How Can I Find and Process Java Classes with Specific Annotations at Runtime?

Finding Annotated Classes at Runtime

In Java, annotating classes provides a convenient way to add metadata to code, enabling introspection and customization. For library developers, scanning the classpath for annotated classes at runtime becomes essential to discover and process user-defined annotations. This question explores a solution for such a scenario.

ClassPath Scanning with ClassPathScanningCandidateComponentProvider

The Spring Framework offers a comprehensive solution for classpath scanning. By leveraging the org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider class, you can scan the classpath for candidate classes that match specific criteria, including annotations.

The provider operates by configuring filters to refine the scan results. In this case, you would create an annotation type filter using the desired annotation class:

scanner.addIncludeFilter(new AnnotationTypeFilter(MyAnnotation.class));

Next, specify the base package where the scanning should commence:

for (BeanDefinition bd : scanner.findCandidateComponents("com.example.base.package"))

Iterating through the resulting BeanDefinition objects will provide access to the fully qualified class names of all classes annotated with MyAnnotation, allowing you to discover and process them during library startup.

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