JPA Repository之JpaSpecificationExecutor

package org.springframework.data.jpa.repository;

import java.util.List;
import java.util.Optional;

import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.lang.Nullable;

/**
 * Interface to allow execution of {@link Specification}s based on the JPA criteria API.
 *
 * @author Oliver Gierke
 * @author Christoph Strobl
 */
public interface JpaSpecificationExecutor {

    /**
     * Returns a single entity matching the given {@link Specification} or {@link Optional#empty()} if none found.
     *
     * @param spec can be {@literal null}.
     * @return never {@literal null}.
     * @throws org.springframework.dao.IncorrectResultSizeDataAccessException if more than one entity found.
     */
    Optional findOne(@Nullable Specification spec);

    /**
     * Returns all entities matching the given {@link Specification}.
     *
     * @param spec can be {@literal null}.
     * @return never {@literal null}.
     */
    List findAll(@Nullable Specification spec);

    /**
     * Returns a {@link Page} of entities matching the given {@link Specification}.
     *
     * @param spec can be {@literal null}.
     * @param pageable must not be {@literal null}.
     * @return never {@literal null}.
     */
    Page findAll(@Nullable Specification spec, Pageable pageable);

    /**
     * Returns all entities matching the given {@link Specification} and {@link Sort}.
     *
     * @param spec can be {@literal null}.
     * @param sort must not be {@literal null}.
     * @return never {@literal null}.
     */
    List findAll(@Nullable Specification spec, Sort sort);

    /**
     * Returns the number of instances that the given {@link Specification} will return.
     *
     * @param spec the {@link Specification} to count instances for. Can be {@literal null}.
     * @return the number of instances.
     */
    long count(@Nullable Specification spec);
}