Question 1

How to configure Reflections to scan only specific packages and avoid performance issues?

Accepted Answer

Use ConfigurationBuilder with filterInputsBy() to include or exclude packages, as shown in the README examples, such as .filterInputsBy(new FilterBuilder().includePackage("com.my.project")). This limits scanning to relevant classes, improving startup time.

Question 2

Reflections vs Jandex: which is better for annotation scanning in Java?

Accepted Answer

Reflections is a runtime scanning library with a functional API, ideal for dynamic queries, while Jandex is often used in build-time indexing for frameworks like Quarkus. Choose Reflections if you need runtime flexibility, but Jandex for better performance in pre-compiled scenarios.

Question 3

Is Reflections still maintained or safe to use in 2024?

Accepted Answer

No, Reflections is not actively maintained as per the README warning from October 2021. It may work for existing projects, but for new development, consider alternatives like ClassGraph or native Java reflection enhancements to avoid potential issues.

Question 4

Can I integrate Reflections with Maven or Gradle for build-time scanning?

Accepted Answer

Yes, Reflections supports metadata persistence to XML/JSON or Java code generation, and there's a reflections-maven plugin mentioned in the README. This allows saving scanned data during build for faster runtime loading without rescanning.

Question 5

How to query for all methods that return a specific type using Reflections?

Accepted Answer

Use the MethodsReturn scanner, as shown in the README: reflections.get(MethodsReturn.with(void.class).as(Method.class)). Replace void.class with your desired return type to filter methods efficiently.

Question 6

What are common pitfalls when setting up Reflections scanners?

Accepted Answer

Common issues include not configuring scanners properly (leading to empty results), scanning too many classes without filters (causing performance drops), and missing the need to expand super types for transitive queries, as noted in the README's scan section.

Reflections

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