Modern API Development with Spring and Spring Boot

Sourabh Sharma

• Publisher: Packt Publishing
• Year: 2021
• ISBN:
  9781800562875
• Edition: 1
• Topic: Computer Science
• Subtopic: Programming in Java
• Index: Computer Science

A developer's guide to designing, testing, and securing production-ready modern APIs with the help of practical ideas to improve your application's functionalityKey Features• Build resilient software for your enterprises and customers by understanding the complete API development life cycle• Overcome the challenges of traditional API design by adapting to a new and evolving culture of modern API development• Use Spring and Spring Boot to develop future-proof scalable APIsBook DescriptionThe philosophy of API development has evolved over the years to serve the modern needs of enterprise architecture, and developers need to know how to adapt to these modern API design principles. Apps are now developed with APIs that enable ease of integration for the cloud environment and distributed systems. With this Spring book, you'll discover various kinds of production-ready API implementation using REST APIs and explore async using the reactive paradigm, gRPC, and GraphQL. You'll learn how to design evolving REST-based APIs supported by HATEOAS and ETAGs and develop reactive, async, non-blocking APIs. After that, you'll see how to secure REST APIs using Spring Security and find out how the APIs that you develop are consumed by the app's UI. The book then takes you through the process of testing, deploying, logging, and monitoring your APIs. You'll also explore API development using gRPC and GraphQL and design modern scalable architecture with microservices. The book helps you gain practical knowledge of modern API implementation using a sample e-commerce app. By the end of this Spring book, you'll be able to develop, test, and deploy highly scalable, maintainable, and developer-friendly APIs to help your customers to transform their business.What you will learn• Understand RESTful API development, its design paradigm, and its best practices• Become well versed in Spring's core components for implementing RESTful web services• Implement reactive APIs and explore async API development• Apply Spring Security for authentication using JWT and authorization of requests• Develop a React-based UI to consume APIs• Implement gRPC inter-service communication• Design GraphQL-based APIs by understanding workflows and tooling• Gain insights into how you can secure, test, monitor, and deploy your APIsWho this book is forThis book is for inexperienced Java programmers, comp science, or coding boot camp graduates who have knowledge of basic programming constructs, data structures, and algorithms in Java but lack the practical web development skills necessary to start working as a developer. Professionals who've recently joined a startup or a company and are tasked with creating real-world web APIs and services will also find this book helpful. This book is also a good resource for Java developers who are looking for a career move into web development to get started with the basics of web service development.

Section 1: RESTful Web Services

In this section, you will develop and test the production-ready and evolving REST-based APIs supported by HATEOAS and ETAGs. API specs will be written using OpenAPI specifications (Swagger). You will learn the fundamentals of reactive API development using Spring WebFlux. By the end of this section, you will be familiar with the fundamentals of REST, best practices, and how to write evolving APIs. After completing this section, you will be able to develop sync and reactive async non-blocking APIs.

This section comprises the following chapters:

• Chapter 1, RESTful Web Service Fundamentals
• Chapter 2, Spring Concepts and REST APIs
• Chapter 3, API Specifications and Implementation
• Chapter 4, Writing Business Logic for APIs
• Chapter 5, Asynchronous API Design

Chapter 1: RESTful Web Service Fundamentals

In this chapter, you will go through the fundamentals of RESTful APIs, or REST APIs for short, and their design paradigms. We will take a brief look at the history of REST, learn how resources are formed, and understand methods and status codes before we move on to explore Hypermedia As The Engine Of Application State (HATEOAS). These basics should provide a solid platform for you to develop a RESTful web service. You will also learn the best practices for designing Application Programming Interfaces (APIs).

This chapter will also introduce a sample e-commerce app, which will be used throughout the book as you learn about the different aspects of API development. In this chapter, we will cover the following topics:

• Introducing REST APIs
• Handling resources and Uniform Resource Identifiers (URIs)
• Exploring Hypertext Transfer Protocol (HTTP) methods and status codes
• Learning HATEOAS
• Best practices for designing REST APIs
• Overview of an e-commerce app (our sample app)

Technical requirements

This chapter does not require any specific software. However, knowledge of HTTP is necessary.

Introducing REST APIs

An API is the means by which a piece of code communicates with another piece of code. You might have already written an API for your code or used one in your programs; for example, in Java libraries for collection, input/output, or streams that provide a variety of APIs to perform specific tasks.

Java's SDK APIs allow one part of a program to communicate with another part of a program. You can write a function and then expose it with public access modifiers so that other classes can use it. That function signature is an API for that class. However, APIs that are exposed using these classes or libraries only allow internal communication inside a single application or individual service. So, what happens when two or more applications (or services) want to communicate with each other? In other words, you would like to integrate two or more services. This is where system-wide APIs help us.

Historically, there were different ways to integrate one application with another – RPC, Simple Object Access Protocol (SOAP)-based services, and more. The integration of apps has become an integral part of software architectures, especially after the boom of the cloud and mobile phones. You now have social logins, such as Facebook, Google, and GitHub, which means you can develop your application even without writing an independent login module and get around security issues such as storing passwords in a secure way.

These social logins provide APIs using REST and GraphQL. Currently, REST is the most widely used, and it has become a standard for writing APIs for integration and web app consumption. We'll also discuss GraphQL in detail in the final chapters of this book (in Chapter 13, GraphQL Fundamentals, and Chapter 14, GraphQL Development and Testing).

REST stands for REpresentational State Transfer, which is a style of software architecture. Web services that adhere to the REST style are called RESTful web services. In the following sections, we will take a quick look at the history of REST to understand its fundamentals.

REST history

Before REST adoption, when the internet was just starting to become widely known and Yahoo and Hotmail were the popular mail and social messaging apps, there was no standard software architecture that offered a homogenous way to integrate with web applications. People were using SOAP-based web services, which, ironically, were not simple at all.

Then came the light. Roy Fielding, in his doctoral research, Architectural Styles and the Design of Network-Based Software Architectures (https://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm), came up with REST in 2000. REST's architecture style allowed any server to communicate with any other server over the network. It simplified communication and made integration easier. REST was made to work on top of HTTP, which enables it to be used all over the web and in internal networks.

eBay was the first to exploit REST-based APIs. It introduced the REST API with selected partners in November 2000. Later, Amazon, Delicious (a site-bookmarking web app), and Flickr (the photo-sharing app) started providing REST-based APIs. In fact, Amazon Web Services (AWS) took advantage of Web 2.0 (with the invention of REST) and provided REST APIs to developers for AWS cloud consumption in 2006.

Later Facebook, Twitter, Google, and other companies started using it. Nowadays (in 2021), you will hardly find any web application developed without a REST API. Although, the GraphQL-based API for mobile apps is getting pretty close in terms of popularity.

REST fundamentals

REST works on top of the HTTP protocol. Each URI works as an API resource. Therefore, we should use nouns as endpoints instead of verbs. RPC-style endpoints use verbs, for example, api/v1/getPersons. In comparison, in REST, this endpoint could be simply written as api/v1/persons. You must be wondering, then, how can we differentiate between the different actions performed on a REST resource? This is where HT...