Query record data using the GraphQL API framework

  • Release version: Xanadu
  • Updated August 1, 2024
  • 3 minutes to read
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    Summary of Query record data using the GraphQL API framework

    This topic guides ServiceNow customers on creating custom GraphQL APIs to query record data from platform tables or third-party systems. By defining a GraphQL schema and associated resolvers, you can precisely retrieve the data your Workspace components need, such as cases associated with SLAs, using the Next Experience UI Framework. GraphQL is optimized for client-side development and allows managing multiple queries through a single API endpoint.

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    Key Features

    • GraphQL Schema Definition Language (SDL): Define the structure and data types of queryable fields using SDL in the GraphQL Scripted Schemas table. Supports Query and Mutation operations.
    • Resolvers and Resolver Mappings: Script the logic to fetch data for each schema field and map these resolvers to fields to return appropriate record data.
    • Typeresolvers: Handle GraphQL interfaces and unions by resolving to concrete types, enhancing schema flexibility.
    • Introspection: Disabled by default; can be enabled to allow clients to discover schema queries and mutations.
    • Directives: Use the @source directive to map fields to parent object properties and the @defer directive to delay loading of slow fields for improved user experience, with caution advised for performance.
    • Global Resolver Functions: Access arguments and parent objects within resolver and typeresolver scripts through provided functions.
    • GraphQL Explorer: An integrated tool to test GraphQL queries and mutations against your schemas.
    • Namespace Management: Queries require specifying both application and schema namespaces to ensure uniqueness.

    Limitations

    • Subscription operations and custom scalar types are not supported.
    • Introspective queries are off by default and must be explicitly enabled.

    Practical Steps and Tools

    • Create GraphQL schemas and define resolvers to expose the desired data model.
    • Enable introspective queries to aid in schema exploration and debugging.
    • Use the GraphQL Explorer for interactive testing of your GraphQL APIs.
    • Develop Workspace components that query your GraphQL schemas to access and display record data efficiently.
    • Configure system properties to control GraphQL framework behavior, including introspection settings.
    • Refer to the demo GraphQL Framework Demo Application plugin to explore example PTO calendar schemas with queries and mutations.

    What You Need Before You Begin

    • Knowledge of GraphQL and JavaScript to create schemas and define API behavior.
    • Familiarity with web component development and the ServiceNow data model.
    • Understanding of GlideRecord to map schema fields to record data in resolver scripts.
    • An existing custom Workspace component to consume the queried data.

    Create a custom GraphQL API to query record data from a component or a third-party system.

    For example, you can create a component that displays the cases associated with an SLA. You can use the Next Experience UI Framework to develop the component you need, and access case data from the platform by creating a GraphQL schema that defines data in the Case table.

    To learn more about developing components, see Developing components for Workspace.

    Benefits of GraphQL

    GraphQL is a web query language optimized for client-side development. Using scripted GraphQL, you can:

    • Discover fields and objects available to query through introspection.
    • Query the exact data you need from a component.
    • Manage multiple possible queries from a single API, as opposed to multiple endpoints for a REST request.
    • Integrate with third-party systems by making the schema public.
    • Generate the GraphQL query from your component and handle the response.

    What to know before you begin

    Before you start creating custom GraphQL APIs, make sure you have:

    • GraphQL knowledge to create a schema.
    • JavaScript knowledge to define the API behavior.
    • General knowledge of web component concepts.
    • A custom Workspace component to consume record data.
    • Understanding of the ServiceNow data model that you want to expose in the schema.
    • GlideRecord knowledge to map fields to record data in your resolver scripts.

    GraphQL overview

    Creating a scripted GraphQL API includes these parts:

    GraphQL Schema Definition Language (SDL)
    Define the structure and data type of fields available in a GraphQL query. You can define the SDL using the Schema script field in the GraphQL Scripted Schemas [sys_graphql_schema] table. The SDL only supports Query and Mutation operations.
    Resolvers
    Define the data returned by each field. You can define the resolvers for each field in the GraphQL Scripted Resolvers related list on the GraphQL Scripted Schemas form.
    Typeresolvers
    Resolve interfaces and unions into concrete GraphQL types. For example, you might define a union between an incident type and a problem type. Use the typeresolver script to define when to return which. You can define the typeresolvers in the GraphQL Scripted Typeresolvers related list on the GraphQL Scripted Schemas form.
    Resolver mappings
    Map resolvers to fields in the schema. You can define resolver mappings in the GraphQL Scripted Resolver Mappings related list on the GraphQL Scripted Schemas form.

    To learn more about the GraphQL query language, see the GraphQL website.

    To test queries to your GraphQL APIs, you can use the GraphQL Explorer, an integrated GraphQL testing tool. For more information, see Test GraphQL APIs with GraphQL Explorer.

    Limitations

    The following GraphQL features aren't supported:

    • Subscription operations
    • Custom scalar types

    Introspection

    By default, introspective queries into your custom schemas aren’t enabled. To turn on introspection, see Enable introspective queries for GraphQL schemas.

    Namespaces

    GraphQL APIs have two different namespaces:

    Application namespace
    The namespace for the custom application. To learn more about application namespaces, see Application scope.
    Schema namespace
    The namespace for the schema to ensure that all queries are unique. You can have multiple schema namespaces in a single application.

    When querying data, you must include both namespaces in your query. For example, the following query is searching for data with the following namespaces:

    • Application namespace: x_graph_scope
    • Schema namespace: planet
    query {
      x_graph_scope {
        planet {
          findAll {
            name
            mass
            distance
          }
        }
      }
    }

    Directives and global functions

    @source schema directive

    Maps a GraphQL field to the value of a property of the parent object. If the field has a separate resolver script, the system uses the record that it resolves to instead of the parent object.

    Use the @source directive in your schema script.

    @defer query directive
    Defer processing of a GraphQL fragment until later in the query. Use this query directive to delay returning data for slow-responding fields within a fragment. Stream the field results of the deferred fragment as a multi-part response.
    Note:
    To use the @defer directive, your GraphQL client must accept multipart/mixed HTTP headers. For example, set the HTTP headers to Accept: multipart/mixed; boundary="-".

    Use the @defer directive to improve user time to interaction. Avoid applying this query directive indiscriminately as it can also cause performance degradations. Conduct performance testing to determine which fields can be deferred for better performance.

    Resolver functions

    These functions are available on the global env object.

    • getArguments(): Returns the arguments of the previous field.
    • getSource(): Returns the parent object.

    Use in your resolver script.

    Typeresolver functions

    These functions are available on the global env object.

    • getArguments(): Returns the arguments of the previous field.
    • getObject(): Returns the parent object.
    • getTypeName(): Returns the name of the interface or union type.

    Use in your typeresolver script.

    Demo application

    To see a demo GraphQL PTO calendar schema with mutations and queries, enable the GraphQL Framework Demo Application plugin (com.glide.graphql.framework.demo).