# loopback-datasource-juggler-connector Loopback connectors provide access to backend systems including databases, REST APIs and other services. Connectors are not used directly by application code. We create a DataSource to interact with the connector. For example, var DataSource = require('loopback-datasource-juggler').DataSource; var oracleConnector = require('loopback-connector-oracle'); var ds = new DataSource(oracleConnector, { host : '166.78.158.45', database : 'XE', username : 'strongloop', password : 'str0ng100pjs', debug : true }); The connector argument passed the DataSource constructor can be one of the following: * The connector module from `require(connectorName)` * The full name of the connector module, such as 'loopback-connector-oracle' * The short name of the connector module, such as 'oracle', which will be converted to 'loopback-connector-' * A local module under ./connectors/ folder ## Generic connector implmentations A connector module can implement the following methods to interact with the datasource. exports.initialize = function (dataSource, postInit) { var settings = dataSource.settings || {}; // The settings is passed in from the dataSource var connector = new MyConnector(settings); // Construct the connector instance dataSource.connector = connector; // Attach connector to dataSource connector.dataSource = dataSource; // Hold a reference to dataSource /** * Connector instance can have an optional property named as DataAccessObject that provides * static and prototype methods to be mixed into the model constructor. The property can be defined * on the prototype. */ connector.DataAccessObject = function {}; /** * Connector instance can have an optional function to be called to handle data model definitions. * The function can be defined on the prototype too. * @param model The name of the model * @param properties An object for property definitions keyed by propery names * @param settings An object for the model settings */ connector.define = function(model, properties, settings) { ... }; connector.connect(..., postInit); // Run some async code for initialization // process.nextTick(postInit); } Another way is to directly export the connection function which takes a settings object. module.exports = function(settings) { ... } ## CRUD connector implmentations To support CRUD operations for a model class that is attached to the dataSource/connector, the connector needs to provide the following functions: /** * Create a new model instance */ CRUDConnector.prototype.create = function (model, data, callback) { }; /** * Save a model instance */ CRUDConnector.prototype.save = function (model, data, callback) { }; /** * Check if a model instance exists by id */ CRUDConnector.prototype.exists = function (model, id, callback) { }; /** * Find a model instance by id */ CRUDConnector.prototype.find = function find(model, id, callback) { }; /** * Update a model instance or create a new model instance if it doesn't exist */ CRUDConnector.prototype.updateOrCreate = function updateOrCreate(model, data, callback) { }; /** * Delete a model instance by id */ CRUDConnector.prototype.destroy = function destroy(model, id, callback) { }; /** * Query model instances by the filter */ CRUDConnector.prototype.all = function all(model, filter, callback) { }; /** * Delete all model instances */ CRUDConnector.prototype.destroyAll = function destroyAll(model, callback) { }; /** * Count the model instances by the where criteria */ CRUDConnector.prototype.count = function count(model, callback, where) { }; /** * Update the attributes for a model instance by id */ CRUDConnector.prototype.updateAttributes = function updateAttrs(model, id, data, callback) { };