AEM GraphQL API for use with Content Fragments

Learn how to use Content Fragments in Adobe Experience Manager (AEM) as a Cloud Service with the AEM GraphQL API for headless content delivery.

AEM as a Cloud Service GraphQL API used with Content Fragments is heavily based on the standard, open source GraphQL API.

Using the GraphQL API in AEM enables the efficient delivery of Content Fragments to JavaScript clients in headless CMS implementations:

  • Avoiding iterative API requests as with REST,
  • Ensuring that delivery is limited to the specific requirements,
  • Allowing for bulk delivery of exactly what is needed for rendering as the response to a single API query.
NOTE

GraphQL is currently used in two (separate) scenarios in Adobe Experience Manager (AEM) as a Cloud Service:

The GraphQL API

GraphQL is:

  • …a query language for APIs and a runtime for fulfilling those queries with your existing data. GraphQL provides a complete and understandable description of the data in your API, gives clients the power to ask for exactly what they need and nothing more, makes it easier to evolve APIs over time, and enables powerful developer tools.”.

    See GraphQL.org

  • …an open spec for a flexible API layer. Put GraphQL over your existing backends to build products faster than ever before…”.

    See Explore GraphQL.

  • “…a data query language and specification developed internally by Facebook in 2012 before being publicly open sourced in 2015. It provides an alternative to REST-based architectures with the purpose of increasing developer productivity and minimizing amounts of data transferred. GraphQL is used in production by hundreds of organizations of all sizes…”

    See GraphQL Foundation.

For further information about the GraphQL API, see the following sections (amongst many other resources):

The GraphQL for AEM implementation is based on the standard GraphQL Java Library. See:

GraphQL Terminology

GraphQL uses the following:

See the (GraphQL.org) Introduction to GraphQL for comprehensive details, including the Best Practices.

GraphQL Query Types

With GraphQL you can perform queries to return either:

AEM provides capabilities to convert queries (both types) to Persisted Queries, that can be cached by Dispatcher and the CDN.

GraphQL Query Best Practices (Dispatcher and CDN)

The Persisted Queries are the recommended method to be used on publish instances as:

  • they are cached
  • they are managed centrally by AEM as a Cloud Service
NOTE

Usually there is no dispatcher/CDN on author, so there is no gain in using persisted queries there; apart from testing them.

GraphQL queries using POST requests are not recommended as they are not cached, so on a default instance the Dispatcher is configured to block such queries.

While GraphQL also supports GET requests, these can hit limits (for example the length of the URL) that can be avoided using Persisted Queries.

NOTE

To allow direct, and/or POST, queries in the Dispatcher you can ask your System Administrator to:

NOTE

The ability to perform direct queries may be deprecated at some point in the future.

GraphiQL IDE

You can test and debug GraphQL queries using the GraphiQL IDE.

Use Cases for Author and Publish Environments

The use cases can depend on the type of AEM as a Cloud Service environment:

  • Publish environment; used to:

    • Query data for JS application (standard use-case)
  • Author environment; used to:

    • Query data for “content management purposes”:
      • GraphQL in AEM as a Cloud Service is currently a read-only API.
      • The REST API can be used for CR(u)D operations.

Permissions

The permissions are those required for accessing Assets.

GraphQL queries are executed with the permission of the AEM user of the underlying request. If the user does not have read access to some fragments (stored as Assets), they will not become part of the result set.

Also, the user needs to have access to a GraphQL endpoint to be able to execute GraphQL queries.

Schema Generation

GraphQL is a strongly typed API, which means that data must be clearly structured and organized by type.

The GraphQL specification provides a series of guidelines on how to create a robust API for interrogating data on a certain instance. To do this, a client needs to fetch the Schema, which contains all the types necessary for a query.

For Content Fragments, the GraphQL schemas (structure and types) are based on Enabled Content Fragment Models and their data types.

CAUTION

All the GraphQL schemas (derived from Content Fragment Models that have been Enabled) are readable through the GraphQL endpoint.

This means that you need to ensure that no sensitive data is available, as it could be leaked this way; for example, this includes information that could be present as field names in the model definition.

For example, if a user created a Content Fragment Model called Article, then AEM generates a GraphQL type ArticleModel. The fields within this type correspond to the fields and data types defined in the model. In addition, it creates some entrypoints for the queries that operate on this type, such as articleByPath or articleList.

  1. A Content Fragment Model:

    Content Fragment Model for use with GraphQL
  2. The corresponding GraphQL schema (output from GraphiQL automatic documentation):
    GraphQL Schema based on Content Fragment Model

    This shows that the generated type ArticleModel contains several fields.

    • Three of them have been controlled by the user: author, main and referencearticle.

    • The other fields were added automatically by AEM, and represent helpful methods to provide information about a certain Content Fragment; in this example, (the helper fields) _path, _metadata, _variations.

  3. After a user creates a Content Fragment based on the Article model, it can then be interrogated through GraphQL. For examples, see the Sample Queries (based on a sample Content Fragment structure for use with GraphQL).

In GraphQL for AEM, the schema is flexible. This means that it is auto-generated each and every time a Content Fragment Model is created, updated or deleted. The data schema caches are also refreshed when you update a Content Fragment Model.

The data schema caches are also refreshed when you update a Content Fragment Model.

The Sites GraphQL service listens (in the background) for any modifications made to a Content Fragment Model. When updates are detected, only that part of the schema is regenerated. This optimization saves time and provides stability.

So for example, if you:

  1. Install a package containing Content-Fragment-Model-1 and Content-Fragment-Model-2:

    1. GraphQL types for Model-1 and Model-2 will be generated.
  2. Then modify Content-Fragment-Model-2:

    1. Only the Model-2 GraphQL type will get updated.

    2. Whereas Model-1 will remain the same.

NOTE

This is important to note in case you want to do bulk updates on Content Fragment Models through the REST api, or otherwise.

The schema is served through the same endpoint as the GraphQL queries, with the client handling the fact that the schema is called with the extension GQLschema. For example, performing a simple GET request on /content/cq:graphql/global/endpoint.GQLschema will result in the output of the schema with the Content-type: text/x-graphql-schema;charset=iso-8859-1.

Schema Generation - Unpublished Models

When Content Fragments are nested it can happen that a parent Content Fragment Model is published, but a referenced model is not.

NOTE

The AEM UI prevents this happening, but if publishing is made programmatically, or with content packages, it can occur.

When this happens, AEM generates an incomplete Schema for the parent Content Fragment Model. This means that the Fragment Reference, which is dependent on the unpublished model, is removed from the schema.

Fields

Within the schema there are individual fields, of two basic categories:

  • Fields that you generate.

    A selection of Data Types are used to create fields based on how you configure your Content Fragment Model. The field names are taken from the Property Name field of the Data Type tab.

    • There is also the Render As setting to take into consideration, as users can configure certain data types. For example, a single line text field can be configured to contain multiple single line texts by choosing multifield from the dropdown.
  • GraphQL for AEM also generates a number of helper fields.

Data Types

GraphQL for AEM supports a list of types. All the supported Content Fragment Model Data Types and the corresponding GraphQL types are represented:

Content Fragment Model - Data Type GraphQL Type Description
Single line Text String, [String] Used for simple strings such as author names, location names, etc.
Multi line Text String, [String] Used for outputting text such as the body of an article
Number Float, [Float] Used to display floating point number and regular numbers
Boolean Boolean Used to display checkboxes → simple true/false statements
Date And Time Calendar Used to display date and time in an ISO 8601 format. Depending on the type selected, there are three flavors available for use in AEM GraphQL: onlyDate, onlyTime, dateTime
Enumeration String Used to display an option from a list of options defined at model creation
Tags [String] Used to display a list of Strings representing Tags used in AEM
Content Reference String, [String] Used to display the path towards another asset in AEM
Fragment Reference A model type Used to reference another Content Fragment of a certain Model Type, defined when the model was created

Helper Fields

In addition to the data types for user generated fields, GraphQL for AEM also generates a number of helper fields in order to help identify a Content Fragment, or to provide additional information about a Content Fragment.

These helper fields are marked with a preceding _ to distinguish between what has been defined by the user and what has been auto-generated.

Path

The path field is used as an identifier in AEM GraphQL. It represents the path of the Content Fragment asset inside the AEM repository. We have chosen this as the identifier of a Content Fragment, because it:

  • is unique within AEM,
  • can be easily fetched.

The following code will display the paths of all Content Fragments that were created based on the Content Fragment Model Author, as provided by the WKND tutorial.

{
  authorList {
    items {
      _path
    }
  }
}

To retrieve a single Content Fragment of a specific type, you also need to determine its path first. For example:

{
  authorByPath(_path: "/content/dam/wknd-shared/en/contributors/sofia-sj-berg") {
    item {
      _path
      firstName
      lastName
    }
  }
}

See Sample Query - A Single Specific City Fragment.

Metadata

Through GraphQL, AEM also exposes the metadata of a Content Fragment. Metadata is the information that describes a Content Fragment, such as the title of a Content Fragment, the thumbnail path, the description of a Content Fragment, the date it was created, amongst others.

Because Metadata is generated through the Schema Editor and as such does not have a specific structure, the TypedMetaData GraphQL type was implemented to expose the metadata of a Content Fragment. TypedMetaData exposes the information grouped by the following scalar types:

Field
stringMetadata:[StringMetadata]!
stringArrayMetadata:[StringArrayMetadata]!
intMetadata:[IntMetadata]!
intArrayMetadata:[IntArrayMetadata]!
floatMetadata:[FloatMetadata]!
floatArrayMetadata:[FloatArrayMetadata]!
booleanMetadata:[BooleanMetadata]!
booleanArrayMetadata:[booleanArrayMetadata]!
calendarMetadata:[CalendarMetadata]!
calendarArrayMetadata:[CalendarArrayMetadata]!

Each scalar type represents either a single name-value pair or an array of name-value pairs, where the value of that pair is of the type it was grouped in.

For example, if you want to retrieve the title of a Content Fragment, we know that this property is a String property, so we would query for all the String Metadata:

To query for metadata:

{
  authorByPath(_path: "/content/dam/wknd-shared/en/contributors/sofia-sj-berg") {
    item {
      _metadata {
        stringMetadata {
          name
          value
        }
      }
    }
  }
}

You can view all the metadata GraphQL types if you view the Generated GraphQL schema. All model types have the same TypedMetaData.

NOTE

Difference between normal and array metadata
Keep in mind that StringMetadata and StringArrayMetadata both refer to what is stored in the repository, not how you retrieve them.

So for example, by calling the stringMetadata field, you would receive an array of all the metadata that was stored in the repository as a String , and if you call stringArrayMetadata you would receive an array of all the metadata that was stored in the repository as String[].

See Sample Query for Metadata - List the Metadata for Awards titled GB.

Variations

The _variations field has been implemented to simplify querying the variations that a Content Fragment has. For example:

{
  authorByPath(_path: "/content/dam/wknd-shared/en/contributors/ian-provo") {
    item {
      _variations
    }
  }
}
NOTE

Note that the _variations field does not contain a master variation, as technically the original data (referenced as Master in the UI) is not considered an explicit variation.

See Sample Query - All Cities with a Named Variation.

NOTE

If the given variation does not exist for a Content Fragment, then the original data (also known as the master variation) will be returned as a (fallback) default.

GraphQL Variables

GraphQL permits variables to be placed in the query. For more information you can see the GraphQL documentation for Variables.

For example, to get all Content Fragments of type Author in a specific variation (if available), you can specify the argument variation in GraphiQL.

GraphQL Variables

Query:

query($variation: String!) {
  authorList(variation: $variation) {
    items {
      _variation
      lastName
      firstName
    }
  }
}

Query Variables:

{
  "variation": "another"
}

This query will return the full list of authors. Authors without the another variation will fall back to the original data (_variation will report master in this case).

If you want to restrict the list to authors that provide the specified variation (and skip authors that would fall back to the original data), you’ll need to apply a filter:

query($variation: String!) {
  authorList(variation: $variation, filter: {
    _variation: {
      _expressions: {
        value: $variation
      }
    }
  }) {
    items {
      _variation
      lastName
      firstName
    }
  }
}

GraphQL Directives

In GraphQL there is a possibility to change the query based on variables, called GraphQL Directives.

For example there you can include the adventurePrice field in a query for all the AdventureModels, based on a variable includePrice.

GraphQL Directives

Query:

query GetAdventureByType($includePrice: Boolean!) {
  adventureList {
    items {
      title
      price @include(if: $includePrice)
    }
  }
}

Query Variables:

{
    "includePrice": true
}

Filtering

You can also use filtering in your GraphQL queries to return specific data.

Filtering uses a syntax based on logical operators and expressions.

The most atomic part is a single expression that can be applied to the content of a certain field. It compares the content of the field with a given constant value.

For example, the expression

{
  value: "some text"
  _op: EQUALS
}

would compare the content of the field with the value some text and succeeds if the content equals the value. Otherwise, the expression will fail.

The

The following operators can be used to compare fields to a certain value:

Operator Type(s) The expression succeeds if …
EQUALS String, ID, Boolean … the value is exactly the same as the content of the field
EQUALS_NOT String, ID … the value is not the same as the content of the field
CONTAINS String … the content of the field contains the value ({ value: "mas", _op: CONTAINS } will match Christmas, Xmas, master, …)
CONTAINS_NOT String … the content of the field does not contain the value
STARTS_WITH ID … the ID starts with a certain value ({ value: "/content/dam/", _op: STARTS_WITH will match /content/dam/path/to/fragment, but not /namespace/content/dam/something
EQUAL Int, Float … the value is exactly the same as the content of the field
UNEQUAL Int, Float … the value is not the same as the content of the field
GREATER Int, Float … the content of the field is greater than the value
GREATER_EQUAL Int, Float … the content of the field is greater than or equal to the value
LOWER Int, Float … the content of the field is lower than the value
LOWER_EQUAL Int, Float … the content of the field is lower than or equal to the value
AT Calendar, Date, Time … the content of the field is exactly the same as the value (including timezone setting)
NOT_AT Calendar, Date, Time … the content of the field is not the same as the value
BEFORE Calendar, Date, Time … the point in time denoted by the value is before the point in time denoted by the content of the field
AT_OR_BEFORE Calendar, Date, Time … the point in time denoted by the value is before or at the same point in time denoted by the content of the field
AFTER Calendar, Date, Time … the point in time denoted by the value is after the point in time denoted by the content of the field
AT_OR_AFTER Calendar, Date, Time … the point in time denoted by the value is after or at the same point in time denoted by the content of the field

Some types also allow to specify additional options that modify how an expression is evaluated:

Option Type(s) Description
_ignoreCase String Ignores the case of a string, e.g. a value of time will match TIME, time, tImE, …
_sensitiveness Float Allows a certain margin for float values to be considered the same (to work around technical limitations due to the internal representation of float values; should be avoided, as this option might have a negative impact on performance

Expressions can be combined to a set with the help of a logical operator (_logOp):

  • OR - the set of expressions will succeed if at least one expression succeeds
  • AND - the set of expressions will succeed if all expressions succeed (default)

Each field can be filtered by its own set of expressions. The expression sets of all fields mentioned in the filter argument will eventually be combined by its own logical operator.

A filter definition (passed as the filter argument to a query) contains:

  • A sub-definition for each field (the field can be accessed through its name, e.g. there’s a lastName field in the filter for the lastName field in the Data (field) Type)
  • Each sub-definition contains the _expressions array, providing the expression set, and the _logOp field that defines the logical operator the expressions should be combined with
  • Each expression is defined by the value (value field) and the operator (_operator field) the content of a field should be compared to

Note that you can omit _logOp if you want to combine items with AND and _operator if you want to check for equality, as these are the default values.

The following example demonstrates a full query that filters all persons that have a lastName of Provo or containing sjö, independent of the case:

{
  authorList(filter: {
    lastname: {
      _logOp: OR
      _expressions: [
        {
          value: "sjö",
          _operator: CONTAINS,
          _ignoreCase: true
        },
        {
          value: "Provo"
        }
      ]
    }
  }) {
    items {
      lastName
      firstName
    }
  }
}

While you can also filter on nested fields, it is not recommended, as it might lead to performance issues.

For further examples, see:

Sorting

This feature allows you to sort the query results according to a specified field.

The sorting criteria:

  • is a comma separated list of values representing the field path
    • the first field in the list will define the primary sort order, the second field will be used if two values of the primary sort criterion are equal, the third one if the first two criteria are equal, etc.
    • dotted notation, i.e field1.subfield.subfield etc…
  • with an optional order direction
    • ASC (ascending) or DESC (descending); as default ASC is applied
    • the direction can be specified per field; this means that you can sort one field in ascending order, another one in descending order (name, firstName DESC)

For example:

query {
  authorList(sort: "lastName, firstName") {
    items {
      firstName
      lastName
    }
  }
}

And also:

{
  authorList(sort: "lastName DESC, firstName DESC") {
    items {
        lastName
        firstName
    }
  }
}

You can also sort on a field within a nested fragment, using the format of nestedFragmentname.fieldname.

NOTE

This might have a negative impact on performance.

For example:

query {
  articleList(sort: "authorFragment.lastName")  {
    items {
      title
      authorFragment {
        firstName
        lastName
        birthDay
      }
      slug
    }
  }
}

Paging

This feature allows you to perform paging on query types that returns a list. Two methods are provided:

  • offset and limit in a List query
  • first and after in a Paginated query

List query - offset and limit

In a ...Listquery you can use offset and limit to return a specific subset of results:

  • offset: Specifies the first data set to return
  • limit: Specifies the maximum number of data sets to be returned

For example, to output the page of results containing up to five articles, starting from the fifth article from the complete results list:

query {
   articleList(offset: 5, limit: 5) {
    items {
      authorFragment {
        lastName
        firstName
      }
    }
  }
}
NOTE
  • Paging requires a stable sort order to work correctly across multiple queries requesting different pages of the same result set. By default it uses the repository path of each item of the result set to make sure the order is always the same. If a different sort order is used, and if that sorting cannot be done at JCR query level, then there will be a negative performance impact as the entire result set must be loaded into memory before the pages can be determined.

  • The higher the offset, the more time it will take to skip the items from the complete JCR query result set. An alternative solution for large result sets is to use the Paginated query with first and after method.

Paginated query - first and after

The ...Paginated query type reuses most of the ...List query type features (filtering, sorting), but instead of using offset/limit arguments, it uses the first/after arguments as defined by the GraphQL Cursor Connections Specification. You can find a less formal introduction in the GraphQL introduction.

  • first: The n first items to return.
    The default is 50.
    The maximum is 100.
  • after: The cursor that determines the beginning of the requested page; note that the item represented by the cursor is not included in the result set; the cursor of an item is determined by the cursor field of the edges structure.

For example, output the page of results containing up to five adventures, starting from the given cursor item in the complete results list:

query {
    adventurePaginated(first: 5, after: "ODg1MmMyMmEtZTAzMy00MTNjLThiMzMtZGQyMzY5ZTNjN2M1") {
        edges {
          cursor
          node {
            title
          }
        }
        pageInfo {
          endCursor
          hasNextPage
        }
    }
}
NOTE
  • By default paging use the UUID of the repository node representing the fragment for ordering to ensure the order of results is always the same. When sort is used, the UUID is implicitly used to ensure a unique sort; even for two items with identical sort keys.

  • Due to internal technical constraints, performance will degrade if sorting and filtering is applied on nested fields. Therefore it is recommended to use filter/sort fields stored at root level. This is also the recommended way if you want to query large paginated result sets.

GraphQL for AEM - Summary of Extensions

The basic operation of queries with GraphQL for AEM adhere to the standard GraphQL specification. For GraphQL queries with AEM there are a few extensions:

Querying the GraphQL endpoint from an External Website

To access the GraphQL endpoint from an external website you need to configure the:

Authentication

See Authentication for Remote AEM GraphQL Queries on Content Fragments.

FAQs

Questions that have arisen:

  1. Q: “How is the GraphQL API for AEM different from Query Builder API?

    • A:
      The AEM GraphQL API offers total control on the JSON output, and is an industry standard for querying content.
      Moving forward, AEM is planning to invest in the AEM GraphQL API.

Tutorial - Getting Started with AEM Headless and GraphQL

Looking for a hands-on tutorial? Check out Getting Started with AEM Headless and GraphQL end-to-end tutorial illustrating how to build-out and expose content using AEM’s GraphQL APIs and consumed by an external app, in a headless CMS scenario.

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