http协议

1.6. Servlet如何处理HTTP协议
 
1.6.1. 如何控制通信数据

HTTP协议在Web容器这端主要表现为通信数据的到达以及响应数据的返回。于是Web容器将这两部分数据解释为两个对象，一个是与请求数据对应的HttpServletRequest对象，一个是与响应数据对应的HttpServletResponse对象。对于Servlet来讲，主要的业务逻辑过程就是从请求对象中获取数据，经过加工后将结果附着在响应对象中发送回客户端。
 
1.6.2. HttpServletRequest对象

借助于HttpServletRequest对象可以实现很多操作，如读取请求行、消息头信息，取得路径信息等。使用如下代码可以实现相关功能。




01.package web;
02.
03.import java.io.IOException;
04.import java.io.PrintWriter;
05.import java.util.Arrays;
06.import java.util.Enumeration;
07.
08.import javax.servlet.ServletException;
09.import javax.servlet.http.HttpServlet;
10.import javax.servlet.http.HttpServletRequest;
11.import javax.servlet.http.HttpServletResponse;
12.
13.
14.public class RequestServlet extends HttpServlet {
15.    
16.    protected void service(HttpServletRequest req, HttpServletResponse resp)
17.            throws ServletException, IOException {
18.        Enumeration e = req.getHeaderNames ();
19.        while (e.hasMoreElements ()){
20.            String headerName = e.nextElement ().toString ();
21.            System.out.println (headerName+":"+req.getHeader (headerName));
22.        }
23.        System.out.println (req.getMethod ());
24.        System.out.println (req.getProtocol ());
25.        System.out.println (req.getRequestURI ());
26.        System.out.println (req.getRequestURL ());
27.        System.out.println (req.getServletPath ());
28.    }
29.}


 
1.6.3. HttpServletResponse对象

HttpServletResponse对象最主要的作用即设置给浏览器的响应内容及浏览器的解码方式，此外设置cookie及重定向也都是响应对象的功能。这些功能对应的代码实现如下所示。




01.package web;
02.
03.import java.io.IOException;
04.import java.io.PrintWriter;
05.
06.import javax.servlet.ServletException;
07.import javax.servlet.http.HttpServlet;
08.import javax.servlet.http.HttpServletRequest;
09.import javax.servlet.http.HttpServletResponse;
10.
11.
12.public class ResponseServlet extends HttpServlet {
13.    
14.     protected void service(HttpServletRequest req, HttpServletResponse resp)
15.            throws ServletException, IOException {
16.        resp.setContentType("text/html;charset=gbk");
17.            resp.setStatus(404);    
18.    }
19.    
20.}