JPA Repository之QueryByExampleExecutor

package org.springframework.data.repository.query;

import java.util.Optional;

import org.springframework.data.domain.Example;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;

/**
 * Interface to allow execution of Query by Example {@link Example} instances.
 *
 * @param <T>
 * @author Mark Paluch
 * @author Christoph Strobl
 * @since 1.12
 */
public interface QueryByExampleExecutor<T> {

    /**
     * Returns a single entity matching the given {@link Example} or {@literal null} if none was found.
     *
     * @param example must not be {@literal null}.
     * @return a single entity matching the given {@link Example} or {@link Optional#empty()} if none was found.
     * @throws org.springframework.dao.IncorrectResultSizeDataAccessException if the Example yields more than one result.
     */
    <S extends T> Optional<S> findOne(Example<S> example);

    /**
     * Returns all entities matching the given {@link Example}. In case no match could be found an empty {@link Iterable}
     * is returned.
     *
     * @param example must not be {@literal null}.
     * @return all entities matching the given {@link Example}.
     */
    <S extends T> Iterable<S> findAll(Example<S> example);

    /**
     * Returns all entities matching the given {@link Example} applying the given {@link Sort}. In case no match could be
     * found an empty {@link Iterable} is returned.
     *
     * @param example must not be {@literal null}.
     * @param sort the {@link Sort} specification to sort the results by, must not be {@literal null}.
     * @return all entities matching the given {@link Example}.
     * @since 1.10
     */
    <S extends T> Iterable<S> findAll(Example<S> example, Sort sort);

    /**
     * Returns a {@link Page} of entities matching the given {@link Example}. In case no match could be found, an empty
     * {@link Page} is returned.
     *
     * @param example must not be {@literal null}.
     * @param pageable can be {@literal null}.
     * @return a {@link Page} of entities matching the given {@link Example}.
     */
    <S extends T> Page<S> findAll(Example<S> example, Pageable pageable);

    /**
     * Returns the number of instances matching the given {@link Example}.
     *
     * @param example the {@link Example} to count instances for. Must not be {@literal null}.
     * @return the number of instances matching the {@link Example}.
     */
    <S extends T> long count(Example<S> example);

    /**
     * Checks whether the data store contains elements that match the given {@link Example}.
     *
     * @param example the {@link Example} to use for the existence check. Must not be {@literal null}.
     * @return {@literal true} if the data store contains elements that match the given {@link Example}.
     */
    <S extends T> boolean exists(Example<S> example);