外文翻譯---servlet和jsp技術(shù)簡(jiǎn)介

1、附錄一 附錄一 外文原文 外文原文（摘自 （摘自 Marty Marty Hall Hall and and Larry Larry Brown Brown，2000-07 2000-07，Core Core Servlets Servlets and and JavaServer JavaServer Pages Pages 第一章 第一章）An Overview of Servlet and JSP Technology1.1 A

2、Servlet's JobServlets are Java programs that run on Web or application servers, acting as a middle layer between requests coming from Web browsers or other HTTP clients and databases or applications on the HTTP serve

3、r. Their job is to perform the following tasks, as illustrated in Figure 1-1.Figure 1-11．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 c

4、ould also come from an applet or a custom HTTP client program.2．Read the implicit HTTP request data sent by the browser.Figure 1-1 shows a single arrow going from the client to the Web server (the layer where servlets an

5、d JSP execute), but there are really two varieties of data: the explicit data that the end user enters in a form and the behind-the-scenes HTTP information. Both varieties are critical. The HTTP information includes cook

6、ies, information about media types and compression schemes the browser understands, and so on.would handle these requests without invoking servlets. In many cases, however, a static result is not sufficient, and a page n

7、eeds to be generated for each request. There are a number of reasons why Web pages need to be built on-the-fly:1． The Web page is based on data sent by the client.For instance, the results page from search engines and or

8、der-confirmation pages at online stores are specific to particular user requests. You don't know what to display until you read the data that the user submits. Just remember that the user submits two kinds of data: e

9、xplicit (i.e., HTML form data) and implicit (i.e., HTTP request headers). Either kind of input can be used to build the output page. In particular, it is quite common to build a user-specific page based on a cookie value

10、.2．The Web page is derived from data that changes frequently.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

11、 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, b

12、ut 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 pa