Imagine you’ve just built an API in Spring Boot, eagerly testing it with Postman. You send a JSON payload, but to your dismay, the data arrives as null in your backend. This seemingly simple problem often baffles many developers, especially those new to Spring Boot or REST APIs. Beyond being an annoyance, it can slow down your development process and leave you questioning your implementation. Let’s dive into the causes of this issue, explore detailed solutions, and analyze related aspects to ensure you never encounter this issue again.