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MongoDB support for Spring Data
/*
* Copyright 2016-2020 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
*
* https://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.data.mongodb.core.aggregation.ExposedFields.ExposedField;
import org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation.InheritsFieldsAggregationOperation;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
/**
* Encapsulates the aggregation framework {@code $lookup}-operation. We recommend to use the static factory method
* {@link Aggregation#lookup(String, String, String, String)} instead of creating instances of this class directly.
*
* @author Alessio Fachechi
* @author Christoph Strobl
* @author Mark Paluch
* @since 1.9
* @see MongoDB Aggregation Framework:
* $lookup
*/
public class LookupOperation implements FieldsExposingAggregationOperation, InheritsFieldsAggregationOperation {
private final Field from;
private final Field localField;
private final Field foreignField;
private final ExposedField as;
/**
* Creates a new {@link LookupOperation} for the given {@link Field}s.
*
* @param from must not be {@literal null}.
* @param localField must not be {@literal null}.
* @param foreignField must not be {@literal null}.
* @param as must not be {@literal null}.
*/
public LookupOperation(Field from, Field localField, Field foreignField, Field as) {
Assert.notNull(from, "From must not be null!");
Assert.notNull(localField, "LocalField must not be null!");
Assert.notNull(foreignField, "ForeignField must not be null!");
Assert.notNull(as, "As must not be null!");
this.from = from;
this.localField = localField;
this.foreignField = foreignField;
this.as = new ExposedField(as, true);
}
/*
* (non-Javadoc)
* @see org.springframework.data.mongodb.core.aggregation.FieldsExposingAggregationOperation#getFields()
*/
@Override
public ExposedFields getFields() {
return ExposedFields.from(as);
}
/*
* (non-Javadoc)
* @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#toDocument(org.springframework.data.mongodb.core.aggregation.AggregationOperationContext)
*/
@Override
public Document toDocument(AggregationOperationContext context) {
Document lookupObject = new Document();
lookupObject.append("from", from.getTarget());
lookupObject.append("localField", localField.getTarget());
lookupObject.append("foreignField", foreignField.getTarget());
lookupObject.append("as", as.getTarget());
return new Document(getOperator(), lookupObject);
}
/*
* (non-Javadoc)
* @see org.springframework.data.mongodb.core.aggregation.AggregationOperation#getOperator()
*/
@Override
public String getOperator() {
return "$lookup";
}
/**
* Get a builder that allows creation of {@link LookupOperation}.
*
* @return never {@literal null}.
*/
public static FromBuilder newLookup() {
return new LookupOperationBuilder();
}
public static interface FromBuilder {
/**
* @param name the collection in the same database to perform the join with, must not be {@literal null} or empty.
* @return never {@literal null}.
*/
LocalFieldBuilder from(String name);
}
public static interface LocalFieldBuilder {
/**
* @param name the field from the documents input to the {@code $lookup} stage, must not be {@literal null} or
* empty.
* @return never {@literal null}.
*/
ForeignFieldBuilder localField(String name);
}
public static interface ForeignFieldBuilder {
/**
* @param name the field from the documents in the {@code from} collection, must not be {@literal null} or empty.
* @return never {@literal null}.
*/
AsBuilder foreignField(String name);
}
public static interface AsBuilder {
/**
* @param name the name of the new array field to add to the input documents, must not be {@literal null} or empty.
* @return new instance of {@link LookupOperation}.
*/
LookupOperation as(String name);
}
/**
* Builder for fluent {@link LookupOperation} creation.
*
* @author Christoph Strobl
* @since 1.9
*/
public static final class LookupOperationBuilder
implements FromBuilder, LocalFieldBuilder, ForeignFieldBuilder, AsBuilder {
private @Nullable Field from;
private @Nullable Field localField;
private @Nullable Field foreignField;
private @Nullable ExposedField as;
/**
* Creates new builder for {@link LookupOperation}.
*
* @return never {@literal null}.
*/
public static FromBuilder newBuilder() {
return new LookupOperationBuilder();
}
@Override
public LocalFieldBuilder from(String name) {
Assert.hasText(name, "'From' must not be null or empty!");
from = Fields.field(name);
return this;
}
@Override
public LookupOperation as(String name) {
Assert.hasText(name, "'As' must not be null or empty!");
as = new ExposedField(Fields.field(name), true);
return new LookupOperation(from, localField, foreignField, as);
}
@Override
public AsBuilder foreignField(String name) {
Assert.hasText(name, "'ForeignField' must not be null or empty!");
foreignField = Fields.field(name);
return this;
}
@Override
public ForeignFieldBuilder localField(String name) {
Assert.hasText(name, "'LocalField' must not be null or empty!");
localField = Fields.field(name);
return this;
}
}
}