HttpServletRequest和ServletRequest的区别以及HttpServletRequest对象方法的用法

    @Override  public void doFilter(ServletRequest request, ServletResponse response,  FilterChain filterChain) throws IOException, ServletException {  // 过滤用户请求，判断是否登录  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. 获得客户机信息
    getRequestURL方法返回客户端发出请求时的完整URL。
    getRequestURI方法返回请求行中的资源名部分。
    getQueryString 方法返回请求行中的参数部分。
    getRemoteAddr方法返回发出请求的客户机的IP地址
    getRemoteHost方法返回发出请求的客户机的完整主机名
    getRemotePort方法返回客户机所使用的网络端口号
    getLocalAddr方法返回WEB服务器的IP地址。
    getLocalName方法返回WEB服务器的主机名
    getMethod得到客户机请求方式
 2.获得客户机请求头

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

 3. 获得客户机请求参数(客户端提交的数据)
    getParameter(name)方法
    getParameterValues（String name）方法
    getParameterNames方法
    getParameterMap方法

例子程序:

    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()-------");  //得到请求的参数Map，注意map的value是String数组类型  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()--------");  //得到请求头的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);  }  }  

浏览器上地址栏：http://localhost:8080/RequestAndResponse/requestmethod?name=sunjob&password=123456&password=haha

控制台输出：

    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