• request 对象和 response 对象


    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

    HttpServletResponse对象代表服务器的响应。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。

    1.向客户端输出中文数据(字节)

    复制代码
    package cn.lsl.response;
    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.ServletOutputStream;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class ResponseDemo1 extends HttpServlet {
    
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            test5(response);
        }
        
        //输出整数:最好转换成字符串输出
        private void test5(HttpServletResponse response) throws IOException{
            int i = 98;
            response.getOutputStream().write((i+"").getBytes());
        }
        
        //以字节流用默认编码向客户端输出中文数据:没有乱码
        //默认的是GBK
        private void test1(HttpServletResponse response) throws IOException{
            String s = "你好!一";
            ServletOutputStream out = response.getOutputStream();
            out.write(s.getBytes());
        }
        
        //以字节流用utf-8编码向客户端输出中文数据
        //以UTF-8编码发送数据,浏览器(默认用GB2312)会出现乱码
        private void test2(HttpServletResponse response) throws IOException{
            String s = "你好!二";
            //通知客户端查看UTF-8码表
            response.setHeader("Content-Type", "text/html;charset=UTF-8");
            ServletOutputStream out = response.getOutputStream();
            out.write(s.getBytes("UTF-8"));
        }
        
        //以字节流用utf-8编码向客户端输出中文数据
        private void test3(HttpServletResponse response) throws IOException{
            String s = "你好!三";
            ServletOutputStream out = response.getOutputStream();
            out.write("<meta http-equiv='Content-Type' content='text/html;charset=UTF-8'>".getBytes("UTF-8"));
            out.write(s.getBytes("UTF-8"));
        }
        
        //以字节流用utf-8编码向客户端输出中文数据
        private void test4(HttpServletResponse response) throws IOException{
            String s = "你好!四";
            response.setContentType("text/html;charset=UTF-8");
            ServletOutputStream out = response.getOutputStream();
            out.write(s.getBytes("UTF-8"));
        }
        
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    }
    复制代码

    分析:出现乱码的图解

    解决办法:

    1)通过更改浏览器的编码方式:IE/”查看”/”编码”/”UTF-8”(不可取)

    2)通过设置响应头告知客户端编码方式:response.setHeader(“Content-type”, “text/html;charset=UTF-8”);//告知浏览器数据类型及编码

    3)通过meta标签模拟请求头:out.write("<meta http-equiv='Content-Type' content='text/html; charset=utf-8' />".getBytes());

    4)通过以下方法:response.setContentType("text/html;charset=UTF-8");

    2.向客户端输出中文数据(字符)

    复制代码
    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 ResponseDemo2 extends HttpServlet {
        
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            test3(response);
        }
    
        //字符流输出中文数据
        private void test1(HttpServletResponse response) throws IOException{
            String s = "你好!一";
            response.setCharacterEncoding("UTF-8");    //设置查的UTF-8(对内容进行编码,查utf-8)
            response.setHeader("Content-Type", "text/html;charset=UTF-8");//通知浏览器以utf-8打开
            PrintWriter out = response.getWriter();
            out.write(s);//默认查的是ISO-8859-1码表
        }
        //字符流输出中文数据
        private void test2(HttpServletResponse response) throws IOException{
            String s = "你好!二";
            response.setCharacterEncoding("UTF-8");
            response.setContentType("text/html;charset=UTF-8");
            PrintWriter out = response.getWriter();
            out.write(s);
        }
        //字符流输出中文数据
        private void test3(HttpServletResponse response) throws IOException{
            String s = "你好!三";
            response.setContentType("text/html;charset=UTF-8");
            PrintWriter out = response.getWriter();
            out.write(s);
        }
    
        
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    }
    复制代码

    分析:

    乱码原因:以默认编码发送数据 ISO-8859-1(没有中国二字编码),此时会发生乱码

    解决办法:

    1)

    setCharacterEncoding(“UTF-8”);//更改编码为UTF-8

    response.setHead(“Context-type”,”text/html;charset=UTF-8”);//告诉客户端编码方式

    2)response.setContentType("text/html;charset=utf-8");

    在字符流输出中文数据时:

    response.setContentType("text/html;charset=utf-8");有两个作用:

    通知字符流以UTF-8编码输出

    通知客户端以UTF-8解码显示

    3.输出随机验证码

    复制代码
    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.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;
    
    public class ResponseDemo3 extends HttpServlet {
    
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            //通知浏览器不要缓存
            response.setHeader("Expires", "-1");
            response.setHeader("Cache-Control", "no-cache");
            response.setHeader("Pragma", "no-cache");
            
            int width = 120;
            int height = 25;
            //创建一副内存图像BufferedImage
            BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
            //得到属于该图片的画笔:Graphics();
            Graphics g = image.getGraphics();
            //画边框
            g.setColor(Color.BLUE);
            g.drawRect(0, 0, width, height);
            //填充背景色
            g.setColor(Color.YELLOW);
            g.fillRect(1, 1, width-2, height-2);
            //画干扰线
            g.setColor(Color.GRAY);
            Random r = new Random();
            for(int i=0; i<10; i++)
                g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width), r.nextInt(height));
            //随机数字
            g.setColor(Color.RED);
            g.setFont(new Font("宋体",Font.BOLD|Font.ITALIC,20));
            int x = 23;
            for(int i=0; i<4; i++){
                g.drawString(r.nextInt(10)+"", x, 20);
                x = x+20;
            }
            //输出到浏览器的页面上:ImageIO
            ImageIO.write(image, "jpg", response.getOutputStream());
        }
    
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    }
    复制代码

    4.定时刷新

    复制代码
    package cn.lsl.response;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    import java.util.Random;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class ResponseDemo4 extends HttpServlet {
        
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            test2(response);
        }
        
        //定时刷新到自己
        private void test1(HttpServletResponse response) throws IOException{
            Random r = new Random();
            int i = r.nextInt();
            response.setIntHeader("Refresh", 1);
            response.getOutputStream().write((i+"").getBytes());
        }
        
        //刷到别的页面
        private void test2(HttpServletResponse response) throws IOException{
            response.setContentType("text/html;charset=UTF-8");
            PrintWriter out = response.getWriter();
            response.setHeader("Refresh", "2;URL=/Response/index.jsp");
            out.write("登陆成功!2秒后将跳转到主页!若没有跳转,请猛点<a href='/Response/index.jsp'>这里</a>");
        }
        
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    }
    复制代码

    5.控制缓存时间

    复制代码
    package cn.lsl.response;
    
    import java.io.IOException;
    
    import javax.servlet.ServletException;
    
    import javax.servlet.http.HttpServlet;
    
    import javax.servlet.http.HttpServletRequest;
    
    import javax.servlet.http.HttpServletResponse;
    
    public class ResponseDemo5 extends HttpServlet {
    
       public void doGet(HttpServletRequest request, HttpServletResponse response)
    
               throws ServletException, IOException {
    
           //缓存一小时
    
           response.setDateHeader("Expires", System.currentTimeMillis()+60*60*1000);
    
           response.getWriter().write("hello");
    
        }
    
        public void doPost(HttpServletRequest request, HttpServletResponse response)
    
               throws ServletException, IOException {
    
           doGet(request,response);
    
        }
    
    }
    复制代码

    6.请求重定向

    请求重定向:一个web资源收到客户端请求后,通知客户端去访问另外一个web资源,这称之         为请求重定向。

    地址栏会连,并发送2次请求,增加服务器负担。

    实现方式:response.sendRedirect();

    原理:302/307状态码和location头即可实现重定向

    复制代码
    package cn.lsl.response;
    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class ResponseDemo6 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);
        }
    }
    复制代码

    7.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。会抛异常。

    异常为:getOutputStream() has already been called for this response

    复制代码
    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;
    
    //字节流和字符流同时使用,报错
    //getOutputStream() has already been called for this response
    public class ResponseDemo7 extends HttpServlet {
    
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            String s1 = "a";
            response.getOutputStream().write(s1.getBytes());
            String s2 = "b";
            response.getWriter().write(s2);
        }
        
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    
    }
    复制代码

    注:通过字符流或字节流输出的数据并不是直接打给浏览器的。而是把数据写到response对象的缓存中的。服务器从缓存中取出数据,按照HTTP协议的响应格式输出给浏览器。如果你调用的response的输出流没有主动关闭,服务器会替你关的。

    HttpServletRequest

    HttpServletRequest对象代表客户端的请求,当客户端通过HTTP协议访问服务器时,HTTP请求头中的所有信息都封装在这个对象中,通过这个对象的方法,可以获得客户这些信息。

    1.获取客户机信息的方法

    getRequestURL方法返回客户端发出请求时的完整URL。

    getRequestURI方法返回请求行中的资源名部分。

    getQueryString 方法返回请求行中的参数部分。

    getRemoteAddr方法返回发出请求的客户机的IP地址

    getRemoteHost方法返回发出请求的客户机的完整主机名

    getRemotePort方法返回客户机所使用的网络端口号

    getLocalAddr方法返回WEB服务器的IP地址。

    getLocalName方法返回WEB服务器的主机名

    getMethod得到客户机请求方式

    eg:

    复制代码
    package cn.lsl.request;
    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    //获取客户机信息
    public class RequestDemo1 extends HttpServlet {
    
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            //获取URL和URI
            //url:http://localhost:8080/Request/servlet/RequestDemo1
            //uri:/Request/servlet/RequestDemo1
            System.out.println("url:"+request.getRequestURL());
            System.out.println("uri:"+request.getRequestURI());
            
            //通过getQueryString可以获得get方式提交查询串url中?后面部分
            System.out.println("queryString:"+request.getQueryString());
            //获得客户端ip
            System.out.println("ip:"+request.getRemoteAddr());
            //通过getContextPath获得工程虚拟目录名称
            System.out.println("工程虚拟目录名称:"+request.getContextPath());
            //通过getMethod获得请求方式
            System.out.println("请求方式:"+request.getMethod());
            //获得当前访问资源路径 ----/servlet/RequestDemo1
            System.out.println("当前访问资源路径:"+request.getRequestURI().substring(request.getContextPath().length()));
        }
    
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    }
    复制代码

    注:

    1)URL和URI的区别

    URL: http://localhost:8080/Request/servlet/RequestDemo1

    URI: /Request/servlet/RequestDemo1

    URI 包含 URL的 ,URL 一定完成路径,URI可以相对路径

    http://localhost:8080/Request/servlet/RequestDemo1

    是一个URL 同时也是 URI

    /Request/servlet/RequestDemo1 ---- 都是URI 不是URL

    2)获得当前访问资源路径 :

    request.getRequestURI().substring(request.getContextPath().length());

    2.获取请求头信息

    getHeader 获得头信息的值,转换一个字符串

    getHeaders 获得头信息值 ,获得Enumeration

    getHeaderNames 获得所有头信息名称  返回 Enumeration

    eg:

    复制代码
    package cn.lsl.request;
    
    import java.io.IOException;
    import java.util.Enumeration;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class RequestDemo2 extends HttpServlet {
    
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            //获取指定头信息字段
            String value = request.getHeader("Accept-Encoding");
            System.out.println(value);
            System.out.println("---------------");
            //获得所有头信息内容
            Enumeration<String> enumeration = request.getHeaderNames();
            while(enumeration.hasMoreElements()){
                String name = enumeration.nextElement();
                System.out.println(name+":"+request.getHeader(name));
            }
        }
    
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    
    }
    复制代码

    3.防盗链程序

    referer.html

    复制代码
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
        <title>referer.html</title>
        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
        <meta http-equiv="description" content="this is my page">
        <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      </head>
      
      <body>
        <h1>通过链接访问RequestDemo3 不是盗链</h1>
        <a href="/Request/servlet/RequestDemo3">link</a>
      </body>
    </html>
    复制代码
    复制代码
    package cn.lsl.request;
    
    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class RequestDemo3 extends HttpServlet {
    
        //防盗链
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            //通过getHeader获得referer头信息
            String referer = request.getHeader("referer");
            //判断头信息可以知道是不是盗链
            response.setContentType("text/html;charset=utf-8");
            if(referer == null || !referer.startsWith("http://localhost")){
                //盗链
                response.getWriter().println("是盗链");
            }else{
                //不是盗链
                response.getWriter().println("真不是盗链");
            }
        }
    
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    }
    复制代码

    4.获取客户机请求参数

    常用API四个

    getParameter

    getParameterValues

    getParameterNames

    getParameterMap

    eg:

    复制代码
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
        <title>request.html</title>
        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
        <meta http-equiv="description" content="this is my page">
        <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      </head>
      
      <body>
        <h1>分别以get和post方式提交数据</h1>
        <h1>第一种:通过超链接提交数据以?方式</h1>
        <a href="/Request/servlet/RequestDemo4?name=zhangsan&city=shenzhen">超链接提交数据</a>
        <h1>第二种:通过form的post方式提交数据</h1>
        <form action="/Request/servlet/RequestDemo4" method="post">
            姓名<input type="text" name="name" /><br/>
            城市<input type="text" name="city" /><br/>
            <input type="submit" value="提交">
        </form>
      </body>
    </html>
    复制代码
    复制代码
    package cn.lsl.request;
    
    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 RequestDemo4 extends HttpServlet {
        
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            String name = request.getParameter("name");
            System.out.println(name);
            String city = request.getParameter("city");
            System.out.println(city);
        }
        
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    }
    复制代码

    5.获取复杂表单的数据及解决中文乱码问题

    regist.html

    复制代码
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
        <head>
            <title>regist.html</title>
            <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
            <meta http-equiv="description" content="this is my page">
            <meta http-equiv="content-type" content="text/html; charset=UTF-8">
        </head>
    
        <body>
            <form action="/Request/servlet/RequestDemo5" method="post">
                <table>
                    <tr>
                        <td>
                            用户名
                        </td>
                        <td>
                            <input type="text" name="username" />
                        </td>
                    </tr>
                    <tr>
                        <td>
                            密码
                        </td>
                        <td>
                            <input type="password" name="password" />
                        </td>
                    </tr>
                    <tr>
                        <td>
                            性别
                        </td>
                        <td>
                            <input type="radio" name="gender" value="male" /><input type="radio" name="gender" value="female" /></td>
                    </tr>
                    <tr>
                        <td>
                            爱好
                        </td>
                        <td>
                            <input type="checkbox" name="hobby" value="sport" />
                            运动
                            <input type="checkbox" name="hobby" value="music" />
                            音乐
                            <input type="checkbox" name="hobby" value="game" />
                            游戏
                        </td>
                    </tr>
                    <tr>
                        <td>
                            城市
                        </td>
                        <td>
                            <select name="city">
                                <option value="beijing">
                                    北京
                                </option>
                                <option value="shanghai">
                                    上海
                                </option>
                                <option value="shenzhen">
                                    深圳
                                </option>
                            </select>
                        </td>
                    </tr>
                    <tr>
                        <td>
                            个人简介
                        </td>
                        <td>
                            <textarea rows="5" cols="60" name="introduce"></textarea>
                        </td>
                    </tr>
                    <tr>
                        <td colspan="2">
                            <input type="submit" value="注册" />
                        </td>
                    </tr>
                </table>
            </form>
        </body>
    </html>
    复制代码
    复制代码
    package cn.lsl.request;
    
    import java.io.IOException;
    import java.net.URLDecoder;
    import java.net.URLEncoder;
    import java.util.Arrays;
    import java.util.Enumeration;
    import java.util.Map;
    import java.util.Set;
    
    import javax.activation.URLDataSource;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class RequestDemo5 extends HttpServlet {
        
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            //解决post乱码
            request.setCharacterEncoding("utf-8");
            //通过getParameter获得指定数据
            String username = request.getParameter("username");
            System.out.println(username);
            
            //解决get乱码
    //        username = URLEncoder.encode(username, "ISO-8859-1");    //用ISO-8859-1编码
    //        username = URLDecoder.decode(username, "utf-8");    //用utf-8解码
    //        username = new String(username.getBytes("ISO-8859-1"),"UTF-8");
    //        System.out.println(username);
            String gender = request.getParameter("gender");
            System.out.println(gender);
            
            //获取checkbox所有提交数据 --- getParameterValues
            String[] hobbies = request.getParameterValues("hobby");
            System.out.println(Arrays.toString(hobbies));
            
            //打印所有请求提交的参数
            //方式一
            Enumeration<String> names = request.getParameterNames();
            while(names.hasMoreElements()){
                String name = names.nextElement();    //获取每一个参数的名称
                System.out.println(name + ":" +Arrays.toString(request.getParameterValues(name)));
            }
            System.out.println("----------------");
            Map<String, String[]> parameterMap = request.getParameterMap();
            Set<String> keys = parameterMap.keySet();
            for (String key : keys) {
                System.out.println(key + ":" + Arrays.toString(parameterMap.get(key)));
            }
        }
        
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    
    }
    复制代码

    注:解决中文乱码问题

    //解决post乱码

    request.setCharacterEncoding("utf-8");

    //解决get乱码(手动编码)

    username = URLEncoder.encode(username, "ISO-8859-1");   //用ISO-8859-1编码

    username = URLDecoder.decode(username, "utf-8"); //用utf-8解码

    或    

    username = new String(username.getBytes("ISO-8859-1"),"UTF-8");

    6.请求转发

    1)request对象实现请求转发:请求转发指一个web资源收到客户端请求后,通知服务器调用另外一个web资源进行处理。

    2)request对象提供了一个getRequestDispatcher方法,该方法返回一个RequestDispatcher对象,调用这个对象的forward方法可以实现请求转发。

    3)request对象同时也是一个域对象,开发人员通过request对象在实现转发时,把数据通过request对象带给其它web资源处理。

    eg:AServlet转发到BServlet

    复制代码
    package cn.lsl.request;
    
    import java.io.IOException;
    
    import javax.servlet.RequestDispatcher;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class AServlet extends HttpServlet {
        
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            //通过request对象传递
            //向request域对象保存一个属性
            request.setAttribute("name", "lsl");
            //传递数据给BServlet
            RequestDispatcher dispatcher = request.getRequestDispatcher("/servlet/BServlet");
            dispatcher.forward(request, response);
        }
    
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    
    }
    复制代码
    复制代码
    package cn.lsl.request;
    
    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class BServlet extends HttpServlet {
        
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            System.out.println(request.getAttribute("name"));
        }
        
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    
    }
    复制代码

    注:1、ServletContext对象的getRequestDispather(String path1)

        path1必须用绝对路径,即以”/”开头,若用相对路径会抛出异常     IllegalArgumentException

        2、ServletRequest对象的getRequestDispatcher(String path2)           path2可以用绝对路径也可以用相对路径

    拓展:转发与重定向区别

    1).转发一次请求、一次响应。重定向两次请求,两次响应

    2).转发只能跳转到站内程序,重定向可定向任何站点

    3).转发URL地址不变,重定向URL地址改变

    4).转发对客户端不可见,重定向对客户度可见

    5).转发共享一个Request中数据,重定向两次请求,不同Request对象,不能共享Request数据

    7.包含

    logo.html

    复制代码
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
        <title>logo.html</title>
        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
        <meta http-equiv="description" content="this is my page">
        <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      </head>
      
      <body>
        <h1>LOGO</h1>
      </body>
    </html>
    复制代码

    footer.html

    复制代码
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
        <title>footer.html</title>
        <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
        <meta http-equiv="description" content="this is my page">
        <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      </head>
      
      <body>
        <h1>@COPY</h1>
      </body>
    </html>
    复制代码
    复制代码
    package cn.lsl.request;
    
    import java.io.IOException;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class MainServlet1 extends HttpServlet {
        
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            request.getRequestDispatcher("/logo.html").include(request, response);
            response.getOutputStream().write("<h1>Main 1</h1>".getBytes());
            request.getRequestDispatcher("/footer.html").include(request, response);
        }
        
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    
    }
    复制代码
    复制代码
    package cn.lsl.request;
    
    import java.io.IOException;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    public class MainServlet2 extends HttpServlet {
        
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            request.getRequestDispatcher("/logo.html").include(request, response);
            response.getOutputStream().write("<h1>Main 2</h1>".getBytes());
            request.getRequestDispatcher("/footer.html").include(request, response);
        }
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request,response);
        }
    }
    复制代码
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  • 原文地址:https://www.cnblogs.com/wl0000-03/p/6098552.html
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