request和response簡介
response常見應用：
向客戶端輸出中文數據：
1.用OutputStream輸出：
Servlet代碼：
//在servlet中用outputStream(可以寫任何類型數據)輸出數據的問題以及輸出中文的問題
public class ResponseDemo1 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
test4(response);
}
//用OutputStream輸出1，也必須把1轉爲字節再輸出
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，下面響應頭寫錯了，瀏覽器會提示下載
response.setHeader("content-type", "text/html,charset=UTF-8");
String data = "中國";
OutputStream out = response.getOutputStream();
out.write(data.getBytes("UTF-8"));
}
private void test2(HttpServletResponse response) throws IOException,
UnsupportedEncodingException {
//用html技術中的meta標籤模擬了一個http響應頭，來控制瀏覽器的行爲
String data = "中國";
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 {
//程序以什麼碼錶輸出了，程序就一定要控制瀏覽器以什麼碼錶打開
response.setHeader("content-type", "text/html;charset=UTF-8");
String data = "中國";
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輸出：
Servlet代碼：
//通過response的write流輸(只能寫字符和字符串)出數據的問題
public class ResponseDemo2 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
test2(response);
}
//小細節
private void test2(HttpServletResponse response) throws IOException {
//設置response使用的碼錶，以控制response以什麼碼錶向瀏覽器寫出數據
response.setCharacterEncoding("UTF-8");
//指定瀏覽器以什麼碼錶打開服務器發送的數據
response.setHeader("content-type", "text/html;charset=utf-8");
//這這句話把以上兩句話的功能都實現了
// response.setContentType("text/html;charset=UTF-8");
String data = "中國";
PrintWriter out = response.getWriter();
out.write(data);
}
private void test1(HttpServletResponse response) throws IOException {
//設置response使用的碼錶，以控制response以什麼碼錶向瀏覽器寫出數據
response.setCharacterEncoding("UTF-8");
//指定瀏覽器以什麼碼錶打開服務器發送的數據
response.setHeader("content-type", "text/html;charset=utf-8");
String data = "中國";
PrintWriter out = response.getWriter();
out.write(data);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}文件下載和中文文件的下載：
Servlet代碼：
//文件下載
public class ResponseDemo3 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String path = this.getServletContext().getRealPath("/download/埃琳娜和達蒙.jpg");
String filename = path.substring(path.lastIndexOf("\\")+1);
//如果下載文件是中文文件，則文件名需要通過url編碼
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);
}
}輸出隨機圖片(驗證碼)：
Servlet代碼：
//輸出一張隨機圖片
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.設置背景色
setBackground(g);
//2.設置邊框
setBorder(g);
//3.畫干擾線
drawRandomLine(g);
//4.寫隨機數
drawRandomNum((Graphics2D)g);
//5.圖形寫給瀏覽器
response.setHeader("Content-Type", "image/jpeg");
//發頭控制瀏覽器不要緩存
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("宋體",Font.BOLD,20));
//[\u4e00-\u9fa5] 表示：所有的漢字在unicode編碼4e00~9fa5之間
//常用漢字的unicode編碼
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; //第一個字的x座標
for(int i = 0;i<4;i++){
int degree = new Random().nextInt()%30;//-30~30
String ch = base.charAt(new Random().nextInt(base.length()))+"";
g.rotate(degree*Math.PI/180, x, 20);//設置旋轉角度
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代碼：
<!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="">
用戶名：<input type="text" name="username"/><br/>
密碼：<input type="password" name="password"/><br/>
認證碼：<input type="text" name="checkcode"/>
<img src="/day06/servlet/ResponseDemo4" οnclick="changeImage(this)" alt="換一張" style="cursor:hand"/><br/>
<input type="submit" value="註冊"/>
</form>
</body>
</html>發送http頭，控制瀏覽器定時刷新網頁(refresh)：
Servlet代碼：
//控制瀏覽器定時刷新
public class ResponseDemo5 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
test3(request,response);
}
//使用的自動跳轉技術
private void test3(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException {
//假設這是一個用於處理登錄的servlet
//假設程序運行到此，用戶登錄成功了
String message = "<meta http-equiv='refresh' content='3;url=/day06/index.jsp'/>恭喜你，登錄成功，本瀏覽器將在3秒後跳轉到首頁，如果沒有跳，請點擊<a href=''>超鏈接</a>";
this.getServletContext().setAttribute("message", message);
this.getServletContext().getRequestDispatcher("/message.jsp").forward(request, response);
}
//開發中不會這麼用，因爲數據是呈現在jsp頁面中的
private void test2(HttpServletResponse response) throws IOException {
//假設這是一個用於處理登錄的servlet
//假設程序運行到此，用戶登錄成功了
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，登錄成功，本瀏覽器將在3秒後跳轉到首頁，如果沒有跳，請點擊<a href=''>超鏈接</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代碼：
<%@ 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>
發送http頭，控制瀏覽器緩存當前內容
Servlet代碼：
//控制瀏覽器緩存
public class ResponseDemo6 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//設置數據緩存一小時，1小時內不會再次請求服務器，而直接訪問緩存
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);
}
}通過response實現請求重定向
Servlet代碼：
/**
* 重定向特點：
* 1.瀏覽器會向服務器發送兩次，意味着有2對request\response
* 2.用重定向技術，瀏覽器地址欄會發生變化
* 3.用戶登錄和顯示購物車時，通常會用到重定向技術，因爲可以提示用戶地址改變
* 4.除了特定情況，儘量不用
* 5.轉發技術，地址欄則不會變，刷新後重覆上一次操作（所以不適合做購物車）
*/
public class ResponseDemo7 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// response.setStatus(302);
// response.setHeader("Location", "/day06/index.jsp");
//這句話實現了以上兩句話的功能
response.sendRedirect("/day06/index.jsp");
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
Response細節
Servlet代碼：
//response同時調用getoutputStream和getWriter方法會拋：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();//該流不用關，服務器自己關
this.getServletContext().getRequestDispatcher("/servlet/ResponseDemo9").forward(request, response);
//重定向則不會出錯，因爲重定向是2個response，轉發是同一個
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);
}
}