Java : loop on all the classes in the classpath [duplicate]

Answer 1

If you use spring-context in your project: Here a working example to enumerate all types with the desired annotation:

/**
 * Lists all types in the given package (recursive) which are annotated by the given annotation.
 * 

 * All types which match the criteria are returned, no further checks (interface, abstract, embedded, etc.
 * are performed.
 * 

 *
 * @param aAnnotation
 *        the desired annotation type
 * @param aRoot
 *        the package name where to start the search.
 * @return a list of found types
 */
private Collection> findCandidatesByAnnotation( Class aAnnotation,
                                                                   String aRoot )
{
    List> result = new ArrayList>();

    ClassPathScanningCandidateComponentProvider scanner =
            new ClassPathScanningCandidateComponentProvider( false )
    {
        @Override
        protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition)
        {
            return true;
        }
    };

    scanner.addIncludeFilter( new AnnotationTypeFilter( aAnnotation ) );
    Set canditates = scanner.findCandidateComponents( aRoot );
    for ( BeanDefinition beanDefinition : canditates )
    {
        try
        {
            String classname = beanDefinition.getBeanClassName();
            Class clazz = Class.forName( classname );
            result.add( clazz );
        }
        catch ( ClassNotFoundException t )
        {
            myLog.error( "Springs type scanner returns a class name whose class cannot be evaluated!!!", t );
        }
    }

    return result;
}

This code was tested against spring-context-4.1.1.RELEASE under java 8.