How to Upload Files to S3 Server using Apex

Uploading and Reading files from AWS S3 server is one of frequently used requirement in Salesforce project.  This post will give complete detail, how to write files of current record to S3 Server using Apex.

Important information about writing file to S3 Server.

1. We require Write permission on bucket
2. If multiple files with same name saved on destination, then it will override last uploaded file.
3. Use Content-MD5 for transport security
4. We can use AWS inbuild encryption or custom encryption logic also work while writing file to S3 server
5. We should provide access level permission on files using request headers.  By default files will be saved as private.
6.  We can do versioning of file.  If required, enable versioning on S3 server bucket.

Required request parameter

1. 1. Content-Type: This is required as it describe content type like PDF, JPEG, JPG etc. See method ContentType in below code.
   2. Content-Length: This specify size of body in bytes. Ideally it is determined automatically but if automatic size determination does not work, specify this piece.
   3. Host :  It will contain information about your bucket name and region information on S3 Server.Value pattern is : {bucketName}.S3.{regionName}.amazonaws.com 
   4. Content-Encoding: This parameter store information about what content encoding is used to store file. So that same will be applied when reading files.
   5. ACL: Access-Control-List will provide access to object after uploading in S3 server. Example – public-read, public-read-write. 
   6. Endpoint: It is file url in S3 bucket
   7. Authorization:  Authorization detail to write file in S3 server. See method CreateAuthHeader in code.

Reading files in Apex:

To upload files in S3 Server, We have to first read it from ContentVersion object. ContentVersion object is holding files content and ContentDocumentLink has file sharing detail.  To get content of files we have to first get content document from ContentDocumentLink object and then we can get file content using ContentVersion object.

   List links=[SELECT ContentDocumentId,LinkedEntityId FROM ContentDocumentLink where LinkedEntityId=:recordId];
        Set ids=new Set();
        for(ContentDocumentLink link:links)
        {
            ids.add(link.ContentDocumentId);
        }
        List versions=[SELECT VersionData,Title,ContentDocumentId,FileExtension FROM ContentVersion WHERE ContentDocumentId = :ids AND IsLatest = true];
        
        for(ContentVersion attach:versions)
        {
         .....
        }

Complete Code:

Exception class for custom exception in your code.

BaseException class code

Now our code is ready. Let us use above AWSService using controller by passing S3 credential.

S3Controller Class Code

This S3Controller class can be used by any caller like Lightning Component, Lightning Web Component, another apex class.

Reference:

AWS Documentation: https://docs.aws.amazon.com/AmazonS3/latest/API/API_PutObject.html