How do you create GraphQL queries in Spring Boot?

Table of Contents

• Introduction
• Steps to Create GraphQL Queries in Spring Boot
  • 1. Add Dependencies to Your Spring Boot Project
    • Example: Add GraphQL Dependency to pom.xml
  • 2. Define the GraphQL Schema
    • Example: schema.graphqls
  • 3. Create Resolvers to Handle Queries
    • Example: Create a Resolver Class
  • 4. Define the Product Class
    • Example: Product.java
  • 5. Expose the GraphQL Endpoint
    • Example: Configure Endpoint in application.properties
  • 6. Test the GraphQL Queries
    • Example: Query to Get a Product
    • Example: Query to Get All Products
• Conclusion

Introduction

GraphQL is a powerful query language that allows clients to request specific data from an API. In a Spring Boot application, creating GraphQL queries involves defining the schema, writing resolvers to handle the queries, and exposing them through an endpoint. This guide will walk you through the steps to create and handle GraphQL queries in a Spring Boot application.

Steps to Create GraphQL Queries in Spring Boot

1. Add Dependencies to Your Spring Boot Project

To use GraphQL in your Spring Boot application, first, add the necessary dependencies to your pom.xml. You'll need spring-boot-starter-graphql to integrate GraphQL with Spring Boot.

Example: Add GraphQL Dependency to pom.xml

This starter includes everything you need to define GraphQL queries and expose them via HTTP endpoints.

2. Define the GraphQL Schema

In GraphQL, the schema defines the structure of your API, including types, queries, and mutations. You need to create a schema.graphqls file to define your queries and the types that the queries will return.

Example: schema.graphqls

• The Query type defines two queries: getProduct (which retrieves a product by its ID) and getAllProducts (which retrieves all products).
• The Product type defines the structure of a product object, which includes id, name, and price.

3. Create Resolvers to Handle Queries

GraphQL resolvers are responsible for fetching data for each query defined in the schema. In Spring Boot, you can use resolver methods annotated with @QueryMapping to handle these queries.

Example: Create a Resolver Class

In this example:

• getProduct(Long id) fetches a single product by its ID.
• getAllProducts() fetches all products.

The @QueryMapping annotation automatically binds these methods to the queries in the GraphQL schema.

4. Define the Product Class

For this example, you'll also need a simple Product class to represent the product data.

Example: Product.java

5. Expose the GraphQL Endpoint

Spring Boot, with spring-boot-starter-graphql, automatically exposes a GraphQL endpoint at /graphql. You can configure the endpoint URL in the application.properties or application.yml file if needed.

Example: Configure Endpoint in application.properties

This setup ensures that your GraphQL queries are accessible via HTTP POST requests at the /graphql URL.

6. Test the GraphQL Queries

Once the application is running, you can test the queries using a GraphQL client like GraphiQL, Postman, or any other tool that supports GraphQL.

Example: Query to Get a Product

Example: Query to Get All Products

Conclusion

Creating GraphQL queries in Spring Boot involves defining a schema, writing resolvers to handle the queries, and configuring the Spring Boot application to expose the GraphQL endpoint. The @QueryMapping annotation simplifies the process of mapping methods to GraphQL queries, reducing the amount of boilerplate code. With this setup, you can easily build powerful and flexible APIs using GraphQL in Spring Boot.