java和internet計(jì)算機(jī)專業(yè)畢業(yè)設(shè)計(jì)外文翻譯(已修改)
2025-06-19 16:30 本頁面
【正文】 Java and the Inter If Java is, in fact, yet another puter programming language, you may question why it is so important and why it is being promoted as a revolutionary step in puter programming. The answer isn’t immediately obvious if you’re in g from a traditional programming perspective. Although Java is very useful for solving traditional standalone programming problems, it is also important because it will solve programming problems on the World Wide Web. What is the Web? The Web can seem a bit of a mystery at first, with all this talk of “surfing,” “presence,” and “home pages.” It’s helpful to step back and see what it really is, but to do this you must understand client/server systems, another aspect of puting that’s full of confusing iss ues. Client/Server puting The primary idea of a client/server system is that you have a central repository of information— some kind of data, often in a database— that you want to distribute on demand to some set of people or machines. A key to the client/server concept is that the repository of information is centrally located so that it can be changed and so that those changes will propagate out to the information consumers. Taken together, the information repository, the software that distributes the information and the machine where the information and software reside is called the server. The software that resides on the remote machine, municates with the server, fetches the information, processes it, and then displays it on the remote machine is called the client. The basic concept of client/server puting, then, is not so plicated. The problems arise because you have a single server trying to serve many clients at once. Generally, a database management system is involved, so the designer “bala nces” the layout of data into tables for optimal use. In addition, systems often allow a client to insert new information into a server. This means you must ensure that one client’s new data doesn’t walk over another client’s new data, or that data isn’t l ost in the process of adding it to the database (this is called transaction processing). As client software changes, it must be built, debugged, and installed on the client machines, which turns out to be more plicated and expensive than you might think. It’s especially problematic to support multiple types of puters and operating systems. Finally, there’s the all important performance issue: You might have hundreds of clients making requests of your server at any one time, so any small delay is crucial. To minimize latency, programmers work hard to offload processing tasks, often to the client machine, but sometimes to other machines at the server site, using socalled middleware. (Middleware is also used to improve maintainability.) The simple idea of distributing information has so many layers of plexity that the whole problem can seem hopelessly enigmatic. And yet it’s crucial: Client/server puting accounts for roughly half of all programming activities. It’s responsible for everything from ta king orders and creditcard transactions to the distribution of any kind of data— stock market, scientific, government, you name it. What we’ve e up with in the past is individual solutions to individual problems, inventing a new solution each time. These were hard to create and hard
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