基于jsp的在線考試系統設計與實現-資料下載頁

【導讀】在我國，政府上網工程、電子商務、教育科研一系列圍繞Internet的Web技術及應用的建設正全面展開。遠程教育已成為當今的新型教育形式，大力發展遠程教育，提高全民的科學文化素質，實現教育普及，是增強我國綜合國力刻不容緩的有力舉措，實現教育面向現代化、面向未來。考試是考察學生對所學習知識的接受和理解程度的重要手段，無紙化的考卷，考試的隨時性，隨地性，這些特點都是研究并開發網絡考試系統主要的原因，網絡考試系統遠遠超越了傳統考試固定時間，固定地點的考試模式的限制，將給學生和老師帶來極大的便利。從實際應用問題的需要出發，該系統的設計環境主要基于B/S模式，采用了JSP語言，利用國內流行的開發平臺J2SE、SQL2005數據庫，進行JavaBean類封裝，實現JDBC數據池的連接，這樣大大減少了數據的頻繁調度。此外，在開發過程中，我們還挖掘了大量JSP所特有的開發形式，從而使在線考試系統具有自己鮮明的特色。

　　

【正文】 he default request method, so if you type a URL in the browser39。s address field, or click on a link, the request is sent as a GET request to the server.The request headers provide additional information the server may use to process the request. The message body is included only in some types of requests, like the POST request discussed later.Here39。s an example of a valid HTTP request message:GET / HTTP/Host: UserAgent: Mozilla/ (Windows。 U。 Win 9x 。 enUS。 rv: )Accept: image/gif, image/jpeg, image/pjpeg, image/png, */*AcceptLanguage : enAcceptCharset : iso88591,*,utf8The request line specifies the GET method and asks for the resource named / to be returned using the HTTP/ protocol version. The various headers provide additional information.The Host header tells the server the hostname used in the URL. A server may have multiple names, so this information is used to distinguish between multiple virtual web servers sharing the same web server process.The UserAgent header contains information about the type of browser making the request. The server can use this to send different types of responses to different types of browsers. For instance, if the server knows whether Internet Explorer or Netscape Navigator is used, it can send a response that takes advantage of each browser39。s unique features. It can also tell if a client other than an HTML browser is used, such as a Wireless Markup Language (WML) browser on a cell phone or a PDA device, and generate an appropriate response.The Accept headers provide information about the languages and file formats the browser accepts. These headers can be used to adjust the response to the capabilities of the browser and the user39。s preferences, such as use a supported image format and the preferred language. These are just a few of the headers that can be included in a request message. The resource identifier (URL) doesn39。t necessarily correspond to a static file on the server. It can identify an executable program, a record in a database, or pretty much anything the web server knows about. That39。s why the generic term resource is used. In fact, there39。s no way to tell if the / URL corresponds to a file or something else。 it39。s just a name that means something to the server. The web server is configured to map these unique names to the real resources.Responses in DetailWhen the web server receives the request, it looks at the URL and decides, based on configuration information, how to handle it. It may handle it internally by simply reading an HTML file from the filesystem, or it can forward the request to some ponent that is responsible for the resource corresponding to the URL. This can be a program that uses database information, for instance, to dynamically generate an appropriate response. To the browser it makes no difference how the request is handled。 all it cares about is getting a response.The response message looks similar to the request message. It consists of three things: a status line, response headers, and an optional response body. Here39。s an example:HTTP/ 200 OKLastModified: Mon, 20 Dec 2002 23:26:42 GMTDate: Tue, 11 Jan 2003 20:52:40 GMTStatus: 200ContentType: text/htmlServletEngine: Tomcat web Server/ContentLength: 59htmlbodyh1Hello World!/h1/body/htmlThe status line starts with the name of the protocol, followed by a status code and a short description of the status code. Here the status code is 200, meaning the request was executed successfully. The response message has headers just like the request message. In this example, the LastModified header gives the date and time for when the resource was last modified. The browser can use this information as a timestamp in a local cache。 the next time the user asks for this resource, he can ask the server to send it only if it39。s been updated since the last time it was requested. The ContentType header tells the browser what type of response data the body contains and the ContentLength header how large it is. The other headers are selfexplanatory. A blank line separates the headers from the message body. Here the body is a simple HTML pagehtmlbodyh1Hello World!/h1/body/htmlOf course, the body can contain a more plex HTML page or any other type of content. For example, the request may return an HTML page with img elements. When the browser reads the first response and finds the img elements, it sends a new request for the resource identified by each element, often in parallel. The server returns one response for each image request, with a ContentType header telling what type of image it is (for instance image/gif) and the body containing the bytes that make up the image. The browser then bines all responses to render the plete page.附錄2：英文文獻翻譯HTTP和Servlet的基礎知識詳敘Requests讓我們仔細看看Requests。用戶發送請求到服務器，通過點擊一個鏈接的網頁上，提交表單時，或輸入一個網頁地址在瀏覽器的地址欄。發送請求后，瀏覽器需要知道與哪些服務器交換數據，并要求得到資源。URL必須跟據服務器名詳細描術端口號,例如：第一部分所顯示的URL中指定的Requests是使用HTTP協議的。其次是服務器的名稱。Web服務器等待請求將在某一特定的TCP/IP端口。端口號80是標準端口，用于HTTP請求。如果Web服務器使用另一個端口，URL必須跟據服務器名稱指定端口號。例如：:8080/這一請求被發送到一臺服務器，使用端口8080而不是80。最后部分的URL,/,確定了客戶端請求的資源。網址實際上是一個專業化的統一資源標識符（URL，所界定的符合RFC2396規格）。URL跟據地址確定部份資源，例如服務器，其中包含的資源。另一種類型的URL是一個統一資源名稱（URN），這是一個全局唯一標識符,無論在什么地方都有效的資源的位置。HTTP只處理URL的不同。該條款的URN和URL常常被互換，不幸的是，他們有不同的定義略有不同的規格。我試圖使用條款所界定的HTTP/（符合RFC2616年） ，這是相當接近，以他們是如何也用在Servlet和JSP規范。因此，我只有當URL以開頭時才使用的term URL（或，為HTTP加密連線），其次是服務器名稱，并可能有一個端口號，如以前的例子。我使用的URL作為一個通用術語的任何字符串，確定了資源，確定位置可以從上下文而不要URL。例如，當請求已被交付給服務器，位置已經定確，只有資源標識符是很重要的。瀏覽器使用URL信息創造的請求消息使用指定的協議發送到指定的服務器。 HTTP請求消息由三部份組成：一個請求行，請求標頭，請求體。請求行以方法名稱的開頭，隨后進行了資源標識符和協議版本所使用的瀏覽器：GET/ HTTP/最常用的方法是GET。顧名思義，GET請求用于從服務器檢索資源。這是默認的請求方法，因此，如果您輸入網址在瀏覽器的地址欄，或者點擊一個鏈接，發送的請求是作為一個GET請求到服務器。標題要求提供額外的信息可以使用服務器來處理請求。郵件正文是只包含在某些類型的requests，如POST請求以后討論。下面是一個例子，一個有效的HTTP請求消息：GET/ HTTP/Host：用戶代理： Mozilla/ (Windows。 U。 Win 9x 。 enUS。 rv: )接受：image/gif,image/jpeg