Regular Expression Pocket Reference
Tony Stubblebine
Tribe of Hackers: Red Team
Marcus J. Carey & Jennifer Jin
Cloud Native Infrastructure
Justin Garrison & Kris Nova
Network Programmability and Automation
Christian Adell & Scott S. Lowe & Matt Oswalt & Jason Edelman
Persistence with Spring
Baeldung
Move on to JUnit 5
A Microservice Architecture with Spring Boot and Spring Cloud
Build Your API with Spring
Get the Most out of HTTP Client
Do JSON with Jackson