Java使用Socket技术获取网页

1.代码

• 接口

package com.lawson.crawler.inface;

/**
 * 1.interface
 */
public interface Crawler {
    public void crawler(String url);
}

• 实现类

package com.lawson.crawler.impl;

import com.lawson.crawler.inface.Crawler;

import java.io.*;
import java.net.Socket;

public class CrawlerImpl implements Crawler {
    public void crawler(String url) {
        BufferedWriter bw =null;
        BufferedReader br = null;
        try {
            // Creates a stream socket and connects it to the specified port number on the named host.
            Socket socket = new Socket(url,80);//build a socket

            //bw = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
            //The abbreviation of following code
            OutputStream outputStream = socket.getOutputStream();//Returns an output stream for this socket.
            OutputStreamWriter oSWriter = new OutputStreamWriter(outputStream);//Creates an OutputStreamWriter that uses the default character encoding.
            bw = new BufferedWriter(oSWriter);//Creates a buffered character-output stream that uses a default-sized output buffer.

            //be care of the pattern of request
            bw.write("GET /"+url+ " HTTP/1.1\r\n");
            bw.write("HOST:" + url + "\r\n");
            bw.write("\r\n");//HTTP head end!
            bw.flush();
            br = new BufferedReader(new InputStreamReader(socket.getInputStream()));

            String line ;
            while((line = br.readLine())!=null){
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(bw != null){
                try {
                    bw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if (br != null) {
                try {
                    br.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public static void main(String[] args) {
        Crawler crawler = new CrawlerImpl();
        String url = "www.baidu.com";
        crawler.crawler(url);
    }
}

2. 运行结果

到这里，就表明一个通过socket获取网页是成功的。【但是可以仔细发现，返回的结果是一个"​​​https://www.baidu.com/search/error/html​​​"】

但是有时候一不小心，也会得到如下的结果：

可以看到这个是一个请求错误。表示的意思是：在请求报文中存在语法错误。