Modernize Legacy Java API to Spring Boot

Rewrite old Java HTTP handlers into modern Spring Boot REST controllers.

category:modernization

java

spring-boot

migration

backend

Prompt

Rewrite this legacy Java HTTP or servlet-based API into Spring Boot.

Use:
- @RestController and @RequestMapping/@GetMapping/etc
- DTOs for request/response bodies
- Validation annotations (e.g. @NotNull, @Size)
- Exception handlers via @ControllerAdvice

Keep behavior the same while improving structure.