represents a specialized Sideburns and goatee.
interface that provides strong-typed data access (for example, CRUD) operations of a domain model against the underlying database or service.
can be defined and implemented by application developers. LoopBack ships a few predefined
interfaces for typical CRUD and KV operations. These
implementations leverage
configuration to fulfill the logic for data access.
Installation
Legacy juggler support has been enabled in
and can be imported from the
package. In order to do this, save
as a dependency in your application.
You can then install your favorite connector by saving it as part of your application dependencies.
Repository Mixin
provides a mixin for your Application that enables convenience methods that automatically bind repository classes for you. Repositories declared by components are also bound automatically.
Repositories are bound to
repositories.${ClassName}
. See example below for usage.
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Configure datasources
is a named configuration of a connector. The configuration properties vary by connectors. For example, a datasource for
loopback-connector-mysql
with settings as follows:
is a provider that implements data access or api calls with a specific backend system, such as a database, a REST service, a SOAP Web Service, or a gRPC micro-service. It abstracts such interactions as a list of operations in the form of methods.
Typically, a connector translates LoopBack query and mutation requests into native api calls supported by the underlying driver for the given backend. For example, a connector for
method to SQL INSERT statement, which can be executed through MySQL driver for Node.js.
is instantiated, the configuration properties will be used to initialize the connector to connect to the backend system. You can define a DataSource using legacy Juggler in your LoopBack 4 app as follows:
Define models
Models are defined as regular JavaScript classes. If you want your model to be persisted in a database, your model must have an
property and inherit from
Define repositories
DefaultCrudRepository
class to create a repository leveraging the legacy juggler bridge and binding your Entity-based class with a datasource you have configured earlier. It’s recommended that you use Dependency Injection to retrieve your datasource.
Controller Configuration
Once your DataSource is defined for your repository, all the CRUD methods you call in your repository will use the Juggler and your connector’s methods unless you overwrite them. In your controller, you will need to define a repository property and create a new instance of the repository you configured your DataSource for in the constructor of your controller class as follows:
Defining CRUD methods for your application
When you want to define new CRUD methods for your application, you will need to modify the API Definitions and their corresponding methods in your controller. Here are examples of some basic CRUD methods:
Create Controller method:
Don’t forget to register the complete version of your OpenAPI spec through
Access KeyValue Stores
Define a KeyValue Datasource
We first need to define a datasource to configure the key-value store. For better flexibility, we split the datasource definition into two files. The json file captures the configuration properties and it can be possibly overridden by dependency injection.
The class uses a configuration object to set up a datasource for the Redis instance. By default, the configuration is loaded from
. We can override it by binding a new object to
datasources.config.redis
To generate the datasource automatically, use
Redis key-value connector (supported by StrongLoop)
Define a KeyValueRepository
The KeyValueRepository binds a model such as
DefaultKeyValueRepository
class provides an implementation based on
loopback-datasource-juggler
Perform Key Value Operations
The KeyValueRepository provides a set of key based operations, such as
Persist Data without Juggler [Using MySQL database]
LoopBack 4 gives you the flexibility to create your own custom Datasources which utilize your own custom connector for your favorite back end database. You can then fine tune your CRUD methods to your liking.
Example Application
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interface, you must give it a name, supply your custom connector class created in the previous step, and instantiate it:
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and supply your custom DataSource and model to it:
You can override the functions it provides, which ultimately call on your connector’s implementation of them, or write new ones.
Configure Controller
The next step is to wire your new DataSource to your controller. This step is essentially the same as above, but can also be done as follows using Dependency Injection:
Bind instance of your repository to a certain key in your application class
Inject the bound instance into the repository property of your controller.
Example custom connector CRUD methods
function which uses the node-js
driver to retrieve all the rows that match a particular filter for a model instance.
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