mongo之map-reduce笔记

package com.sy.demo;

import com.mongodb.MongoClient;

import com.mongodb.client.FindIterable;
import com.mongodb.client.MapReduceIterable;
import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.MongoDatabase;
import org.bson.Document;
import java.io.File;
import java.io.FileOutputStream;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class MongoDBJDBC2 {
    public static void main(String[] args) {
        try {
            MongoClient mongoClient = new MongoClient("localhost", 27017);
            MongoDatabase db = mongoClient.getDatabase("data");
            MongoCollection<Document> coll = db.getCollection("factPunishment");
            Calendar cal = Calendar.getInstance();
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
            cal.add(Calendar.MONTH, -6);
            String compareDate = format.format(cal.getTime());
            String currentDate = format.format(Calendar.getInstance().getTime());
            String mapFunc = "function(){" + "if(this.factName=='诈骗数额特别巨大'){" +
                "if(this.createDate<='" + currentDate +
                "' && this.createDate>='" + compareDate + "'){" +
                "emit(this.factPunishment, 1);" + "}" + "};" + "}";
            String reduceFunc = "function( key, values ){ return Array.sum(values); }";
            MapReduceIterable<Document> result = coll.mapReduce(mapFunc,reduceFunc);
            String str = "";

            for (Document d : result) {
                str += ("起刑点：" + d.get("_id") + "，案件量：" + d.get("value") + "\n");
                System.out.println("起刑点：" + d.get("_id") + "，案件量：" + d.get("value"));
            }

            FileOutputStream out = new FileOutputStream(new File("D://test//factPunishment.txt"));
            out.write(str.getBytes());
            out.close();
        } catch (Exception e) {
            System.err.println(e.getClass().getName() + ": " + e.getMessage());
        }
    }
}