Env Vars

Formn provides a helper class, ConnectionsFileReader, that can be used to read and validate a connections.json file. Its readConnectionOptions method takes a path to a connections.json file and returns an array of ConnectionOptions. Because it’s common to use environment variables to store database connection details, a connections.json file can be defined in such a way that some or all of the connection options come from environment variables. Here’s an example connections.json file that’s set up to get the database host and password from env vars.

{
  "host": {
    "ENV": "DB_HOST"
  },
  "user": "formn-user",
  "password": {
    "ENV": "DB_PASS"
  },
  "database": "formn_test_db",
  "port": 3306,
  "poolSize": 10
}

Here, the host is expected to be in the DB_HOST environment variable, and the password in DB_PASS. Once that file is defined, it can be read as follows.

import { ConnectionsFileReader, ConnectionOptions } from 'formn';

// Read connection details.  DB_HOST and DB_PASS should be defined
// as env vars, otherwise an exception will be raised.
const connOpts: ConnectionOptions = new ConnectionsFileReader()
  .readConnectionOptions('connections.env.json')[0];

There are a few key differences from the last example.

1. readConnectionOptions takes the path to a connections.json file. If the path is relative, it’s assumed to be relative to the current working directory, which is likely the root of your application. In the last example the connections.json file was simply read using require.
2. readConnectionOptions returns an array of ConnectionOptions. Some applications need to connect to multiple databases, so a connections.json file can define an array of connection details.

The two files referenced above can be found in the formn-example repository: connections.env.json; read-connections-env.ts.