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Problem4J Project Launch

· 3 min read
Damian Malczewski
Damian Malczewski
Creator of Problem4J

Hi everyone 👋

Allow me to introduce Problem4J to y'all. It's another set of Java libraries implementing RFC7807 - Problem Details for HTTP APIs.

Problem4J is a package of libraries that introduces RFC Problem Details to the Java ecosystem. It combines an imperative approach, based on extending a common exception type (ProblemException), with a declarative, annotation-based approach (via @ProblemMapping). As a primary set of modules, problem4j-core, problem4j-jackson, and problem4j-spring were introduced, providing a core (framework-agnostic) module, Jackson integration (both v2 - com.fasterxml.jackson and v3 - tools.jackson), as well as Spring Boot integration (supporting both leading versions - v3 and v4). Other integrations may (or may not) eventually arrive.

Why should I care?

If you are building HTTP APIs in Java, Problem4J aims to reduce the boilerplate around error handling while keeping your domain logic clean and explicit. By clearly separating the Problem representation from exceptions, and by offering both imperative and declarative mapping options, the library helps you produce consistent, standards-compliant error responses without tightly coupling your code to a specific framework. This becomes especially useful in high-end framework applications (such as Spring Boot), where sensible defaults and simple extension points can significantly improve both developer experience and maintainability.

The following modules and versions are considered the first public releases of this library. Previous versions were developed as a "personal playground" under the io.github.malczuuu.problem4j group namespace.

  • Core
    • io.github.problem4j:problem4j-core:1.3.0
  • Jackson Integration
    • io.github.problem4j:problem4j-jackson2:1.3.0 (Jackson 2 - com.fasterxml.jackson)
    • io.github.problem4j:problem4j-jackson3:1.3.0 (Jackson 3 - tools.jackson)
  • Spring Boot 3.x Integration
    • io.github.problem4j:problem4j-spring-bom:1.2.0
    • io.github.problem4j:problem4j-spring-web:1.2.0
    • io.github.problem4j:problem4j-spring-webflux:1.2.0
    • io.github.problem4j:problem4j-spring-webmvc:1.2.0
  • Spring Boot 4.x Integration
    • io.github.problem4j:problem4j-spring-bom:2.1.0
    • io.github.problem4j:problem4j-spring-web:2.1.0
    • io.github.problem4j:problem4j-spring-webflux:2.1.0
    • io.github.problem4j:problem4j-spring-webmvc:2.1.0

The main inspiration was the idea of taking a slightly different approach than zalando/problem, as well as the fact that zalando/problem-spring-web does not seem to have received an update for Spring Boot 4 at the time of writing this post. What differentiates this library from Zalando's is the separation of the Problem model from the throwable ProblemException, including a declarative approach with @ProblemMapping annotation, as well as making Spring Boot's predefined exception handlers more beginner-friendly (simple ProblemResolver implementations declared as @Components). Moreover, predefined Spring Boot error messages tend to hide exception internals and do not expose plain exception messages in HTTP responses.

Feedback, ideas, and contributions are very welcome 🚀

References