[TOC]

HttpServletResponse

web服务器接收到客户端的http请求，针对这个请求，分别创建一个代表请求的HttpServletRequest对象，代表响应的一个HttpServletResponse;

• 如果要获取客户端请求过来的参数:找HttpServletRequest
• 如果要给客户端响应一些信息:找HttpServletResponse

简单分类

负责向浏览器发送数据的方法

ServletoutputStream getoutputStream() throws IOException;PrintWriter getWriter() throws IOException;(中文最好用这个)

负责向浏览器发送响应头的方法

void setCharacterEncoding(String var1);void setContentLength(int var1);void setContentLengthLong(long var1);void setContentType(String var1);void setDateHeader(String name, long date);void addDateHeader(String name, long date);void setHeader(String name, String value);void addHeader(String name, String value);void setIntHeader(String name, int value);void addIntHeader(String name, int value);

常见应用

1.向浏览器输出消息

2.下载文件

​ 1.要获取下载文件的路径

​ 2.下载的文件名是啥？

​ 3.设置想办法让浏览器能够支持下载我们需要的东西

​ 4.获取下载文件的输入流

​ 5.创建缓冲区

​ 6.获取OutputStream对象

​ 7.将FileOutputStream流写入到buffer缓冲区

​ 8.使用OutputStream将缓冲区的数据输出到客户端

通过response.getOutputStream的方式下载文件，为文件设置文件名:

//1.设置文件ContentType类型，这样设置，会自动判断下载文件类型response.setContentType("multipart/form-data");//2.设置文件头：最后一个参数是设置下载文件名(假如我们叫a.pdf)response.setHeader("Content-Disposition", "attachment;fileName="+"a.pdf");

public class FileServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 1.要获取下载文件的路径String realPath = "D:\\\\java_work\\\\javaweb-test\\\\response\\\\src\\\\main\\\\resources\\\\贝贝子.png";System.out.println("下载文件的路径"+realPath);// 2.下载的文件名是啥?String filename = realPath.substring(realPath.lastIndexOf("\\\\") + 1);//3.设置想办法让浏览器能够支持（Content-Disposition）下载我们需要的东西（中文文件名需要使用：URLEncoder.encode(filename,"UTF-8")，否则可能乱码或出现编码问题）resp.setHeader("Content-Disposition", "attachment;fileName="+ URLEncoder.encode(filename,"UTF-8"));// 4.获取下校文件的输入流FileInputStream in = new FileInputStream(realPath);// 5.创建缓冲区int len=0;byte[] buffer = new byte[1024];// 6．获取Outputstream对象ServletOutputStream out = resp.getOutputStream();//7.将FiLeoutputstream流写入到buffer缓冲区,使用outputStream将缓冲区中的数擦输出到客户端!while((in.read(buffer))>0){out.write(buffer,0,len);}in.close();out.close();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}

3、验证码功能

验证怎么来的？

• 前端实现
• 后端实现，需要用到Java的图片类，生成一个图片

package com.bbz.servlet;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.awt.*;import java.awt.image.BufferedImage;import java.io.IOException;import java.util.Random;public class ImageServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//如何让浏览器5秒自动刷新一次resp.setHeader("refresh","3");//在内存中创建一个图片BufferedImage bufferedImage = new BufferedImage(80,20,BufferedImage.TYPE_INT_RGB);//得到图片Graphics2D g=(Graphics2D) bufferedImage.getGraphics();//设置图片背景颜色g.setColor(Color.yellow);g.fillRect(0,0,80,20);//给图片写数据g.setColor(Color.BLUE);g.setFont(new Font(null,1,20));g.drawString(makeNum(),0,20);//告诉浏览器，这个请求用图片的方式打开resp.setContentType("image/png");//网站存在缓存，不让浏览器缓存resp.setDateHeader("expires",-1);resp.setHeader("Cache-Control","no-cache");resp.setHeader("Pragma","no-cache");//把图片写给浏览器boolean write = ImageIO.write(bufferedImage,"png", resp.getOutputStream());}//生成随机数private String makeNum(){Random random=new Random();String num = random.nextInt(9999999) + "";StringBuffer sb = new StringBuffer();for(int i=0;i<7- num.length();i++){sb.append("0");}	//保证验证码一定是7位数num = sb.toString() + num;return num;}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}

4.重定向

一个web资源B收到客户端A请求后，通知客户端A访问另一个web资源C，该过程叫重定向。常见场景：用户登录；

public void sendRedirect(String location) throws IOException;

重定向：

public class RedirectServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {/*重定向原理resp.setHeader("Location","/resp/img");resp.setStatus(302);*/resp.sendRedirect("/resp/img");//重定向}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}

重定向与转发的异同点：

• 相同：页面都会跳转

public class RequestTes extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//处理请求String username = req.getParameter("username");String password = req.getParameter("password");System.out.println(username+":"+password);//重定向的时候一定要注意路径问题resp.sendRedirect("/resp/success.jsp");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}

<%@page language="java" contentType="text/html; charset=UTF-8" pageEncoding="utf-8" %><html><body><h2>Hello World!</h2><%-- 这里提交的路径，需要寻找到项目的路径 --%><%-- ${pageContext.request.contextPath}代表当前项目 --%><form action="${pageContext.request.contextPath}/request" method="get">用户名： <input type="text" name="username" /> <br/>密  码: <input type="password" name="password" /> <br/><input type="submit"></form></body></html>

request.getParameter(String s) //取单个值request.getParameterValues(String s) //取多个值

package com.bbz.servlet;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.Arrays;public class LoginServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// 解决后台接受中文乱码问题req.setCharacterEncoding("utf-8");resp.setCharacterEncoding("utf-8");String username = req.getParameter("username");String password = req.getParameter("password");String[] hobbys = req.getParameterValues("hobbys");System.out.println(username);System.out.println(password);System.out.println(Arrays.toString(hobbys));// 重定向// resp.sendRedirect("/resuest-01/success.jsp");// 通过请求转发， 此处的 / 就是当前web应用，不需要在多写了。req.getRequestDispatcher("/success.jsp").forward(req, resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}

<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head><title>Login</title></head><body><h1>登录</h1><div style="text-align: center"><%-- 这里表单表示的意思：以post方式提交表单，提交到我们的login请求       --%><form action="${pageContext.request.contextPath}/login" method="post">用户名：<input type="text" name="username"> <br/>密码：<input type="password" name="password"> <br/>爱好：<input type="checkbox" name="hobbys" value="女孩">女孩<input type="checkbox" name="hobbys" value="代码">代码<input type="checkbox" name="hobbys" value="唱歌">唱歌<input type="checkbox" name="hobbys" value="电影">电影<br/><input type="submit"></form></div></body></html>