How to Import Existing Resources in AWS CDK

Importing Existing Resources in CDK #

In order to import existing resources in CDK we have to use the static fromResource* methods on the resource's construct, for instance:

• the S3 Bucket construct exposes the fromBucketArn, fromBucketName and fromBucketAttributes static methods

• the Dynamodb Table construct exposes the fromTableArn, fromTableName and fromTableAttributes static methods

• the Lambda Function construct exposes the fromFunctionArn, fromFunctionAttributes static methods

As a general rule of thumb, we use the fromResourceName and fromResourceArn methods unless we don't have access to the name or ARN of the resource, in which case we use the fromResourceAttributes method.

To import an existing bucket by name into a CDK stack we can use the fromBucketName static method:

const existingBucketFromName = s3.Bucket.fromBucketName(
  this,
  'bucket-from-name-id',
  'YOUR_BUCKET_NAME',
);

console.log('existingBucketFromName 👉 ', existingBucketFromName.bucketName);

If I now execute the cdk synth command we can see that the value is resolved at synthesis time:

To import an existing bucket by ARN we can use the fromBucketArn static method:

const existingBucketFromArn = s3.Bucket.fromBucketArn(
  this,
  'bucket-from-arn-id',
  'YOUR_BUCKET_ARN',
);

And to import an existing bucket from Attributes, we use the fromBucketAttributes static method:

const existingBucketFromAttributes = s3.Bucket.fromBucketAttributes(
  this,
  'bucket-from-attributes-id',
  {
    region: 'us-east-1',
    bucketArn: 'arn:aws:s3:::YOUR_BUCKET_NAME',
  },
);

All of the above methods resolve at synthesis time.

Most Level 2 Constructs implement at least 2 of the 3 fromResource* methods.

For example, to import an existing Dynamodb table by name, we have to use the fromTableName static method:

const existingTableFromName = dynamodb.Table.fromTableName(
  this,
  'table-from-name-id',
  'YOUR_TABLE_NAME',
);

console.log('existingTableFromName 👉 ', existingTableFromName.tableName);

The value again resolves at synthesis time:

To import an existing table from ARN we have to use the fromFunctionArn static method:

const existingTableFromArn = dynamodb.Table.fromTableArn('YOUR_TABLE_ARN');

And to import an existing table from attributes we have to use the fromTableAttributes static method:

const existingTableFromAttributes = dynamodb.Table.fromTableAttributes(
  this,
  'table-from-attributes-id',
  {
    tableName: 'YOUR_TABLE_NAME',
  },
);

It's quite repetitive once we know what the naming convention of the methods is.

Most of the time we end up using the fromResourceName and fromResourceArn methods, and resort to using fromResourceAttributes when we don't have the name or the ARN of the resource.

Further Reading #

• AWS CDK Tutorial for Beginners - Step-by-Step Guide
• How does AWS CDK work
• What is a Token in AWS CDK
• CDK Constructs - Complete Guide
• What is an identifier (id) in AWS CDK
• How to use Context in AWS CDK
• How to use Parameters in AWS CDK