Request 和 Response

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区别

要取得客户端为服务端提交过来的数据，需要找Request。
要从服务端向客户端传送数据，需要找Response。

服务器端设置编码

@Overrideprotected void service(HttpServletRequest arg0, HttpServletResponse arg1)            throws ServletException, IOException {    response.setCharacterEncoding("UTF-8");//更改服务器发送数据的默认编码    response.setHeader("Content-Type","text/html;charset=UTF-8");//还要通知客户端解码方式//字节流    String data = "你好,中国";      OutputStream out = response.getOutputStream();      response.setContentType("text/html;charset=UTF-8");      out.write(data.getBytes("UTF-8"));//以UTF-8进行编码或者//字符流    PrintWriter writer = response.getWriter();//默认编码是iso-8859-1 创建该对象前必须设置好编码方式    writer.write(data);}

指定数据以下载的方式打开

通过设置response的响应头就可以实现，content-disposition服务器通过这个响应头告诉浏览器通过下载方式打开文件。

@Overrideprotected void service(HttpServletRequest arg0, HttpServletResponse arg1)            throws ServletException, IOException {    String path = "C:\\Users\\wwhhf\\Pictures\\Camera Roll\\QQ图片20160210090519.jpg";      String filename = path.substring(path.lastIndexOf("\\") + 1);      arg1.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(filename, "UTF-8"));      InputStream in = null;      OutputStream out = null;      try {          in = new FileInputStream(path);          int len = 0;          byte[] buffer = new byte[1024];          out = arg1.getOutputStream();          while((len = in.read(buffer)) > 0) {              out.write(buffer,0,len);          }      }catch(Exception e) {          throw new RuntimeException(e);      }finally {          if(in != null) {              try {                  in.close();              }catch(Exception e) {                  throw new RuntimeException(e);              }          }      }  }

生成验证码图片

@Overrideprotected void service(HttpServletRequest arg0, HttpServletResponse arg1)        throws ServletException, IOException {    // TODO Auto-generated method stub    //      super.service(arg0, arg1);    arg1.addHeader("Pragma", "no-cache");       arg1.setHeader("Cache-Control", "no-cache");       arg1.setHeader("Expires", "0");      //1.内存图像 BufferedImage      BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);      //2.创建画笔      Graphics g = image.getGraphics();      //2.1画边框      g.setColor(Color.GRAY);//设置边框颜色      g.drawRect(0, 0, WIDTH, HEIGHT);//画矩形边框      //2.2填充边框      g.fillRect(1, 1, WIDTH-1, HEIGHT-1);      //2.3输出验证随机数字4个      Random r = new Random();      g.setColor(Color.BLUE);      int x = 5;      for(int i=0;i<4;i++)      {          g.setFont(new Font("宋体",Font.BOLD,20));          g.drawString(r.nextInt(10)+"", x, 20);          x+=30;      }      //2.4画干扰线      g.setColor(Color.YELLOW);      for(int i = 0;i<9;i++)      {                          g.drawLine(r.nextInt(WIDTH),r.nextInt(HEIGHT),r.nextInt(WIDTH), r.nextInt(HEIGHT));      }      //3 利用response输出流输出image      ImageIO.write(image,"jpeg",arg1.getOutputStream());    arg1.setDateHeader("Expires",System.currentTimeMillis()+10*24*1000*60*60);}在后台生成验证码的一般处理程序中除了在session写入验证码的内容，在cookie中也写一个验证码的内容

控制url跳转(延迟跳转)

@Overrideprotected void service(HttpServletRequest arg0, HttpServletResponse arg1)            throws ServletException, IOException {    // TODO Auto-generated method stub    //      super.service(arg0, arg1);    arg1.setHeader("Refresh", "5;URL=http://www.qq.com/");//5秒后跳转，url是跳转的链接  }

缓存作用：Expires实体报头域给出响应过期的日期和时间。为了让代理服务器或浏览器在一段时间以后更新缓存中（再次访问曾访问过的页面时，直接从缓存中加载，缩短响应时间和降低服务器负载）的页面，我们可以使用Expires实体报头域指定页面过期时间

用response实现请求重定向（状态码302重定向）

response.sendRedirect("login.jsp")->http://localhost:8080/xxxSearch/login.jsp需用绝对路径，因为重定向是发生在客户端的

[重定向]http://blog.chinaunix.net/uid-11121450-id-3221825.html)

获取客户端请求的信息

String locale = request.getLocalName();//传输协议  String url = request.getRequestURL().toString();//请求的地址  String uri = request.getRequestURI();//没有主机名的地址  String protocol = request.getProtocol();//获取协议  String add = request.getRemoteAddr();//客户端IP  String host = request.getRemoteHost();//客户端主机名  String port = request.getRemotePort()+"";//客户端端口号  String method = request.getMethod();//客户端的请求方式  String localAddr = request.getLocalAddr();//获取服务器地址  String username = request.getParameter("username");//地址后面?请求的参数  String serverPort = request.getServerPort()+"";//服务器端口号  String serverName = request.getServerName();//服务器名

获取请求参数的值

@Overrideprotected void service(HttpServletRequest arg0, HttpServletResponse arg1)        throws ServletException, IOException {    // TODO Auto-generated method stub    //      super.service(arg0, arg1);    Enumeration names = arg0.getParameterNames();      while(names.hasMoreElements())  {  //根据参数名得到值            String name = (String)names.nextElement();            System.out.println(name+"------->"+arg0.getParameter(name));      }}

显示图片在html上

private static final String PNG  = "image/png;charset=utf-8";// 设定输出的类型  private static final String JPG = "image/jpeg;charset=utf-8";  @Overrideprotected void service(HttpServletRequest arg0, HttpServletResponse arg1)        throws ServletException, IOException {    String imagePath = "C:\\Users\\wwhhf\\Pictures\\Camera Roll\\zen-icons.png";      Image img=ImageIO.read(new File(imagePath));    BufferedImage bi = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);    bi.getGraphics().drawImage(img.getScaledInstance(WIDTH, HEIGHT, Image.SCALE_SMOOTH), 0, 0, null);     arg1.reset();      if (imagePath.toLowerCase().endsWith(".jpg"))// 使用编码处理文件流的情况：      {          arg1.setContentType(JPG);// 设定输出的类型          ImageIO.write(bi,"jpeg",arg1.getOutputStream());     arg1.setDateHeader("Expires",System.currentTimeMillis()+10*24*1000*60*60);    }      if (imagePath.toLowerCase().endsWith(".png"))// 使用编码处理文件流的情况：      {          arg1.setContentType(PNG);// 设定输出的类型          ImageIO.write(bi,"png",arg1.getOutputStream());            arg1.setDateHeader("Expires",System.currentTimeMillis()+10*24*1000*60*60);    }  }

Header知识

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