1.[代碼]那位幫忙提供一個java mongodb多個collection進行mapreduce的操作。

package com.zuidaima.mongodb.test.main;

import java.net.UnknownHostException;

import java.text.SimpleDateFormat;

import java.util.Calendar;

import java.util.Random;

import org.junit.After;

import org.junit.Before;

import org.junit.Test;

import com.mongodb.BasicDBObject;

import com.mongodb.DB;

import com.mongodb.DBCollection;

import com.mongodb.DBObject;

import com.mongodb.MapReduceCommand;

import com.mongodb.Mongo;

import com.mongodb.MongoException;

/**

*@author www.zuidaima.com

**/

public class MapReduceTest {

private Mongo mongo = null;

private DB db = null;

@Before

public void init() {

try {

mongo = new Mongo("localhost");

db = mongo.getDB("stat");

initData();

} catch (UnknownHostException e) {

e.printStackTrace();

} catch (MongoException e) {

e.printStackTrace();

}

}

/**

* map reduce for today

*/

@Test

public void dayMapReduce() {

String map = " function() {emit(this.videoid,this.play)}";

String reduce = "function(key,values) {var count = 0;values.forEach(function(value){count += value;});return count;}";

Calendar calendar = Calendar.getInstance();

String datePattern = "yyyy-MM";

SimpleDateFormat sdf = new SimpleDateFormat(datePattern);

String monthOfYear = sdf.format(calendar.getTime());

for (int day = 1; day <= 31; day++) {

String collectionName = monthOfYear + "-" + day;

DBCollection collection = db.getCollection(collectionName);

collection

.mapReduce(map, reduce, collectionName + "_daystat", null);

}

}

/**

* map reduce for current month

*/

@Test

public void monthMapReduce() {

// do day mapreduce before month mapreduce

dayMapReduce();

String map = " function() {emit(this._id,this.value)}";

String reduce = "function(key,values) {var count = 0;values.forEach(function(value){count += value;});return count;}";

Calendar calendar = Calendar.getInstance();

String datePattern = "yyyy-MM";

SimpleDateFormat sdf = new SimpleDateFormat(datePattern);

String monthOfYear = sdf.format(calendar.getTime());

for (int day = 1; day <= 31; day++) {

String collectionName = monthOfYear + "-" + day + "_daystat";

DBCollection collection = db.getCollection(collectionName);

MapReduceCommand cmd = new MapReduceCommand(collection, map,

reduce, monthOfYear + "_monthstat",

MapReduceCommand.OutputType.REDUCE, null);

collection.mapReduce(cmd);

}

}

private void initData() {

db.dropDatabase();

Calendar calendar = Calendar.getInstance();

String datePattern = "yyyy-MM";

SimpleDateFormat sdf = new SimpleDateFormat(datePattern);

String monthOfYear = sdf.format(calendar.getTime());

for (int day = 1; day <= 31; day++) {

String collectionName = monthOfYear + "-" + day;

DBCollection collection = db.getCollection(collectionName);

for (int j = 1; j <= 100; j++) {

DBObject play = new BasicDBObject();

play.put("videoid", new Random().nextInt(100));

play.put("play", new Random().nextInt(1000));

collection.insert(play);

}

}

}

@After

public void destory() {

if (mongo != null)

mongo.close();

mongo = null;

db = null;

}

}

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