如何使用套接字下载图像[重复]

Posted 2023-02-25

【中文标题】如何使用套接字下载图像[重复]

【英文标题】：How to download an image with Sockets [duplicate]

【发布时间】：2019-01-09 14:46:52

【问题描述】：

所以我正在练习使用 Sockets 从 Web 获取图像。我不确定在存储图像字节然后创建文件时使用哪个类。到目前为止我的代码是：

    import java.io.*;
    import java.net.*;
    import java.awt.image.*;
    import javax.imageio.stream.ImageInputStream;
    import javax.imageio.ImageIO;

    class MyClass
        public static void main(String[] args)throws IOException
            Socket s = new Socket();
            ImageInputStream s_in = null; //I'm not sure about this
            PrintWriter s_out = null;

            try
                s.connect(new InetSocketAddress("data.pr4e.org",80));
                System.out.println("Connected");

                s_out = new PrintWriter(s.getOutputStream(), true);

                s_in = ImageIO.createImageInputStream(s.getInputStream());//nor this
            
            catch (UnknownHostException e)
                System.err.println("Don't know about host");
                System.exit(1);
            

            //Message to server
            String message = "GET http://data.pr4e.org/cover3.jpg HTTP/1.0\r\n\r\n";
            s_out.println(message);

            //This is where it gets confusing
            OutputStream out = null;
            while (true)
            try
            out = new BufferedOutputStream(new 
            FileOutputStream("C:\\Users\\Steff\\Desktop\\Java ejemplos\\cover3.jpg"));
            out.write(s_in.read());
            
            finally
              if(out != null)
              out.close();
             
        
    

【参考方案1】：

我稍微修正了你的代码。它将所有数据保存到文件中。

public static void main(String[] args) throws IOException 
    Socket s = new Socket();
    InputStream s_in = null;
    PrintWriter s_out = null;

    try 
        s.connect(new InetSocketAddress("data.pr4e.org", 80));
        System.out.println("Connected");
        s_out = new PrintWriter(s.getOutputStream(), true);
        s_in = s.getInputStream();
     catch (UnknownHostException e) 
        System.err.println("Don't know about host");
        System.exit(1);
    

    // Message to server
    String message = "GET http://data.pr4e.org/cover3.jpg HTTP/1.0\r\n\r\n";
    s_out.println(message);

    OutputStream out = new BufferedOutputStream(new FileOutputStream("C:\\Users\\Steff\\Desktop\\Java ejemplos\\cover3.jpg"));
    int count;
    byte[] buffer = new byte[4096];
    while ((count = s_in.read(buffer)) > 0) 
        out.write(buffer, 0, count);
    
    out.close();

不幸的是，图像不可读。为什么？因为保存的数据包含整个流以及 HTTP 响应。这就是您在不使用诸如 Apache HttpClient 之类的 HTTP 感知库的情况下使用套接字的结果。您可以使用任何文本编辑器打开文件以查看内容。

如果您确定并想继续使用套接字，请咨询duplicate linked by gtgaxiola。它包含更多代码来处理将标头与实际数据分开的问题。