co.aurasphere.mongodb.university.classes.m101j.homework31.MainClass.java Source code

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Here is the source code for co.aurasphere.mongodb.university.classes.m101j.homework31.MainClass.java

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/*
 * MIT License
 *
 * Copyright (c) 2017 Donato Rimenti
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package co.aurasphere.mongodb.university.classes.m101j.homework31;

import java.util.Arrays;
import java.util.List;

import org.bson.Document;

import com.mongodb.MongoClient;
import com.mongodb.client.AggregateIterable;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.model.Accumulators;
import com.mongodb.client.model.Aggregates;
import com.mongodb.client.model.Filters;
import com.mongodb.client.model.Sorts;

/**
 * Solution of Homework 3-1 from MongoDB University M101J's class.
 * 
 * @author Donato Rimenti
 */
public class MainClass {

    /**
     * The main method.
     *
     * @param args
     *            the arguments
     */
    @SuppressWarnings("unchecked")
    public static void main(String[] args) {
        MongoClient client = new MongoClient();
        MongoDatabase db = client.getDatabase("school");
        MongoCollection<Document> students = db.getCollection("students");

        // Gets all the students.
        MongoCursor<Document> cursor = students.find().iterator();

        try {
            while (cursor.hasNext()) {
                Document student = cursor.next();
                List<Document> scores = (List<Document>) student.get("scores");

                // Finds the lowest homework score.
                Document minScoreObj = null;
                double minScore = Double.MAX_VALUE;

                for (Document scoreDocument : scores) {
                    double score = scoreDocument.getDouble("score");
                    String type = scoreDocument.getString("type");

                    // Swaps the scores.
                    if (type.equals("homework") && score < minScore) {
                        minScore = score;
                        minScoreObj = scoreDocument;
                    }
                }

                // Removes the lowest score.
                if (minScoreObj != null) {
                    scores.remove(minScoreObj);
                }

                // Updates the record.
                students.updateOne(Filters.eq("_id", student.get("_id")),
                        new Document("$set", new Document("scores", scores)));
            }

            // Gets the student with the highest average in the class.
            AggregateIterable<Document> results = students.aggregate(Arrays.asList(Aggregates.unwind("$scores"),
                    Aggregates.group("$_id", Accumulators.avg("average", "$scores.score")),
                    Aggregates.sort(Sorts.descending("average")), Aggregates.limit(1)));

            // There should be only one result. Prints it.
            System.out.println("Solution : " + results.iterator().next().toJson());

        } finally {
            cursor.close();
        }

        client.close();
    }

}