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());
         }
     }
 }