/*
* Copyright 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 $sample}-operation.
* <p>
* We recommend to use the static factory method {@link Aggregation#sample(long)} instead of creating instances of this
* class directly.
*
* @author Gustavo de Geus
* @since 2.0
* @see <a href="https://docs.mongodb.com/master/reference/operator/aggregation/sample/">MongoDB Aggregation Framework:
* $sample</a>
*/
public class SampleOperation implements AggregationOperation {
private final long sampleSize;
/**
* @param sampleSize number of documents to be randomly selected from its input.
*/
public SampleOperation(long sampleSize) {
Assert.isTrue(sampleSize > 0, "Sample size must be greater than zero!");
this.sampleSize = sampleSize;
}
/*
(non-Javadoc)
* @see org.springframework.data.mongodb.core.aggregation.BucketOperationSupport#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
*/
@Override
public Document toDocument(AggregationOperationContext context) {
return new Document("$sample", new Document("size", this.sampleSize));
}
}