@Override  
    public void doFilter(ServletRequest request, ServletResponse response,  
            FilterChain filterChain) throws IOException, ServletException {  
        // 過濾使用者請求，判斷是否登入  
        HttpServletRequest httpServletRequest = (HttpServletRequest)request;  
        HttpServletResponse httpServletResponse = (HttpServletResponse)response;  
        httpServletResponse .setContentType("text/html;charset=utf-8");  
        httpServletRequest.setCharacterEncoding("utf-8");  
        httpServletResponse.setCharacterEncoding("utf-8");  
          
        String username = (String)httpServletRequest.getSession().getAttribute("username");  
        if (username == null) {  
            String path = httpServletRequest.getContextPath();  
            httpServletResponse.sendRedirect(path+"/index.jsp");  
        }  
        filterChain.doFilter(httpServletRequest, httpServletResponse);  
    }  
 

1. 獲得客戶機資訊
    getRequestURL方法返回客戶端發出請求時的完整URL。
    getRequestURI方法返回請求行中的資源名部分。
    getQueryString 方法返回請求行中的引數部分。
    getRemoteAddr方法返回發出請求的客戶機的IP地址
    getRemoteHost方法返回發出請求的客戶機的完整主機名
    getRemotePort方法返回客戶機所使用的網路埠號
    getLocalAddr方法返回WEB伺服器的IP地址。
    getLocalName方法返回WEB伺服器的主機名
    getMethod得到客戶機請求方式
 2.獲得客戶機請求頭

    getHeader(string name)方法
    getHeaders(String name)方法
    getHeaderNames方法 

 3. 獲得客戶機請求引數(客戶端提交的資料)
    getParameter(name)方法
    getParameterValues（String name）方法
    getParameterNames方法
    getParameterMap方法

例子程式:

    public void doGet(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException {  
            System.out.println("getRequestURL: "+request.getRequestURL());  
            System.out.println("getRequestURI: "+request.getRequestURI());  
            System.out.println("getQueryString: "+request.getQueryString());  
            System.out.println("getRemoteAddr: "+request.getRemoteAddr());  
            System.out.println("getRemoteHost: "+request.getRemoteHost());  
            System.out.println("getRemotePort: "+request.getRemotePort());  
            System.out.println("getRemoteUser: "+request.getRemoteUser());  
            System.out.println("getLocalAddr: "+request.getLocalAddr());  
            System.out.println("getLocalName: "+request.getLocalName());  
            System.out.println("getLocalPort: "+request.getLocalPort());  
            System.out.println("getMethod: "+request.getMethod());  
            System.out.println("-------request.getParamterMap()-------");  
            //得到請求的引數Map，注意map的value是String陣列型別  
            Map map = request.getParameterMap();  
            Set<String> keySet = map.keySet();  
            for (String key : keySet) {  
            String[] values = (String[]) map.get(key);  
            for (String value : values) {  
                System.out.println(key+"="+value);  
            }  
         }  
            System.out.println("--------request.getHeader()--------");  
            //得到請求頭的name集合  
            Enumeration<String> em = request.getHeaderNames();  
            while (em.hasMoreElements()) {  
            String name = (String) em.nextElement();  
            String value = request.getHeader(name);  
            System.out.println(name+"="+value);  
        }  
              
    }  
 

瀏覽器上位址列：http://localhost:8080/RequestAndResponse/requestmethod?name=sunjob&password=123456&password=haha

控制檯輸出：

    getRequestURL: http://localhost:8080/RequestAndResponse/requestmethod  
    getRequestURI: /RequestAndResponse/requestmethod  
    getQueryString: name=sunjob&password=123456&password=haha  
    getRemoteAddr: 127.0.0.1  
    getRemoteHost: 127.0.0.1  
    getRemotePort: 2374  
    getRemoteUser: null  
    getLocalAddr: 127.0.0.1  
    getLocalName: localhost  
    getLocalPort: 8080  
    getMethod: GET  
    -------request.getParamterMap()-------  
    name=sunjob  
    password=123456  
    password=haha  
    --------request.getHeader()--------  
    host=localhost:8080  
    user-agent=Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/20100101 Firefox/17.0  
    accept=text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8  
    accept-language=zh-cn,en-us;q=0.8,zh;q=0.5,en;q=0.3  
    accept-encoding=gzip, deflate  
    connection=keep-alive  
    cache-control=max-age=0