org.eiichiro.acidhouse

Class Aggregations

java.lang.Object

org.eiichiro.acidhouse.Aggregations

public abstract class Aggregations
extends Object

Aggregations has some factory methods to provide useful Aggregation instances. You can get popular aggregations by using this class. For example:

 import org.eiichiro.acidhouse.Aggregations;
 import org.eiichiro.acidhouse.Session;
 import org.eiichiro.acidhouse.metamodel.Metamodels;
 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 max value of "Entity3"'s 'i' property from 'Entity3' instances which 
 // their 'i' property value is less than 5.
 int max = session
                .get(Aggregations.max(entity3_.i))
                .filter(entity3_.i.lessThan(5))
                .execute();
 

Better to static-import this class.

Author:

Eiichiro Uchiumi

See Also:

Aggregation

Method Summary

Methods

Modifier and Type	Method and Description
static <T extends Comparable<T>> Aggregation<T>	max(Property<?,T> property) Get the max aggregation implementation for the specified property.
static <T extends Comparable<T>> Aggregation<T>	min(Property<?,T> property) Get the min aggregation implementation for the specified property.
static <T extends Number & Comparable<T>> Aggregation<T>	sum(Property<?,T> property) Get the sum aggregation implementation for the specified property.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

max

public static <T extends Comparable<T>> Aggregation<T> max(Property<?,T> property)

Get the max aggregation implementation for the specified property.

Type Parameters:

T - The property value type that this max aggregation aggregates.

Parameters:

property - The metamodel property that this max aggregation aggregates.

Returns:

Max aggregation implementation for the specified property.

min

public static <T extends Comparable<T>> Aggregation<T> min(Property<?,T> property)

Get the min aggregation implementation for the specified property.

Type Parameters:

T - The property value type that this min aggregation aggregates.

Parameters:

property - The metamodel property that this min aggregation aggregates.

Returns:

Min aggregation implementation for the specified property.

sum

public static <T extends Number & Comparable<T>> Aggregation<T> sum(Property<?,T> property)

Get the sum aggregation implementation for the specified property.

Type Parameters:

T - The property value type that this sum aggregation aggregates.

Parameters:

property - The metamodel property that this sum aggregation aggregates.

Returns:

Sum aggregation implementation for the specified property.