When you build REST APIs with Spring MVC / Spring Boot, you almost never write to the HTTP response body yourself. You just return Java objects… and message converters + @ResponseBody do the heavy lifting for you. 😎
🔸 TL;DR
▪️ Spring Boot auto-configures HTTP message converters (JSON, XML…) based on what’s on the classpath 📦
▪️ With @RestController, every method is treated as @ResponseBody → return a Java object, get JSON in the response ✨
▪️ Use ResponseEntity when you need fine-grained control over headers, status codes, cache hints, etc. 🧾
🔸 WHAT MESSAGE CONVERTERS DO
▪️ Take your Java objects (Order, User, etc.)
▪️ Use the right converter (e.g. Jackson for JSON)
▪️ Serialize to the HTTP response body (application/json, application/xml, …)
▪️ Work the same way for request bodies with @RequestBody (JSON → Java)
You focus on the domain model, Spring handles the HTTP marshalling/unmarshalling. 🪄
🔸 @RESPONSEBODY VS @RESTCONTROLLER
▪️ @ResponseBody on a method → return value goes directly in the HTTP body
▪️ @RestController = @Controller + @ResponseBody on all methods
▪️ For REST APIs, always start with @RestController to avoid repeating yourself 🙌
🔸 WHEN TO USE RESPONSEENTITY 🚥
Use ResponseEntity when you need:
▪️ To tune the status code (201, 204, 404, …)
▪️ To set custom headers (ETag, Last-Modified, cache headers…)
▪️ To handle conditional requests or advanced HTTP semantics
▪️ To return an empty body with specific status (e.g. ResponseEntity.noContent().build())
🔸 TAKEAWAYS
- ▪️ Let message converters handle JSON/XML, not your controllers.
- ▪️ Use @RestController for clean, concise REST controllers.
- ▪️ Use ResponseEntity when HTTP details matter (headers, status, cache).
- ▪️ Think “return domain objects”, not “write to the response”.
#java #spring #springboot #springmvc #restapi #webdev #backend #javadeveloper #cleanarchitecture #http