HttpServletResponse与HttpServletRequest

HttpServletResponse与HttpServletRequest

1.HttpServletResponse

1.概述

image-20220407150038592

image-20220407145607316

image-20220407145849992

补充：response，request对象销毁之前，服务器拿到响应数据

2.HttpServletResponse对象方法的探索

1.响应头方法

image-20220407152129347

image-20220407151829526

更正一下：开发中常用的方法是setHeader();

2.响应正文

image-20220407152716204

image-20220407153004526

image-20220520154756288

3.应用--服务器解码与客户端编码

1.客户端编码设置方式1

image-20220407160613655

2.客户端编码方式设置2

image-20220407160837673

3.服务器解码与客户端编码方式设置

image-20220407162158587

图示：

image-20220520154915010

补充：setCharacterEncoding

image-20220520154930940

代码参考：

package com.xu.httpservletresponse;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

/**
 * @auther xu
 * @date 2022/4/7 - 15:36
 */
public class HttpServletResponseDemo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //服务器中默认编码为ISO-8859-1,她不支持中文（Tomcat）
        //告诉服务器使用UTF-8解析文本
//        resp.setCharacterEncoding("UTF-8");

        //方式1：告诉客户端使用UTF-8编码
//        resp.setHeader("content-type","text/html;charset=UTF-8");

        //方式3：告诉服务器使用UTF-8解析文本，告诉客户端使用UTF-8编码（该方法将上面两个方法封装）
        resp.setContentType("text/html;charset=UTF-8");

        //得到一个字符输出流
        PrintWriter out = resp.getWriter();
//        out.write(" <html><head></head><body><meta charset=\"UTF-8\"/>你好呀!</body></html>");//方式2
        out.write("使用封装的编码与解码方法");


    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}
4.响应编码字节输出流
500错误：

image-20220407165136243

以上错误是getBytes()方法中的参数传错了

乱码错误：

image-20220407170118662

解决：告诉浏览器使用UTF-8编码

image-20220407165741821

image-20220407164317569

3.文件下载

1.505报错：

image-20220520155011892

image-20220520155023202

image-20220520155034118

image-20220520155046241

代码：

package com.xu.httpservletresponse;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.PrintWriter;

/**
 * @auther xu
 * @date 2022/4/7 - 20:03
 */
public class DownLoadFile extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
       //需求：客户端访问服务器端（Tomcat服务器）的图片，并将其下载到面

        //1.首先：获取文件路径
        String realPath = this.getServletContext().getRealPath("/WEB-INF/classes/美女.jpg");
        //2.获取字节流对象
        FileInputStream fis = new FileInputStream(realPath);
        //3.创建字节输出流
        ServletOutputStream sos = resp.getOutputStream();

        //创建缓冲区
        int len;//记录读入字节的个数
        byte[] buffer = new byte[1024];
        while ((len = fis.read(buffer)) != -1) {
            sos.write(buffer,0,len);
        }

        //管理操作：
        sos.close();
        fis.close();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

2.以上解决了客户端得到想要访问的图片数据，但是并未实现在客户端实现图片的下载的功能

1.用于下载图片时，文件名的编码

image-20220520161018770

2.获取字符串的子串

image-20220520161030058

image-20220520161037979

image-20220520161049020

package com.xu.httpservletresponse;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.net.URLEncoder;

/**
 * @auther xu
 * @date 2022/4/7 - 20:03
 */
public class DownLoadFile extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
       //需求：客户端访问服务器端（Tomcat服务器）的图片，并将其下载到面

        //1.首先：获取文件路径
        String realPath = this.getServletContext().getRealPath("/WEB-INF/classes/美女.jpg");
        //2.获取字节流对象
        FileInputStream fis = new FileInputStream(realPath);
        //3.创建字节输出流
        ServletOutputStream sos = resp.getOutputStream();

        //4.得到待下载的文件名
        String imageName = realPath.substring(realPath.lastIndexOf("\\")+1);

        //5.设置文件名的编码
        imageName = URLEncoder.encode(imageName,"UTF-8");

        //6.在响应头中，告诉客户端下载文件
        resp.setHeader("content-disposition","attachment;fileName="+imageName);
        resp.setHeader("content-type","image/jpeg");

        //创建缓冲区
        int len;//记录读入字节的个数
        byte[] buffer = new byte[1024];
        while ((len = fis.read(buffer)) != -1) {
            sos.write(buffer,0,len);
        }

        //管理操作：
        sos.close();
        fis.close();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

4.验证码--涉及知识没有学（不理解）

5.告诉浏览器不缓存

image-20220520155134570

6.页面刷新

image-20220520155146261

image-20220520155156844

package com.xu.httpservletresponse;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Random;

/**
 * @auther xu
 * @date 2022/4/8 - 7:09
 */
public class RefreshDemo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
       //实现页面的刷新
        resp.setHeader("refresh","1");//1s刷新一次
        Random random = new Random();
        resp.getWriter().write(random.nextInt()+"");//为字符流，将数字转变为字符串（防止出现数字97输出为a）
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

1.实现页面跳转到主页面

报404错误：

image-20220520155208906

2.跳转成功：

image-20220520155222400

image-20220520155232874

代码参考：

package com.xu.httpservletresponse;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Random;

/**
 * @auther xu
 * @date 2022/4/8 - 7:09
 */
public class RefreshDemo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
       //实现页面的刷新
//        resp.setHeader("refresh","1");//1s刷新一次
//        Random random = new Random();
//        resp.getWriter().write(random.nextInt()+"");

        //实现3秒钟跳到主页
        resp.setContentType("text/html;charset=UTF-8");
        resp.getWriter().write("注册成功，3秒钟跳到主页");
        resp.setHeader("refresh","3;url=http://localhost:8080/secondServlet/servlet/mainP");

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

image-20220520161219113

7.上午总结：

image-20220520155243009

更正：URLEncoder.encode(文件名，"UTF-8");

7.重定向

image-20220520155252326

image-20220520155314671

1.程序验证：重定向之后访问下一个Servlet8与之前Servlet7没有一点关系

image-20220520155327509

image-20220520155339815

注意：image-20220520155357947

image-20220520155411537

代码参考：

package com.xu.httpservletresponse;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @auther xu
 * @date 2022/4/8 - 11:11
 */
public class ServletForward1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("客户端：我要借钱");
        System.out.println("ServletForword1:我没钱，我知道ServletForward2有钱");

        //设置响应行状态
        resp.setStatus(302);
        //设置头部信息，告诉服务器待重定向的地址
        resp.setHeader("location","/secondServlet/servletforward2");

        System.out.println("此输出语句验证是先输出本句话，还是ServletForward2中的输出语句");

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}


package com.xu.httpservletresponse;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @auther xu
 * @date 2022/4/8 - 11:11
 */
public class ServletForward2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("Servlet2:我有钱,我借给你");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

8总结：

image-20220520155423529

2.HttpServletRequest

因为涉及到操作访问客户端的报文，肯定是一个实现类而不是HttpServletRequest()接口

image-20220520162111783

1.请求消息行相关方法

image-20220520155447896

package com.xu.httpservletrequest;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @auther xu
 * @date 2022/4/8 - 21:06
 */
public class RequestHeadMethodDemo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //查看HttpServletRequest接口的实现类
//        System.out.println(req.getClass().getName());
//        System.out.println(resp);

        //request方法的探索

        //1.获取请求方式
        System.out.println(req.getMethod());

        //2.返回客户端发送请求时完整的URL
        System.out.println(req.getRequestURL());

        //3.返回请求行中的资源名称
        System.out.println(req.getRequestURI());

        //4.当前应用的虚拟目录（也就是8080后面开始那一个路径）----/secondServlet
        System.out.println(req.getContextPath());

        //5.返回请求行中的参数部分
        System.out.println(req.getQueryString());

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

image-20220520155500254

客户端访问路径：

image-20220520155508894

服务器输出：

image-20220520155519224

给参数部分一个名称输出：

image-20220520155529370

image-20220520155545349

2.获取请求消息头的相关信息

image-20220520155553345

1.应用--获取请求头部信息---req.getHeader("User-Agent");
 /**
     * 利用请求头部信息判断所发送的请求报文来自哪一个浏览器
     * @param req
     */
    public void showClientType(HttpServletRequest req) {
        //获取请求信息的头部信息
        String headerInfo = req.getHeader("User-Agent");
        //写一个判断语句，判断客户端浏览器类型
        if (headerInfo.toLowerCase().contains("chrome")) {
            System.out.println("该请求报文从google浏览器发送过来");
        } else if (headerInfo.toLowerCase().contains("edge")) {
            System.out.println("该请求报文从微软浏览器发送过来");
        } else {
            System.out.println("请求数据报文从其他浏览器发送过来");
        }
    }

输出结果：

image-20220520155603708

2.获取所有消息请求头的名字---req.getHeaderNames()
 /**
     * 获取所有消息请求头的名字,以及对应名字所包含的内容
     * @param req
     */
    public void getAllName(HttpServletRequest req) {
        Enumeration<String> headerNames = req.getHeaderNames();//获取所有请求消息的名字
        while (headerNames.hasMoreElements()) {
            String element = headerNames.nextElement();
            System.out.println(element+":"+req.getHeader(element));
        }
    }

输出结果：

host:localhost:8080
connection:keep-alive
cache-control:max-age=0
sec-ch-ua:" Not A;Brand";v="99", "Chromium";v="99", "Google Chrome";v="99"
sec-ch-ua-mobile:?0
sec-ch-ua-platform:"Windows"
upgrade-insecure-requests:1
user-agent:Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/99.0.4844.82 Safari/537.36
accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
sec-fetch-site:none
sec-fetch-mode:navigate
sec-fetch-user:?1
sec-fetch-dest:document
accept-encoding:gzip, deflate, br
accept-language:zh-CN,zh;q=0.9
cookie:JSESSIONID=B26F20D8B7EE7B9B6270E39F91E7861F
3.获得相同类型的消息头---req.getHeaders("accept-encoding")

image-20220520155621678

image-20220520155630767

3.请求正文-获取表单数据相关的方法

image-20220520155640661

1.ISO-8859-1导致的乱码问题

编码器操作出站数据，而解码器处理入站数据。编码器是将消息转换为适合于传输的格式，而对应的解码器则是将网络字节流转换回应用程序的消息格式。

image-20220520155651488

image-20220520155702189

2.解决ISO-8859-1导致的服务器解析乱码的问题：告诉服务器使用UTF-8解析由UTF-8编码的文件

image-20220520155712477

代码参考：

 /**
     * 根据表单中name属性的名，获取value属性值的方法
     * @param req
     */
    public void getFormDate1(HttpServletRequest req) {
        String userName = req.getParameter("userName");
        String password = req.getParameter("pwd");
        String sex = req.getParameter("sex");//性别只能选一个
        String[] hobbies = req.getParameterValues("hobby");
        String city = req.getParameter("city");

        System.out.println(userName);
        System.out.println(password);
        System.out.println(sex);
        for (int i = 0; hobbies != null && i < hobbies.length; i++) {
            System.out.println(hobbies[i]+"\t");
        }
        System.out.println(city);
    }

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>用户登录</title>
</head>
<body>
    <form action="/secondServlet/form" method="post">
        用户名：<input type="text" name="userName"/><br/>
        密码：<input type="password" name="pwd"/><br/>
        性别：<input type="radio" name="sex" value="男" checked="checked"/>男
            <input type="radio" name="sex" value="女" />女<br/>

        爱好：
            <input type="checkbox" name="hobby" value="篮球">篮球
            <input type="checkbox" name="hobby" value="唱歌">唱歌
            <input type="checkbox" name="hobby" value="编码">编码
            <br/>
        所在城市：
        <select name="city">
            <option>-----请选择----</option>
            <option value="北京">北京</option>
            <option value="上海">上海</option>
            <option value="广州">广州</option>
        </select>
        <br/>
        <input type="submit" value="登录"/>
    </form>
</body>
</html>
3.改进版1

image-20220520155724658

/**
     * 得到表单数据改进版
     * @param req
     */
    public void getFormDate2(HttpServletRequest req) {
        Enumeration<String> parameterNames = req.getParameterNames();//得到表单中所有的name属性名的枚举
        while (parameterNames.hasMoreElements()) {
 
            String name = parameterNames.nextElement();//得到其中一个名字
            String[] parameterValues = req.getParameterValues(name);//将名字所对应的值都封装为String数组，即使只有一个值
            for (int i = 0; parameterNames != null && i < parameterValues.length; i++) {
                System.out.println(parameterValues[i]);
            }
        }
    }
4.改进版2：为了将数据存入到数据库，需要将登入的数据映射到实体类，然后再存入到数据库中
 /**
     * 为了将数据存入到数据库，需要将登入的数据映射到实体类，然后再存入到数据库中
     * @param req
     */
    public void formDateToEntry(HttpServletRequest req) {
        try {
            req.setCharacterEncoding("UTF-8");
            //根据表单中name属性的名，获取value属性值的方法
//        getFormDate1(req);
//        getFormDate2(req);
            User user = new User();
            System.out.println("数据封装前User状态："+user);

            //获取表单数据
            Map<String, String[]> parameterMap = req.getParameterMap();
            for (Map.Entry<String,String[]> m:parameterMap.entrySet()){
                String key = m.getKey();
                String[] value = m.getValue();

                //使用反射知识完成对数据的封装
                PropertyDescriptor pd = new PropertyDescriptor(key,User.class);//该对象封装了每一个名字对应的get和ser方法

                //相当与获取对应名称的set方法
                Method setter = pd.getWriteMethod();

                //判断value是一个值还是多个值，然后进行数据填充
                if (value.length == 1) {
                    setter.invoke(user,value[0]);//对应名称只有一个值的封装
                } else {
                    setter.invoke(user,(Object) value);//给复选框变量封装赋值
                }

            }

            System.out.println("数据封装后User状态："+user);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

输出：

image-20220520155737249

image-20220520155750732

5.改进版本3

使用框架实现：

image-20220520155804967

package com.xu.httpservletrequest;

import org.apache.commons.beanutils.BeanUtils;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.beans.IntrospectionException;
import java.beans.PropertyDescriptor;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Enumeration;
import java.util.Map;

/**
 * @auther xu
 * @date 2022/4/9 - 11:12
 */
public class GetFormDate extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//        formDateToEntry(req);

        try {
            req.setCharacterEncoding("UTF-8");//指定服务器的解码方式
            User user = new User();
            System.out.println(user);
            BeanUtils.populate(user,req.getParameterMap());
            System.out.println(user);
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    /**
     * 为了将数据存入到数据库，需要将登入的数据映射到实体类，然后再存入到数据库中
     * @param req
     */
    public void formDateToEntry(HttpServletRequest req) {
        try {
            req.setCharacterEncoding("UTF-8");
            //根据表单中name属性的名，获取value属性值的方法
//        getFormDate1(req);
//        getFormDate2(req);
            User user = new User();
            System.out.println("数据封装前User状态："+user);

            //获取表单数据
            Map<String, String[]> parameterMap = req.getParameterMap();
            for (Map.Entry<String,String[]> m:parameterMap.entrySet()){
                String key = m.getKey();
                String[] value = m.getValue();

                //使用反射知识完成对数据的封装
                PropertyDescriptor pd = new PropertyDescriptor(key,User.class);//该对象封装了每一个名字对应的get和ser方法

                //相当与获取对应名称的set方法
                Method setter = pd.getWriteMethod();

                //判断value是一个值还是多个值，然后进行数据填充
                if (value.length == 1) {
                    setter.invoke(user,value[0]);//对应名称只有一个值的封装
                } else {
                    setter.invoke(user,(Object) value);//给复选框变量封装赋值
                }

            }

            System.out.println("数据封装后User状态："+user);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 得到表单数据改进版
     * @param req
     */
    public void getFormDate2(HttpServletRequest req) {
        Enumeration<String> parameterNames = req.getParameterNames();//得到表单中所有的name属性名的枚举
        while (parameterNames.hasMoreElements()) {

            String name = parameterNames.nextElement();//得到其中一个名字
            String[] parameterValues = req.getParameterValues(name);//将名字所对应的值都封装为String数组，即使只有一个值
            for (int i = 0; parameterNames != null && i < parameterValues.length; i++) {
                System.out.println(parameterValues[i]);
            }
        }
    }

    /**
     * 根据表单中name属性的名，获取value属性值的方法
     * @param req
     */
    public void getFormDate1(HttpServletRequest req) {
        String userName = req.getParameter("userName");
        String password = req.getParameter("pwd");
        String sex = req.getParameter("sex");//性别只能选一个
        String[] hobbies = req.getParameterValues("hobby");
        String city = req.getParameter("city");

        System.out.println(userName);
        System.out.println(password);
        System.out.println(sex);
        for (int i = 0; hobbies != null && i < hobbies.length; i++) {
            System.out.println(hobbies[i]+"\t");
        }
        System.out.println(city);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

4.获取表单字节流方式（乱码问题没有解决）

package com.xu.httpservletrequest;

import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @auther xu
 * @date 2022/4/9 - 22:38
 */
public class ServletInputStreamDemo extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        //一般应用于操作照片等数据
        ServletInputStream inputStream = req.getInputStream();
        int len;
        byte[] buffer = new byte[1024];
        while ((len = inputStream.read(buffer)) != -1) {
            //将字节转变为字符串输出
            String s = new String(buffer, "UTF-8");
            System.out.println(s);
        }

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

控制台输出：

image-20220520155818157

image-20220520155827975

5.操作非表单数据的方法---请求转发

image-20220520155838541

image-20220520155849207

image-20220520155859673

image-20220520155943315

1.request维护一个Map集合，转发过程中，可以将当前页面得到的数据传递给下一个页面

RequestAndForwardDemo1页面：

package com.xu.httpservletrequest;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @auther xu
 * @date 2022/4/9 - 22:58
 */
public class RequestAndForwardDemo1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html;charset=UTF-8");

        //定义字符串，模拟该页面所得数据，保存req中，转发给下一个页面（request维护了一个Map集合）
        String str= "aaaaaaaaa";
        req.setAttribute("s",str);//s相当于键，str相当于所存储的值str

        //探索转发过程
        System.out.println("client:我想办事");
        System.out.println("RequestAndForwardDemo1:我办不了，但是我可以找别人帮你办");
        req.getRequestDispatcher("/requestAndForward2").forward(req,resp);
        System.out.println("RequestAndForwardDemo1:事情办完了");
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         this.doGet(req,resp);
    }
}

RequestAndForwardDemo2页面：

package com.xu.httpservletrequest;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @auther xu
 * @date 2022/4/9 - 23:05
 */
public class RequestAndForwardDemo2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html;charset=UTF-8");
        System.out.println("RequestAndForwardDemo2：我帮你办");

        //得到上一个页面的数据
        String str = (String)req.getAttribute("s");
        System.out.println(str);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         this.doGet(req,resp);
    }
}

输出：

image-20220520155956798

image-20220520160015729

2.removeAttribute()方法

image-20220520160026413

6.重定向与转发的对比：

1.请求转发不改变当前页面的地址栏（从别的页面反馈过来的数据经过当前页面响应给客户端），而重定向会改变地址栏实现跳转

image-20220520160043437

2.重定向不能传递数据，请求转发能够传递数据

image-20220520160053793

image-20220520160115455

image-20220520160124404

3.请求转发只能够在当前服务器的上的servlet引用程序进行跳转，而重定向能够访问别的服务器的应用程序
1.验证请求转发不能转发到百度服务器的应用程序

image-20220520160137623

image-20220520160149255

2.重定向可以跳转到别的服务器的页面（相当一浏览器向别的服务器访问资源）

image-20220520160203243

image-20220520160214115

4.总结：

image-20220520160222676

5.请求包含，将别的资源的页面包含进该页面，实现资源的合并

image-20220520160232078

image-20220520160242492

image-20220520160256387

7.请求编码相关的方法

image-20220520160305706

1.使用get提交数据

image-20220520160314619

image-20220520160323738

image-20220520160337874

image-20220520160346327

3.总结：

image-20220520160356072

image-20220520160420387

image-20220520162400150

image-20220520160439853

image-20220520160448109

image-20220520160514296

image-20220520160523521

image-20220520160533520

image-20220520160552971

image-20220520160602746

补充：

1.向RequestAndForwardDemo1页面提交的表单，通过请求转发，可以在RequestAndForwardDemo2页面通过名字得到表单数据

image-20220520160613327

image-20220520160626087

image-20220520160634376

image-20220520160648955

posted @ 2022-05-20 16:26  远道而重任  阅读(6)  评论(0)  编辑  收藏  举报