Fragments and Node Patterns

Liferay DXP’s GraphQL APIs also supports GraphQL fragments, reusable sets of fields that are needed in different requests. A special type of fragments are inline fragments, which access the underlying concrete type when querying generic types or interfaces.

You’ll use inline fragments to query objects that inherit from a common interface, like the kind of objects returned from a ContentSet. ContentSets allow defining lists of assets that comply with a set of rules, a segment, or are manually selected. ContentSets can return any type of asset. This makes them a perfect fit for inline fragments.

Here’s an example of GraphQL querying ContentSets:

query {
  contentSetContentSetElements(contentSetId: 42345) {
    items {
      id
      title
      content {
        ... on BlogPosting {
          headline
        }
        ... on StructuredContent {
          relatedContents {
            id
            title
          }
        }
      }
    }
    page
    pageSize
    totalCount
  }
}

This query returns a set of objects, each of a different type.

Node pattern

graphQLNode is a special query that leverages the power of inline fragments. This query accepts a dataType and an ID and returns any kind of entity that has a query of the type {dataType} and receives an id as a parameter. Inline fragments can specify the fields you want to return in this special case:

query{
  graphQLNode(dataType: ______, id: ______){
    id
    ... on BlogPosting {
      headline
    }
  }
}

You can also use graphQLNode as a field in entities that contain contentType and id properties. Those entities have a generated property called GraphQLNode that can return any type, queried by using inline fragments. A common use case is returning an asset linked as relatedContents (asset links).