Package com.flowingcode.backendcore.service

Interface QueryService<T,K>

Type Parameters:

T - the type of the entity to be queried

K - the type of the entity's identifying key

All Known Subinterfaces:

CrudService<T,K>

public interface QueryService<T,K>

Specifies the contract of a generic service that handles querying operations on entities.

Author:

mlopez

Method Summary

Modifier and Type	Method	Description
long	count(QuerySpec filter)	Count the number of entities that match a certain query specification.
List<T>	filter(QuerySpec filter)	Apply filtering to entities in the system based on a certain query specification.
Optional<T>	filterWithSingleResult(QuerySpec filter)	Apply filtering to entities in the system based on a certain query specification and retrieve a single result.
List<T>	findAll()	Find all entities.
Optional<T>	findById(K id)	Find an entity by its identifying key.

Method Details

findById

Optional<T> findById(K id)

Find an entity by its identifying key.

Parameters:

id - the entity's identifying key

Returns:

an Optional instance containing the entity if it exists; otherwise empty

findAll

List<T> findAll()

Find all entities.

Returns:

a List containing all entities in the system

filter

List<T> filter(QuerySpec filter)

Apply filtering to entities in the system based on a certain query specification.

Parameters:

filter - the query specification used for filtering

Returns:

a List containing all entities matching the query specification

count

long count(QuerySpec filter)

Count the number of entities that match a certain query specification.

Parameters:

filter - the query specification used for filtering

Returns:

the number of entities that match the query specification

filterWithSingleResult

Optional<T> filterWithSingleResult(QuerySpec filter)

Apply filtering to entities in the system based on a certain query specification and retrieve a single result.

Parameters:

filter - the query specification used for filtering

Returns:

an Optional instance containing a single entity matching the query specification if it exists; otherwise empty