How to download file from URL in java

以你之姓@ 2024-02-18 20:57 27阅读 0赞

**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：

*  Using Java input output stream
 *  Using [apache common IO][]
 *  Using NIO

#### 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：

![20180607104519773][]

![20180607104554458][]

[apache common IO]: http://commons.apache.org/proper/commons-io/
[20180607104519773]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/fbd7a79d73a74a469c954b63eeb2f564.png
[20180607104554458]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/f8612b081cfe43f5b149bb06adf77848.png