【正文】 外文翻譯 3 language suitable for a client. With the arrival of more options on the browser (DHTML and JavaScript coding, for example), the increase in graphic artist talent in the Web domain, and tools that could create plex interfaces using standard HTML, the demand for fancy user interfaces has grown faster than our ability to develop these front ends to our applications. And this has given rise to presentation technology was designed to perform a single task: convert content, namely data without display details, into presentation meaning the various user interfaces you see on your phone, PalmPilot, or Web browser. What are the problems that these presentation technologies claimed to solve? Let39。s presentation technology. A bit of historyBefore diving into an explanation of presentation technology, it39。 and, most importantly, ease of use. The Unified Expression Language (EL) The simple EL included in JSP technology offers many advantages to the page author. Using simple expressions, page authors can easily access external data objects from their pages. The JSP technology container evaluates and resolves these expressions as it encounters them. It then immediately returns a response because the JSP requestprocessing model has only one phase, the render phase. However, because the requestprocessing model does not support a postback, all JSP expressions are readonly. Unlike JSP technology, JavaServer Faces technology supports a multiphase life cycle. When a user enters values into the JavaServer Faces UI ponents and submits the page, those values are converted, validated, and propagated to serverside data objects, after which ponent events are processed. In order to perform all these tasks in an orderly fashion, the JavaServer Faces life cycle is split into separate phases. Therefore, JavaServer Faces technology evaluates expressions at different phases of the life cycle rather than immediately, as JSP technology would do. 東華理工大學(xué)畢業(yè)設(shè)計(jì) 外文翻譯 2 JSP technology friend or foe? Presentation technology was designed to transform plain ol39。 enhanced performance。 they are application ponents that are downloaded, on demand, to the part of the system that needs them. Together, JSP technology and servlets provide an attractive alternative to other types of dynamic Web scripting/programming by offering: platform independence。 extensibility into the enterprise。t have to be limited to this single technology. In fact, these days a number of presentation technologies are available. This article begins by defining the problems presentation technologies were designed to solve. It then examines the specific strengths and weaknesses of the JSP model. Finally, it introduces some viable alternatives to Sun39。t support at least three of four MLisms such as HTML, XML, and WML is considered shabby, if not an outright failure. And, of course, that means we all care very deeply about the ability to easily develop a Web presentation it turns out, using the new Inter, and all the languages we have at our disposal Java, C, Perl, Pascal, and Ada, among others hasn39。s usefulness is the amount of rework that it eliminates. The divergence of presentation and content enforces a divergence in the roles of those developing the content. A programmer can focus on the raw content presented in the examples above, and a graphic artist or webmaster can attend to the presentation. A slight overlap of roles remains, however, in the process of taking the presentation or markup designed by the artist and applying it to the content the programmer39。s source code from the developer are off limits. Of course, this is an errorprone, dangerous way to operate. Once you39。 you39。s list of features is something that might raise a bit of concern. JSP coding lets you insert Java code directly into a page of markup. To understand why this decision was made, recall that when the JSP specification was being developed, Sun39。 % TR BGCOLOR=FFCCCC TH width=50% ALIGN=center %=()% /TH TH width=50% ALIGN=center %=()% /TH /TR % } % /TABLE /CENTER /BODY /HTML 東華理工大學(xué)畢業(yè)設(shè)計(jì) 外文翻譯 9 Remember that so far I am simply describing the initial design goals of JSP technology。ve spelled out what a good presentation technology should provide, as well as the specific problems that JSP technology seeks to address. Now, I39。t really be J2EE applications. In fact, the platform boasts more APIs than most applications need. If you have problems with or doubts about JSP technology, you don39。m disregarding the Microsoft .NET platform for the smoke and mirrors it is. Only time will tell whether that platform will develop into one that is truly languageindependent. (I39。re probably pretty sick of hearing about this, so now39。 } else { actors = ()。t ring true, consider why the Java language immediately gained popularity over C and C++: Java disallowed many of the features that were problematic in C, such as pointer addition. While you can always argue that you don39。t fair to hold JSP to an impossible standard. Most template engines, like FreeMarker and WebMacro, have this same inline coding facility, often with a Perlanalogue language. However, technologies like Enhydra39。t see what those elements look like. When designers can39。t allow the various JSP custom tag libraries. More important, though, is that the code snippets inserted in JSP pages are not any form of markup and will create loads of parser errors once they are processed by another you go quoting me on this, l