com.querydsl.core.Fetchable Maven / Gradle / Ivy
/*
* Copyright 2015, The Querydsl Team (http://www.querydsl.com/team)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.querydsl.core;
import java.util.List;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;
import com.mysema.commons.lang.CloseableIterator;
import org.jetbrains.annotations.Nullable;
/**
* {@code Fetchable} defines default projection methods for {@link Query} implementations.
* All Querydsl query implementations should implement this interface.
*
* @param result type
*
* @author tiwe
*/
public interface Fetchable {
/**
* Get the projection as a typed List
*
* @return results in list form
*/
List fetch();
/**
* Get the first result of Get the projection or null if no result is found
*
* @return first result or null
*/
@Nullable
T fetchFirst();
/**
* Get the projection as a unique result or null if no result is found
*
* @throws NonUniqueResultException if there is more than one matching result
* @return first result or null
*/
@Nullable
T fetchOne() throws NonUniqueResultException;
/**
* Get the projection as a typed closeable Iterator
*
* @return closeable iterator
*/
CloseableIterator iterate();
/**
* Get the projection as a typed closeable Stream.
*
* @return closeable stream
*/
default Stream stream() {
final CloseableIterator iterator = iterate();
final Spliterator spliterator = Spliterators.spliteratorUnknownSize(iterator, Spliterator.ORDERED);
return StreamSupport.stream(spliterator, false)
.onClose(iterator::close);
}
/**
* Get the projection in {@link QueryResults} form.
*
* Make sure to use {@link #fetch()} instead if you do not rely on the {@link QueryResults#getOffset()} or
* {@link QueryResults#getLimit()}, because it will be more performant. Also, count queries cannot be
* properly generated for all dialects. For example: in JPA count queries can't be generated for queries
* that have multiple group by expressions or a having clause.
* Get the projection in {@link QueryResults} form.
*
* Use {@link #fetch()} instead if you do not need the total count of rows in the query result.
*
* @return results
* @see #fetch()
*/
QueryResults fetchResults();
/**
* Get the count of matched elements
*
* Note: not all QueryDSL modules might optimize fetchCount using a count query.
* An implementation is allowed to fall back to {@code fetch().size()}.
*
* @return row count
*/
long fetchCount();
}