如何知道對象是否已經完全上傳到amazon s3？

Question

我們如何檢查一個對象是否已經完全上傳到Amazon s3？我正在將圖像上傳到Android應用程序的s3，然後調用lambda函數。我想確保在我調用lambda之前將對象上傳到s3。目前大文件上傳正在產生問題。

Answer 1

而不是上傳對象到Amazon S3後調用一個AWS LAMBDA功能，只需配置S3存儲觸發拉姆達本身：

這樣，功能纔會被觸發時該對象已成功上傳到S3，並且您的應用程序的工作量較少。

參見：Using AWS Lambda with Amazon S3

（哦，如果你真的想分開做，那麼你可以使用ETag，其中MD5校驗，確認爲預計該文件已被上傳）

Answer 2

您可以使用PutObjectResult進行檢查響應表明該對象已成功存儲。 Amazon S3從不存儲部分對象：如果您收到成功的響應，則可以確信整個對象已存儲。所以主要參與者是MD5算法，通過這種算法，您可以確認您想要上傳的對象是否與上傳的對象相同，爲了讓您知道任何文檔的MD5值，可以說它是可以使用的圖像下面找到這麼

` package aws.example.s3; 

    import java.io.File; 
    import java.io.FileInputStream; 
    import java.io.IOException; 
    import java.security.MessageDigest; 
    import java.security.NoSuchAlgorithmException; 

    public class MD5demo { 
     public static String MD5check(String path){ 
     // TODO Auto-generated method stub 
     //Create checksum for this file 
     File file = new File(path); 

     //Get the checksum 
     String checksum="null"; 
     try { 
      //Use MD5 algorithm 
      MessageDigest md5Digest; 
      try { 
       md5Digest = MessageDigest.getInstance("MD5"); 
       checksum = getFileChecksum(md5Digest, file); 
       //see checksum 
       //System.out.println("Checksum: "+checksum); 
      } catch (NoSuchAlgorithmException e) { 
       // TODO Auto-generated catch block 
       e.printStackTrace(); 
      } 
     }catch (IOException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     } 
     return checksum; 

    } 

    private static String getFileChecksum(MessageDigest digest, File file) 
    throws IOException 
    { 
     //Get file input stream for reading the file content 
     FileInputStream fis = new FileInputStream(file); 

     //Create byte array to read data in chunks 
     byte[] byteArray = new byte[1024]; 
     int bytesCount = 0; 

     //Read file data and update in message digest 
     while ((bytesCount = fis.read(byteArray)) != -1) { 
      digest.update(byteArray, 0, bytesCount); 
     }; 

     //close the stream; We don't need it now. 
     fis.close(); 

     //Get the hash's bytes 
     byte[] bytes = digest.digest(); 

     //This bytes[] has bytes in decimal format; 
     //Convert it to hexadecimal format 
     StringBuilder sb = new StringBuilder(); 
     for(int i=0; i< bytes.length ;i++) 
     { 
      sb.append(Integer.toString((bytes[i] & 0xff) + 0x100, 
     16).substring(1)); 
     } 

     //return complete hash 
     return sb.toString(); 
     } 
}` 

所以，你只需要通過在MD5check（字符串路徑）的文件路徑，它將返回的MD5值現在

，在你的課堂，你正在寫的代碼上傳任何文檔，只需使用下面的代碼

PutObjectResult putObjectResult = null; 
    try { 
      putObjectResult = s3.putObject(new PutObjectRequest(<Enter your Bucket name here>, <KeyName> , <pass your file object here>)); 

      String MD5=MD5check(<pls enter your file path here>); //you can pass your file also directly, for that please change the method implementation of MD5Demo class accepting a file instead of path 

      System.out.println("Etag: "+putObjectResult.getETag()); //getting the Etag which is nothing but same as MD5 value of the file that got uploaded in S3 
      System.out.println("MD5: "+MD5); 

      if(MD5==putObjectResult.getETag()) { 
       System.out.println("Congrats!! Document Uploaded Successfully"); 
      }else { 
       System.out.println("Sorry! Could not upload the document"); 
      } 

H操作它有幫助，請讓我知道如果您有任何建議:)