【文章內(nèi)容簡介】 d without difficult reinstallation. Because of the way Java is designed, the programmer needs to create only a single program, and that program automatically works with all puters that have browsers with builtin Java interpreters. (This safely includes the vast majority of machines.) Since Java is a fullfledged programming language, you can do as much work as possible on the client before and after making requests of the server. For example, you won’t need to send a request form across the Inter to discover that you’ve gotten a date or some other parameter wrong, and your client puter can quickly do the work of plotting data instead of waiting for the server to make a plot and ship a graphic image back to you. Not only do you get the immediate win of speed and responsiveness, but the general work traffic and load on servers can be reduced, preventing the entire Inter from slowing down. One advantage a Java applet has over a scripted program is that it’s in piled form, so the source code isn’t available to the client. On the other hand, a Java applet can be depiled without too much trouble, but hiding your code is often not an important issue. Two other factors can be important. As you will see later in this book, a piled Java applet can prise many modules and take multiple server “hits” (accesses) to download. (In Java and higher this is minimized by Java archives, called JAR files, that allow all the required modules to be packaged together and pressed for a single download.) A scripted program will just be integrated into the Web page as part of its text (and will generally be smaller and reduce server hits). This could be important to the responsiveness of your Web site. Another factor is the allimportant learning curve. Regardless of what you’ve heard, Java is not a trivial language to learn. If you’re a Visual Basic programmer, moving to VBScript will be your fastest solution, and since it will probably solve most typical client/server problems you might be hard pressed to justify learning Java. If you’re experienced with a scripting language you will certainly benefit from looking at JavaScript or VBScript before mitting to Java, since they might fit your needs handily and you’ll be more productive run its applets withi To some degree, the petitor to Java is Microsoft’s ActiveX, although it takes a pletely different approach. ActiveX was originally a Windowsonly solution, although it is now being developed via an independent consortium to bee crossplatform. Effectively, ActiveX says “if your program connects to its environment just so, it can be dropped into a Web page and run under a browser that supports ActiveX.” (IE directly supports ActiveX and Netscape does so using a plugin.) Thus, ActiveX does not constrain you to a particular language. If, for example, you’re already an experienced Windows programmer using a language such as C++, Visual Basic, or Borland’s Delphi, you can create ActiveX ponents with almost no changes to your programming knowledge. ActiveX also provides a path for the use of legacy code in your Web pages. vs. intra The Web is the most general solution to the client/server problem, so it makes sense that you can use the same technology to solve a subset of the problem, in particular the classic client/server problem within a pany. With traditional client/server approaches you have the problem of multiple types of client puters, as well as the difficulty of installing new client software, both of which are handily solved with Web browsers and clientside programming. When Web technology is used for an information work that is restricted to a particular pany, it is referred to as an intra. Intras provide much greater security than the Inter, since you can physically control access to the servers within your pany. In terms of training, it seems that once people understand the general concept of a browser it’s much easier for them to deal with differences in the way pages and applets look, so the learning curve for new kinds of systems seems to be reduced. The security problem brings us to one of the di