com.tengen.home.Week1Homework4.java Source code

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Here is the source code for com.tengen.home.Week1Homework4.java

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/*
 * Copyright (c) 2008 - 2013 10gen, Inc. <http://10gen.com>
 *
 * 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.tengen.home;

import com.mongodb.AggregationOutput;
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBObject;
import com.mongodb.MongoClient;
import com.mongodb.ServerAddress;
import freemarker.template.Configuration;
import freemarker.template.Template;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import spark.Request;
import spark.Response;
import spark.Route;
import spark.Spark;

import java.io.StringWriter;
import java.net.UnknownHostException;
import java.util.HashMap;
import java.util.Map;

public class Week1Homework4 {
    private static final Logger logger = LoggerFactory.getLogger("logger");

    public static void main(String[] args) throws UnknownHostException {
        final Configuration configuration = new Configuration();
        configuration.setClassForTemplateLoading(Week1Homework4.class, "/");

        MongoClient client = new MongoClient(new ServerAddress("localhost", 27017));

        DB database = client.getDB("m101");
        final DBCollection collection = database.getCollection("funnynumbers");

        Spark.get(new Route("/") {
            @Override
            public Object handle(final Request request, final Response response) {
                StringWriter writer = new StringWriter();
                try {
                    Template helloTemplate = configuration.getTemplate("answer.ftl");

                    // Not necessary yet to understand this.  It's just to prove that you
                    // are able to run a command on a mongod server
                    AggregationOutput output = collection.aggregate(
                            new BasicDBObject("$group",
                                    new BasicDBObject("_id", "$value").append("count",
                                            new BasicDBObject("$sum", 1))),
                            new BasicDBObject("$match", new BasicDBObject("count", new BasicDBObject("$lte", 2))),
                            new BasicDBObject("$sort", new BasicDBObject("_id", 1)));

                    int answer = 0;
                    for (DBObject doc : output.results()) {
                        answer += (Double) doc.get("_id");
                    }

                    Map<String, String> answerMap = new HashMap<String, String>();
                    answerMap.put("answer", Integer.toString(answer));

                    helloTemplate.process(answerMap, writer);
                } catch (Exception e) {
                    logger.error("Failed", e);
                    halt(500);
                }
                return writer;
            }
        });
    }
}