/graphql-demo

GraphQL Demo Spring Boot Application.

Primary LanguageJava

Introduction to GraphQL

Getting Started

This is a demo Spring Boot, Gradle project for GraphQL.

Reference Documentation

Application Requirements:

  • Java 8+
  • H2 In-Memory Database (Demo only, not suitable for production)
  • GraphQL Dependencies for Spring Boot with Gradle:
compile group: 'com.graphql-java', name: 'graphql-spring-boot-starter', version: '5.0.2'
compile group: 'com.graphql-java', name: 'graphiql-spring-boot-starter', version: '5.0.2'
compile group: 'com.graphql-java', name: 'graphql-java-tools', version: '5.2.4'

Guides

Running the applications & Using GraphiQL & H2-DB Console:

  1. Run the demo application:

    • ./gradlew bootRun

  2. GraphiQL Web Tool is a user-friendly GUI for constructing Queries and Mutation operations:

    • http://localhost:8080/graphiql

  3. H2 In-Memory Database Console for checking records if needed:

    • Web URL: http://localhost:8080/h2-console
    • Driver Class: org.h2.Driver
    • JDBC URL: jdbc:h2:mem:test
    • Username: user
    • Password: password

Sample Data and Code:

  • The application has a sample data that is bootstrapped in the following file: src/main/java/de/neofonie/techly/graphql/SetupDataLoader.java

  • The entities include Author, Post, Comments as a simple blog with one to many relations and relevant repositories. src/main/java/de/neofonie/techly/graphql/persistence/*

  • Few services to run queries and mutation operations such as read and save: src/main/java/de/neofonie/techly/graphql/services/*

  • GraphQL specific resolvers for Queries and Mutations that bind GraphQL schema methods to services: src/main/java/de/neofonie/techly/graphql/query/* src/main/java/de/neofonie/techly/graphql/mutation/*

  • A GraphQL schema file that contains types and methods: resources/graphql/schema.graphqls

Queries

  • Queries are GET calls for single endpoint with a parameter, e.g.: ?query={posts{.....}}
  • There are client libraries for GraphQL to construct such HTTP GET queries.
  • Fields and methods are documented in the right hand panel titled Documentation Explorer
  • To test GraphQL queries, in the GUI tool GraphiQL, see link above, here is an example query to get all posts, related author and comments:
    query {
      posts {
        id
        title
        content
        created
        author {
          id
          name
        }
        comments {
          id
          content
          created
        }
      }
    }
  • The query above could be modified with more or less fields and types, for example author could be removed if not needed or any other fields.
  • The query is flexible on the client side where we could ask only for hte data we need, here is a different version of the query:
    query {
      posts {
        title
        created
        comments {
          content
          created
        }
      }
    }

Mutations

  • Mutations are HTTP POST requests to predefined methods.
  • The following mutation example demonstrates how we create a new comment by adding required fields post_id and content as parameters. Also, we could define the response of the operation and type of data, to be returned from the response, in the body of createComment method.
mutation {
  createComment(post_id: 8, content: "TEST") {
    id
    content
    post {
      id
      title
    }
  }
}
  • The createComment mutation method maps to the backend CommentMutation.createComment method which uses service method CommentService.createComment to create a new comment.
  • Fields and methods are documented in the right hand panel titled Documentation Explorer.

Subscriptions

  • Subscriptions are event-based, pushed updates from the server to the client when data is added or updated.
  • No example in this demo since it requires implementation on the client side as well.

Additional Links

Official GraphQL Documentation:

GraphQL Clients & Servers: