Can you find all classes in a package using reflection?

Question

Is it possible to find all classes or interfaces in a given package? (Quickly looking at e.g. Package, it would seem like no.)

Answer 1

Yeah using few API's you can, here is how I like doing it, faced this problem which I was using hibernate core & had to find classes which where annotated with a certain annotation.

Make these an custom annotation using which you will mark which classes you want to be picked up.

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface EntityToBeScanned {

}

Then mark your class with it like

@EntityToBeScanned 
public MyClass{

}

Make this utility class which has the following method

public class ClassScanner {

    public static Set> allFoundClassesAnnotatedWithEntityToBeScanned(){
        Reflections reflections = new Reflections(".*");
        Set> annotated = reflections.getTypesAnnotatedWith(EntityToBeScanned.class);
        return annotated;
    }

}

Call the allFoundClassesAnnotatedWithEntityToBeScanned() method to get a Set of Classes found.

You will need libs given below

    
        com.google.guava
        guava
        21.0
    


    org.javassist
    javassist
    3.22.0-CR1



    org.reflections
    reflections
    0.9.10