Module storm.foundation

Package st.orm

Annotation Interface ProjectionQuery

@Target(TYPE)
@Retention(RUNTIME)
public @interface ProjectionQuery

Projection records marked with this annotation type can specify a SQL query that represents the projection.

Usage examples:

Define a projection record with a SQL query.

Java:

 @ProjectionQuery("""
     SELECT b.id, COUNT(*) AS item_count, SUM(price) AS total_price
     FROM basket b
       LEFT JOIN basket_item bi ON b.id = bi.basket_id
     GROUP BY b.id""")
 record BasketSummary(@PK @FK("id") Basket basket,
                      int itemCount,
                      BigDecimal totalPrice
 ) implements Projection<Integer> {}
 

Kotlin:

 @ProjectionQuery("""
     SELECT b.id, COUNT(*) AS item_count, SUM(price) AS total_price
     FROM basket b
       LEFT JOIN basket_item bi ON b.id = bi.basket_id
     GROUP BY b.id""")
 data class BasketSummary(@PK @FK("id") val basket: Basket,
                          val itemCount: Int,
                          val totalPrice: BigDecimal
 ) : Projection<Int>
 

Then, you can use the projection in a query like this:

 var baskets = ...
 List<BasketSummary> summaries = ORM(dataSource).projection(BasketSummary.class)
     .select()
     .where(baskets)  // Type-safe.
     .getResultList();
 

Or use it as a foreign key in an entity.

Java:

 record User(@PK int id,
             @FK("basket_id") BasketSummary basketSummary
 ) implements Entity<Integer> {}
 

Kotlin:

 data class User(@PK val id: Int,
                 @FK("basket_id") val basketSummary: BasketSummary
 ) : Entity<Int>
 

Then, you can query all users having a basket with at least 1 item:

 List<User> users = ORM(dataSource).projection(User.class)
     .select()
     .where(User_.basketSummary.itemCount, GREATER_THAN, 0)   // Type-safe metamodel.
     .getResultList();
 

Required Element Summary

Required Elements

Modifier and Type	Required Element	Description
String	value	The SQL query that represents the projection.

Element Details

value

String value

The SQL query that represents the projection.