org.apache.rya.mongodb.document.operators.aggregation.VariableOperators.java Source code

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Here is the source code for org.apache.rya.mongodb.document.operators.aggregation.VariableOperators.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.rya.mongodb.document.operators.aggregation;

import static com.google.common.base.Preconditions.checkNotNull;

import com.mongodb.BasicDBObject;
import com.mongodb.BasicDBObjectBuilder;
import com.mongodb.DBObject;

/**
 * Utility methods for variable operators.
 */
public final class VariableOperators {
    /**
     * Private constructor to prevent instantiation.
     */
    private VariableOperators() {
    }

    /**
     * Applies an expression to each item in an array and returns an array with
     * the applied results.
     * @param input an expression that resolves to an array.
     * @param as the variable name for the items in the {@code input} array.
     * The {@code in} expression accesses each item in the {@code input} array
     * by this variable.
     * @param in the expression to apply to each item in the {@code input}
     * array. The expression accesses the item by its variable name.
     * @return the $map expression {@link BasicDBObject}.
     */
    public static BasicDBObject map(final String input, final String as, final DBObject in) {
        final BasicDBObjectBuilder builder = BasicDBObjectBuilder.start();
        return (BasicDBObject) map(builder, input, as, in).get();
    }

    /**
     * Applies an expression to each item in an array and returns an array with
     * the applied results.
     * @param builder the {@link BasicDBObjectBuilder}. (not {@code null})
     * @param input an expression that resolves to an array.
     * @param as the variable name for the items in the {@code input} array.
     * The {@code in} expression accesses each item in the {@code input} array
     * by this variable.
     * @param in the expression to apply to each item in the {@code input}
     * array. The expression accesses the item by its variable name.
     * @return the $map expression {@link BasicDBObjectBuilder}.
     */
    public static BasicDBObjectBuilder map(final BasicDBObjectBuilder builder, final String input, final String as,
            final DBObject in) {
        checkNotNull(builder);
        builder.push("$map").add("input", input).add("as", as).add("in", in);
        return builder;
    }
}