AWS CDK SSM: A construct for accessing SSM values from a stack as Cloud Formation tokens to resolve on deploy.

construct.ts

import { Construct } from 'constructs'
import { aws_ssm as SSM } from 'aws-cdk-lib'

/**
 * Create a resource for accessing SSM values (as Cloud Formation tokens to resolve on deploy).
 */
export class ParamsConstruct extends Construct {
  private configPath: string
  private secretPath?: string

  constructor (scope: Construct, id: string, options: { configPath: string, secretPath?: string }) {
    super(scope, id)
    this.configPath = options.configPath
    this.secretPath = options.secretPath
  }

  config (key: string) {
    return SSM.StringParameter.valueForStringParameter(this, `${this.configPath}/${key}`)
      .toString()
  }

  secret (key: string) {
    return SSM.StringParameter.fromSecureStringParameterAttributes(this, key, {
      parameterName: `${this.secretPath}/${key}`
    }).stringValue
  }
}

example.ts

import { App, Stack, StackProps } from 'aws-cdk-lib'
import { Construct } from 'constructs'
import { ParamsConstruct } from './construct'

const app = new App()

class ExampleStack extends Stack {
  constructor(scope: Construct, id: string, props: StackProps = {}) {
    super(scope, id, props)

    //... add construct here to define SSM params
    
    const configPath = `/my-app/config`
    const secretPath = `/my-app/secret`
    const params = new ParamsConstruct(this, 'TestParams', { configPath, secretPath })
    
    console.log('My config token', params.config('MY_CONFIG'))
    console.log('My secret token', params.secret('MY_SECRET'))
  }
}

new ExampleStack(app, 'TestStack')