/*
* Copyright 2013 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.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
import org.springframework.util.Assert;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
/**
* Encapsulates the aggregation framework {@code $unwind}-operation.
*
* @see http://docs.mongodb.org/manual/reference/aggregation/unwind/#pipe._S_unwind
* @author Thomas Darimont
* @author Oliver Gierke
* @since 1.3
*/
public class UnwindOperation implements AggregationOperation {
private final ExposedField field;
/**
* Creates a new {@link UnwindOperation} for the given {@link Field}.
*
* @param field must not be {@literal null}.
*/
public UnwindOperation(Field field) {
Assert.notNull(field);
this.field = new ExposedField(field, true);
}
/*
* (non-Javadoc)
* @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDBObject(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
*/
@Override
public DBObject toDBObject(AggregationOperationContext context) {
return new BasicDBObject("$unwind", context.getReference(field).toString());
}
}