Java Servlet 編程及應用之四 – JAVA編程語言程序開發技術文章

 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 中用於指定機器的那部分;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 之後的,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:

https://localhost:8080/examples/servlet/SnoopServlet
  則會輸出結果。

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