HTTP协议
1,请求消息:客户端发送给服务器的数据。
数据格式:
- 请求行
- 请求头
- 请求空行
- 请求体
2,响应消息:服务器端发送给客户端的数据。
数据格式:
1,响应行:
组成:协议/版本 响应状态码(三位数字) 状态码描述,
响应状态码:服务器告诉客户端浏览器本次请求和响应的一个状态
状态码: - 1??:服务器接受客户端消息,但没有接受完成,等待一段时间后发送1??多状态码
- 2??:成功,代表:200
- 3??:重定向 ,代表:302(重定向),304(访问缓存)
- 4??:客户端错误,代表:404(请求路径没有对应的资源)405(请求方式没有对应的do???方法)
- 5??:服务器端错误。代表:500(服务器内部出现异常)
2,响应头:
头名称:值
常见响应头:
1,Content-Type:服务器告诉客户端本次响应体数据格式以及编码格式
2,Content-diposition:服务器告诉客户端以什么格式打开响应体数据
值为in-line:默认值,在当前页面内打开
值为attachment;filename=xxx:以附件形式打开响应体。文件下载
3,响应空行
4,响应体:传输的数据
例子:
HTTP/1.1 200 OK
Content-Type: text/html;charset=UTF-8
Content-Length: 101
Date: Wed, 06 Jun 2018 07:08:42 GMT
<html>
<head>
<title>$Title$</title>
</head>
<body>
hello , response
</body>
</html>
Response对象
功能:响应消息
1,设置响应行:1-格式:HTTP/1.1 200 ok 2-设置状态码:setStatus(int sc)
2,设置响应头:setHeader(String name,String value)
3,设置响应体:
- 获取输出流:字符输出流:PrintWriter getWriter() 字节输出流:ServletOutputStream getOutputStream()
- 使用输出流:将数据输出到客户端
重定向案例:
package com.wzc.web.servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
//重定向
@WebServlet("/responseDemo1")
public class ResponseDemo1 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("demo1被访问了");
//访问这个资源会自动跳转到/responseDemo2资源
/*// 设置状态码为302
response.setStatus(302);
// 设置响应头location
response.setHeader("location","/day15/responseDemo2");*/
// 简单的重定向方法
response.sendRedirect("/day15/responseDemo2");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
package com.wzc.web.servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/responseDemo2")
public class ResponseDemo2 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
System.out.println("demo2被访问了");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
重定向和转发的区别:
重定向的特点:redirect
1,地址栏发生变化
2,重定向可以访问其他站点(服务器)的资源
3,重定向是两次请求,不能使用request对象来共享数据
转发的特点:forward
1,转发地址栏路径不变
2,转发只能访问当前服务器下的资源
3,转发是一次请求,可以使用request对象来共享数据
路径:
通过相对路径不可以确定唯一资源,通过绝对路径可以确定唯一资源
如何判断定义的路径是给谁用的?
给客户端浏览器使用:需要加虚拟目录(项目的访问路径)虚拟目录动态获取:request.getContextPath()
给服务器使用就不需要加虚拟目录,例如转发路径
服务器输出字符数据到浏览器:
1.获取字符输出流
2.输出数据
package com.wzc.web.servlet;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
@WebServlet("/responseDemo3")
public class ResponseDemo3 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//获取流对象之前,设置流的默认编码设置为GBK
// response.setCharacterEncoding("utf-8");
// 告诉浏览器,服务器发送的消息体数据的编码,建议浏览器使用该编码解码
// response.setHeader("content-type","text/html;charset=utf-8");
// 简单的形式,设置编码
response.setContentType("text/html;charset=utf-8");
// 获取字符输出流
PrintWriter pw = response.getWriter();
// 输出数据
pw.write("<h1>hello response</h1>");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}package com.wzc.web.servlet;
1.获取字节输出流
2.输出数据
package com.wzc.web.servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/responseDemo4")
public class ResponseDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
// 获取字节输出流
ServletOutputStream sos = response.getOutputStream();
// 输出数据
sos.write("你好".getBytes("utf-8"));
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
ServletContext对象
代表整个web应用,可以和服务器来通信
有两种获取方式,通过request对象和HttpServlet获取
package com.wzc.web.servletcontext;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/servletContextDemo1")
public class ServletContextDemo1 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// ServletContext对象获取
// 通过request对象获取
ServletContext context1 = request.getServletContext();
// 通过HttpServlet获取
ServletContext context2 = this.getServletContext();
System.out.println(context1);
System.out.println(context2);
System.out.println(context1 == context2);
// true
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
有三种功能:
- 获取MIME类型:在互联网通信过程中定义的一种文件数据类型 格式:大类型/小类型 text/html
- 域对象:共享数据 对象范围:所有用户所有请求的数据
- 获取文件真实服务器路径
第一种:
package com.wzc.web.servletcontext;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/servletContextDemo2")
public class ServletContextDemo2 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 通过HttpServlet获取
ServletContext context= this.getServletContext();
// 定义文件名称
String filename = "a.jpg";
// 获取MIME类型
String mimeType = context.getMimeType(filename);
System.out.println(mimeType);
// image/jpeg
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
第二种:
package com.wzc.web.servletcontext;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/servletContextDemo3")
public class ServletContextDemo3 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// ServletContext对象获取
ServletContext context = this.getServletContext();
// 设置数据
context.setAttribute("msg","haha");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
package com.wzc.web.servletcontext;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/servletContextDemo4")
public class ServletContextDemo4 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// ServletContext对象获取
ServletContext context = request.getServletContext();
Object msg = context.getAttribute("msg");
System.out.println(msg);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
第三种:
主要分为三种情况,a.txt,b.txt,c.txt分别代表
src下的比较特殊,是在目录WEB-INF下的classes文件里
package com.wzc.web.servletcontext;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
@WebServlet("/servletContextDemo5")
public class ServletContextDemo5 extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
ServletContext context = this.getServletContext();
// 获取文件的服务器路径
// web目录下访问
String realPath = context.getRealPath("/b.txt");
System.out.println(realPath);
File file = new File(realPath);
// WEB-INF目录下资源的访问
String c = context.getRealPath("/WEB-INF/c.txt");
System.out.println(c);
// src目录下资源访问
String a = context.getRealPath("/WEB-INF/classes/a.txt");
System.out.println(a);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
验证码案例
本质:图片
目的:防止恶意表单注册
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>register</title>
<script>
/*点击超链接或者图片需要换一张*/
// 给超链接和图片绑定单击事件
// 重新设置图片的src属性值
window.onload = function(){
// 获取图片对象
var img = document.getElementById("checkCode");
// 绑定单击事件
img.onclick = function () {
//加时间戳
var date =new Date().getTime();
img.src = "/day15/checkCodeServlet?"+date;
}
}
</script>
</head>
<body>
<img src="/day15/checkCodeServlet">
<a id=“change” href="">看不清,换一张</a>
</body>
</html>
package com.wzc.web.servlet;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
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;
@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
int width = 100;
int height = 50;
// 创建一对象,在内存中图片(验证码图片对象)
BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
// 美化图片
// 填充背景色,画笔对象
Graphics g = image.getGraphics();
// 设置画笔颜色
g.setColor(Color.pink);
g.fillRect(0,0,width,height);
// 画边框
g.setColor(Color.BLUE);
g.drawRect(0,0,width-1,height-1);
String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
// 生成随机角标
Random random = new Random();
// 写验证码
for (int i = 1; i <=4 ; i++) {
int index = random.nextInt(str.length());
// 获取字符
char ch = str.charAt(index);
g.drawString(ch+"",width/5*i,height/2);
}
// 画干扰线
g.setColor(Color.gray);
// 随机生成左边点
for (int i = 0; i <10 ; i++) {
int x1 = random.nextInt(width);
int x2 = random.nextInt(width);
int y1 = random.nextInt(height);
int y2 = random.nextInt(height);
g.drawLine(x1,y1,x2,y2);
}
// 图片输出到页面展示
ImageIO.write(image,"jpg",response.getOutputStream());
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}