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Using Libraries

In this guide, you'll learn how to use DBOS library functions. Examples will be based on @dbos-inc/communicator-email-ses, a DBOS library for sending emails using AWS Simple Email Service.

Installing and Importing a Library​

First, install the library.

npm install @dbos-inc/communicator-email-ses

Second, import the key classes from the library for use in your source files:

import { SendEmailCommunicator } from "@dbos-inc/communicator-email-ses";

Calling Simple Functions​

Libraries such as @dbos-inc/communicator-bcrypt or @dbos-inc/communicator-datetime are comprised of functions that can be invoked from their classes. Using the context (named ctx below), the invoke method can be used to call the library function:

ctx.invoke(BcryptCommunicator).bcryptHash('myString');

Working With Configured Classes​

While libraries such as @dbos-inc/communicator-bcrypt or @dbos-inc/communicator-datetime have simple functions that can be called directly from their classes, more complex DBOS libraries use "configured instances" so that they can be used in multiple scenarios within the same application. To create and configure an instance:

import { configureInstance } from "@dbos-inc/dbos-sdk";
import { SendEmailCommunicator } from "@dbos-inc/communicator-email-ses";

const sesMailer = configureInstance(SendEmailCommunicator, 'marketing', {awscfgname: 'marketing_email_aws_config'});

Note that the configureInstance call above serves multiple purposes:

  • Creates an instance of SendEmailCommunicator
  • Provides the instance with enough information to find essential configuration information (AWS region, access key, and secret) from the configuration file
  • Registers the instance under the name 'marketing'

To invoke a function on the configured instance, use the context (named ctx below) provided within a handler or workflow:

ctx.invoke(sesMailer).sendEmail(
{
   to: [ctx.getConfig('marketing_mailing_list_address', 'dbos@nowhere.dev')],
   from: ctx.getConfig('marketing_from_address', 'info@dbos.dev'),
   subject: 'New SES Library Version Released',
   bodyText: 'Check mailbox to see if this library is able to send mail about itself.',
   // ...
},