Java – How to download a file from the Internet
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2022-06-10 09:40:07
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参考链接:https://www.mkyong.com/java/java-how-to-download-a-file-from-the-internet/
1、Apache Commons IO
2、Java NIO
3、多线程下载文件
1、Apache Commons IO
<dependency> <groupId>commons-io</groupId> <artifactId>commons-io</artifactId> <version>2.5</version> </dependency>
String fromFile = "ftp://ftp.arin.net/pub/stats/arin/delegated-arin-extended-latest"; String toFile = "F:\\arin.txt"; try { // connectionTimeout, readTimeout = 10 seconds FileUtils.copyURLToFile(new URL(fromFile), new File(toFile), 10000, 10000); } catch (IOException e) { e.printStackTrace(); }
2、Java NIO
String fromFile = "https://download-cf.jetbrains.com/idea/ideaIU-2018.1.6.win.zip"; String toFile = "F:\\IDEA\\ideaIU-2018.1.6.win.zip"; try { URL website = new URL(fromFile); ReadableByteChannel rbc = Channels.newChannel(website.openStream()); FileOutputStream fos = new FileOutputStream(toFile); fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE); fos.close(); rbc.close(); System.out.println("---------success----------------"); } catch (IOException e) { e.printStackTrace(); }
static final String FILE_URL = "https://download-cf.jetbrains.com/idea/ideaIU-2018.1.6.exe"; static final String FILE_NAME = "F:\\IDEA\\ideaIU-2018.1.6.exe"; public static void main(String[] args) throws Exception { javaIO(); } static void javaIO() { try (BufferedInputStream in = new BufferedInputStream(new URL(FILE_URL).openStream()); FileOutputStream fileOutputStream = new FileOutputStream(FILE_NAME)) { byte dataBuffer[] = new byte[1024]; int bytesRead; while ((bytesRead = in.read(dataBuffer, 0, 1024)) != -1) { System.out.println("read >" + bytesRead); fileOutputStream.write(dataBuffer, 0, bytesRead); } } catch (IOException e) { // handle exception } }
3、多线程下载文件
package net.liuzidong.download; import java.io.InputStream; import java.io.RandomAccessFile; import java.net.HttpURLConnection; import java.net.URL; /** * 多线程下载文件 */ public class DownloadUtil { // 定义成员变量 private String path; // 远程资源路径 private String targetPath; // 本地存储路径 private DownFileThread[] threads; // 线程list private int threadNum; // 线程数量 private long length; // 下载的文件大小 // 构造初始化 public DownloadUtil(String path, String targetPath, int threadNum) { super(); this.path = path; this.targetPath = targetPath; this.threads = new DownFileThread[threadNum]; this.threadNum = threadNum; } // 多线程下载文件资源 public void download() { URL url; try { url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setReadTimeout(5 * 1000); // 设置超时时间为5秒 conn.setRequestMethod("GET"); conn.setRequestProperty("connection", "keep-alive"); conn.setRequestProperty("accept", "*/*"); // 获取远程文件的大小 length = conn.getContentLength(); conn.disconnect(); // 设置本地文件大小 RandomAccessFile targetFile = new RandomAccessFile(targetPath, "rw"); targetFile.setLength(length); // 每个线程下载大小 long avgPart = length / threadNum + 1; // 下载文件 for (int i = 0; i < threadNum; i++) { long startPos = avgPart * i; RandomAccessFile targetTmp = new RandomAccessFile(targetPath, "rw"); targetTmp.seek(startPos); // 分段下载 threads[i] = new DownFileThread(startPos, targetTmp, avgPart); threads[i].start(); } } catch (Exception e) { e.printStackTrace(); } } // 监控下载进度 public double getDownRate() { int currentSize = 0; for (int i = 0; i < threadNum; i++) { currentSize += threads[i].length; } return currentSize * 1.0 / length; } // 定义线程类 class DownFileThread extends Thread { private long startPos; private RandomAccessFile raf; private long size; private long length; public DownFileThread(long startPos, RandomAccessFile raf, long size) { super(); this.startPos = startPos; this.raf = raf; this.size = size; } public void run() { URL url; try { url = new URL(path); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setReadTimeout(5 * 1000); // 设置超时时间为5秒 conn.setRequestMethod("GET"); conn.setRequestProperty("connection", "keep-alive"); conn.setRequestProperty("accept", "*/*"); InputStream in = conn.getInputStream(); in.skip(this.startPos); byte[] buf = new byte[1024]; int hasRead = 0; while (length < size && (hasRead = in.read(buf)) != -1) { raf.write(buf, 0, hasRead); length += hasRead; } raf.close(); in.close(); } catch (Exception e) { e.printStackTrace(); } } } // 测试 public static void main(String[] args) { String path = "http://ftp.jaist.ac.jp/pub/eclipse/technology/epp/downloads/release/photon/R/eclipse-jee-photon-R-win32-x86_64.zip"; String targetPath = "F:\\download\\eclipse\\eclipse-jee-photon-R-win32-x86_64.zip"; final DownloadUtil download = new DownloadUtil(path, targetPath, 3); download.download(); System.out.println("开始下载..."); // 主线程负责下载文件,在启动一个线程负责监控下载的进度 new Thread(new Runnable() { @Override public void run() { while (download.getDownRate() < 1) { try { Thread.sleep(2000); // 200毫秒扫描一次 } catch (InterruptedException e) { e.printStackTrace(); } } System.out.println("下载完成..."); } }).start(); } }
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