Using H2 Database for GraphQL APIs with Spring Boot

November 04, 2025

#1

This guide explains how to build GraphQL APIs with Spring Boot and use H2 as the backend database for testing and development.

1. Add Dependencies

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-graphql</artifactId>
</dependency>
<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
  <groupId>com.h2database</groupId>
  <artifactId>h2</artifactId>
</dependency>

2. Configure H2

spring.datasource.url=jdbc:h2:mem:graphql
spring.datasource.driver-class-name=org.h2.Driver
spring.jpa.hibernate.ddl-auto=create
spring.h2.console.enabled=true

3. Create Entity

@Entity
public class Book {
  @Id @GeneratedValue
  private Long id;
  private String title;
  private String author;
}

4. Repository

public interface BookRepository extends JpaRepository<Book, Long> {}

5. Define GraphQL Schema (schema.graphqls)

type Book {
  id: ID!
  title: String
  author: String
}

type Query {
  books: [Book]
}

type Mutation {
  addBook(title: String, author: String): Book
}

6. GraphQL Controller

@Controller
public class BookGraphQLController {
  private final BookRepository repo;

  public BookGraphQLController(BookRepository repo) {
    this.repo = repo;
  }

  @QueryMapping
  public List<Book> books() {
    return repo.findAll();
  }

  @MutationMapping
  public Book addBook(@Argument String title, @Argument String author) {
    return repo.save(new Book(null, title, author));
  }
}

7. Test GraphQL

Go to /graphiql or /graphql and run:

mutation {
  addBook(title: "GraphQL Guide", author: "John Doe") {
    id
    title
    author
  }
}

query {
  books {
    id
    title
    author
  }
}