Pre-Signed URL (AWS)
Pre-Signed URL (AWS)
pre-signed URL is URL which is used to give access to person for some time with authentication token /Signature and expiry on.it . The user need not have the AWS console Sign in credentials .This URL has Following format query string with
Http url resource + AWSAccessKeyId+ Expires+Signature
AWSAccessKeyId=ACCESSKEYXXXX&Expires=1459944479&Signature=vba%2BH0F0p9b02n2qyhTFY4Bxjkg%3D
Example
https://my-first-s3-bucket-e3ee683e-b260-4aad-923b-31fa838c6a2e.s3.amazonaws.com/PresignedUrlAndUploadObject.txt?AWSAccessKeyId=ACCESSKEYXXXX&Expires=1459897385&Signature=zJhX0CfSnD6QFgD6fzOlfqk%2FsxM%3D
https://my-first-s3-bucket-e3ee683e-b260-4aad-923b-31fa838c6a2e.s3.amazonaws.com/MyObjectKey?AWSAccessKeyId=ACCESSKEYXXXX&Expires=1459879476&Signature=5Bh1AUuF3U5Vjw0Ah7EdojE9XDY%3D
https://my-first-s3-bucket-63529645-5e01-4406-bf85-75ffc0fd00b1.s3.amazonaws.com/PresignedUrlAndUploadObject.txt?AWSAccessKeyId=ACCESSKEYXXXX&Expires=1459879632&Signature=ypaabCtSnztLp%2FpzxjT2ZvMxhkg%3D
https://my-first-s3-bucket-63529645-5e01-4406-bf85-75ffc0fd00b1.s3.amazonaws.com/PresignedUrlAndUploadObject.txt?AWSAccessKeyId=ACCESSKEYXXXX&Expires=1459883171&Signature=VvcDoikAKnnMWAPuVIg18bG3FcE%3D
Sometime Pre-Signed URL gives error downloading the file with below mentioned Message.
<Error><Code>SignatureDoesNotMatch</Code><Message>The request signature we calculated does not match the signature you provided. Check your key and signing method.</Message>
The error is when you send a presigned url which has been created for HTTP PUT to upload a file and you are trying to view the file via Browser .
URL are different for PUT .GET ,….other DELETE etc VERBS
generatePresignedUrlRequest.setMethod(HttpMethod.PUT); This Line has different HttpMethod verbs
So make sure the URL youa re using is for right Verb
To generate a URL for download via browser you have to comment this line
//generatePresignedUrlRequest.setMethod(HttpMethod.PUT);
Aa We knoe pre-signed URL gives you access to the object identified in the URL, provided that the creator of the pre-signed URL has permissions to access that object.
A pre-signed URL can be made for HTTP PUT get or download via browser and all may have different urls
generatePresignedUrlRequest.setMethod(HttpMethod.PUT); This Line has different HttpMethod verbs
where PUT is used to upload file via url HTTP PUT method.
So Its not mandatory to upload an object to get a pre-signed url .
We can get pre-signed url for existing object also in S3 to send it to user to download files from S3 so that they can download file from browser .
It is Something similar to google drive where user shares a link and the link owner can see the File even he does not have google account. GOOGLE DRIVE get shareable link
Example code for generating pre-signed url for existing object also in S3
| Create an instance of the AmazonS3 class. |
| Generate a pre-signed URL by executing the AmazonS3.generatePresignedUrl method.
You provide a bucket name, an object key, and an expiration date by creating an instance of the GeneratePresignedUrlRequest class. You don’t have to specify the HTTP verb PUT when creating this URL as you are not upload an object. |
| Anyone with the pre-signed URL can upload an object.
The upload creates an object or replaces any existing object with the same key that is specified in the pre-signed URL. |
public static String generatepreassignedkeyforexistingfile (String bucketName ,String objectKey) {
AmazonS3 s3client = new AmazonS3Client(new ProfileCredentialsProvider());
Region usWest2 = Region.getRegion( Regions.US_WEST_2
);
s3client.setRegion(usWest2);
URL url = null;
try {
System.out.println(“Generating pre-signed URL.”);
java.util.Date expiration = new java.util.Date();
long milliSeconds = expiration.getTime();
milliSeconds += 1000 * 60 * 60; // Add 1 hour.
expiration.setTime(milliSeconds);
GeneratePresignedUrlRequest generatePresignedUrlRequest =
new GeneratePresignedUrlRequest(bucketName, objectKey);
//generatePresignedUrlRequest.setMethod(HttpMethod.PUT);
generatePresignedUrlRequest.setExpiration(expiration);
url = s3client.generatePresignedUrl(generatePresignedUrlRequest);
System.out.println(“Pre-Signed URL = ” + url.toString());
} catch (AmazonServiceException exception) {
System.out.println(“Caught an AmazonServiceException, ” +
“which means your request made it ” +
“to Amazon S3, but was rejected with an error response ” +
“for some reason.”);
System.out.println(“Error Message: ” + exception.getMessage());
System.out.println(“HTTP Code: ” + exception.getStatusCode());
System.out.println(“AWS Error Code:” + exception.getErrorCode());
System.out.println(“Error Type: ” + exception.getErrorType());
System.out.println(“Request ID: ” + exception.getRequestId());
} catch (AmazonClientException ace) {
System.out.println(“Caught an AmazonClientException, ” +
“which means the client encountered ” +
“an internal error while trying to communicate” +
” with S3, ” +
“such as not being able to access the network.”);
System.out.println(“Error Message: ” + ace.getMessage());
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return “Pre-Signed URL = ” + url.toString();
}
Lets see what can we do from Eclipse UI
so in order to use Eclispe we have to install new software
http://aws.amazon.com/eclipse – http://aws.amazon.com/eclipse
Once you finish this step
you can install explorer view to see s3 bucket and files
Go to explorer view by Show AWS explorer view in AWS toolbar icon
It will ask you for credential for aws console once you place those credentials you can choose your region
and see all your AWS resource
So here we are just talking about S3 but same can be use to create table, Query for Dynamodb also .
So right click on S3 node gives you menu to create new bucket Delete etc
now in this screenshot you can see i went to bucket screen
On click bucket
Developer can open contents of bucket in Open in bucket editor screen
We have another option to upload file
Just drag the file from desktop to the screen and you will see file is getting uploaded to s3 bucket which was mentioned in bucket editor screen
its asking for objectkey wich is filename in this context and it will upload a file
In java you can upload file via these 3 lines
System.out.println(“Uploading a new object to S3 from a file\n”);
s3.putObject(new PutObjectRequest(bucketName, key, SampleFile));
SampleFileis a File object
and
S3 is AmazonS3Client
AmazonS3 s3 = new AmazonS3Client(credentials);
Some code fragments to loop the s3 file and summary are mentioned below to do
the process in java
AWSCredentials credentials = null;
try {
credentials = new ProfileCredentialsProvider(“default”).getCredentials();
} catch (Exception e) {
throw new AmazonClientException(
“Cannot load the credentials from the credential profiles file. ” +
“Please make sure that your credentials file is at the correct ” +
“location (C:\\Users\\Jitender.Thakur\\.aws\\credentials), and is in valid format.”,
e);
}
AmazonS3 s3 = new AmazonS3Client(credentials);
Region usWest2 = Region.getRegion( Regions.US_WEST_2
);
s3.setRegion(usWest2);
- To delete a bucket you have to delete all files in Bucket first .When bucket is Empty delete Bucket
System.out.println(“Listing objects”);
ObjectListing objectListing = s3.listObjects(new ListObjectsRequest()
.withBucketName(bucketName)
);
for (S3ObjectSummary objectSummary : objectListing.getObjectSummaries()) {
System.out.println(” – ” + objectSummary.getKey() + ” ” +
“(size = ” + objectSummary.getSize() + “)”);
//new method
generatepreassignedkeyforexistingfile(bucketName,objectSummary.getKey()) ;
s3.deleteObject(bucketName, key);
}
System.out.println();
then
s3.deleteBucket(bucketName);
- Check all buckets you have
for (Bucket bucket : s3.listBuckets()) {
System.out.println(” – ” + bucket.getName());
}
Creating bucket with check for existing bucket as bucket should be globally unique
try {
credentials = new ProfileCredentialsProvider(“default”).getCredentials();
} catch (Exception e) {
throw new AmazonClientException(
“Cannot load the credentials from the credential profiles file. ” +
“Please make sure that your credentials file is at the correct ” +
“location (C:\\Users\\Jitender.Thakur\\.aws\\credentials), and is in valid format.”,
e);
}
AmazonS3 s3 = new AmazonS3Client(credentials);
Region usWest2 = Region.getRegion(Regions.US_WEST_2);
s3.setRegion(usWest2);
tx = new TransferManager(s3);
private void createAmazonS3Bucket() {
try {
if (tx.getAmazonS3Client().doesBucketExist(bucketName) == false) {
tx.getAmazonS3Client().createBucket(bucketName);
}
} catch (AmazonClientException ace) {
// JOptionPane.showMessageDialog(frame, “Unable to create a new Amazon S3 bucket: ” + ace.getMessage(),
// “Error Creating Bucket”, JOptionPane.ERROR_MESSAGE);
}
}