Blog — page 2 of 3 | LeetJourney

7 September 20263 min read

What goes wrong when a JPA entity is also your API response, and how DTOs fix it without much ceremony.

7 September 20263 min read

Where @Valid actually takes effect, why your constraints are being ignored, and how to write a custom one.

7 September 20263 min read

How to turn thrown exceptions into consistent HTTP responses using @RestControllerAdvice and ProblemDetail.

6 September 20263 min read

Where Spring actually reads config from, how profiles layer on top, and why secrets never belong in application.properties.

5 September 20263 min read

@Data on a JPA entity, @Builder with required fields, and the other Lombok shortcuts that cost more than the boilerplate they remove.

4 September 20263 min read

Offset pagination, its two failure modes at scale, and how to move to keyset pagination in Spring Data without breaking clients.

3 September 20263 min read

How one innocent-looking getter turns a single query into hundreds, and the four ways to stop it.

2 September 20264 min read

Buckets, treeification, resizing, and the practical consequences: sizing, mutable keys, and why HashMap is not thread-safe in an interesting way.

1 September 20263 min read

Which actuator endpoints to expose, how liveness and readiness differ, and the custom health indicator that takes your service down.

31 August 20263 min read

The proxy rule behind Spring's most confusing silent failure, and the three ways to fix it.

29 August 20263 min read

How Spring configures Jackson, why dates come out as numbers, and the annotations that keep an API contract stable as the code changes.

28 August 20263 min read

How to run work off the request thread in Spring, why the default executor is a liability, and what gets lost when you leave the thread.