Modern frontend applications require flexible APIs that minimize over-fetching and under-fetching. REST APIs, while powerful, often return fixed responses that may not match a client’s exact data needs. This is where GraphQL shines.

With Spring Boot and GraphQL, you can design APIs where clients control the shape of the response. This results in better performance, faster development cycles, and a cleaner separation of concerns.

In this post, you’ll learn how to build GraphQL APIs in Spring Boot, define schemas, create resolvers, and implement pagination, filtering, and best practices for production-ready GraphQL services.

Why Use GraphQL?

GraphQL is a query language for APIs developed by Facebook. It allows clients to:

  • Request exactly the data they need
  • Combine multiple resources in a single request
  • Avoid multiple round trips

Key benefits include:

  • Client-driven queries
  • Strongly-typed schemas
  • Built-in documentation via introspection
  • Efficient bandwidth usage

Setting Up Spring Boot with GraphQL

Spring Boot supports GraphQL via the spring-boot-starter-graphql module.

Add dependencies in pom.xml:

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-graphql</artifactId>
</dependency>
<dependency>
<groupId>com.graphql-java</groupId>
<artifactId>graphql-java-tools</artifactId>
<version>13.0</version>
</dependency>

Enable GraphQL UI via:

<dependency>
<groupId>com.graphql-java-kickstart</groupId>
<artifactId>graphiql-spring-boot-starter</artifactId>
<version>11.1.0</version>
</dependency>

Now start your Spring Boot app and access /graphiql to test queries.

Defining GraphQL Schemas

GraphQL uses a schema file to define types and relationships.

Create a file: src/main/resources/graphql/schema.graphqls

type Query {
users: [User]
userById(id: ID!): User
}

type User {
id: ID!
name: String
email: String
}

This defines a User type and two queries: users and userById.

Implementing Resolvers in Java

Create a resolver class to provide data for your schema:

@Component
public class UserQueryResolver implements GraphQLQueryResolver {

    private final UserService userService;

    public UserQueryResolver(UserService userService) {
        this.userService = userService;
    }

    public List<User> users() {
        return userService.getAllUsers();
    }

    public User userById(Long id) {
        return userService.getUserById(id);
    }
}

Resolvers map directly to the queries and fields in your schema.

Adding Arguments and Filtering

GraphQL allows argument-based filtering without defining new endpoints:

type Query {
searchUsers(name: String): [User]
}

Implement in the resolver:

public List<User> searchUsers(String name) {
return userRepository.findByNameContainingIgnoreCase(name);
}

This gives clients control over search functionality.

Pagination Support

For large datasets, use pagination with custom arguments:

type Query {
usersPaginated(page: Int = 0, size: Int = 10): [User]
}

In the resolver:

public List<User> usersPaginated(int page, int size) {
Pageable pageable = PageRequest.of(page, size);
return userRepository.findAll(pageable).getContent();
}

Alternatively, implement cursor-based pagination for better performance.

Nested Queries and Relationships

GraphQL shines with nested and relational data:

type Post {
id: ID!
title: String
author: User
}

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

Resolvers can fetch related data dynamically, avoiding over-fetching.

Error Handling

Throw application-level exceptions in resolvers and handle them globally:

@Component
public class GraphQLExceptionHandler extends DataFetcherExceptionResolverAdapter {
@Override
protected GraphQLError resolveToSingleError(Throwable ex, DataFetchingEnvironment env) {
return GraphqlErrorBuilder.newError(env)
.message(ex.getMessage())
.build();
}
}

Use GraphQLError objects to return structured error messages.

GraphQL vs REST

Feature GraphQL REST
Flexibility High (client-driven) Low (server-defined)
Overfetching Avoided Common
Tooling Schema-first, typed Often ad hoc
Documentation Built-in introspection Swagger/OpenAPI

Use GraphQL when your clients need dynamic control or multiple related datasets in one call.

Best Practices

  • Use DTOs to decouple internal models from schema
  • Avoid N+1 query problems with batching tools like DataLoader
  • Secure queries with depth limiting and whitelisting
  • Document schema evolution strategies for backward compatibility
  • Expose health endpoints for GraphQL uptime monitoring

Conclusion

Spring Boot and GraphQL make it easy to build APIs that are both developer-friendly and performance-efficient. With a flexible schema, powerful resolver model, and seamless integration with existing Spring services, GraphQL is a great choice for building modern backend services.

By mastering Spring Boot + GraphQL, you unlock a more client-focused, scalable, and elegant way to expose data to frontend applications.