英文文獻(xiàn)及翻譯(servlet和jsp技術(shù)簡(jiǎn)述)(已修改)
2025-06-12 23:24 本頁(yè)面
【正文】 An Overview of Servlet and JSP TechnologyNagle ,WiegleyAbstract: 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. .Keywords: JSP Technology。Servlet。HTTP server1. A Servlet39。s JobServlets 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 Web middleware role 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. 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 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. 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 speak HTTP or return results in HTML, so the Web browser can39。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. 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. 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. Again, both varieties are critical to effective development. Sending HTTP response data involves telling the browser or other client what type of document is being returned (., HTML), setting cookies and caching parameters, and other such tasks. 2 Why Build Web Pages Dynamically?many client requests can be satisfied by prebuilt documents, and the server would handle these requests without invoking servlets. In many cases, however, a static result is not sufficient, and a page needs to be generated for each request. There are a number of reasons why Web pages need to be built onthefly: The Web page is based on data sent by the client.For instance, the results page from search engines and orderconfirmation pages at online stores are specific to particular user requests. You don39。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. 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 two ways: you could periodically build a new Web page on the server
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