Build GraphQL Federation with Spring Boot 3 and NetFlix DGS

In this episode, we'll cover:

• Learn to set up Spring Boot GraphQL project using JDK 21 and Spring Boot 3.0.

• Familiarizing with the project layout and configuring the IDE for seamless development.

• Running and verifying a basic Spring Boot GraphQL application, ensuring all dependencies are correctly resolved and integrated.

In this chapter, we'll cover:

• Develop a basic Account Management System with entities such as Account, Client, and Currency, featuring functionalities to list accounts.

• Create a GraphQL schema for Account, Client, and Currency types.

• Demonstrate  GraphQL queries to demonstrate requesting a list of Accounts along with Client details in a single query.

In this chapter, we'll cover:

• Understand the foundation and structure of GraphQL schemas using schema definition language (SDL).

• Overview of default scalar types and custom scalar types.

• Query and mutation types in defining read and write operations.

• The significance of non-nullable fields and how they ensure reliable data responses.

• Installation of plugins for enhancing GraphQL development within IntelliJ IDE.

In this chapter, we'll cover:

• How to structure and execute GraphQL queries to fetch specific data fields.

• Use of aliases in queries.

• Creating reusable sets of fields with fragments to avoid repetition and query management.

• Understanding the use of HTTP POST for sending GraphQL queries and mutations.

• Using introspection queries to explore and troubleshoot issues.

In this chapter, we'll cover:

• Understanding the N+1 problem and its impact on performance in GraphQL implementations.

• Introducing Batch Mapping as a solution to efficiently handle data fetching and mitigate the N+1 problem.

• Learn to implement Batch Mapping in Spring Boot GraphQL applications.

• Demonstrate how @BatchMapping reduces database hits and improves performance with a real-world example.

• Understand the basics of implementing GraphQL mutations in a Spring Boot environment..

• Walk through the steps to install and set up PostgreSQL for development.

In this chapter, we'll cover:

• How to design GraphQL schema mutations for creating, updating, and deleting data.

• Defining custom input types and passing arguments to mutations.

• Use of scalar types like ID  to uniquely identify objects.

• The significance of non-nullable assertions in GraphQL schema design to ensure data integrity.

In this chapter, we'll cover:

• How to integrate Spring Boot with JPA and PostgreSQL to streamline database operations in a GraphQL API.

• Develop an accountById method in the AccountsController, using @QueryMapping and @Argument annotations to handle GraphQL queries.

• Learn to create and annotate methods with @MutationMapping to handle GraphQL mutations like addAccount, editAccount, and deleteAccount.

• Map GraphQL arguments to method parameters - using the @Argument to method parameters in your Spring Boot application.

• Implement - create, read, update, and delete  Database operations to integrate Spring Boot with JPA and PostgreSQL and  GraphQL API.

Execute and validate GraphQL mutations using Postman:

• Test addAccount, editAccount, and deleteAccount, and verify their success through returned responses.

• Understand mutation scripts and interpret the responses.

• Verify database changes in PostgreSQL

In this chapter, we'll cover:

• The need for extended scalar types in GraphQL.

• Configure extended scalars in a Spring Boot application.

• Define and use custom scalar types such as DateTime, CountryCode, and PositiveFloat in a GraphQL schema to enforce specific data formats and constraints.

In this chapter, we'll cover:

• GraphQL Response Structure : Understanding the consistent format of GraphQL responses, including data, errors, and extensions.

• Components of an Error Object: Detailing the fields within an error object, such as message, locations, path, and extensions.

• Partial Response Handling: Implement and demonstrate GraphQL's "Partial Response" capability.

• Compare GraphQL's error handling approach with REST.

In this chapter, we'll cover:

1. GraphQL Exception Handling Basics: How GraphQL manages errors differently from REST APIs, including partial success scenarios.

2. Implementing Exception Handlers: Utilizing the @GraphQlExceptionHandler annotation in Spring Boot for custom error responses.

3. Practical Demonstration: Running example mutations to show partial responses and detailed error reporting.

In this chapter, we'll cover:

1. Global exception handling in a GraphQL service using @ControllerAdvice and @GraphQLExceptionHandler.

2. Learn to create custom exception classes and handle them in a centralized manner within GraphQL error specifications.

3. Construct detailed GraphQLError objects, including using the extensions map for additional error context.

4. Practical application of handling partial responses in GraphQL.