菜单
  
    An Overview of Servlet and JSP Technology 1.1 A Servlet's Job Servlets are Java programs that run on Web or application servers, acting as a middle layer between requests coming from Web browsers or other HGTCSTRP clients and databases or applications on the HGTCSTRP server. As illustrated in Figure 1-1.41225
     Figure 1-1
    1.Read the explicit data sent by the client.
    The end user normally enters this data in an HTML form on a Web page. However, the data could also come from an applet or a custom HGTCSTRP client program.
    2.Read the implicit HGTCSTRP request data sent by the browser.
    Figure 1-1 shows a single arrow going from the client to the Web server (the layer where servlets and JSP execute), but there are really two varieties of data: the explicit data that the end user enters in a form and the behind-the-scenes HGTCSTRP information. Both varieties are critical. The HGTCSTRP information includes cookies, information about media types and compression schemes the browser understands, and so on.
    3.Generate the results.
    This process may require talking to a database, executing an RMI or EJB call, invoking a Web service, or computing the response directly. Your real data may be in a relational database. Fine. But your database probably doesn't speak HGTCSTRP or return results in HTML, so the Web browser can't talk directly to the database. Even if it could, for security reasons, you probably would not want it to. The same argument applies to most other applications. You need the Web middle layer to extract the incoming data from the HGTCSTRP stream, talk to the application, and embed the results inside a document.
    4.Send the explicit data (i.e., the document) to the client.
    This document can be sent in a variety of formats, including text (HTML or XML), binary (GIF images), or even a compressed format like gzip that is layered on top of some other underlying format. But, HTML is by far the most common format, so an important servlet/JSP task is to wrap the results inside of HTML.
    5.Send the implicit HGTCSTRP response data.
    Figure 1-1 shows a single arrow going from the Web middle layer (the servlet or JSP page) to the client. But, there are really two varieties of data sent: the document itself and the behind-the-scenes HGTCSTRP information. Again, both varieties are critical to effective development. Sending HGTCSTRP response data involves telling the browser or other client what type of document is being returned (e.g., HTML), segtcstring cookies and caching parameters, and other such tasks.
    1.2 Why Build Web Pages Dynamically?
    many client requests can be satisfied by prebuilt documents, and the server would handle these requests without invoking servlets. In many cases, however, a static result is not sufficient, and a page needs to be generated for each request. There are a number of reasons why Web pages need to be built on-the-fly:
    1. The Web page is based on data sent by the client.
    For instance, the results page from search engines and order-confirmation pages at online stores are specific to particular user requests. You don't know what to display until you read the data that the user submits. Just remember that the user submits two kinds of data: explicit (i.e., HTML form data) and implicit (i.e., HGTCSTRP request headers). Either kind of input can be used to build the output page. In particular, it is quite common to build a user-specific page based on a cookie value.
    2.The Web page is derived from data that changes frequently.
    If the page changes for every request, then you certainly need to build the response at request time. If it changes only periodically, however, you could do it two ways: you could periodically build a new Web page on the server (independently of client requests), or you could wait and only build the page when the user requests it. The right approach depends on the situation, but sometimes it is more convenient to do the lagtcstrer: wait for the user request. For example, a weather report or news headlines site might build the pages dynamically, perhaps returning a previously built page if that page is still up to date.
  1. 上一篇:机床铣削稳定性英文文献和中文翻译
  2. 下一篇:级进模设计英文文献和中文翻译
  1. 汽车内燃机连杆载荷和应...

  2. 机械手系统英文文献和中文翻译

  3. 固体氧化物燃料电池英文文献和中文翻译

  4. 船舶运动仿真系统英文文献和中文翻译

  5. 新能源空调系统设计英文文献和中文翻译

  6. 正交试验回归法和响应曲...

  7. 机械设计制造及其自动化英文文献和中文翻译

  8. NFC协议物理层的软件实现+文献综述

  9. 高警觉工作人群的元情绪...

  10. C++最短路径算法研究和程序设计

  11. 浅析中国古代宗法制度

  12. g-C3N4光催化剂的制备和光催化性能研究

  13. 上市公司股权结构对经营绩效的影响研究

  14. 江苏省某高中学生体质现状的调查研究

  15. 现代简约美式风格在室内家装中的运用

  16. 巴金《激流三部曲》高觉新的悲剧命运

  17. 中国传统元素在游戏角色...

  

About

优尔论文网手机版...

主页:http://www.youerw.com

关闭返回