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name s3sdk
description Use this skill when working with Amazon S3 (or S3-compatible storage) in ColdBox/BoxLang using the s3sdk module. Covers injection, bucket operations, object upload/download/delete, presigned URLs, metadata, ACLs, multipart uploads, and integration with cbfs or direct usage.
applyTo **/*.{bx,cfc,cfm,bxm}

S3SDK Skill

When to Use This Skill

Load this skill when:

  • Uploading files to Amazon S3 or S3-compatible storage (MinIO, DigitalOcean Spaces, Backblaze)
  • Generating presigned URLs for time-limited public or private file access
  • Listing, copying, moving, or deleting S3 objects or buckets
  • Setting object metadata, ACLs, or storage class
  • Implementing large-file multipart uploads

Installation

box install s3sdk

Configuration

config/modules/s3sdk.cfc

function configure() {
    return {
        accessKey      : getSystemSetting( "S3_ACCESS_KEY_ID",     "" ),
        secretKey      : getSystemSetting( "S3_SECRET_ACCESS_KEY", "" ),
        region         : getSystemSetting( "S3_REGION",            "us-east-1" ),
        // For S3-compatible providers set a custom host:
        awsDomain      : getSystemSetting( "S3_ENDPOINT", "s3.amazonaws.com" ),
        ssl            : true,
        defaultBucket  : getSystemSetting( "S3_BUCKET", "my-app-bucket" ),
        signatureType  : "v4",
        throwOnError   : true
    }
}

Core API

Injection

property name="s3" inject="AmazonS3@s3sdk";

Object Operations

// Upload from a file path
s3.putObject(
    bucketName   = "my-bucket",
    uri          = "uploads/profile-#userId#.jpg",
    filePath     = expandPath( "/tmp/upload.jpg" ),
    contentType  = "image/jpeg",
    acl          = "private"
)

// Upload binary/string content
s3.putObject(
    bucketName  = "my-bucket",
    uri         = "reports/#reportId#.json",
    data        = serializeJSON( reportData ),
    contentType = "application/json"
)

// Download to file
s3.getObjectSave(
    bucketName = "my-bucket",
    uri        = "uploads/document.pdf",
    destFile   = expandPath( "/tmp/document.pdf" )
)

// Get as binary
var bytes = s3.getObject( bucketName = "my-bucket", uri = "uploads/file.png" )

// Check existence
var exists = s3.objectExists( bucketName = "my-bucket", uri = "uploads/file.png" )

// Delete
s3.deleteObject( bucketName = "my-bucket", uri = "uploads/old-file.png" )

// Copy
s3.copyObject(
    fromBucket = "my-bucket",
    fromURI    = "uploads/original.jpg",
    toBucket   = "my-bucket",
    toURI      = "processed/thumb.jpg"
)

// List objects
var objects = s3.getBucket( bucketName = "my-bucket", prefix = "uploads/" )

Presigned URLs

// Presigned GET URL — expires in 15 minutes
var url = s3.getAuthenticatedURL(
    bucketName = "my-bucket",
    uri        = "private/document-#rc.id#.pdf",
    minutesValid = 15,
    method       = "GET"
)

// Presigned PUT URL — for direct browser uploads
var putUrl = s3.getAuthenticatedURL(
    bucketName   = "my-bucket",
    uri          = "uploads/user-#userId#/#createUUID()#.jpg",
    minutesValid = 5,
    method       = "PUT"
)

Metadata

var meta = s3.getObjectInfo(
    bucketName = "my-bucket",
    uri        = "uploads/file.pdf"
)
// meta.content-type, meta.content-length, meta.last-modified, meta.etag

s3.putObject(
    bucketName  = "my-bucket",
    uri         = "uploads/doc.pdf",
    filePath    = filePath,
    metaHeaders = {
        "x-amz-meta-uploaded-by" : userId,
        "x-amz-meta-original-name" : originalFileName
    }
)

Production Patterns

File Upload Handler

function upload( event, rc, prc ) {
    var uploadedFile = event.getHTTPContent()
    var mimeType     = event.getHTTPHeader( "Content-Type" )
    var allowedTypes = [ "image/jpeg", "image/png", "application/pdf" ]

    // Validate MIME type
    if ( !allowedTypes.find( mimeType ) ) {
        return event.renderData(
            type       = "json",
            statusCode = 415,
            data       = { error: "Unsupported file type" }
        )
    }

    var key = "uploads/#security.getCurrentUser().getId()#/#createUUID()#"
    // Append safe extension based on MIME
    key &= ( mimeType == "application/pdf" ? ".pdf" : ".jpg" )

    s3.putObject(
        bucketName  = "my-bucket",
        uri         = key,
        data        = uploadedFile,
        contentType = mimeType,
        acl         = "private"
    )

    event.renderData( type = "json", statusCode = 201, data = {
        key : key,
        url : s3.getAuthenticatedURL( "my-bucket", key, 60 )
    } )
}

Serve Private File via Presigned URL

function download( event, rc, prc ) {
    var file = fileService.getOrFail( rc.id )

    // Verify user can access this file
    if ( file.getUserId() != security.getCurrentUser().getId() ) {
        security.secure( "admin" )
    }

    var url = s3.getAuthenticatedURL(
        bucketName   = "my-bucket",
        uri          = file.getS3Key(),
        minutesValid = 5,
        method       = "GET"
    )

    relocate( url )
}

Cleanup Old Files

function purgeOldUploads() {
    var cutoff  = dateAdd( "d", -30, now() )
    var objects = s3.getBucket( bucketName = "my-bucket", prefix = "temp/" )

    for ( var obj in objects ) {
        if ( obj.lastModified < cutoff ) {
            s3.deleteObject( bucketName = "my-bucket", uri = obj.key )
        }
    }
}

Best Practices

  • Store credentials in environment variables — never hardcode access keys in source
  • Use acl = "private" for user uploads — only generate presigned URLs for access
  • Validate MIME type server-side before accepting uploads — do not trust client-provided Content-Type
  • Generate a random key/UUID for each upload — never use user-supplied filenames directly (path traversal risk)
  • Set short expiry on presigned GET URLs (≤15 min for sensitive files)
  • Use presigned PUT URLs for direct browser uploads — avoids routing large files through your server
  • Namespace keys by user ID (uploads/{userId}/{uuid}) to enable easy per-user cleanup
  • Enable S3 server-side encryption (x-amz-server-side-encryption: AES256) for sensitive data

Documentation