how to download image from any web page in java 下载图片

(throws IOException)

Image image = null;
try {
    URL url = new URL("http://www.yahoo.com/image_to_read.jpg");
    image = ImageIO.read(url);
} catch (IOException e) {
}

See javax.imageio package for more info. That‘s using the AWT image. Otherwise you could do:

 URL url = new URL("http://www.yahoo.com/image_to_read.jpg");
InputStream in = new BufferedInputStream(url.openStream());
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buf = new byte[1024];
int n = 0;
while (-1!=(n=in.read(buf)))
{
   out.write(buf, 0, n);
}
out.close();
in.close();
byte[] response = out.toByteArray();

And you may then want to save the image so do:

FileOutputStream fos = new FileOutputStream("C://borrowed_image.jpg");
fos.write(response);
fos.close();

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You are looking for a web crawler. You can use JSoup to do this, here is basic example

It works for me)

URL url = new URL("http://upload.wikimedia.org/wikipedia/commons/9/9c/Image-Porkeri_001.jpg");
InputStream in = new BufferedInputStream(url.openStream());
OutputStream out = new BufferedOutputStream(new FileOutputStream("Image-Porkeri_001.jpg"));

for ( int i; (i = in.read()) != -1; ) {
    out.write(i);
}
in.close();
out.close();

If you want to save the image and you know its URL you can do this:

try(InputStream in = new URL("http://example.com/image.jpg").openStream()){
    Files.copy(in, Paths.get("C:/File/To/Save/To/image.jpg"));
}

You will also need to handle the IOExceptions which may be thrown.

The following code downloads an image from a direct link to the disk into the project directory. Also note that it uses try-with-resources.

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.MalformedURLException;
import java.net.URL;

import org.apache.commons.io.FilenameUtils;

public class ImageDownloader
{
    public static void main(String[] arguments) throws IOException
    {
        downloadImage("https://upload.wikimedia.org/wikipedia/commons/7/73/Lion_waiting_in_Namibia.jpg",
                new File("").getAbsolutePath());
    }

    public static void downloadImage(String sourceUrl, String targetDirectory)
            throws MalformedURLException, IOException, FileNotFoundException
    {
        URL imageUrl = new URL(sourceUrl);
        try (InputStream imageReader = new BufferedInputStream(
                imageUrl.openStream());
                OutputStream imageWriter = new BufferedOutputStream(
                        new FileOutputStream(targetDirectory + File.separator
                                + FilenameUtils.getName(sourceUrl)));)
        {
            int readByte;

            while ((readByte = imageReader.read()) != -1)
            {
                imageWriter.write(readByte);
            }
        }
    }
}