org.eiichiro.acidhouse

Interface GetScalar<E,R>

All Superinterfaces:

Command<R>

public interface GetScalar<E,R>
extends Command<R>

GetScalar is a command interface to get the scalar value as the result for aggregating of entity list matches to the specified Filters and sorted by the specified sort orders. This command's execution result is the returned value of the specified Aggregation instance's Aggregation#aggregate(java.util.List) method. You can build & execute this command as the following code, in App Engine:

 import org.eiichiro.acidhouse.Session;
 import org.eiichiro.acidhouse.appengine.AppEngineDatastoreSession;
 ...
 
 // Create 'Session' instance.
 Session session = new AppEngineDatastoreSession();
 // Get metamodel instance of 'Entity3' class.
 Entity3$ entity3$ = Metamodels.metamodel(Entity3.class);
 // Get summary of 'i' field of the 'Entity3' entities which their 'i' field 
 // is less than 5.
 int sum = session
                .get(Aggregations.sum(entity3$.i))
                .filter(entity3$.i.lessThan(5))
                .execute();
 

Author:

Eiichiro Uchiumi

See Also:

Aggregation, Aggregations

Method Summary

Methods

Modifier and Type	Method and Description
GetScalar<E,R>	filter(Filter<?>... filters) Qualifies entities to be retrieved with the specified Filters.
GetScalar<E,R>	sort(Order<?,?>... orders) Specifies sort orders by which the list passed to Aggregation#aggregate(java.util.List) method is sorted.

Methods inherited from interface org.eiichiro.acidhouse.Command

execute

Method Detail

sort

GetScalar<E,R> sort(Order<?,?>... orders)

Specifies sort orders by which the list passed to Aggregation#aggregate(java.util.List) method is sorted.

Parameters:

orders - The sort orders by which the returned list is sorted.

Returns:

The GetScalar which the execution result passed to Aggregation#aggregate(java.util.List) is sorted by the specified sort orders.

filter

GetScalar<E,R> filter(Filter<?>... filters)

Qualifies entities to be retrieved with the specified Filters. Each of the specified filters is combined with "logical and".

Parameters:

filters - Filters to qualify the retrieved entities.

Returns:

The GetScalar which the execution result passed to Aggregation#aggregate(java.util.List) is qualified by the specified filters.