@Retention(value=RUNTIME)
@Target(value={TYPE,PARAMETER,METHOD})
@Documented
public @interface Union
Declares that a Java type should be represented by an Avro union schema.
May be used for base classes or interfaces whose instantiable subclasses can
be listed in the parameters to the @Union annotation. If applied to method
parameters this determines the reflected message parameter type. If applied
to a method, this determines its return type.