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The MongoDB Java Driver uber-artifact, containing mongodb-driver, mongodb-driver-core, and bson
/*
* Copyright 2008-present MongoDB, Inc.
*
* 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 com.mongodb.client.model;
import org.bson.BsonArray;
import org.bson.BsonDocument;
import org.bson.BsonInt32;
import org.bson.BsonString;
import org.bson.BsonValue;
import org.bson.codecs.configuration.CodecRegistry;
import org.bson.conversions.Bson;
import java.util.List;
import static com.mongodb.assertions.Assertions.notNull;
import static java.util.Arrays.asList;
/**
* A factory for projections. A convenient way to use this class is to statically import all of its methods, which allows usage like:
*
*
* collection.find().projection(fields(include("x", "y"), excludeId()))
*
*
* @mongodb.driver.manual tutorial/project-fields-from-query-results/#limit-fields-to-return-from-a-query Projection
* @since 3.0
*/
public final class Projections {
private Projections() {
}
/**
* Creates a projection of a field whose value is computed from the given expression. Projection with an expression is only supported
* using the $project aggregation pipeline stage.
*
* @param fieldName the field name
* @param expression the expression
* @param the expression type
* @return the projection
* @see Aggregates#project(Bson)
*/
public static Bson computed(final String fieldName, final TExpression expression) {
return new SimpleExpression(fieldName, expression);
}
/**
* Creates a projection that includes all of the given fields.
*
* @param fieldNames the field names
* @return the projection
*/
public static Bson include(final String... fieldNames) {
return include(asList(fieldNames));
}
/**
* Creates a projection that includes all of the given fields.
*
* @param fieldNames the field names
* @return the projection
*/
public static Bson include(final List fieldNames) {
return combine(fieldNames, new BsonInt32(1));
}
/**
* Creates a projection that excludes all of the given fields.
*
* @param fieldNames the field names
* @return the projection
*/
public static Bson exclude(final String... fieldNames) {
return exclude(asList(fieldNames));
}
/**
* Creates a projection that excludes all of the given fields.
*
* @param fieldNames the field names
* @return the projection
*/
public static Bson exclude(final List fieldNames) {
return combine(fieldNames, new BsonInt32(0));
}
/**
* Creates a projection that excludes the _id field. This suppresses the automatic inclusion of _id that is the default, even when
* other fields are explicitly included.
*
* @return the projection
*/
public static Bson excludeId() {
return new BsonDocument("_id", new BsonInt32(0));
}
/**
* Creates a projection that includes for the given field only the first element of an array that matches the query filter. This is
* referred to as the positional $ operator.
*
* @param fieldName the field name whose value is the array
* @return the projection
* @mongodb.driver.manual reference/operator/projection/positional/#projection Project the first matching element ($ operator)
*/
public static Bson elemMatch(final String fieldName) {
return new BsonDocument(fieldName + ".$", new BsonInt32(1));
}
/**
* Creates a projection that includes for the given field only the first element of the array value of that field that matches the given
* query filter.
*
* @param fieldName the field name
* @param filter the filter to apply
* @return the projection
* @mongodb.driver.manual reference/operator/projection/elemMatch elemMatch
*/
public static Bson elemMatch(final String fieldName, final Bson filter) {
return new ElemMatchFilterProjection(fieldName, filter);
}
/**
* Creates a projection to the given field name of the textScore, for use with text queries.
*
* @param fieldName the field name
* @return the projection
* @mongodb.driver.manual reference/operator/projection/meta/#projection textScore
*/
public static Bson metaTextScore(final String fieldName) {
return new BsonDocument(fieldName, new BsonDocument("$meta", new BsonString("textScore")));
}
/**
* Creates a projection to the given field name of a slice of the array value of that field.
*
* @param fieldName the field name
* @param limit the number of elements to project.
* @return the projection
* @mongodb.driver.manual reference/operator/projection/slice Slice
*/
public static Bson slice(final String fieldName, final int limit) {
return new BsonDocument(fieldName, new BsonDocument("$slice", new BsonInt32(limit)));
}
/**
* Creates a projection to the given field name of a slice of the array value of that field.
*
* @param fieldName the field name
* @param skip the number of elements to skip before applying the limit
* @param limit the number of elements to project
* @return the projection
* @mongodb.driver.manual reference/operator/projection/slice Slice
*/
public static Bson slice(final String fieldName, final int skip, final int limit) {
return new BsonDocument(fieldName, new BsonDocument("$slice", new BsonArray(asList(new BsonInt32(skip), new BsonInt32(limit)))));
}
/**
* Creates a projection that combines the list of projections into a single one. If there are duplicate keys, the last one takes
* precedence.
*
* @param projections the list of projections to combine
* @return the combined projection
*/
public static Bson fields(final Bson... projections) {
return fields(asList(projections));
}
/**
* Creates a projection that combines the list of projections into a single one. If there are duplicate keys, the last one takes
* precedence.
*
* @param projections the list of projections to combine
* @return the combined projection
*/
public static Bson fields(final List projections) {
notNull("projections", projections);
return new FieldsProjection(projections);
}
private static class FieldsProjection implements Bson {
private final List projections;
FieldsProjection(final List projections) {
this.projections = projections;
}
@Override
public BsonDocument toBsonDocument(final Class documentClass, final CodecRegistry codecRegistry) {
BsonDocument combinedDocument = new BsonDocument();
for (Bson sort : projections) {
BsonDocument sortDocument = sort.toBsonDocument(documentClass, codecRegistry);
for (String key : sortDocument.keySet()) {
combinedDocument.remove(key);
combinedDocument.append(key, sortDocument.get(key));
}
}
return combinedDocument;
}
@Override
public String toString() {
return "Projections{"
+ "projections=" + projections
+ '}';
}
}
private static class ElemMatchFilterProjection implements Bson {
private final String fieldName;
private final Bson filter;
ElemMatchFilterProjection(final String fieldName, final Bson filter) {
this.fieldName = fieldName;
this.filter = filter;
}
@Override
public BsonDocument toBsonDocument(final Class documentClass, final CodecRegistry codecRegistry) {
return new BsonDocument(fieldName, new BsonDocument("$elemMatch", filter.toBsonDocument(documentClass, codecRegistry)));
}
@Override
public String toString() {
return "ElemMatch Projection{"
+ "fieldName='" + fieldName + '\''
+ ", filter=" + filter
+ '}';
}
}
private static Bson combine(final List fieldNames, final BsonValue value) {
BsonDocument document = new BsonDocument();
for (String fieldName : fieldNames) {
document.remove(fieldName);
document.append(fieldName, value);
}
return document;
}
}
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