, or StarNine WebStar. They are part of the Java 2 Platform, Enterprise Edition (J2EE。然而，數(shù)據(jù)還有可能來(lái)自applet 或定制的 HTTP 客戶程序。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。 圖 中顯示了一條 從 Web 中間層到客戶端的單箭頭。在沒(méi)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。例如，天氣預(yù)報(bào)或新聞網(wǎng)站可能會(huì)動(dòng)態(tài)地構(gòu)建頁(yè)面，也有可能會(huì)返回之前構(gòu)建的頁(yè)面（如果它還是最新的話）。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。這種方式減少了服務(wù)器的內(nèi)存需求，通過(guò)實(shí)例化更少的對(duì)象從而節(jié)省了時(shí)間。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。 iPla Enterprise Server。印度接近列表的頂端，可能僅次于美國(guó)。他們的 servelt 和 jsp 不需要重寫(xiě)編寫(xiě)。他們還是不需要做出任何更改。即使 servelt 執(zhí)行系統(tǒng)調(diào)用激活本地操作系統(tǒng)上的程序，它也不會(huì)用到外殼來(lái)完成這