Question

I have this interface:

public interface IDbTable extends Serializable
{
    public int getId();
}

I need to obligate all the classes that implements IDbTable, to have an annotation “@DatabaseTable” and at least one field inside class that have “@DatabaseField”.
The only way of implementing IDbTable needs to be like this:

@DatabaseTable(tableName = "Something")
public static class TestTable implements IDbTable
{
            @DatabaseField
            public int id;

    public int getId()
    {
        return id;
    }
}

Is this possible with interface or inheritance?
Today i have an unit test that scan all the classes and check this requirements. Is this a good practice?

Answer 1

You can’t apply annotations to an interface that will be inherited by the implementing class, according to Java documentation: http://docs.oracle.com/javase/6/docs/api/java/lang/annotation/Inherited.html

Indicates that an annotation type is automatically inherited. If an
Inherited meta-annotation is present on an annotation type
declaration, and the user queries the annotation type on a class
declaration, and the class declaration has no annotation for this
type, then the class’s superclass will automatically be queried for
the annotation type. This process will be repeated until an annotation
for this type is found, or the top of the class hierarchy (Object) is
reached. If no superclass has an annotation for this type, then the
query will indicate that the class in question has no such annotation.

Note that this meta-annotation type has no effect if the annotated
type is used to annotate anything other than a class. Note also that
this meta-annotation only causes annotations to be inherited from
superclasses; annotations on implemented interfaces have no effect.