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response

独兜曲 2022-12-13 阅读 49
javajavawebservletweb服务器Linux系统/运维


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);
    }
}

response_javaweb


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

response_服务器_02

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;

response_javaweb_03

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);
    }
}

response_java_04

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);
    }
}

response_javaweb_05


有三种功能：

  1. 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
  2. 域对象：共享数据 对象范围：所有用户所有请求的数据
  3. 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);
    }
}

response_javaweb_06


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);
    }
}

response_web_07


第三种：

response_服务器_08


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);
    }
}

response_javaweb_09

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);
    }
}

response_服务器_10


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