/*
* Copyright 2013-2016 the original author or authors.
*
* 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 org.springframework.data.mongodb.core.aggregation;
/**
* {@link AggregationOperation} that exposes {@link ExposedFields} that can be used for later aggregation pipeline
* {@code AggregationOperation}s. A {@link FieldsExposingAggregationOperation} implementing the
* {@link InheritsFieldsAggregationOperation} will expose fields from its parent operations. Not implementing
* {@link InheritsFieldsAggregationOperation} will replace existing exposed fields.
*
* @author Thomas Darimont
* @author Mark Paluch
*/
public interface FieldsExposingAggregationOperation extends AggregationOperation {
/**
* Returns the fields exposed by the {@link AggregationOperation}.
*
* @return will never be {@literal null}.
*/
ExposedFields getFields();
/**
* Marker interface for {@link AggregationOperation} that inherits fields from previous operations.
*/
static interface InheritsFieldsAggregationOperation extends FieldsExposingAggregationOperation {
}
}