一、HttpServletResponse及response运行过程：
1．HttpServletResponse概述：
我们在创建Servlet时，会覆盖service方法，或doGet和doPost方法，这些方法都有两个参数request和response，前者代表请求，后者代表响应。
service方法中response的类型是ServletResponse，而doGet和doPost方法中的response的类型是HttpServletResponse，其中，HTTPServletResponse 是ServletResponse的子接口。
2.response运行过程：
3.通过抓包工具抓取Http响应:
4.通过response设置响应行
（1）设置响应行的状态码
setStatus(int sc)
（2）通过response设置响应头
addHeader(String name, String value)
addIntHeader(String name, int value)
addDateHeader(String name, long date)
setHeader(String name, String value)
setDateHeader(String name, long date)
setIntHeader(String name, int value)
重定向
// response.setStatus(302);
// response.setHeader("location", "/WEB14A/servlet2");
response.sendRedirect("/WEB14A/servlet2");
定时跳转
response.setHeader("refresh", "5;url=http://www.baidu.com");
案例：定时跳转
success.html
Insert title here
恭喜你，注册成功，5秒后将跳转到登录页面，如不跳转，请点击这里
5.响应体设置文本
中文乱码问题：
//设置response查询的码表
response.setCharacterEncoding("UTF-8");
//设置头。开发中一般用这种
response.setContentType("text/html;charset=UTF-8");
6.响应头设置字节
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//使用response获得字节输出流
ServletOutputStream out = response.getOutputStream();
//获得服务器上的图片
String realPath = this.getServletContext().getRealPath("a.jpg");
InputStream in = new FileInputStream(realPath);
int len=0;
byte[] buffer = new byte[1024];
while((len=in.read(buffer))>0){
out.write(buffer, 0, len);
}
in.close();
out.close();
}
7.文件下载：
首先，有download.html
Insert title here
使用a标签直接指向服务器上的资源
a.flv
a.jpg
a.mp3
a.mp4
a.txt
a.zip
使用服务器端编码的方式实现文件下载
a.flv
a.jpg
a.mp3
a.mp4
a.txt
a.zip
美女.jpg
此时，有两种情况：
文件名为英文的：
package com.zl.content;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
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 DownloadServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获得要下载的文件的名称
String filename = request.getParameter("filename");//a.jpg
//要下载的这个文件的类型-----客户端通过文件的MIME类型去区分类型
response.setContentType(this.getServletContext().getMimeType(filename));
//告诉客户端该文件不是直接解析 而是以附件形式打开(下载)
response.setHeader("Content-Disposition","attachment;filename="+filename );
//获取文件的绝对路径
String realPath = this.getServletContext().getRealPath("download/"+filename);
//获得该文件的输入流
InputStream in = new FileInputStream(realPath);
//获得输出流---通过response获得的输出流 用于向客户端写内容
ServletOutputStream out = response.getOutputStream();
//文件拷贝的模板代码
int len=0;
byte[] buffer = new byte[1024];
while((len=in.read(buffer))>0){
out.write(buffer, 0, len);
}
in.close();
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
文件名为中文的：
package com.zl.content;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URLEncoder;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import sun.misc.BASE64Encoder;
public class DownloadServlet2 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// *******文件名称是中文的下载*******
// 获得要下载的文件的名称
String filename = request.getParameter("filename");// ????.jpg
// 解决获得中文参数的乱码
filename = new String(filename.getBytes("ISO8859-1"), "UTF-8");// 美女.jpg
// 获得请求头中的User-Agent
String agent = request.getHeader("User-Agent");
// 根据不同浏览器进行不同的编码
String filenameEncoder = "";
if (agent.contains("MSIE")) {
// IE浏览器
filenameEncoder = URLEncoder.encode(filename, "utf-8");
filenameEncoder = filenameEncoder.replace("+", " ");
} else if (agent.contains("Firefox")) {
// 火狐浏览器
BASE64Encoder base64Encoder = new BASE64Encoder();
filenameEncoder = "=?utf-8?B?" + base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
} else {
// 其它浏览器
filenameEncoder = URLEncoder.encode(filename, "utf-8");
}
// 要下载的这个文件的类型-----客户端通过文件的MIME类型去区分类型
response.setContentType(this.getServletContext().getMimeType(filename));
// 告诉客户端该文件不是直接解析 而是以附件形式打开(下载)----filename="+filename 客户端默认对名字进行解码
response.setHeader("Content-Disposition", "attachment;filename=" + filenameEncoder);
// 获取文件的绝对路径
String realPath = this.getServletContext().getRealPath("download/" + filename);
// 获得该文件的输入流
InputStream in = new FileInputStream(realPath);
// 获得输出流---通过response获得的输出流 用于向客户端写内容
ServletOutputStream out = response.getOutputStream();
// 文件拷贝的模板代码
int len = 0;
byte[] buffer = new byte[1024];
while ((len = in.read(buffer)) > 0) {
out.write(buffer, 0, len);
}
in.close();
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
验证码的实现：
new_words.txt文件放在WEB-INF下
CheckImgServlet.java
此为工具类：直接复制粘贴即可。
package com.itheima.checkimg;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
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;
/**
* 验证码生成程序
*
*
*
*/
public class CheckImgServlet extends HttpServlet {
// 集合中保存所有成语
private List words = new ArrayList();
@Override
public void init() throws ServletException {
// 初始化阶段，读取new_words.txt
// web工程中读取 文件，必须使用绝对磁盘路径
String path = getServletContext().getRealPath("/WEB-INF/new_words.txt");
try {
BufferedReader reader = new BufferedReader(new FileReader(path));
String line;
while ((line = reader.readLine()) != null) {
words.add(line);
}
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// 禁止缓存
// response.setHeader("Cache-Control", "no-cache");
// response.setHeader("Pragma", "no-cache");
// response.setDateHeader("Expires", -1);
int width = 120;
int height = 30;
// 步骤一 绘制一张内存中图片
BufferedImage bufferedImage = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
// 步骤二 图片绘制背景颜色 ---通过绘图对象
Graphics graphics = bufferedImage.getGraphics();// 得到画图对象 --- 画笔
// 绘制任何图形之前 都必须指定一个颜色
graphics.setColor(getRandColor(200, 250));
graphics.fillRect(0, 0, width, height);
// 步骤三 绘制边框
graphics.setColor(Color.WHITE);
graphics.drawRect(0, 0, width - 1, height - 1);
// 步骤四 四个随机数字
Graphics2D graphics2d = (Graphics2D) graphics;
// 设置输出字体
graphics2d.setFont(new Font("宋体", Font.BOLD, 18));
Random random = new Random();// 生成随机数
int index = random.nextInt(words.size());
String word = words.get(index);// 获得成语
// 定义x坐标
int x = 10;
for (int i = 0; i < word.length(); i++) {
// 随机颜色
graphics2d.setColor(new Color(20 + random.nextInt(110), 20 + random
.nextInt(110), 20 + random.nextInt(110)));
// 旋转 -30 --- 30度
int jiaodu = random.nextInt(60) - 30;
// 换算弧度
double theta = jiaodu * Math.PI / 180;
// 获得字母数字
char c = word.charAt(i);
// 将c 输出到图片
graphics2d.rotate(theta, x, 20);
graphics2d.drawString(String.valueOf(c), x, 20);
graphics2d.rotate(-theta, x, 20);
x += 30;
}
// 将验证码内容保存session
request.getSession().setAttribute("checkcode_session", word);
// 步骤五 绘制干扰线
graphics.setColor(getRandColor(160, 200));
int x1;
int x2;
int y1;
int y2;
for (int i = 0; i < 30; i++) {
x1 = random.nextInt(width);
x2 = random.nextInt(12);
y1 = random.nextInt(height);
y2 = random.nextInt(12);
graphics.drawLine(x1, y1, x1 + x2, x2 + y2);
}
// 将上面图片输出到浏览器 ImageIO
graphics.dispose();// 释放资源
//将图片写到response.getOutputStream()中
ImageIO.write(bufferedImage, "jpg", response.getOutputStream());
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
/**
* 取其某一范围的color
*
* @param fc
* int 范围参数1
* @param bc
* int 范围参数2
* @return Color
*/
private Color getRandColor(int fc, int bc) {
// 取其随机颜色
Random random = new Random();
if (fc > 255) {
fc = 255;
}
if (bc > 255) {
bc = 255;
}
int r = fc + random.nextInt(bc - fc);
int g = fc + random.nextInt(bc - fc);
int b = fc + random.nextInt(bc - fc);
return new Color(r, g, b);
}
}
login.html文件如下：
Insert title here
表单部分：
