Migrating datasources - Loopback Next

{% include tip.html content=" Missing instructions for your LoopBack 3 use case? Please report a Migration docs issue on GitHub to let us know. " %}

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:

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
```

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):

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:

json

{
  "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',
};

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

{% include note.html content="We are working on a CLI command lb4 import-lb3-datasources that will migrate datasources from a mounted LoopBack 3 application to a LoopBack 4 project automatically. See GitHub issue #4346 for more details." %}

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.