JavaServlet編程及應用之四
| Java關鍵字 |
| 網絡 J2ME 手機游戲 JavaCard Struts 游戲 分析器 JAAS EJB JavaMail 設計模式 J2EE |
| XML EJB JavaBean Servlet JDBC |
HttpServlet 是從GenericServlet 繼承而來，因此它具有GenericServlet 類似的方法和對象，是我們使用Servlet編程經常用到的包，它支持HTTP 的post 和 get 等方法。
編程思路：下面的例子，運行結果是輸出簡單地返回客戶發送給服務器的請求行和頭部信息，以及一些可訪問的HTTP 信息等。
SnoopServlet.java 的源代碼如下：
| import java.io.IOException; import java.io.PrintWriter; import java.util.Enumeration; import javax.servlet.*; import javax.servlet.http.*; public class SnoopServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getWriter(); response.setContentType("text/plain"); out.println("Snoop Servlet"); out.println(); out.println("Servlet init parameters:"); Enumeration e = getInitParameterNames(); while (e.hasMoreElements()) { String key = (String)e.nextElement(); String value = getInitParameter(key); out.println(" " + key + " = " + value); } out.println(); out.println("Context init parameters:"); ServletContext context = getServletContext(); Enumeration enum = context.getInitParameterNames(); while (enum.hasMoreElements()) { String key = (String)enum.nextElement(); Object value = context.getInitParameter(key); out.println(" " + key + " = " + value); } out.println(); out.println("Context attributes:"); enum = context.getAttributeNames(); while (enum.hasMoreElements()) { String key = (String)enum.nextElement(); Object value = context.getAttribute(key); out.println(" " + key + " = " + value); } out.println(); out.println("Request attributes:"); e = request.getAttributeNames(); while (e.hasMoreElements()) { String key = (String)e.nextElement(); Object value = request.getAttribute(key); out.println(" " + key + " = " + value); } out.println(); out.println("Servlet Name: " + getServletName()); out.println("Protocol: " + request.getProtocol()); out.println("Scheme: " + request.getScheme()); out.println("Server Name: " + request.getServerName()); out.println("Server Port: " + request.getServerPort()); out.println("Server Info: " + context.getServerInfo()); out.println("Remote Addr: " + request.getRemoteAddr()); out.println("Remote Host: " + request.getRemoteHost()); out.println("Character Encoding: " + request.getCharacterEncoding()); out.println("Content Length: " + request.getContentLength()); out.println("Content Type: "+ request.getContentType()); out.println("Locale: "+ request.getLocale()); out.println("Default Response Buffer: "+ response.getBufferSize()); out.println(); out.println("Parameter names in this request:"); e = request.getParameterNames(); while (e.hasMoreElements()) { String key = (String)e.nextElement(); String[] values = request.getParameterValues(key); out.print(" " + key + " = "); for(int i = 0; i < values.length; i++) { out.print(values[i] + " "); } out.println(); } out.println(); out.println("Headers in this request:"); e = request.getHeaderNames(); while (e.hasMoreElements()) { String key = (String)e.nextElement(); String value = request.getHeader(key); out.println(" " + key + ": " + value); } out.println(); out.println("Cookies in this request:"); Cookie[] cookies = request.getCookies(); if (cookies != null) { for (int i = 0; i < cookies.length; i++) { Cookie cookie = cookies[i]; out.println(" " + cookie.getName() + " = "+ cookie.getValue()); } } out.println(); out.println("Request Is Secure: " + request.isSecure()); out.println("Auth Type: " + request.getAuthType()); out.println("HTTP Method: " + request.getMethod()); out.println("Remote User: " + request.getRemoteUser()); out.println("Request URI: " + request.getRequestURI()); out.println("Context Path: " + request.getContextPath()); out.println("Servlet Path: " + request.getServletPath()); out.println("Path Info: " + request.getPathInfo()); out.println("Path Trans: " + request.getPathTranslated()); out.println("Query String: " + request.getQueryString()); out.println(); HttpSession session = request.getSession(); out.println("Requested Session Id: " + request.getRequestedSessionId()); out.println("Current Session Id: " + session.getId()); out.println("Session Created Time: " + session.getCreationTime()); out.println("Session Last Accessed Time: " +session.getLastAccessedTime()); out.println("Session Max Inactive Interval Seconds: " + session.getMaxInactiveInterval()); out.println(); out.println("Session values: "); Enumeration names = session.getAttributeNames(); while (names.hasMoreElements()) { String name = (String) names.nextElement(); out.println(" " + name + " = " + session.getAttribute(name)); } } } |
編程技巧說明：
程序輸出Init Parameters(初始化參數)、Attribute names in this request、Parameter names in this request、Headers in this request、Cookies in this request 和 Session Information等信息。
方法getRequestURI返回的對象URI 是作為URL 的一部分，是去掉URL 中用于指定機器的那部分；方法getPathInfo 返回的字符串是客戶向Servlet 傳送的各種選項，這些選項是跟在Servlet 的URL 之后的，方法getPathTranslated 返回的字符串是Servlet 的自己的絕對路徑名，SnoopServlet.class 文件位置是C:jswdk-1.0.1examplesWEB-INFservletsSnoopServlet.class，則方法getPathTranslated 返回的字符串值就是它。
在瀏覽器中輸入如下的地址：
| http://localhost:8080/examples/servlet/SnoopServlet |
則會輸出結果。
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