Servlet4 - response

作者: 老茂在北京 | 来源:发表于2017-04-08 13:02 被阅读87次

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

HttpServletResponse对象

该对象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

响应

部分常用方法

继承关系

代码案例

重定向
页面定时刷新
禁用浏览器缓存
向页面输出中文
实现文件下载
实现验证码

重定向

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
    <form action="/day10/login" method="post"> <!-- action 提交到该servlet-->
        <table border="1" width="50%">
            <tr>
                <td>输入姓名</td>
                <td><input type="text" name="username"></td>
            </tr>
            <tr>
                <td>输入密码</td>
                <td><input type="password" name="password"></td>
            </tr>
            <tr>        
                <td colspan="2"><input type="submit" value="提交"></td>
            </tr>
        </table>
    </form>
</body>
</html>

界面

/**
 * 重定向
 * @author limaoquan
 *
 */
public class login extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        /**
         * 先获取表单的内容（request）
         * 判断姓名和密码是否都是admin
         * 如果有一个不是，就重定向到登陆页面，否则就登陆成功
         */
        String username = request.getParameter("username");//程序入口
        String password = request.getParameter("password");
        if("admin".equals(username) && "admin".equals(password)){
            //登陆成功
            response.setContentType("text/html;charset=UTF-8");//否则会乱码
            response.getWriter().write("登陆成功...");
        }else{
            //重定向登陆页面
            //设置302的状态码
            response.setStatus(302);
            response.setHeader("location", "/day10/response/login.html");

           //第二种方法重定向，把上面两步合起来
            response.sendRedirect("/day10/response/login.html");
        }
    }

页面定时刷新

/**
 * 页面的定时跳转
 * @author limaoquan
 * 
 */
public class RefreshServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");
              //response.setHeader("ContentType","text/html;charset=UTF-8");
        response.getWriter().write("<h1>页面将在5秒后跳转</h1>");
        
        response.setHeader("refresh", "5, url=/day10/response/login.html");
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

}

html与response

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta http-equiv="refresh" content="5;url=/day10/response/login.html">
<title>Insert title here</title>
</head>
<body onload="run()">

    <h2>页面将在<span id="spanId">5</span>秒后跳转</h2>

</body>
<script type="text/javascript">
    /*
        读秒的操作
        加载事件 onload
    */
    var x = 5;
    
    function run(){
        var span = document.getElementById("spanId");
        span.innerHTML = x;
        x--;
        window.setTimeout("run()", 1000);
    }
    
</script>
</html>

禁用浏览器缓存

public class cep extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        //设置三个头信息禁用缓存
        response.setHeader("Cache-Control", "no-cache");
        response.setHeader("Pragma", "no-cache");
        response.setDateHeader("Expires", -1);
        
        //向页面输出当前的时间
        Date date = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        
        response.getWriter().write(sdf.format(date));
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

向页面输出中文（乱码问题）

     ServletOutputStream getOutputStream()      字节输出流
            * 解决办法：
            *       * 设置浏览器打开文件时采用的编码
            *       * 获取字符串byte数组时编码和打开文件时编码一致1
            //设置浏览器打开文件的编码
            response.setHeader("Content-Type", "text/html; charset= UTF-8");
            //获取字节输出流
            OutputStream os = response.getOutputStream();
            //输出中文
            os.write("哈喽我的".getBytes("UTF-8"));
            
            
        PrintWriter getWriter()                 字符输出流
            //设置缓冲区的编码
            response.setCharacterEncoding("UTF-8");
            //设置浏览器打开文件时的编码
            response.setHeader("Content-Type", "text/html; charset= UTF-8");
            response.getWriter().write("花生及多个");
            
            
            //简写的形式
            response.setContentType("text/html; charset= UTF-8");
            response.getWriter().write("花生及多个");

文件下载初级

超链接下载
- 如果浏览器不能识别的格式，会弹出下载窗口
- 如果识别的话，会默认打开文件
后台程序下载
- response.setHeader(Content-Disposition”,” attachment;filename=”文件名称)
- 通过response.getOutputStream()向浏览器端输出

//第一个版本
public class DownloadServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        String path = getServletContext().getRealPath("/img/Koala.jpg");//服务器端不带项目名
        //设置头信息
        response.setHeader("Content-Disposition", "attachment;filename = Koala.jpg");
        
        System.out.println(request.getRemoteAddr());//打印请求端ip
        
        //先获取文件，读入输入流中
        InputStream in = new FileInputStream(path);
        //通过response读出到客户端
        OutputStream os = response.getOutputStream();
        //io的拷贝
        byte[] b = new byte[1024];
        int len = 0;
        while((len = in.read(b))!= -1){
            os.write(b,0,len);
        }
        in.close();
        //os.close(); 服务器会管理
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

}

//第二个版本
public class DownloadServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        String path = getServletContext().getRealPath("/img/Koala.jpg");//服务器端不带项目名
        //包含文件名称 C:\tomcat\webapps\day10\img\Koala.jpg
        //截取文件的名称 Koala.jpg
        String filename = null;
        int index = path.lastIndexOf("\\");
        if(index !=  -1){
            filename = path.substring(index+1);
        }
        
        //设置头信息
        response.setHeader("Content-Disposition", "attachment;filename = "+ filename);
        
        System.out.println(request.getRemoteAddr());//打印请求端ip
        
        //先获取文件，读入输入流中
        InputStream in = new FileInputStream(path);
        //通过response读出到客户端
        OutputStream os = response.getOutputStream();
        //io的拷贝
        byte[] b = new byte[1024];
        int len = 0;
        while((len = in.read(b))!= -1){
            os.write(b,0,len);
        }
        in.close();
        //os.close(); 服务器会管理
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

//中文乱码问题
public class DownloadServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        String path = getServletContext().getRealPath("/img/考拉.jpg");//服务器端不带项目名
        //包含文件名称 C:\tomcat\webapps\day10\img\Koala.jpg
        //截取文件的名称 Koala.jpg
        String filename = null;
        int index = path.lastIndexOf("\\");
        if(index !=  -1){
            filename = path.substring(index+1);
        }
        
        //如果文件名为中文会出现乱码，需要判断什么浏览器
        String agent = request.getHeader("User-agent");
        if(agent.contains("MSIE")){//IE浏览器,只适用IE
            filename = URLEncoder.encode(filename,"UTF-8");
        }
        
        //设置头信息
        response.setHeader("Content-Disposition", "attachment;filename = "+ filename);
        
        System.out.println(request.getRemoteAddr());//打印请求端ip
        
        //先获取文件，读入输入流中
        InputStream in = new FileInputStream(path);
        //通过response读出到客户端
        OutputStream os = response.getOutputStream();
        //io的拷贝
        byte[] b = new byte[1024];
        int len = 0;
        while((len = in.read(b))!= -1){
            os.write(b,0,len);
        }
        in.close();
        //os.close(); 服务器会管理
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

验证码

大体步骤：

在内存中生成图片
- 可以使用BufferedImage对象
- getGraphics() 获取画笔对象
随机生成字母或数字
- Random对象
把生成的数字或字母写在图片上
- 通过画笔中的方法
把图片生成到页面上
- 可以使用ImageIO对象

验证码的分析

/**
 * 验证码
 * @author limaoquan
 *
 */
public class yanzhengma extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //在内存中生成图片
        int width = 120;
        int height = 30;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        // 获取画笔对象
        Graphics g = image.getGraphics();
        g.setColor(Color.yellow);
        //画一个矩形
        g.fillRect(0, 0, width, height);
        g.setColor(Color.black);
        g.drawRect(1, 0, width-1, height-1);
        //准备数据，随机获取4个字符
        String words = "ASDFWEIDDFJKFKSHDKFHSJSKD1234858976";

        Random random = new Random();
        g.setColor(Color.red);
        g.setFont(new Font("隶书",Font.BOLD,20));
        Graphics2D g2 = (Graphics2D)g;
        int x = 20;
        int y = 20;
        for(int i = 0;i<4;i++){
            int degree = random.nextInt(60)-30;
            double hudu = degree * Math.PI / 180;
            g2.rotate(hudu,x,y);
            int index = random.nextInt(words.length());
            char ch = words.charAt(index);
            g2.drawString(""+ch, x, y);
            g2.rotate(-hudu,x,y);
            x= x + 30;
        }
        //把内存中的图片写到浏览器端
        ImageIO.write(image, "jpg", response.getOutputStream());
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}

 //常用汉字，只需要把以上String words替换掉就可以
  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";

登录界面与验证码结合

<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
    <form action="/day10/login" method="post">
        <table border="1" width="50%">
            <tr>
                <td>输入姓名</td>
                <td><input type="text" name="username"></td>
            </tr>
            <tr>
                <td>输入密码</td>
                <td><input type="password" name="password"></td>
            </tr>
            <tr>
                <td>输入验证码</td>
                <td>
                    <input type="text" name="code">
                    ![](/day10/yanzheng)
                    <a href="#" onclick="run()">看不清，换一张</a>
                </td>
            </tr>
            <tr>        
                <td colspan="2"><input type="submit" value="提交"></td>
            </tr>
        </table>
    </form>


</body>
<script type="text/javascript">
    //看不清，换一张,时间戳
    function run(){
        var image = document.getElementById("imgId");
        image.src = "/day10/yanzheng?"+ new Date().getTime();//加时间戳
    }
</script>
</html>

界面

Servlet4 - response

HttpServletResponse对象

代码案例

重定向

页面定时刷新

禁用浏览器缓存

向页面输出中文（乱码问题）

文件下载初级

验证码

登录界面与验证码结合

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