摘要：在这篇文章中，我们将了解如何从java中的URL下载文件。当您想要使用java从URL自动下载任何文件时，可以使用它。

有很多方法可以做到这一点，其中一些是：

Java Program:

package cn.micai.io;

import org.apache.commons.io.FileUtils;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URL;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;

/**
 * 描述：How to download file from URL in java
 * <p>
*    Using Java input output stream
     Using apache common IO
     Using NIO
 *
 * @author: 赵新国
 * @date: 2018/6/7 10:15
 */
public class FileDownloadFromURLMain {

    public static void main(String [] args) {

        String dirName = "D://";

        System.out.println("---------------------------");
        System.out.println("Downloading file from github using java file IO");

        // Using java IO
        downloadFileFromUrlWithJavaIO(dirName + "/sampleFile1.zip",
                "https://github.com/arpitmandliya/SpringRestfulWebServicesWithJSONExample/archive/master.zip");

        System.out.println("Downloaded file from github using java file IO");
        System.out.println("---------------------------");

        System.out.println("Downloading file from github using apache common IO");
        // Using Apache common IO
        downloadFileFromUrlWithCommonsIO(dirName + "/sampleFile2.zip",
                "https://github.com/arpitmandliya/SpringRestfulWebServicesWithJSONExample/archive/master.zip");
        System.out.println("Downloaded file from github using apache common IO");
        System.out.println("---------------------------");

        System.out.println("Downloading file from github using NIO");
        // Using NIO
        downloadFileFromURLUsingNIO(
                dirName + "/sampleFile3.zip",
                "https://github.com/arpitmandliya/SpringRestfulWebServicesWithJSONExample/archive/master.zip");
        System.out.println("Downloaded file from github using NIO");
        System.out.println("---------------------------");

    }

    // Using Java IO
    private static void downloadFileFromUrlWithJavaIO(String fileName, String fileUrl) {
        BufferedInputStream inputStream = null;
        FileOutputStream outputStream = null;
        try {
            URL url = new URL(fileUrl);
            inputStream = new BufferedInputStream(url.openStream());
            outputStream = new FileOutputStream(fileName);

            byte data[] = new byte[1024];
            int count;
            while ((count = inputStream.read(data, 0, 1024)) != -1) {
                outputStream.write(data, 0, count);
            }

        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (inputStream != null) {
                    inputStream.close();
                }
                if (outputStream != null) {
                    outputStream.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    // Using Apache common IO
    private static void downloadFileFromUrlWithCommonsIO(String fileName, String fileUrl) {
        try {
            FileUtils.copyURLToFile(new URL(fileUrl), new File(fileName));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // Using NIO
    private static void downloadFileFromURLUsingNIO(String fileName, String fileUrl) {
        try {
            URL url = new URL(fileUrl);
            ReadableByteChannel readableByteChannel = Channels.newChannel(url.openStream());
            FileOutputStream fileOutputStream = new FileOutputStream(fileName);
            fileOutputStream.getChannel().transferFrom(readableByteChannel, 0, Long.MAX_VALUE);
            fileOutputStream.close();
            readableByteChannel.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

当您运行上述程序时，文件将被下载到上述目录中。您将得到以下输出：

How to download file from URL in java_java

How to download file from URL in java_download file_02