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There are a few ways to implement projections. One way is to is to use the convention `T find[Domain Class][Property]`. For example say the `Book` class has a `releaseDate` property of type `Date`:

[source,groovy]
----
@Service(Book)
interface BookService {
   Date findBookReleaseDate(String title)
}
----

This also works for multiple results:

[source,groovy]
----
@Service(Book)
interface BookService {
   List<Date> findBookReleaseDate(String publisher)
}
----

And you can use the `Map` argument to provide ordering and pagination if necessary:

[source,groovy]
----
@Service(Book)
interface BookService {
   List<Date> findBookReleaseDate(String publisher, Map args)
}
----

===== JPA-QL Projections

You can also use a JPA-QL query to perform a projection:

[source,groovy]
----
@Service(Book)
interface BookService {
   @Query("select $b.releaseDate from ${Book b} where $b.publisher = $publisher order by $b.releaseDate")
   List<Date> findBookReleaseDates(String publisher)
}
----

===== Interface Projections

Sometimes you want to expose a more limited set of a data to the calling class. In this case it is possible to use interface projections.

For example:


[source,groovy]
----
class Author {
    String name
    Date dateOfBirth <1>
}
interface AuthorInfo {
    String getName() <2>
}
@Service(Author)
interface AuthorService {
   AuthorInfo find(String name) <3>
}
----

<1> The domain class `Author` has a property called `dateOfBirth` that we do not want to make available to the client
<2> You can define an interface that only exposes the properties you want to expose
<3> Return the interface from the service.

NOTE: If a property exists on the interface but not on the domain class you will receive a compilation error.
