response

request和response简介

 

 

response常见应用：

 

向客户端输出中文数据：

1.用OutputStream输出：

Servlet代码：

//在servlet中用outputStream(可以写任何类型数据)输出数据的问题以及输出中文的问题public class ResponseDemo1 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {test4(response);}//用OutputStream输出1，也必须把1转为字节再输出private void test4(HttpServletResponse response) throws IOException,UnsupportedEncodingException {OutputStream out = response.getOutputStream();out.write((1+"").getBytes());}private void test3(HttpServletResponse response) throws IOException,UnsupportedEncodingException {//注意，下面响应头写错了，浏览器会提示下载 response.setHeader("content-type", "text/html,charset=UTF-8");String data = "中国";OutputStream out = response.getOutputStream();out.write(data.getBytes("UTF-8"));}private void test2(HttpServletResponse response) throws IOException,UnsupportedEncodingException {//用html技术中的meta标签模拟了一个http响应头，来控制浏览器的行为String data = "中国";OutputStream out = response.getOutputStream();out.write("<meta http-equiv='content-type' content='text/html;charset=utf-8'>".getBytes());out.write(data.getBytes("UTF-8"));}private void test1(HttpServletResponse response) throws IOException,UnsupportedEncodingException {//程序以什么码表输出了，程序就一定要控制浏览器以什么码表打开response.setHeader("content-type", "text/html;charset=UTF-8");String data = "中国";OutputStream out = response.getOutputStream();out.write(data.getBytes("UTF-8"));}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

2.用PrintWriter输出：

Servlet代码：

//通过response的write流输(只能写字符和字符串)出数据的问题public class ResponseDemo2 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {test2(response);}//小细节private void test2(HttpServletResponse response) throws IOException {//设置response使用的码表，以控制response以什么码表向浏览器写出数据response.setCharacterEncoding("UTF-8");//指定浏览器以什么码表打开服务器发送的数据response.setHeader("content-type", "text/html;charset=utf-8");//这这句话把以上两句话的功能都实现了//response.setContentType("text/html;charset=UTF-8");String data = "中国";PrintWriter out = response.getWriter();out.write(data);}private void test1(HttpServletResponse response) throws IOException {//设置response使用的码表，以控制response以什么码表向浏览器写出数据response.setCharacterEncoding("UTF-8");//指定浏览器以什么码表打开服务器发送的数据response.setHeader("content-type", "text/html;charset=utf-8");String data = "中国";PrintWriter out = response.getWriter();out.write(data);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

文件下载和中文文件的下载：

Servlet代码：

//文件下载public class ResponseDemo3 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String path = this.getServletContext().getRealPath("/download/埃琳娜和达蒙.jpg");String filename = path.substring(path.lastIndexOf("\\")+1);//如果下载文件是中文文件，则文件名需要通过url编码response.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 = response.getOutputStream();while((len=in.read(buffer))>0){out.write(buffer, 0, len);}}finally{if(in!=null){try{in.close();}catch(Exception e){e.printStackTrace();}}if(out!=null){try{out.close();}catch(Exception e){e.printStackTrace();}}}}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

输出随机图片(验证码)：

Servlet代码：

//输出一张随机图片public class ResponseDemo4 extends HttpServlet {public static final int WIDTH = 120;public static final int HEIGHT = 35;public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);Graphics g = image.getGraphics();//1.设置背景色setBackground(g);//2.设置边框setBorder(g);//3.画干扰线drawRandomLine(g);//4.写随机数drawRandomNum((Graphics2D)g);//5.图形写给浏览器response.setHeader("Content-Type", "image/jpeg");//发头控制浏览器不要缓存response.setDateHeader("expries", -1);response.setHeader("Cache-Control", "no-cache");response.setHeader("Pragma", "no-cache");ImageIO.write(image,"jpg",response.getOutputStream());}private void setBackground(Graphics g){g.setColor(Color.WHITE);g.fillRect(0, 0, WIDTH, HEIGHT);}private void setBorder(Graphics g){g.setColor(Color.BLUE);g.drawRect(1, 1, WIDTH-2, HEIGHT-2);}private void drawRandomLine(Graphics g){g.setColor(Color.GREEN);for(int i = 0 ;i < 5; i++){int x1 = new Random().nextInt(WIDTH);int y1 = new Random().nextInt(HEIGHT);int x2 = new Random().nextInt(WIDTH);int y2 = new Random().nextInt(HEIGHT);g.drawLine(x1, y1, x2, y2);}}private void drawRandomNum(Graphics2D g){g.setColor(Color.RED);g.setFont(new Font("宋体",Font.BOLD,20));//[\u4e00-\u9fa5] 表示：所有的汉字在unicode编码4e00~9fa5之间//常用汉字的unicode编码String base = "\u7684\u4e00\u4e86\u662f\u6211\u4e0d\u5728\u4eba\u4eec\u6709\u6765\u4ed6\u8fd9\u4e0a\u7740\u4e2a\u5730\u5230\u5927\u91cc\u8bf4\u5c31\u53bb\u5b50\u5f97\u4e5f\u548c\u90a3\u8981\u4e0b\u770b\u5929\u65f6\u8fc7\u51fa\u5c0f\u4e48\u8d77\u4f60\u90fd\u628a\u597d\u8fd8\u591a\u6ca1\u4e3a\u53c8\u53ef\u5bb6\u5b66\u53ea\u4ee5\u4e3b\u4f1a\u6837\u5e74\u60f3\u751f\u540c\u8001\u4e2d\u5341\u4ece\u81ea\u9762\u524d\u5934\u9053\u5b83\u540e\u7136\u8d70\u5f88\u50cf\u89c1\u4e24\u7528\u5979\u56fd\u52a8\u8fdb\u6210\u56de\u4ec0\u8fb9\u4f5c\u5bf9\u5f00\u800c\u5df1\u4e9b\u73b0\u5c71\u6c11\u5019\u7ecf\u53d1\u5de5\u5411\u4e8b\u547d\u7ed9\u957f\u6c34\u51e0\u4e49\u4e09\u58f0\u4e8e\u9ad8\u624b\u77e5\u7406\u773c\u5fd7\u70b9\u5fc3\u6218\u4e8c\u95ee\u4f46\u8eab\u65b9\u5b9e\u5403\u505a\u53eb\u5f53\u4f4f\u542c\u9769\u6253\u5462\u771f\u5168\u624d\u56db\u5df2\u6240\u654c\u4e4b\u6700\u5149\u4ea7\u60c5\u8def\u5206\u603b\u6761\u767d\u8bdd\u4e1c\u5e2d\u6b21\u4eb2\u5982\u88ab\u82b1\u53e3\u653e\u513f\u5e38\u6c14\u4e94\u7b2c\u4f7f\u5199\u519b\u5427\u6587\u8fd0\u518d\u679c\u600e\u5b9a\u8bb8\u5feb\u660e\u884c\u56e0\u522b\u98de\u5916\u6811\u7269\u6d3b\u90e8\u95e8\u65e0\u5f80\u8239\u671b\u65b0\u5e26\u961f\u5148\u529b\u5b8c\u5374\u7ad9\u4ee3\u5458\u673a\u66f4\u4e5d\u60a8\u6bcf\u98ce\u7ea7\u8ddf\u7b11\u554a\u5b69\u4e07\u5c11\u76f4\u610f\u591c\u6bd4\u9636\u8fde\u8f66\u91cd\u4fbf\u6597\u9a6c\u54ea\u5316\u592a\u6307\u53d8\u793e\u4f3c\u58eb\u8005\u5e72\u77f3\u6ee1\u65e5\u51b3\u767e\u539f\u62ff\u7fa4\u7a76\u5404\u516d\u672c\u601d\u89e3\u7acb\u6cb3\u6751\u516b\u96be\u65e9\u8bba\u5417\u6839\u5171\u8ba9\u76f8\u7814\u4eca\u5176\u4e66\u5750\u63a5\u5e94\u5173\u4fe1\u89c9\u6b65\u53cd\u5904\u8bb0\u5c06\u5343\u627e\u4e89\u9886\u6216\u5e08\u7ed3\u5757\u8dd1\u8c01\u8349\u8d8a\u5b57\u52a0\u811a\u7d27\u7231\u7b49\u4e60\u9635\u6015\u6708\u9752\u534a\u706b\u6cd5\u9898\u5efa\u8d76\u4f4d\u5531\u6d77\u4e03\u5973\u4efb\u4ef6\u611f\u51c6\u5f20\u56e2\u5c4b\u79bb\u8272\u8138\u7247\u79d1\u5012\u775b\u5229\u4e16\u521a\u4e14\u7531\u9001\u5207\u661f\u5bfc\u665a\u8868\u591f\u6574\u8ba4\u54cd\u96ea\u6d41\u672a\u573a\u8be5\u5e76\u5e95\u6df1\u523b\u5e73\u4f1f\u5fd9\u63d0\u786e\u8fd1\u4eae\u8f7b\u8bb2\u519c\u53e4\u9ed1\u544a\u754c\u62c9\u540d\u5440\u571f\u6e05\u9633\u7167\u529e\u53f2\u6539\u5386\u8f6c\u753b\u9020\u5634\u6b64\u6cbb\u5317\u5fc5\u670d\u96e8\u7a7f\u5185\u8bc6\u9a8c\u4f20\u4e1a\u83dc\u722c\u7761\u5174\u5f62\u91cf\u54b1\u89c2\u82e6\u4f53\u4f17\u901a\u51b2\u5408\u7834\u53cb\u5ea6\u672f\u996d\u516c\u65c1\u623f\u6781\u5357\u67aa\u8bfb\u6c99\u5c81\u7ebf\u91ce\u575a\u7a7a\u6536\u7b97\u81f3\u653f\u57ce\u52b3\u843d\u94b1\u7279\u56f4\u5f1f\u80dc\u6559\u70ed\u5c55\u5305\u6b4c\u7c7b\u6e10\u5f3a\u6570\u4e61\u547c\u6027\u97f3\u7b54\u54e5\u9645\u65e7\u795e\u5ea7\u7ae0\u5e2e\u5566\u53d7\u7cfb\u4ee4\u8df3\u975e\u4f55\u725b\u53d6\u5165\u5cb8\u6562\u6389\u5ffd\u79cd\u88c5\u9876\u6025\u6797\u505c\u606f\u53e5\u533a\u8863\u822c\u62a5\u53f6\u538b\u6162\u53d4\u80cc\u7ec6";int x = 5;//第一个字的x坐标for(int i = 0;i<4;i++){int degree = new Random().nextInt()%30;//-30~30String ch = base.charAt(new Random().nextInt(base.length()))+"";g.rotate(degree*Math.PI/180, x, 20);//设置旋转角度g.drawString(ch, x, 20);g.rotate(-degree*Math.PI/180, x, 20);x = x + 30;}}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

html代码：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <title>register.html</title>        <script type="text/javascript">    function changeImage(img){    img.src = img.src + "?" + new Date().getTime();    }    </script>      </head>    <body>    <form action="">    用户名：<input type="text" name="username"/><br/>    密码：<input type="password" name="password"/><br/>    认证码：<input type="text" name="checkcode"/>    <img src="/day06/servlet/ResponseDemo4" onclick="changeImage(this)" alt="换一张" style="cursor:hand"/><br/>    <input type="submit" value="注册"/>    </form>  </body></html>

发送http头，控制浏览器定时刷新网页(refresh)：

Servlet代码：

//控制浏览器定时刷新public class ResponseDemo5 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {test3(request,response);}//使用的自动跳转技术private void test3(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException {//假设这是一个用于处理登录的servlet//假设程序运行到此，用户登录成功了String message = "<meta http-equiv='refresh' content='3;url=/day06/index.jsp'/>恭喜你，登录成功，本浏览器将在3秒后跳转到首页，如果没有跳，请点击<a href=''>超链接</a>";this.getServletContext().setAttribute("message", message);this.getServletContext().getRequestDispatcher("/message.jsp").forward(request, response);}//开发中不会这么用，因为数据是呈现在jsp页面中的private void test2(HttpServletResponse response) throws IOException {//假设这是一个用于处理登录的servlet//假设程序运行到此，用户登录成功了response.setCharacterEncoding("UTF-8");response.setHeader("Content-type", "text/html;charset=UTF-8");response.setHeader("refresh","3;url='/day06/index.jsp'");response.getWriter().write("恭喜你，登录成功，本浏览器将在3秒后跳转到首页，如果没有跳，请点击<a href=''>超链接</a>");}private void test1(HttpServletResponse response) throws IOException {response.setHeader("refresh","3");String data = new Random().nextInt(1000000) + "";response.getWriter().write(data);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

jsp代码：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <title>My JSP 'message.jsp' starting page</title>  </head>    <body>    <%    String message = (String)application.getAttribute("message");    out.write(message);     %>  </body></html>

发送http头，控制浏览器缓存当前内容

Servlet代码：

//控制浏览器缓存public class ResponseDemo6 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//设置数据缓存一小时，1小时内不会再次请求服务器，而直接访问缓存response.setDateHeader("expires", System.currentTimeMillis() + 1000*3600);String data = "aaaaaaaaaa";response.getWriter().write(data);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

通过response实现请求重定向

Servlet代码：

/** * 重定向特点： * 1.浏览器会向服务器发送两次，意味着有2对request\response * 2.用重定向技术，浏览器地址栏会发生变化 * 3.用户登录和显示购物车时，通常会用到重定向技术，因为可以提示用户地址改变 * 4.除了特定情况，尽量不用 * 5.转发技术，地址栏则不会变，刷新后重复上一次操作（所以不适合做购物车） */public class ResponseDemo7 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//response.setStatus(302);//response.setHeader("Location", "/day06/index.jsp");//这句话实现了以上两句话的功能response.sendRedirect("/day06/index.jsp");}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

Response细节

Servlet代码：

//response同时调用getoutputStream和getWriter方法会抛：java.lang.IllegalStateException: getOutputStream() has already been called for this response public class ResponseDemo8 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.getOutputStream();//该流不用关，服务器自己关this.getServletContext().getRequestDispatcher("/servlet/ResponseDemo9").forward(request, response);//重定向则不会出错，因为重定向是2个response，转发是同一个response.sendRedirect("/day06/servlet/ResponseDemo9");}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

public class ResponseDemo9 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.getWriter();}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}