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ViewsAWS Lambda and S3 - uploaded pdf file is blank
I have a pretty simple function that uploads a PDF file to an AWS S3 (https://codedestine.com/aws-s3-putobject-java/) using AWS Lambda with Amazon API Gateway.
I try to upload a PDF file which has 2 pages with text. After upload, the PDF file(on AWS S3) has 2 blank pages.
This is the method I use to upload the PDF file on AWS S3.
public static void uploadFile2(MultipartFile mpFile, String fileName) throws IOException{
String dirPath = System.getProperty("java.io.tmpdir", "/tmp");
File file = new File(dirPath + "/" + fileName);
OutputStream ops = new FileOutputStream(file);
ops.write(mpFile.getBytes());
s3client.putObject("fakebucketname", fileName, file);
}
Why the uploaded PDF file is blank?
3 answers
Answer question0
Turns out that this will do this trick. Its all about encoding, thanks to the help of @KunLun. In my scenario, file is the multipart file (pdf) that is passed to aws via a POST to the url.
- server gets a file with this byte -> 0010 (this will not be interpreted right, because a standard byte has 8 bits)
- so, we encode it in base 64 -> doesn't matter what result, decode it to get a standard byte -> 0000 0010 (now this is a standard byte and is interpreted right by aws)
- This source here helped a lot as well --> https://www.javaworld.com/article/3240006/base64-encoding-and-decoding-in-java-8.html?page=2
Base64.Encoder enc = Base64.getEncoder();
byte[] encbytes = enc.encode(file.getBytes());
for (int i = 0; i < encbytes.length; i++)
{
System.out.printf("%c", (char) encbytes[i]);
if (i != 0 && i % 4 == 0)
System.out.print(' ');
}
Base64.Decoder dec = Base64.getDecoder();
byte[] barray2 = dec.decode(encbytes);
InputStream fis = new ByteArrayInputStream(barray2);
PutObjectResult objectResult = s3client.putObject("xxx",
file.getOriginalFilename(), fis, data);
Another very important piece to include is that the API Gateway settings must be properly configured to support binary data types. AWS Console --> API Gateway --> Settings --> include what I have below in the attached photo
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You're using an output stream as input to the upload request. Just use File, and include content type, for example:
File file = new File(fileName);
PutObjectRequest request = new PutObjectRequest("bucketname", "keyname", file);
ObjectMetadata metadata = new ObjectMetadata();
metadata.setContentType("application/pdf");
request.setMetadata(metadata);
s3Client.putObject(request);
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When you are uploading files using FORM-DATA from client to server-side, The server will get that file as base64. So, you have to decode it in order to get the actual file to be uploaded to your aws S3 bucket.
Quick reference using nodeJS.
const decodedFile = Buffer.from(<--add your encode base64 file -->, 'base64');
That [const decodedFile] is going to be your value for the {Body} params for s3. You can do the same concept or logic to any programming language out there!
Thank you.