Learn first-hand from the founder of GraphQL Java and co-author of Spring for GraphQL how to build GraphQL services in Java.
This book is for anyone who wants to build a production GraphQL service with Java. By the end of this book, you will be confident building your own production GraphQL service with Spring for GraphQL, the official Spring integration built on top of the GraphQL Java engine. Spring for GraphQL makes it easier than ever to build a GraphQL service by eliminating boilerplate code and seamlessly integrating with the Spring ecosystem.
GraphQL Java is the dominant Java implementation of GraphQL, powering services at Twitter, AirBnB, Netflix, Atlassian, and many other companies. By the end of this book, you’ll be leveraging the same engine with Spring for GraphQL.
In this book, you’ll learn key GraphQL concepts, paired with practical advice from our experiences running production GraphQL services at scale. At the end of this book, you’ll have in depth knowledge of Spring for GraphQL and the GraphQL Java engine, so you will have the confidence to run production ready GraphQL services.
This book is suitable for beginners building their first production GraphQL service. There are also advanced topics later in the book for intermediate readers.
We do not assume any prior knowledge of GraphQL. To make the most of this book, we assume basic Java knowledge, and we assume very basic Spring knowledge such as familiarity with the @Component annotation. Optionally, if you intend to build a reactive service, you should be familiar with the Reactor concepts of Mono and Flux.
Author(s): Andreas Marek; Donna Zhou
Publisher: Leanpub
Year: 2023
Language: English
Pages: 252
GraphQL with Java and Spring
GraphQL with Java and Spring
Prologue
Andi (Andreas)
Donna
About this book
Introduction
Your first Spring for GraphQL service
What is GraphQL?
A brief history of GraphQL
From GraphQL Java to Spring for GraphQL
Overview
Three layers
Schema and SDL
GraphQL query language
Request and Response
Execution and DataFetcher
How concepts relate to each other
GraphQL Java
Spring for GraphQL
Schema
Schema-first
Loading schema resources in Spring for GraphQL
GraphQL schema elements
GraphQL types
Fields everywhere
Scalar
Enum
Object
Input object
Interface
Union
List and NonNull
Directives
Arguments
Documentation with descriptions
Comments
GraphQL query language
Literals
Operations
Query operations
Mutation operations
Subscription operations
Arguments
Fragments
Inline fragments
Variables
Aliases
GraphQL document
Named and unnamed operations
Query language in GraphQL Java
DataFetchers
Spring for GraphQL annotated methods
PropertyDataFetchers in Spring for GraphQL
DataFetchers and schema mapping handler methods
TypeResolver in Spring for GraphQL
Arguments in Spring for GraphQL
More Spring for GraphQL inputs
Adding custom scalars in Spring for GraphQL
Under the hood: DataFetchers inside GraphQL Java
DataFetchers in GraphQL Java
Source objects in GraphQL Java
RuntimeWiring in GraphQL Java
Creating an executable schema in GraphQL Java
TypeResolver in GraphQL Java
Building a GraphQL service
Spring for GraphQL
GraphQL Java
Spring WebFlux or Spring MVC
Reading schemas
Configuration properties
Expanding our Spring for GraphQL service
Pet schema
Controllers
Fetching data from an external service
Source object
GraphQL arguments
Mutations
Unions, interfaces, and TypeResolver
Subscriptions
Getting started
Execution
Protocol
Client support
Request and response
Transport protocols and serialization
Request
Response
HTTP status codes
HTTP headers
Intercepting requests
GraphQL errors
Request errors
Field errors
How errors appear in the response
Error classifications
How to return errors
Throw exception during DataFetcher invocation
Customizing exception resolution
Return data and errors with DataFetcherResult
Schema design
Schema-first and implementation-agnostic
Evolution over versioning
Connected
Schema elements are cheap
Nullable fields
Nullable input fields and arguments
Pagination for lists with Relay’s cursor connection specification
Relay’s cursor connections specification
Schema
Query and response
Requesting more pages
Key concepts of Relay’s cursor connections specification
Expected errors
Mutation format
Naming standards
DataFetchers in depth
More DataFetcher inputs
Global context
Local context
DataFetcher implementation patterns
Spring for GraphQL Reactor support
Directives
Schema and operation directives
Built-in directives
@skip and @include
@deprecated
@specifiedBy
Defining your own schema and operation directives
Defining schema directives
Defining operation directives
Repeatable directives
Implementing logic for schema directives
Changing execution logic with schema directives
Validation with schema directives
Adding metadata with schema directives
Implementing logic for operation directives
Execution
Initializing execution objects
How Spring for GraphQL starts execution
Execution steps
Parsing and validation
Coercing variables
Fetching data
Reactive concurrency-agnostic
Completing a field
TypeResolver
Query vs mutation
Instrumentation
Instrumentation in Spring for GraphQL
Writing a custom instrumentation
InstrumentationContext
InstrumentationState
ChainedInstrumentation
Built-in instrumentations
List of instrumentation hooks
DataLoader
The n+1 problem
Solving the n+1 problem
DataLoader overview
DataLoader and GraphQL Java
DataLoader and Spring for GraphQL
@BatchMapping method signature
Testing
Unit testing DataFetcher
GraphQlTester
document or documentName
GraphQlTester.Request and execute
GraphQlTester.Response, path, entity, entityList
errors
Testing different layers
End-to-end over HTTP
Application test
WebGraphQlHandler test
ExecutionGraphQlService test
Focused GraphQL testing with @GraphQlTest
Subscription testing
Testing recommendations
Security
Securing a Spring for GraphQL service
Spring for GraphQL support for security
Method security
Testing auth
Java client
HTTP client
WebSocket client
GraphQlClient
