Service authors can implement the Metadata Transforms API in their transforms code, which returns a Map of capabilities (with keys such as filter, sort, fetchByKeys) supported by a particular service endpoint.

The default transforms implementations for Business Objects services processes the endpoint metadata to determine the level of support and returns a Map of capabilities for that endpoint, that can then be understood by Data Provider implementations. The capabilities can be retrieved using the Metadata.capabilities().

The following is a sample structure of the capabilities for a Business Objects based service. The list of capabilities generally applies to all endpoints that the service includes, but authors can provide custom capabilities for different endpoints.

{
    "fetchByKeys": {
        "implementation": "lookup",
        "multiKeyLookup": "yes"
    },
    "fetchFirst": {
        "implementation": "iteration"
    },
    "fetchByOffset": {
        "implementation": "randomAccess"
    },
    "sort": {
        "attributes": "single"
    },
    "filter": {
        "operators": [
            "$eq",
            "$ne",
            "$co",
            "..."
        ],
        "textFilter": true
    }
}

The Service Data Provider determines its own capabilities based on the information above.

Signature

The metadata transforms capabilities function has the following signature:

function capabilities(configuration) {
    const caps = {};
    
    // process the endpoint configuration and build the capabilities for this endpoint
    return caps; 
}

The parameters to this function are

• configuration: An object that has the following properties:
  • endpointDefinition: The metadata pertaining to the endpoint
  • initConfig: The configuration for the current Rest call. The 'initConfig' exactly matches the 'init' parameter of the request, as described in Request.
  • parameters: Server variables, path and query parameters
  • url: The full URL of the request.

The return value is a Map of capabilities whose JSON structure resembles the example in the previous section. For the full list of properties in the capabilities, refer to the Visual Builder Runtime public serviceTransforms.js API, and the JET Data Provider docs for the right set of values for each capability. Business Objects service transforms implementations only support a subset of the capabilities defined by JET Data Provider.

Example

A default implementation for the capabilities supported on an endpoint for a Business Objects based service is already provided as part of the default Business Objects transforms. It returns an object like the example shown below. The capabilities for an endpoint are cached once it's determined that the capabilities are not being modified. It's uncommon for page authors to want to override the default capabilities, but it can be set on the Service Data Provider variable, if needed.

define([], function () {
  /**
   * transforms pertaining to a service or endpoint and not tied to a request.
   *
   * @type {{capabilities: (function(*): {})}}
   */
  class MetadataTransforms {
    /**
     * Returns the capabilities as defined by a DataProvider
     * @param configuration
     * @return {Object}
     * @private
     */
    // eslint-disable-next-line no-underscore-dangle
    static getCapabilities(configuration) {
      const caps = {};
      const c = configuration;
      const epDef = c.endpointDefinition;
      const paramsDef = epDef && epDef.parameters;
      if (paramsDef) {
        const queryParamsDef = paramsDef.query || {};

        if (queryParamsDef) {
          // using the endpoint definition build the capabilities
        }
      }

      return caps;
    }
  }

  class Response {};
  class Request {};

  // Note: as an example, the metadata object is expanded to include just the sort property
  return {
    metadata: { capabilities: MetadataTransforms.getCapabilities },
    request: Request,
    response: Response
  };
});