/*
* Copyright 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;
import java.util.ArrayList;
import java.util.List;
import org.bson.Document;
import org.springframework.data.mongodb.core.aggregation.ExposedFields.DirectFieldReference;
import org.springframework.data.mongodb.core.aggregation.ExposedFields.ExposedField;
import org.springframework.data.mongodb.core.aggregation.ExposedFields.FieldReference;
import org.springframework.data.mongodb.core.aggregation.Fields.AggregationField;
import org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation.InheritsFieldsAggregationOperation;
/**
* Rendering support for {@link AggregationOperation} into a {@link List} of {@link org.bson.Document}.
*
* @author Mark Paluch
* @author Christoph Strobl
* @since 1.10
*/
class AggregationOperationRenderer {
static final AggregationOperationContext DEFAULT_CONTEXT = new NoOpAggregationOperationContext();
/**
* Render a {@link List} of {@link AggregationOperation} given {@link AggregationOperationContext} into their
* {@link Document} representation.
*
* @param operations must not be {@literal null}.
* @param context must not be {@literal null}.
* @return the {@link List} of {@link Document}.
*/
static List<Document> toDocument(List<AggregationOperation> operations, AggregationOperationContext rootContext) {
List<Document> operationDocuments = new ArrayList<Document>(operations.size());
AggregationOperationContext contextToUse = rootContext;
for (AggregationOperation operation : operations) {
operationDocuments.add(operation.toDocument(contextToUse));
if (operation instanceof FieldsExposingAggregationOperation) {
FieldsExposingAggregationOperation exposedFieldsOperation = (FieldsExposingAggregationOperation) operation;
ExposedFields fields = exposedFieldsOperation.getFields();
if (operation instanceof InheritsFieldsAggregationOperation) {
contextToUse = new InheritingExposedFieldsAggregationOperationContext(fields, contextToUse);
} else {
contextToUse = fields.exposesNoFields() ? DEFAULT_CONTEXT
: new ExposedFieldsAggregationOperationContext(exposedFieldsOperation.getFields(), contextToUse);
}
}
}
return operationDocuments;
}
/**
* Simple {@link AggregationOperationContext} that just returns {@link FieldReference}s as is.
*
* @author Oliver Gierke
*/
private static class NoOpAggregationOperationContext implements AggregationOperationContext {
/*
* (non-Javadoc)
* @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getMappedObject(org.bson.Document)
*/
@Override
public Document getMappedObject(Document document) {
return document;
}
/*
* (non-Javadoc)
* @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getReference(org.springframework.data.mongodb.core.aggregation.ExposedFields.AvailableField)
*/
@Override
public FieldReference getReference(Field field) {
return new DirectFieldReference(new ExposedField(field, true));
}
/*
* (non-Javadoc)
* @see org.springframework.data.mongodb.core.aggregation.AggregationOperationContext#getReference(java.lang.String)
*/
@Override
public FieldReference getReference(String name) {
return new DirectFieldReference(new ExposedField(new AggregationField(name), true));
}
}
}