response常见应用(中文数据乱码解决,中文文件下载,随机图片等)
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1.Web服务器收到客户端的http请求,会针对每一次请求,分别创建一个用于代表请求的request对象、和代表响应的response对象。
2.request和response对象即然代表请求和响应,那我们要获取客户机提交过来的数据,只需要找request对象就行了。要向客户机输出数据,只需要找response对象就行了。
3.HttpServletResponse对应服务器的响应。这个对象中封装了向客户端发送数据、发送响应头,发送响应状态码的方法。
4.向客户端输出中文数据
(1)用outputStream输出中文数据的问题
- package cn.lsl.response;
- import java.io.IOException;
- import java.io.OutputStream;
- import java.io.PrintWriter;
- import javax.servlet.ServletException;
- import javax.servlet.http.HttpServlet;
- import javax.servlet.http.HttpServletRequest;
- import javax.servlet.http.HttpServletResponse;
- //用outputStream输出中文数据的问题
- public class ResponseDemo1 extends HttpServlet {
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- test4(response);
- }
- //输出gb2312的数据,没出现中文乱码问题
- public void test1(HttpServletResponse response) throws IOException{
- String data = "你好";
- OutputStream out = response.getOutputStream();
- out.write(data.getBytes());
- }
- //输出UTF-8的数据,有出现乱码问题,需要控制浏览器以UTF-8打开
- public void test2(HttpServletResponse response) throws IOException{
- response.setHeader("content-type", "text/html;charset=UTF-8");
- String data = "你好";
- OutputStream out = response.getOutputStream();
- out.write(data.getBytes("UTF-8"));
- }
- //用<meta>模拟一个http响应头,控制浏览器以UTF-8打开数据
- public void test3(HttpServletResponse response) throws IOException{
- response.getOutputStream().write("<meta http-equiv='content-type' content='text/html;charset=UTF-8'>".getBytes());
- String data = "你好";
- OutputStream out = response.getOutputStream();
- out.write(data.getBytes("UTF-8"));
- }
- //控制数字乱码的问题
- public void test4(HttpServletResponse response) throws IOException{
- response.getOutputStream().write((120+"").getBytes("UTF-8"));
- }
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- doGet(request,response);
- }
- }
(2)用writer输出中文数据
- package cn.lsl.response;
- import java.io.IOException;
- import java.io.PrintWriter;
- import javax.servlet.ServletException;
- import javax.servlet.http.HttpServlet;
- import javax.servlet.http.HttpServletRequest;
- import javax.servlet.http.HttpServletResponse;
- //用writer输出中文数据
- public class ResponseDemo2 extends HttpServlet {
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- test2(response);
- }
- public void test1(HttpServletResponse response) throws IOException{
- //更改response的码表,通知服务器用UTF-8码表去取response中的数据,然后写给客户机
- response.setCharacterEncoding("UTF-8");
- //通知浏览器以UTF-8码表打开回送的数据
- //response.setHeader("content-type", "text/html;charset=UTF-8");
- response.setContentType("text/html;charset=UTF-8");
- String data = "你好";
- PrintWriter writer = response.getWriter();
- writer.write(data);
- }
- public void test2(HttpServletResponse response) throws IOException{
- //调用了这句话,相当于把response.setCharacterEncoding("UTF-8");也设好了
- response.setContentType("text/html;charset=UTF-8");
- String data = "你好";
- PrintWriter writer = response.getWriter();
- writer.write(data);
- }
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- doGet(request,response);
- }
- }
5.中文文件的下载
- package cn.lsl.response;
- import java.io.FileInputStream;
- import java.io.IOException;
- import java.io.OutputStream;
- import java.io.PrintWriter;
- import java.net.URLEncoder;
- import javax.servlet.ServletException;
- import javax.servlet.http.HttpServlet;
- import javax.servlet.http.HttpServletRequest;
- import javax.servlet.http.HttpServletResponse;
- //中文文件的下载
- public class ResponseDemo3 extends HttpServlet {
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- //1.获取需要下载的文件
- String path = this.getServletContext().getRealPath("/download/一直很安静.mp3");
- String filename = path.substring(path.lastIndexOf("\\")+1);
- //System.out.println(filename);
- //2.通知浏览器以下载方式打开(下载的中文文件名必须要给过URL编码)
- response.setHeader("content-disposition", "attachment;filename="+URLEncoder.encode(filename,"UTF-8"));
- //3.向浏览器写出数据
- FileInputStream in = null;
- try{
- OutputStream out = response.getOutputStream();
- in = new FileInputStream(path);
- byte buffer[] = new byte[1024];
- int len = 0;
- while((len=in.read(buffer))>0){
- out.write(buffer,0,len);
- }
- }finally{
- if(in!=null){
- in.close(); //关闭流
- }
- }
- }
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- doGet(request,response);
- }
- }
6.随机图片
- package cn.lsl.response;
- import java.awt.Color;
- import java.awt.Font;
- import java.awt.Graphics;
- import java.awt.image.BufferedImage;
- import java.io.IOException;
- import java.io.PrintWriter;
- import java.util.Random;
- import javax.imageio.ImageIO;
- import javax.servlet.ServletException;
- import javax.servlet.http.HttpServlet;
- import javax.servlet.http.HttpServletRequest;
- import javax.servlet.http.HttpServletResponse;
- //输出随机图片
- public class ResponseDemo4 extends HttpServlet {
- private static final int WIDTH = 120;
- private static final int HEIGHT = 25;
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- //1.在内存中创建一个图片
- BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB); //长、宽、图片类型
- //2.得到图片
- Graphics g = image.getGraphics();
- //3.设置背景色
- setBackground(g);
- //4.设置图片边框
- setBorder(g);
- //5.设置图片干扰线
- drawRandomLine(g);
- //6.向图片上写数据
- drawRandomData2(g);
- //7.把图片写给客户机,再通知浏览器以图片方式打开数据,并且要通知浏览器不能缓存图片(若没设置,浏览器将会取缓存图片)
- response.setHeader("Expires", "-1");
- response.setHeader("Cache-Control", "no-cache");
- response.setHeader("Pragma", "no-cache");
- response.setContentType("image/jpeg");
- ImageIO.write(image, "jpg", response.getOutputStream());
- }
- //随机数字
- private void drawRandomData(Graphics g) {
- // TODO Auto-generated method stub
- StringBuffer sb = new StringBuffer();
- for(int i=0;i<5;i++){
- sb.append(new Random().nextInt(10)+ " ");
- }
- String randomData = sb.toString();
- g.setColor(Color.RED);
- g.setFont(new Font("宋体",Font.BOLD,20));
- g.drawString(randomData, 10, 20);
- }
- //随机文字
- private void drawRandomData2(Graphics g){
- StringBuffer sb = new StringBuffer();
- 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";
- for(int i=0;i<4;i++){
- int num = new Random().nextInt(base.length());
- sb.append(base.charAt(num)+" ");
- }
- String randomData = sb.toString();
- g.setColor(Color.RED);
- g.setFont(new Font("宋体",Font.BOLD,20));
- g.drawString(randomData, 0, 20);
- }
- private void drawRandomLine(Graphics g) {
- // TODO Auto-generated method stub
- 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 setBorder(Graphics g) {
- // TODO Auto-generated method stub
- g.setColor(Color.BLUE);
- g.drawRect(1, 1, WIDTH-2, HEIGHT-2);
- }
- private void setBackground(Graphics g) {
- // TODO Auto-generated method stub
- g.setColor(Color.WHITE);
- g.fillRect(0, 0, WIDTH, HEIGHT);
- }
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- doGet(request,response);
- }
- }
7.控制浏览器定时刷新网页
- package cn.lsl.response;
- import java.io.IOException;
- import java.io.PrintWriter;
- import javax.servlet.ServletException;
- import javax.servlet.http.HttpServlet;
- import javax.servlet.http.HttpServletRequest;
- import javax.servlet.http.HttpServletResponse;
- //控制网页定时刷新
- public class ResponseDemo5 extends HttpServlet {
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- String data = "中国的人";
- response.setCharacterEncoding("UTF-8");
- response.setContentType("text/html;charset=UTF-8");
- //response.setHeader("refresh", "3");
- //用<meta>标签模拟
- response.getWriter().write("<meta http-equiv='refresh' content='3;url=/Response/index.jsp'>");
- response.getWriter().write(data);
- }
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- }
- }
8.请求重定向
- package cn.lsl.response;
- import java.io.IOException;
- import java.io.PrintWriter;
- import javax.servlet.ServletException;
- import javax.servlet.http.HttpServlet;
- import javax.servlet.http.HttpServletRequest;
- import javax.servlet.http.HttpServletResponse;
- //请求重定向
- /*1.请求重定向下,浏览器向服务器发送了2次请求,request和response对象分别有两个
- * 2.请求重定向下,浏览器的地址会发生变化
- * 3.请求重定向要少用,它只适合用于一些特定的场景下例如登录(因为用户登录成功后,我们系统希望用户知道他到首页上去了)
- */
- public class ResponseDemo extends HttpServlet {
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- /*response.setStatus(302);
- response.setHeader("location", "/Response/index.jsp");*/
- response.sendRedirect("/Response/index.jsp");
- }
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- doGet(request,response);
- }
- }
9.getOutputStream和getWriter方法冲突的问题
getOutputStream和getWriter方法分别用于得到输出二进制数据、输出文本数据的ServletOuputStream、Printwriter对象。getOutputStream和getWriter这两个方法互相排斥,调用了其中的任何一个方法后,就不能再调用另一方法。
- package cn.lsl.response;
- import java.io.IOException;
- import java.io.OutputStream;
- import java.io.PrintWriter;
- import javax.servlet.ServletException;
- import javax.servlet.http.HttpServlet;
- import javax.servlet.http.HttpServletRequest;
- import javax.servlet.http.HttpServletResponse;
- //getOutputStream和getWriter方法冲突的问题
- //出错:java.lang.IllegalStateException: getWriter() has already been called for this response
- public class ResponseDemo6 extends HttpServlet {
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- /*OutputStream out = response.getOutputStream();
- this.getServletContext().getRequestDispatcher("/index.jsp").forward(request, response);
- //出错,调用流不同,因为转到jsp页面,服务器会自动帮你调用getWriter();*/
- PrintWriter writer = response.getWriter();
- this.getServletContext().getRequestDispatcher("/servlet/ResponseDemo7").forward(request, response);
- //getWriter() has already been called for this response
- //出错,因为ResponseDemo6跟ResponseDemo7调用的流不同
- }
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- doGet(request,response);
- }
- }
- //getOutputStream() has already been called for this response
- //任何数据都可以用字节流输出
ResponseDemo7.java
- package cn.lsl.response;
- import java.io.IOException;
- import java.io.PrintWriter;
- import javax.servlet.ServletException;
- import javax.servlet.http.HttpServlet;
- import javax.servlet.http.HttpServletRequest;
- import javax.servlet.http.HttpServletResponse;
- public class ResponseDemo7 extends HttpServlet {
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- response.getOutputStream();
- }
- public void doPost(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- doGet(request,response);
- }
- }
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