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Example of customizing the data source for a GraphQL API

The following example shows how to customize the data source for an API and some API data object types that are defined in a schema.

The schema sample defines a readIntegratedCase API, that takes a case_id input parameter and returns an object of type DOMIntegratedCase. The sample shows that the DOMIntegratedCase type contains a set of fields where one field is linked to an array of DOMBenefit objects.

The following list outlines some field types:

• GQL_ID represents a unique identifier. GQL_ID is used for all IDs.
• GQL_Date represents a Cúram date type.
• CodeItem is used to define an object that represents a code item.
• @code is a directive, that indicates to the underlying server that a single Java attribute that contains a code value must be converted to a CodeItem object.

For information about the full list of scalars to use for each data type, see Cúram data types and GraphQL scalars.

The following code outlines the schema definition:

type Query {
    readIntegratedCase(case_id: GQL_ID!): DOMIntegratedCase
}

type DOMIntegratedCase {
        id: GQL_ID
        reference: String
        effective_date: GQL_Date
        registration_date: GQL_Date
        status: CodeItem @code
        type: CodeItem @code
        benefits: [DOMBenefit]
}

type DOMBenefit {
        id: GQL_ID
        reference: String
        type: CodeItem @code
        product_name: CodeItem @code
        product_type: CodeItem @code
        status: CodeItem @code
        effective_date: GQL_Date
}

type CodeItem {
        code: String
        description: String
        tableName: String
}

The following code shows the corresponding existing entry in the runtime_wiring.yaml file, that defines the two data fetcher classes to use for the readIntegratedCase API:

Query:
  - name: readIntegratedCase
    data_fetcher: curam.core.graphql.datafetcher.IntegratedCaseDataFetcher
FieldLevelWiring:
  - object_type: DOMIntegratedCase
    field:  benefits
    data_fetcher: curam.core.graphql.datafetcher.BenefitListDataFetcher

Customizing the data source

Two custom data fetcher classes are created, for example, curam.custom.graphql.datafetcher.CustomIntegratedCaseDataFetcher and curam.custom.graphql.datafetcher.CustomBenefitListDataFetcher. The classes reference custom facades. However, they must return the same object types as the existing data fetcher classes, that is DOMIntegratedCase and List<DOMBenefit>. The object types also match the object type definitions in the schema.

For more information, see Creating a data fetcher class.

In a runtime_wiring.yaml file that is located in an EJBServer custom component, an entry is created that references the two new custom data fetcher classes. The following code shows the entry in the runtime_wiring.yaml file:

Query:
  - name: readIntegratedCase
    data_fetcher: curam.custom.graphql.datafetcher.CustomIntegratedCaseDataFetcher
FieldLevelWiring:
  - object_type: DOMIntegratedCase
    field:  benefits
    data_fetcher: curam.custom.graphql.datafetcher.CustomBenefitListDataFetcher

For more information, see Configuring the runtime wiring for APIs.

At build time, because the custom component is listed higher in the SERVER_COMPONENT_ORDER variable, the entries that are in the custom component runtime_wiring.yaml file will overwrite the entries that are in the original component.