Scanning Java annotations at runtime

Question

What is the best way of searching the whole classpath for an annotated class?

I'm doing a library and I want to allow the users to annotate their classes, so when the Web application starts I need to scan the whole classpath for certain annotation.

Do you know a library or a Java facility to do this?

Edit: I'm thinking about something like the new functionality for Java EE 5 Web Services or EJB's. You annotate your class with @WebService or @EJB and the system finds these classes while loading so they are accessible remotely.

Answer 1

Use org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider

API

A component provider that scans the classpath from a base package. It then applies exclude and include filters to the resulting classes to find candidates.

ClassPathScanningCandidateComponentProvider scanner =
new ClassPathScanningCandidateComponentProvider(<DO_YOU_WANT_TO_USE_DEFALT_FILTER>);

scanner.addIncludeFilter(new AnnotationTypeFilter(<TYPE_YOUR_ANNOTATION_HERE>.class));

for (BeanDefinition bd : scanner.findCandidateComponents(<TYPE_YOUR_BASE_PACKAGE_HERE>))
    System.out.println(bd.getBeanClassName());