Annotation Aggregation

Question

I have multiple classes where I have always the same annotations over the fields that define the primary key of the table for example:

@Id 
@Type(type = "uuid-binary")
@GeneratedValue(generator = "uuid")
@GenericGenerator(name = "uuid", strategy = "uuid2", 
parameters = { @Parameter(
        name = "uuid_gen_strategy_class", 
        value = "org.hibernate.id.UUIDGenerationStrategy") 
})
@Column(name="PROFILE_ID", unique = true)
@NotNull(message = "we have one message" , payload =Severity.Info.class)
private UUID profileId;

Now I am looking for a way to aggregate all those annotations to one single annotation something like annotation aggregation when I do validation i.e. I can aggregate the @NotNull and @Size from (javax.validation.constraints ) to the following annotation called “Name”.

 package org.StudentLib.CustomeAnnotations;
 import …
 @Target( {FIELD, ANNOTATION_TYPE, CONSTRUCTOR, PARAMETER})
 @Retention(RUNTIME)
 @Constraint(validatedBy = {})
 @Documented
 @NotNull
 @Id 
 @Size(message = "The size of the name should be between {min} and {max} caracters", 
                min = 1, max = 50, 
                payload = Severity.Info.class
                )
 public @interface Name {
    }

So how do I do the same for persistent annotations, I always get

The annotation @Id is disallowed for this location

Why I am getting this error? Is there a way to combine the persistence annotations and validation annotation in one single annotation. The reason I am asking this is because I have around 40 tables( Entities ) in my code and I feel that I am dong code duplication every time I need to define the primary key of that table.

Answer 1

You are getting this error because the Target meta-annotation applied to the Id annotation type doesn't contain the parameters ANNOTATION_TYPE in its value field. Take a look at the javadoc, and you will see it (ctrl+f '@Target').

The @Target meta-annotation describes to what java language constructs an annotation can be applied. Due to the fact that you are unable to apply this annotation to an ANNOTATION_TYPE, you will be unable to create such a shortcut annotation.

As a side note, you can see by looking at this javadoc, that @Target has a @Target of {ANNOTATION_TYPE}, which is effectively what makes an annotation a meta-annotation.