java下載網路檔案的N種方式

通過java api下載網路檔案的方法有很多，主要方式有以下幾種：

1、使用 common-io庫下載檔案，需要引入commons-io-2.6.jar

public static void downloadByCommonIO(String url, String saveDir, String fileName) {
  try {
    FileUtils.copyURLToFile(new URL(url), new File(saveDir, fileName));
   } catch (IOException e) {
    e.printStackTrace();
   }
}
 

2、使用NIO下載檔案，需要 jdk 1.4+

public static void downloadByNIO(String url, String saveDir, String fileName) {
  ReadableByteChannel rbc = null;
  FileOutputStream fos = null;
  FileChannel foutc = null;
  try {
    rbc = Channels.newChannel(new URL(url).openStream());
    File file = new File(saveDir, fileName);
    file.getParentFile().mkdirs();
    fos = new FileOutputStream(file);
    foutc = fos.getChannel();
    foutc.transferFrom(rbc, 0, Long.MAX_VALUE);
​
   } catch (IOException e) {
    e.printStackTrace();
   } finally {
    if (rbc != null) {
      try {
        rbc.close();
       } catch (IOException e) {
        e.printStackTrace();
       }
     }
    if (foutc != null) {
      try {
        foutc.close();
       } catch (IOException e) {
        e.printStackTrace();
       }
     }
   }
​
}
 

3、使用NIO下載檔案，需要 jdk 1.7+

public static void downloadByNIO2(String url, String saveDir, String fileName) {
  try (InputStream ins = new URL(url).openStream()) {
    Path target = Paths.get(saveDir, fileName);
    Files.createDirectories(target.getParent());
    Files.copy(ins, target, StandardCopyOption.REPLACE_EXISTING);
   } catch (IOException e) {
    e.printStackTrace();
   }
}
 

4、使用傳統io stream下載檔案

public static void downloadByIO(String url, String saveDir, String fileName) {
  BufferedOutputStream bos = null;
  InputStream is = null;
  try {
    byte[] buff = new byte[8192];
    is = new URL(url).openStream();
    File file = new File(saveDir, fileName);
    file.getParentFile().mkdirs();
    bos = new BufferedOutputStream(new FileOutputStream(file));
    int count = 0;
    while ((count = is.read(buff)) != -1) {
      bos.write(buff, 0, count);
     }
   } catch (IOException e) {
    e.printStackTrace();
   } finally {
    if (is != null) {
      try {
        is.close();
       } catch (IOException e) {
        e.printStackTrace();
       }
     }
    if (bos != null) {
      try {
        bos.close();
       } catch (IOException e) {
        e.printStackTrace();
       }
     }
   }
}

5、使用Byte Array獲得stream下載檔案

public static void downLoadFromUrl(String urlStr,String fileName,String savePath) throws IOException{
  URL url = new URL(urlStr); 
  HttpURLConnection conn = (HttpURLConnection)url.openConnection(); 
  //設定超時間為5秒
  conn.setConnectTimeout(5*1000);
  //防止遮蔽程式抓取而返回403錯誤
  conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");
​
  //得到輸入流
  InputStream input = conn.getInputStream(); 
  //獲取自己陣列
  byte[] getData = readInputStream(input);  
​
  //檔案儲存位置
  File saveDir = new File(savePath);
  if(!saveDir.exists()){
    saveDir.mkdir();
   }
  File file = new File(saveDir+File.separator+fileName);  
  FileOutputStream output = new FileOutputStream(file);   
  output.write(getData); 
  if(output!=null){
    output.close(); 
   }
  if(input!=null){
    input.close();
   }
  System.out.println("download success!!");
}
​
public static byte[] readInputStream(InputStream inputStream) throws IOException { 
  byte[] buffer = new byte[10240]; 
  int len = 0; 
  ByteArrayOutputStream bos = new ByteArrayOutputStream(); 
  while((len = inputStream.read(buffer)) != -1) { 
    bos.write(buffer, 0, len); 
   } 
  bos.close(); 
  return bos.toByteArray(); 
}

轉載自：java下載網路檔案的N種方式 - Jaywen - 部落格園 (cnblogs.com)