GraphQL on Apache Sling

Friday, March 17th 2023

Apache Sling provides support for GraphQL through the Sling GraphQL Core bundle. Here are the steps to use GraphQL with Apache Sling:

  1. Install the Sling GraphQL Core bundle: The first step is to install the Sling GraphQL Core bundle into your Apache Sling instance. You can download the bundle from the Apache Sling website and install it using the Sling Web Console or by deploying the bundle to the Felix OSGi container.

  2. Define the GraphQL schema: Once the Sling GraphQL Core bundle is installed, you can define your GraphQL schema using the SDL (Schema Definition Language) syntax. You can define your schema using a file or inline within your application code.

  3. Configure the GraphQL endpoint: Next, you need to configure the GraphQL endpoint in Apache Sling. You can do this using a configuration file in the /apps or /libs folder. The configuration file should specify the GraphQL schema file location and other settings, such as the endpoint URL and request method.

  4. Create your GraphQL resolvers: GraphQL resolvers are functions that resolve the queries and mutations defined in your schema. You can create your resolvers using any programming language, such as Java or JavaScript.

  5. Test your GraphQL API: Finally, you can test your GraphQL API using a GraphQL client, such as the GraphiQL web interface or the Apollo GraphQL client. You can send queries and mutations to the endpoint and receive responses in the GraphQL format.

These are the basic steps for using GraphQL with Apache Sling. The Sling GraphQL Core bundle provides additional features and configuration options for working with GraphQL in Apache Sling.

Example Schema

Sure, here is an example of an SDL (Schema Definition Language) for Apache Sling:

type Query { page(path: String!): Page } type Page { title: String body: String children: [Page] }

This SDL defines a simple schema with a single query type (Query) and a single object type (Page). The Query type includes a single field (page) that takes a required string argument (path) and returns a Page object. The Page object includes three fields (title, body, and children) that return string and list values.

To use this schema in Apache Sling, you would need to create a GraphQL resolver that implements the field and returns a Page object with the specified fields. You would also need to configure the GraphQL endpoint in Apache Sling to use the schema file and specify the endpoint URL and request method.

Once the endpoint is configured, you could test the API by sending a query to the endpoint, such as:

query { page(path: "/content/mypage") { title body children { title body } } }

This query would return the title and body of the mypage content node and the title and body of any child nodes of the mypage node.