Package com.github.collinalpert.java2db.queries

Class EntityProjectionQuery<E extends BaseEntity,R>

java.lang.Object

com.github.collinalpert.java2db.queries.SingleEntityProjectionQuery<E,R>

com.github.collinalpert.java2db.queries.EntityProjectionQuery<E,R>

Type Parameters:

E - The entity which the query is supposed to be executed for.

R - The return type of the projection this query represents.

All Implemented Interfaces:

Queryable<R>, SingleQueryable<R>

Direct Known Subclasses:

AsyncEntityProjectionQuery

public class EntityProjectionQuery<E extends BaseEntity,R>
extends SingleEntityProjectionQuery<E,R>
implements Queryable<R>

A query which represents a projection from an EntityQuery to a single column on the database.

Author:

Collin Alpert

Field Summary

Fields inherited from class com.github.collinalpert.java2db.queries.SingleEntityProjectionQuery

originalQuery, returnType

Constructor Summary

Constructors

Constructor	Description
EntityProjectionQuery(com.github.collinalpert.lambda2sql.functions.SqlFunction<E,R> projection, EntityQuery<E> originalQuery)

Method Summary

Modifier and Type	Method	Description
java.util.Optional<R>	first()	Gets the first value from the database result.
R[]	toArray()	Executes a new query and returns the result as an array.
java.util.List<R>	toList()	Executes the query and returns the result as a List.
<K> java.util.Map<K,R>	toMap(java.util.function.Function<R,K> keyMapping)	Executes a new query and returns the result as a Map.
<K,V> java.util.Map<K,V>	toMap(java.util.function.Function<R,K> keyMapping, java.util.function.Function<R,V> valueMapping)	Executes a new query and returns the result as a Map.
java.util.stream.Stream<R>	toStream()	Executes the query and returns the result as a Stream.

Methods inherited from class com.github.collinalpert.java2db.queries.SingleEntityProjectionQuery

getQuery

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.github.collinalpert.java2db.queries.SingleQueryable

getQuery

Constructor Detail

EntityProjectionQuery

public EntityProjectionQuery(com.github.collinalpert.lambda2sql.functions.SqlFunction<E,R> projection,
                             EntityQuery<E> originalQuery)

Method Detail

first

public java.util.Optional<R> first()

Description copied from interface: SingleQueryable

Gets the first value from the database result. This method should be used when only one result is expected.

Specified by:

first in interface SingleQueryable<E extends BaseEntity>

Overrides:

first in class SingleEntityProjectionQuery<E extends BaseEntity,R>

Returns:

The first row as an entity wrapped in an Optional if there is at least one row. Otherwise Optional.empty() is returned. If the value from the database is null, an empty Optional is also returned.

toList

public java.util.List<R> toList()

Description copied from interface: Queryable

Executes the query and returns the result as a List.

Specified by:

toList in interface Queryable<E extends BaseEntity>

Returns:

A list of entities representing the result rows.

toStream

public java.util.stream.Stream<R> toStream()

Description copied from interface: Queryable

Executes the query and returns the result as a Stream.

Specified by:

toStream in interface Queryable<E extends BaseEntity>

Returns:

A list of entities representing the result rows.

toArray

public R[] toArray()

Description copied from interface: Queryable

Executes a new query and returns the result as an array.

Specified by:

toArray in interface Queryable<E extends BaseEntity>

Returns:

An array of entities representing the result rows.

toMap

public <K> java.util.Map<K,R> toMap(java.util.function.Function<R,K> keyMapping)

Executes a new query and returns the result as a Map. This method is equivalent to the call Queryable#toMap(keyMapping, x -> x).

Specified by:

toMap in interface Queryable<E extends BaseEntity>

Type Parameters:

K - The type of the field representing the keys.

Parameters:

keyMapping - The field representing the keys of the map.

Returns:

A map containing the result of the query.

toMap

public <K,V> java.util.Map<K,V> toMap(java.util.function.Function<R,K> keyMapping,
                                                  java.util.function.Function<R,V> valueMapping)

Executes a new query and returns the result as a Map.

Specified by:

toMap in interface Queryable<E extends BaseEntity>

Type Parameters:

K - The type of the field representing the keys.

V - The type of the field representing the values.

Parameters:

keyMapping - The field representing the keys of the map.

valueMapping - The field representing the values of the map.

Returns:

A map containing the result of the query.