Java-web-HttpServletResponse
Java-web-HttpRunner
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HttoServletResponse
- 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HttoServletResponse
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;
- 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);
- 设置响应头
void setDateHeader(String var1, long var2);
void addDateHeader(String var1, long var2);
void setHeader(String var1, String var2);
void addHeader(String var1, String var2);
void setIntHeader(String var1, int var2);
void addIntHeader(String var1, int var2);
响应码参量:
int SC_CONTINUE = 100;
int SC_SWITCHING_PROTOCOLS = 101;
int SC_OK = 200;
int SC_CREATED = 201;
int SC_ACCEPTED = 202;
int SC_NON_AUTHORITATIVE_INFORMATION = 203;
int SC_NO_CONTENT = 204;
int SC_RESET_CONTENT = 205;
int SC_PARTIAL_CONTENT = 206;
int SC_MULTIPLE_CHOICES = 300;
int SC_MOVED_PERMANENTLY = 301;
int SC_MOVED_TEMPORARILY = 302;
int SC_FOUND = 302;
int SC_SEE_OTHER = 303;
int SC_NOT_MODIFIED = 304;
int SC_USE_PROXY = 305;
int SC_TEMPORARY_REDIRECT = 307;
int SC_BAD_REQUEST = 400;
int SC_UNAUTHORIZED = 401;
int SC_PAYMENT_REQUIRED = 402;
int SC_FORBIDDEN = 403;
int SC_NOT_FOUND = 404;
int SC_METHOD_NOT_ALLOWED = 405;
int SC_NOT_ACCEPTABLE = 406;
int SC_PROXY_AUTHENTICATION_REQUIRED = 407;
int SC_REQUEST_TIMEOUT = 408;
int SC_CONFLICT = 409;
int SC_GONE = 410;
int SC_LENGTH_REQUIRED = 411;
int SC_PRECONDITION_FAILED = 412;
int SC_REQUEST_ENTITY_TOO_LARGE = 413;
int SC_REQUEST_URI_TOO_LONG = 414;
int SC_UNSUPPORTED_MEDIA_TYPE = 415;
int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416;
int SC_EXPECTATION_FAILED = 417;
int SC_INTERNAL_SERVER_ERROR = 500;
int SC_NOT_IMPLEMENTED = 501;
int SC_BAD_GATEWAY = 502;
int SC_SERVICE_UNAVAILABLE = 503;
int SC_GATEWAY_TIMEOUT = 504;
int SC_HTTP_VERSION_NOT_SUPPORTED = 505;
文件下载,
- 向浏览器输出消息
- 下载文件
- 要获取下载文件的路径
- 下载的文件名是啥
- 设置想办法让浏览器能够支持下载我们需要的东西
- 获取下载文件的输入流
- 创建缓冲区
- 获取OutputStream对象
- 将FileOutputStream流写入到Buffer缓冲区
- 使用OutputStream将缓冲区中的数据输出到客户端!
package com.xinyudoufuf.servlet;
import sun.net.www.content.image.png;
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.net.URLEncoder;
public class FileServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
// 1. 要获取下载文件的路径
String realpath = "E:\\javaweb\\javaweb-02-servlet\\response\\target\\response\\WEB-INF\\classes\\咸鱼豆腐.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("\\") + 2);
// 3. 设置想办法让浏览器能够支持下载我们需要的东西,中文文件名,URLEncoder.encode编码,否则有可能会乱码
resp.setHeader("Content-Disposition","attachment;filename="+ URLEncoder.encode(filename,"utf-8"));
// 4. 获取下载文件的输入流
FileInputStream fis = 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将缓冲区中的数据输出到客户端!
while ((len = fis.read(buffer)) > 0) {
out.write(buffer,0,len);
}
fis.close();
out.close();
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req,resp);
}
}
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,生产一个图片
验证码
package com.xinyudoufuf.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 {
@Override
protected 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 image = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);
//得到图片
Graphics2D g = (Graphics2D) image.createGraphics();
//设置图片的背景颜色
g.setColor(Color.white);
g.fillRect(0, 0, 80, 20);
//给图片写数据
g.setColor(Color.BLUE);
g.setFont(new Font(null, Font.BOLD, 20));
g.drawString(makeNum(),0,20);
//告诉浏览器，这请求用图片的方法打开
resp.setContentType("image/jpeg");
//网站存在缓存,
resp.setDateHeader("expires", -1);
resp.setHeader("Cache-Control", "no-cache");
resp.setHeader("Pragma", "no-cache");
//把图片写给浏览器
ImageIO.write(image, "jpg", resp.getOutputStream());
}
//生成随机数
protected String makeNum() {
Random random = new Random();
String num = random.nextInt(99999999) + "";
StringBuffer sb = new StringBuffer();
for (int i = 0; i < 7 - num.length(); i++) {
sb.append("0");
}
String s = sb.toString() + num;
return num;
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req,resp);
}
}
实现重定向
一个web资源收到客户端请求后，他会通知客户端去访问另外一个web资源C，这个过程叫重定向
常见场景
- 用户登录
void sendRedirect(String var1) throws IOException;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
/*
resp.setHeader("Location","/r1/aa");
resp.setStatus(HttpServletResponse.SC_MOVED_TEMPORARILY);
* */
resp.sendRedirect("/r1/aa"); //重定向
}
重定向和转发的区别
相同点
- 页面都会实现跳转
不同点 - 请求转发的时候,url不会产生变化
- 重定向的时候,url地址栏会发送变化