Java Servlet 編程及應用之四

　　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，它支援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伺服器的請求行和頭部資訊，以及一些可訪問的HTTP 資訊等。

　　SnoopServlet.java 的原始碼如下：

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：