Spring GraphQL

https://github.com/spring-boot-tutorials/spring-graphql

In this article we will configure Spring Boot to serve GraphQL endpoints.

Create Initial Code Base

• Go to https://start.spring.io/

• Add the following dependencies:

  • spring-boot-starter-graphql

  • spring-boot-starter-web

  • lombok

• Click Generate

Dependencies

Dependencies used in pom.xml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-graphql</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
</dependency>

Properties

Add the following properties into src/main/resources/application.yaml:

spring:
  graphql:
    graphiql:
      # enables GraphQL UI at http://localhost:8080/graphiql
      enabled: true

GraphQL Schema Files

Create new file src/main/resources/graphql/start.gqls:

type Post {
    id: ID!
    title: String!
    text: String!
    category: String
    author: Author!
}

type Author {
    id: ID!
    name: String!
    thumbnail: String
    posts: [Post]!
}

# The Root Query for the application
type Query {
    recentPosts(count: Int, offset: Int): [Post]!
}

# The Root Mutation for the application
type Mutation {
    createPost(title: String!, text: String!, category: String, authorId: String!) : Post!
}

Model

Let’s create a new POJO src/main/java/com/example/graphql/model/Author.java

@Data
@SuperBuilder
@NoArgsConstructor
public class Author {
    private String id;
    private String name;
    private String thumbnail;
    private List<Post>  posts;
}

Create a new POJO src/main/java/com/example/graphql/model/Post.java:

@Data
@SuperBuilder
@NoArgsConstructor
public class Post {
    private String id;
    private String title;
    private String category;
    private String authorId;
    private String text;
}

Repository

Create a stub repository with fake data src/main/java/com/example/graphql/repository/PostRepository.java:

@Service
public class PostRepository {

    private List<Post> posts = new ArrayList<>();
    private List<Author> authors = new ArrayList<>();

    public PostRepository() {
        posts.add(Post.builder()
                .id("id-1")
                .title("title-1")
                .authorId("author-1")
                .text("text-1")
                .category("category-1")
                .build());
        posts.add(Post.builder()
                .id("id-2")
                .title("title-2")
                .authorId("author-2")
                .text("text-2")
                .category("category-2")
                .build());
        posts.add(Post.builder()
                .id("id-3")
                .title("title-3")
                .authorId("author-3")
                .text("text-3")
                .category("category-3")
                .build());

        authors.add(Author.builder()
                .id("author-1")
                .name("name-1")
                .thumbnail("thumbnail-1")
                .posts(List.of(posts.get(0)))
                .build());
        authors.add(Author.builder()
                .id("author-2")
                .name("name-2")
                .thumbnail("thumbnail-2")
                .posts(List.of(posts.get(1)))
                .build());
        authors.add(Author.builder()
                .id("author-3")
                .name("name-3")
                .thumbnail("thumbnail-3")
                .posts(List.of(posts.get(2)))
                .build());
    }

    public List<Post> getRecentPosts() {
        return this.posts;
    }

    public void savePost(Post post) {
        this.posts.add(post);
    }

    public Author getAuthor(String authorID) {
        return authors.stream()
                .filter(a -> a.getId().equals(authorID)).findFirst()
                .orElse(null);
    }
}

Controller

Create a new class src/main/java/com/example/graphql/controller/PostController.java:

@Controller
public class PostController {

    @Autowired
    private PostRepository postDao;

    @QueryMapping
    public List<Post> recentPosts(@Argument int count, @Argument int offset) {
        return postDao.getRecentPosts();
    }

    @SchemaMapping
    public Author author(Post post) {
        return postDao.getAuthor(post.getAuthorId());
    }

    @MutationMapping
    public Post createPost(@Argument String title,
                           @Argument String text,
                           @Argument String category,
                           @Argument String authorId) {
        Post post = new Post();
        post.setId(UUID.randomUUID().toString());
        post.setTitle(title);
        post.setText(text);
        post.setCategory(category);
        post.setAuthorId(authorId);

        postDao.savePost(post);

        return post;
    }
}

Run & Verify Application

Open terminal at project root and execute the following:

mvn spring-boot:run

Goto: http://localhost:8080/graphiql

Input GraphQL Query:

query {
    recentPosts(count: 10, offset: 0) {
        id
        title
        category
        author {
            id
            name
            thumbnail
        }
    }
}