I tried to read a file from AWS s3 to my java code:
File file = new File("s3n://mybucket/myfile.txt");
FileInputStream fileInput = new FileInputStream(file);
Then I got an error:
java.io.FileNotFoundException: s3n:/mybucket/myfile.txt (No such file or directory) at java.io.FileInputStream.open(Native Method) at java.io.FileInputStream.(FileInputStream.java:146)
Is there a way to open/read a file from AWS s3? Thanks a lot!
The 'File' class from Java doesn't understand that S3 exists. Here's an example of reading a file from the AWS documentation :
AmazonS3 s3Client = new AmazonS3Client(new ProfileCredentialsProvider());
S3Object object = s3Client.getObject(new GetObjectRequest(bucketName, key));
InputStream objectData = object.getObjectContent();
// Process the objectData stream.
objectData.close();
In 2019 there's a bit more optimal way to read a file from S3:
private final AmazonS3 amazonS3Client = AmazonS3ClientBuilder.standard().build();
private Collection<String> loadFileFromS3() {
try (final S3Object s3Object = amazonS3Client.getObject(BUCKET_NAME,
FILE_NAME);
final InputStreamReader streamReader = new InputStreamReader(s3Object.getObjectContent(), StandardCharsets.UTF_8);
final BufferedReader reader = new BufferedReader(streamReader)) {
return reader.lines().collect(Collectors.toSet());
} catch (final IOException e) {
log.error(e.getMessage(), e)
return Collections.emptySet();
}
}
Steps to read S3 file in java can be:
1 >>>
BasicAWSCredentials awsCreds = new BasicAWSCredentials("accessKey", "secretKey");
AmazonS3 s3Client = AmazonS3ClientBuilder.standard()
.withCredentials(new AWSStaticCredentialsProvider(awsCreds))
.withRegion("region_name_here").build();
2 >>>
S3Object object = s3Client.getObject(new GetObjectRequest("bucketName", "key"));
3 >>>
BufferedReader reader = new BufferedReader(new InputStreamReader(object.getObjectContent()));
String s = null;
while ((s = reader.readLine()) != null)
{
System.out.println(s);
//your business logic here
}
Thanks.
If the file's content is a string, then you can use getObjectAsString . Otherwise, you can use IOUtils.toByteArray on getObjectContent()
to read the file's content into a byte array.
Obviously, these are best used on small-ish S3 objects that will easily fit into memory.
private final AmazonS3 amazonS3Client = AmazonS3ClientBuilder.standard().build();
private String loadStringFromS3() {
try {
return amazonS3Client.getObjectAsString(BUCKET_NAME, FILE_NAME);
} catch (final IOException e) {
log.error(e.getMessage(), e)
return null;
}
}
private byte[] loadDataFromS3() {
try (final S3Object s3Object = amazonS3Client.getObject(BUCKET_NAME, FILE_NAME)) {
return IOUtils.toByteArray(s3Object.getObjectContent());
} catch (final IOException e) {
log.error(e.getMessage(), e)
return null;
} finally {
IOUtils.closeQuietly(object, log);
}
}
We can also use software.amazon.awssdk:s3
//Assuming the credentials are read from Environment Variables, so no hardcoding here
S3Client client = S3Client.builder()
.region(regionSelected)
.build();
GetObjectRequest getObjectRequest = GetObjectRequest.builder()
.bucket(bucketName)
.key(fileName)
.build();
ResponseInputStream<GetObjectResponse> responseInputStream = client.getObject(getObjectRequest);
InputStream stream = new ByteArrayInputStream(responseInputStream.readAllBytes());
System.out.println("Content :"+ new String(responseInputStream.readAllBytes(), StandardCharsets.UTF_8));
This is my solution. I'm using spring boot 2.4.3
Create an amazon s3 client
AmazonS3 amazonS3Client = AmazonS3ClientBuilder
.standard()
.withRegion("your-region")
.withCredentials(
new AWSStaticCredentialsProvider(
new BasicAWSCredentials("your-access-key", "your-secret-access-key")))
.build();
Create an amazon transfer client .
TransferManager transferManagerClient = TransferManagerBuilder.standard()
.withS3Client(amazonS3Client)
.build();
Create a temporary file in /tmp/{your-s3-key} so that we can put the file we download in this file.
File file = new File(System.getProperty("java.io.tmpdir"), "your-s3-key");
try {
file.createNewFile(); // Create temporary file
} catch (IOException e) {
e.printStackTrace();
}
file.mkdirs(); // Create the directory of the temporary file
Then, we download the file from s3 using transfer manager client
// Note that in this line the s3 file downloaded has been transferred in to the temporary file that we created
Download download = transferManagerClient.download(
new GetObjectRequest("your-s3-bucket-name", "your-s3-key"), file);
// This line blocks the thread until the download is finished
download.waitForCompletion();
Now that the s3 file has been successfully transferred into the temporary file that we created. We can get the InputStream of the temporary file .
InputStream input = new DataInputStream(new FileInputStream(file));
Because the temporary file is not needed anymore, we just delete it.
file.delete();
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