JAVA外文文献+翻译.docx

1、JAVA外文文献+翻译Java and the InternetIf Java is， in fact， yet another computer programming language, you may question why it is so important and why it is being promoted as a revolutionary step in computer programming。 The answer isnt immediately obvious if youre coming from a traditional programming per

2、spective。 Although Java is very useful for solving traditional stand-alone programming problems， it is also important because it will solve programming problems on the World Wide Web。1.Clientside programmingThe Webs initial server-browser design provided for interactive content， but the interactivit

3、y was completely provided by the server. The server produced static pages for the client browser, which would simply interpret and display them. Basic HTML contains simple mechanisms for data gathering： text-entry boxes， check boxes， radio boxes， lists and drop-down lists, as well as a button that c

4、an only be programmed to reset the data on the form or “submit” the data on the form back to the server. This submission passes through the Common Gateway Interface (CGI) provided on all Web servers. The text within the submission tells CGI what to do with it。 The most common action is to run a prog

5、ram located on the server in a directory thats typically called “cgibin.” (If you watch the address window at the top of your browser when you push a button on a Web page, you can sometimes see “cgi-bin” within all the gobbledygook there。) These programs can be written in most languages。 Perl is a c

6、ommon choice because it is designed for text manipulation and is interpreted, so it can be installed on any server regardless of processor or operating system.Many powerful Web sites today are built strictly on CGI， and you can in fact do nearly anything with it。 However， Web sites built on CGI prog

7、rams can rapidly become overly complicated to maintain, and there is also the problem of response time。 The response of a CGI program depends on how much data must be sent, as well as the load on both the server and the Internet. (On top of this， starting a CGI program tends to be slow.) The initial

8、 designers of the Web did not foresee how rapidly this bandwidth would be exhausted for the kinds of applications people developed. For example, any sort of dynamic graphing is nearly impossible to perform with consistency because a GIF file must be created and moved from the server to the client fo

9、r each version of the graph. And youve no doubt had direct experience with something as simple as validating the data on an input form。 You press the submit button on a page； the data is shipped back to the server; the server starts a CGI program that discovers an error， formats an HTML page informi

10、ng you of the error， and then sends the page back to you; you must then back up a page and try again。 Not only is this slow， its inelegant.The solution is client-side programming。 Most machines that run Web browsers are powerful engines capable of doing vast work, and with the original static HTML a

11、pproach they are sitting there, just idly waiting for the server to dish up the next page. Client-side programming means that the Web browser is harnessed to do whatever work it can, and the result for the user is a much speedier and more interactive experience at your Web site.The problem with disc

12、ussions of client-side programming is that they arent very different from discussions of programming in general。 The parameters are almost the same, but the platform is different： a Web browser is like a limited operating system. In the end, you must still program, and this accounts for the dizzying

13、 array of problems and solutions produced by clientside programming。 The rest of this section provides an overview of the issues and approaches in clientside programming.2.Plug-insOne of the most significant steps forward in clientside programming is the development of the plugin。 This is a way for

14、a programmer to add new functionality to the browser by downloading a piece of code that plugs itself into the appropriate spot in the browser. It tells the browser “from now on you can perform this new activity。 (You need to download the plugin only once.） Some fast and powerful behavior is added t

15、o browsers via plugins, but writing a plugin is not a trivial task, and isnt something youd want to do as part of the process of building a particular site。 The value of the plugin for clientside programming is that it allows an expert programmer to develop a new language and add that language to a

16、browser without the permission of the browser manufacturer. Thus， plugins provide a “back door” that allows the creation of new client-side programming languages (although not all languages are implemented as plug-ins).3。Scripting languagesPlug-ins resulted in an explosion of scripting languages. With a scripting language you embed the source code for your client-side program directly into the HTML page， and the plug-in that interprets that language is