Migrating datasources

Overview

LoopBack 3 datasources are compatible with LoopBack 4 datasources, so migrating datasources from LoopBack 3 to LoopBack 4 is simple.

In LoopBack 3, all datasources are defined in the server/datasources.json file, whereas in LoopBack 4 each datasource is defined in its own file in the src/datasources folder. Each LoopBack 4 datasource is represented as a class, the source file (e.g. mysql-ds.datasource.ts) includes both the configuration and the class definition.

Migration Steps

To migrate a datasource from LoopBack 3 to LoopBack 4, complete the following steps:

1. In the root of your LoopBack 4 application, use the lb4 datasource command to create a new datasource and enter the same datasource name as your LoopBack 3 application’s datasource (e.g. mysqlDs):

   $ lb4 datasource
   ? Datasource name: mysqlDs
   

2. For the remaining prompts from the lb4 datasource command, use the defaults (press Enter for each one) since these will be replaced in the next step:

   ? Select the connector for mysqlDs: In-memory db (supported by StrongLoop)
   ? window.localStorage key to use for persistence (browser only):
   ? Full path to file for persistence (server only):
   

3. Replace content of the config object defined in the newly created src/datasources/{dataSource.dataSourceName}.datasource.ts file in your LoopBack 4 application with the datasource configuration from server/datasources.json in your LoopBack 3 application.

   For example, if your server/datasources.json file contains:

   {
     "mysqlDs": {
       "name": "mysqlDs",
       "connector": "mysql",
       "host": "demo.strongloop.com",
       "port": 3306,
       "database": "getting_started",
       "username": "demo",
       "password": "L00pBack"
     }
   }
   

   Move it to src/datasources/mysql-ds.datasource.ts, so that the config object is defined as follows:

   const config = {
     name: 'mysqlDs',
     connector: 'mysql',
     host: 'demo.strongloop.com',
     port: 3306,
     database: 'getting_started',
     username: 'demo',
     password: 'L00pBack',
   };
   

4. Repeat steps 1-3 for each datasource you want to migrate.

Compatibility

As mentioned before, LoopBack 3 datasources are compatible with LoopBack 4 datasources. In both, a datasource is a connector instance that is used by legacy-juggler-bridge. For example, both a LoopBack 3 MySQL datasource and a LoopBack 4 MySQL datasource will use loopback-connector-mysql.