Question

I have a number of classes of the same type (com.project.abc.abs.Agent) annotated like so;

@Component("WEB.Agent-1"), @Component("WEB.Agent-2"), @Component("WEB.Agent-3")… etc. For now assume that all classes are in the same package (com.project.abc.web.Agent1...).

These classes are all singletons, and I want to load them dynamically into a central ‘Agent manager’ class. I.e. every time a new agent class is added with the @Component("WEB.Agent-#") annotation it is picked up without having to make changes to the Agent Manager. In the AgentManager class I need some method to load any component that matches the name “WEB.Agent-#” (where # is a number or some unique ID) is this possible using any methods in Spring?

If not I’m assuming that I would need to go about loading all classes from a particular folder/package?

Answer 1

You can do this with ClassPathScanningCandidateComponentProvider and add an exclude filter that gets rid of things that don’t match your pattern:

ClassPathScanningCandidateComponentProvider scanner =
    new ClassPathScanningCandidateComponentProvider();

scanner.addIncludeFilter(new AnnotationTypeFilter(Component.class));
scanner.addExcludeFilter(new TypeFilter(){
    public boolean match(MetadataReader metadataReader, 
                         MetadataReaderFactory metadataReaderFactory){
        return metadataReader.getAnnotationMetadata()
                 .getAnnotationAttributes(Component.class.getName())
                 .get("value").matches("WEB.Agent-[0-9]+");
    }
});

for (BeanDefinition bd : scanner.findCandidateComponents("com.project.abc.web.Agent1"))
    System.out.println(bd.getBeanClassName());