/*
* Copyright 2013-2017 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;
import org.bson.Document;
import org.springframework.util.Assert;
/**
* Encapsulates the {@code $limit}-operation.
* <p>
* We recommend to use the static factory method {@link Aggregation#limit(long)} instead of creating instances of this
* class directly.
*
* @author Thomas Darimont
* @author Oliver Gierke
* @author Christoph Strobl
* @since 1.3
* @see <a href="https://docs.mongodb.org/manual/reference/aggregation/limit/">MongoDB Aggregation Framework: $limit</a>
*/
public class LimitOperation implements AggregationOperation {
private final long maxElements;
/**
* @param maxElements Number of documents to consider.
*/
public LimitOperation(long maxElements) {
Assert.isTrue(maxElements >= 0, "Maximum number of elements must be greater or equal to zero!");
this.maxElements = maxElements;
}
/*
* (non-Javadoc)
* @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
*/
@Override
public Document toDocument(AggregationOperationContext context) {
return new Document("$limit", Long.valueOf(maxElements));
}
}