简单的Tomcat实现--1.1浏览器模拟

• 为了更好的了解http协议，实现一个小型的浏览器程序，这个浏览器可以获取html的内容和http响应的头部信息。这个Mini浏览器具备以下的几个功能

1. getHttpBytes 返回二进制的 http 响应

2. getHttpString 返回字符串的 http 响应

3. getContentBytes 返回二进制的 http 响应内容 （可简单理解为去掉头的 html 部分）

4. getContentString 返回字符串的 http 响应内容 （可简单的理解为去掉头的html 部分）

• 代码实现：

package util;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

/**
* @author ：xiaosong
* @description：模拟实现一个小型的浏览器，通过这个浏览器与服务器进行通信
* @date ：2020/7/28 21:22
*/
public class MiniBrowser {
   public static void main(String[] args){
       String url = "http://static.how2j.cn/diytomcat.html";
       String contentString = getContentString(url);
       System.out.println(contentString);
       String httpString = getHttpString(url);
       System.out.println(httpString);
   }

   public static String getContentString(String url){
       return getContentString(url, false);
   }
   public static String getContentString(String url, boolean gzip){
       byte[] result = getContentBytes(url, gzip);
       if (result == null) {
           return null;
       }
       return new String(result, StandardCharsets.UTF_8).trim();
   }

   /**
    *
    * @param url:访问的链接地址
    * @return byte[]:一个字节数组，是二进制的http的响应内容，可以简单理解为去掉头的html部分
    */
   public static byte[] getContentBytes(String url){
       return getContentBytes(url, false);
   }
   public static byte[] getContentBytes(String url, boolean gzip){
       byte[] response = getHttpBytes(url, gzip);
       byte[] doubleReturn = "\r\n\r\n".getBytes();

       int pos = -1;
       for (int i = 0; i< response.length - doubleReturn.length; i++) {
           byte[] temp = Arrays.copyOfRange(response, i, i + doubleReturn.length);
           if (Arrays.equals(temp, doubleReturn)) {
               pos = i;
               break;
           }
       }
       if (pos == -1){
           return null;
       }
       pos += doubleReturn.length;

       return Arrays.copyOfRange(response, pos, response.length);

   }
   public static String getHttpString(String url, boolean gzip) {
       byte[] bytes = getHttpBytes(url, gzip);
       return new String(bytes).trim();
   }
   public static String getHttpString(String url) {
       return getHttpString(url, false);
   }
   public static byte[] getHttpBytes(String url, boolean gzip){
       byte[] result;
       try {
           URL u = new URL(url);
           Socket clientSocket = new Socket();
           int port = u.getPort();
           if (port == -1) {
               port = 80;
           }
           InetSocketAddress inetSocketAddress = new InetSocketAddress(u.getHost(), port);
           clientSocket.connect(inetSocketAddress, 1000);
           Map<String, String> requestHeaders = new HashMap<>();
           requestHeaders.put("Host", u.getHost() + ":" + port);
           requestHeaders.put("Accept","text/html");
           requestHeaders.put("Connection", "close");
           requestHeaders.put("User-Agent", "mini browser/jdk1.8.0_251");
           if (gzip) {
               requestHeaders.put("Accept-Encoding", "gzip");
           }
           String path = u.getPath();
           if (path.length() == 0 ){
               path = "/";
           }
           String firstLine = "GET " + path + " HTTP/1.1\r\n";
           StringBuffer httpRequestString = new StringBuffer();
           httpRequestString.append(firstLine);
           Set<String> headers = requestHeaders.keySet();
           for (String header: headers) {
               String headerLine = header + ":" + requestHeaders.get(header) + "\r\n";
               httpRequestString.append(headerLine);
           }
           // 通过clientSocket向服务器传输请求request
           PrintWriter printWriter = new PrintWriter(clientSocket.getOutputStream(), true);
           printWriter.println(httpRequestString);
           // 通过clientSocket从服务器获取response，浏览器的输入流
           InputStream inputStream = clientSocket.getInputStream();
           result = readBytes(inputStream);
           clientSocket.close();
       }catch(Exception e) {
           e.printStackTrace();
           result = e.toString().getBytes(StandardCharsets.UTF_8);
       }
       return result;
   }

   public static byte[] readBytes(InputStream inputStream) throws IOException {
       int bufferSize = 1024;
       byte[] buffer = new byte[bufferSize];
       ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
       while(true) {
           int length = inputStream.read(buffer);
           if (length == -1) {
               // read函数返回-1说明已经读到尾部, 否则返回读到的字符个数
               break;
           }
           byteArrayOutputStream.write(buffer, 0, length);
           if (length != bufferSize){
               //表明buffer空间没有被读满，说明也没有下文了
               break;
           }
       }
       return byteArrayOutputStream.toByteArray();

   }
}

简单的Tomcat实现--1.1浏览器模拟

原文：https://www.cnblogs.com/xsliu/p/13430521.html