毕业设计外文翻译

概要：10.4 Misconceptions About JSPForgetting JSP Is Server-Side TechnologyHere are some typical questions Marty has received (most of them repeatedly).• Our server is running JDK 1.4. So, how do I put a Swing component in a JSP page?• How do I put an image into a JSP page? I do not know the proper Java I/O commands to read image files.• Since Tomcat does not support JavaScript, how do I make images that are highlighted when the user moves the mouse over them?• Our cl

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10.4 Misconceptions About JSP
Forgetting JSP Is Server-Side Technology
Here are some typical questions Marty has received (most of them repeatedly).
• Our server is running JDK 1.4. So, how do I put a Swing component in a JSP page?
• How do I put an image into a JSP page? I do not know the proper Java I/O commands to read image files.
• Since Tomcat does not support JavaScript, how do I make images that are highlighted when the user moves the mouse over them?
• Our clients use older browsers that do not understand JSP. What should we do?
• When our clients use "View Source" in a browser, how can I prevent them from seeing the JSP tags?
All of these questions are based upon the assumption that browsers know something about the server-side process. But they do not. Thus:
• For putting applets with Swing components into Web pages, what matters is the browser's Java version—the server's version is irrelevant. If the browser supports the Java 2 platform, you use the normal APPLET (or Java plug-in) tag and would do so even if you were using non-Java technology on the server.
• You do not need Java I/O to read image files; you just put the image in the directory for Web resources (i.e., two levels up from WEB-INF/classes) and output a normal IMG tag.
• You create images that change under the mouse by using client-side JavaScript, referenced with the SCRIPT tag; this does not change just because the server is using JSP.
• Browsers do not "support" JSP at all—they merely see the output of the JSP page. So, make sure your JSP outputs HTML compatible with the browser, just as you would do with static HTML pages.
• And, of course you need not do anything to prevent clients from seeing JSP tags; those tags are processed on the server and are not part of the output that is sent to the client.
Confusing Translation Time with Request Time
A JSP page is converted into a servlet. The servlet is compiled, loaded into the server's memory, initialized, and executed. But which step happens when? To answer that question, remember two points:
• The JSP page is translated into a servlet and compiled only the first time it is accessed after having been modified.
• Loading into memory, initialization, and execution follow the normal rules for servlets.
Table 1 gives some common scenarios and tells whether or not each step occurs in that scenario. The most frequently misunderstood entries are highlighted. When referring to the table, note that servlets resulting from JSP pages use the _jspService method (called for both GET and POST requests), not doGet or doPost. Also, for initialization, they use the jspInit method, not the init method.
Table 1. JSP Operations in Various Scenarios
  JSP page translated into servlet Servlet compiled Servlet loaded into server's memory jspInit called _jspService called
Page first written
Request 1 Yes Yes Yes Yes Yes
Request 2 No No No No Yes
Server restarted
Request 3 No No Yes Yes Yes
Request 4 No No No No Yes
Page modified
Request 5 Yes Yes Yes Yes Yes
Request 6 No No No No Yes

中文翻译
JSP技术概述
一、JSP的好处
JSP页面最终会转换成servler。因而，从根本上，JSP页面能够执行的任何任务都可以用servler来完成。然而，这种底层的等同性并不意味着servler和JSP页面对于所有的情况都等同适用。问题不在于技术的能力，而是二者在便利性、生产率和可维护性上的不同。毕竟，在特定平台上能够用Java编程语言完成的事情，同样可以用汇编语言来完成，但是选择哪种语言依旧十分重要。
和单独使用servler相比，JSP提供下述好处：
 JSP中HTML的编写与维护更为简单。JSP中可以使用常规的HTML：没有额外的反斜杠，没有额外的双引号，也没有暗含的Java语法。
 能够使用标准的网站开发工具。即使对那些对JSP一无所知的HTML工具，我们也可以使用，因为它们会忽略JSP标签（JSP tags）。
 可以对开发团队进行划分。Java程序员可以致力于动态代码。Web开发人员可以将经理集中在表示层（presentation layer）上。对于大型的项目，这种划分极为重要。依据开发团队的大小，及项目的复杂程度，可以对静态HTML和动态内容进行弱分离（weaker separation）和强分离（stronger separation）。
在此，这个讨论并不是让您停止使用servlets，只使用JSP。几乎所有的项目都会同时用到这两种技术。针对项目中的某些请求，您可能会在MVC构架下组合使用这两项技术。我们总是希望用适当的工具完成相对应的工作，仅仅是servlet并不能填满您的工具箱。
二、JSP相对于竞争技术的优势
许多年前，Marty受到邀请,参加一个有关软件技术的小型(20个人)研讨会.做在Marty旁边的人是James Gosling--- Java编程语言的发明者。隔几个位置,是来自华盛顿一家大型软件公司的高级经理。在讨论过程中,研讨会的主席提出了Jini的议题,这在当时是一项新的Java技术.主席向该经理询问他的想法.他继续说,他们会持续关注这项技术,如果这项技术变得流行起来,他们会遵循公司的“接受并扩充(embrace and extend)”的策略.此时, Gosling随意地插话说“你的意思其实就是不接受且不扩充(disgrace and distend)。”

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