mongodb.JavaAggregate.java Source code

Introduction

Here is the source code for mongodb.JavaAggregate.java

Source

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
//Generating Aggregated Data from MongoDB in Java Applications.
//To demonstrate the process of implementing an aggregation pipeline in java Application.
package mongodb;

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 java.util.Iterator;

/**
 *
 * @author soham
 */
public class JavaAggregate {
    public static void main(String[] args) {
        try {
            MongoClient mongoClient = new MongoClient("localhost", 27017);
            DB db = mongoClient.getDB("words");
            DBCollection collection = db.getCollection("word_stats");
            JavaAggregate.largeSmallVowels(collection);
            JavaAggregate.top5AverageWordFirst(collection);
        } catch (Exception e) {
            System.out.println(e);
        }
    }

    public static void displayAggregate(AggregationOutput result) {
        for (Iterator<DBObject> items = result.results().iterator(); items.hasNext();) {
            System.out.println(items.next());
        }
    }

    public static void largeSmallVowels(DBCollection collection) {
        BasicDBObject match = new BasicDBObject("$match",
                new BasicDBObject("first", new BasicDBObject("$in", new String[] { "a", "e", "i", "o", "u" })));
        BasicDBObject groupOps = new BasicDBObject("_id", "$first");
        groupOps.append("largest", new BasicDBObject("$max", "$size"));
        groupOps.append("smallest", new BasicDBObject("$min", "$size"));
        groupOps.append("total", new BasicDBObject("$sum", 1));
        BasicDBObject group = new BasicDBObject("$group", groupOps);
        BasicDBObject sort = new BasicDBObject("$sort", new BasicDBObject("first", 1));
        AggregationOutput result = collection.aggregate(match, group, sort);
        System.out.println("\nLargest and smallest word sizes for " + "words beginning with a vowel: ");
        JavaAggregate.displayAggregate(result);
    }

    public static void top5AverageWordFirst(DBCollection collection) {
        BasicDBObject groupOps = new BasicDBObject("_id", "$first");
        groupOps.append("average", new BasicDBObject("$avg", "$size"));
        BasicDBObject group = new BasicDBObject("$group", groupOps);
        BasicDBObject sort = new BasicDBObject("$sort", new BasicDBObject("average", -1));
        BasicDBObject limit = new BasicDBObject("$limit", 5);
        AggregationOutput result = collection.aggregate(group, sort, limit);
        System.out.println("\nFirst letter of top 5 largest average " + "word size: ");
        JavaAggregate.displayAggregate(result);
    }
}