JavaWeb入门:HttpResponse和HttpRequest详解

目录HttpResponse 讲解HttpServletResponse概述:Response运行流程设置响应行设置响应头一个小demo 实现刷新 页面累加设置字符编码 解决中文乱码问题重定向 redirectrequest转发重定向和转发的区别文件下载HttpRequest 讲解HttpServletRequest概述Request 运行流程获取请求携带的参数获取多个参数的值获得请求行的信息request实现转发request是一个域对象ServletContext 作用域：request作用域：总结

HttpResponse 讲解

HttpServletResponse概述:

​ 在创建Servlet时会覆盖service()方法，或doGet()/doPost(),这些方法都有两个参数，一个为代表请求的request和代表响应response。service方法中的response的类型是ServletResponse，而doGet/doPost方法的response的类型是HttpServletResponse，HttpServletResponse是ServletResponse的子接口，功能和方法更加强大。

Response运行流程

响应头有很多这里只介绍常用的。

在浏览器可以按F12 抓包看响应头、请求头、具体的可以再查。

设置响应行

设置响应的状态码

/** * @Author: crush * @Date: 2021-05-09 19:35 * version 1.0 */@WebServlet("/test3")public class HttpResponseTest3 extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        System.out.println("设置状态码,前台通过判断状态码，来判断请求是否成功");        resp.setStatus(404);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doGet(req, resp);    }}

测试

设置响应头

刷新 跳转页面

/** * @Author: crush * @Date: 2021-05-09 19:35 * version 1.0 */@WebServlet("/test4")public class HttpResponseTest4 extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        // 设置响应头 每1秒自动刷新        System.out.println("设置响应头 每1秒自动刷新");        resp.setHeader("Refresh", "1");        //定时跳转 3秒后将自动跳转//        resp.setHeader("Refresh","3;URL=hello.jsp");    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doGet(req, resp);    }}

测试

一个小demo 实现刷新 页面累加

/** * response * @author Adimi */@WebServlet("/test4")public class ResponseTest4 extends HttpServlet {    private static Integer id=1;    @Override    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        response.setHeader("Refresh","1");        PrintWriter writer = response.getWriter();        id++;        writer.print("id==>"+id);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doGet(req, resp);    }}

设置字符编码 解决中文乱码问题

/** * @Author: crush * @Date: 2021-05-09 19:35 * version 1.0 */@WebServlet("/test1")public class HttpResponseTest1 extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        // 解决中文乱码问题        // 设置响应头        // 设置字符编码 resp.setCharacterEncoding("UTF-8");        // 设置响应内容以什么格式展示到页面 什么编码格式 包含了设置字符编码        resp.setContentType("text/html;charset=utf-8");        PrintWriter writer = resp.getWriter();        writer.print("中国,你好！！！");    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doGet(req, resp);    }}

测试

重定向 redirect

/** * 重定向 * @Author: crush * @Date: 2021-05-09 19:35 * version 1.0 */@WebServlet("/test5")public class HttpResponseTest5 extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        resp.sendRedirect("hello.jsp");//        resp.setHeader("location","www.baidu.com"); 通过设置响应头转发    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doGet(req, resp);    }}

request转发

/** * 重定向 * @Author: crush * @Date: 2021-05-09 19:35 * version 1.0 */@WebServlet("/test5")public class HttpResponseTest5 extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//        resp.sendRedirect("hello.jsp");        req.getRequestDispatcher("hello.jsp").forward(req,resp);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doGet(req, resp);    }}

重定向和转发的区别

文件下载

获取路径资源

String path=this.getServletContext().getRealPath("WEB-INF\\classes\\8.jpg");

读取资源

FileInputStream fileInputStream=new FileInputStream(path);

获取到文件名，路径在电脑上保存的形式是 \ \

String fileName=path.substring(path.lastIndexOf("\\")+1);

设置消息头告诉浏览器，我要下载1.png这个图片 设置编码

resp.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName, "UTF-8"));

把读取到的内容回送给浏览器

 int len=0;byte[] bytes=new byte[1024];// ServletOutputStream 提供用于将二进制数据发送到客户端的输出流ServletOutputStream servletOutputStream=resp.getOutputStream();while((len=fileInputStream.read(bytes))>0) {    servletOutputStream.write(bytes,0,len);}

关闭资源

servletOutputStream.close();        fileInputStream.close();

注：8.jpg 放在我的resources 文件夹下 但是这里需要写的是编译完8.jpg存放的位置

具体代码

/** * @Author: crush * @Date: 2021-05-09 19:40 * version 1.0 */@WebServlet("/down")public class ResponseDownFile extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        //获取路径资源        String path=this.getServletContext().getRealPath("WEB-INF\\classes\\8.jpg");        //读取资源        FileInputStream fileInputStream=new FileInputStream(path);        //获取到文件名，路径在电脑上保存的形式是\\        String fileName=path.substring(path.lastIndexOf("\\")+1);        //设置消息头告诉浏览器，我要下载1.png这个图片        // 该方式文件名为中文时会乱码        //防止中文乱码        resp.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(fileName, "UTF-8"));        //把读取到的内容回送给浏览器        int len=0;        byte[] bytes=new byte[1024];        ServletOutputStream servletOutputStream=resp.getOutputStream();        while((len=fileInputStream.read(bytes))>0) {            servletOutputStream.write(bytes,0,len);        }        // 关闭资源        servletOutputStream.close();        fileInputStream.close();    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doGet(req, resp);    }}

HttpRequest 讲解

HttpServletRequest概述

​ 我们在创建Servlet时会覆盖service()方法，或doGet()/doPost(),这些方法都有两个参数，一个为代表请求的request和代表响应response。service（）方法中写了根据请求方式的不同调用doget()和dopost().

service方法中的request的类型是ServletRequest，而doGet/doPost方法的request类型HttpServletRequest，HttpServletRequest是ServletRequest的子接口，功能和方法更加强大.

Request 运行流程

获取请求携带的参数

/** * @Author: crush * @Date: 2021-05-11 16:52 * version 1.0 */@WebServlet("/request1")public class RequestTest1 extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        // 这里是请求的参数名  必须是同名的         String username = req.getParameter("username");         String password = req.getParameter("password");        PrintWriter writer = resp.getWriter();        writer.print("<h1>"+username+":"+password+"</h1>");    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doGet(req, resp);    }}

获取多个参数的值

  @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        // 设置请求的编码  不然会乱码        req.setCharacterEncoding("utf-8");        Enumeration<String>  names = req.getParameterNames();        while (names.hasMoreElements()) {            String name = (String) names.nextElement();            String[]  values = req.getParameterValues(name);            System.out.println(name+":"+ Arrays.toString(values));        }    }

获得请求行的信息

/** * @Author: crush * @Date: 2021-05-11 16:52 * version 1.0 */@WebServlet("/request3")public class RequestTest3 extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        // 获得请求的url        StringBuffer requestURL = req.getRequestURL();        System.out.println("请求的URL===>"+requestURL);        // 获得请求的Servlet的路径        String path = req.getServletPath();        System.out.println("请求的Servlet的路径===>"+path);        //返回发出此请求的HTTP方法的名称，例如GET，POST或PUT        String method = req.getMethod();        System.out.println("返回发出此请求的HTTP方法的名称==>"+method);        //返回发送请求的客户端或最后一个代理的Internet协议（IP）地址        String remoteAddr = req.getRemoteAddr();        System.out.println("remoteAddr==>"+remoteAddr);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doGet(req, resp);    }}

request实现转发

/** * @Author: crush * @Date: 2021-05-11 16:52 * version 1.0 */@WebServlet("/request2")public class RequestTest2 extends HttpServlet {    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        // 访问request2 转发到 request4去        req.getRequestDispatcher("/request4").forward(req,resp);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        doGet(req, resp);    }}

request是一个域对象

request对象也是一个存储数据的区域对象，所以也具有如下方法：

setAttribute(String name, Object o)

getAttribute(String name)

removeAttribute(String name)

ServletContext 作用域：

创建：启动web应用程序的时候创建

销毁：关闭web应用程序的时候销毁

域的作用范围：整个web应用的启动周期

request作用域：

创建：访问时创建request

销毁：响应结束request销毁

域的作用范围：一次请求中

总结

本篇文章就到这里了，希望能给你带来帮助，也希望您能够多多关注的更多内容！

世上没有绝望的处境，只有对处境绝望的人。