Custom Data Provider API Reference

This topic discusses the custom data provider specification.

Registration Object

Every custom data provider has a file named index.js that exports a registration object containing provider information. The object describes how to load and use the provider. The following is the code that is automatically included in the index.js file by the Custom Data Feeds (CDF) command line tool.

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const packageInfo = require('../package.json');
const csconfigInfo = require('../cdconfig.json');
const provider = {
  type: csconfigInfo.type,
  name: csconfigInfo.name,
  version: packageInfo.version,
  hosts: csconfigInfo.properties.hosts,
  disableIdParam: csconfigInfo.properties.disableIdParam,
  Model: require('./model')
};
module.exports = provider;

The table below describes each field in detail:

The auto-generated code pulls the provider version from the package.json file and other fields from the cdconfig.json file. To modify these fields, change the corresponding values in the cdconfig.json file instead of the index.js file.

Model Class

Every custom data provider implements a Model class, which is usually in the model.js file. The Model class includes a required getData() method that will contain code for fetching and tranforming remote data into GeoJSON. It may optionally include editData() for handling feature editing or authorize() for handling custom user authorization. The following table describes the arguments that the getData() method accepts. The callback is optional because the getData() method may be an async function if desired.

Request Object

The following table shows the properties that are availble on the request object. The example column is not exhaustive.

GeoJSON Metadata

Custom Data Feeds requires that the GeoJSON be decorated with a property called metadata. It should have an object as its value. This object contains information important for translating the GeoJSON to its feature service equivalent. The table below describes some of the key metadata properties:

If your data does not contain a field that can be used as the OBJECTID, you can leave idField undefined. In such cases Custom Data Feeds will create an OBJECTID for each feature by default. However, this is less than ideal as it impacts performance and in very rare cases may lead to OBJECTID collisions. The best practice is to have a field on the raw data that meets the requirements of idField. See Setting the idField Property for more details.

Routes and Controllers

Routes

To use provider-specific routes, ensure that the routes field in the index.js file points to a file that exports an array of route definition objects. The following table describes the fields that each route definition object must contain.

Controllers

Set the handler field of each route definition object to the function name that handles requests for that route. You can define these functions in a Controller class. The Controller field in the index.js file must reference the Controller class. Below is an example of how to implement a Controller class.

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function Controller (model) {
  this.model = model;
}
Controller.prototype.test = function (req, res) {
  res.status(200).json({version: '1.0.0'});
};