Mongodb MapReduce-阿里云开发者社区

Mongodb MapReduce

2016-05-18 1941

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本文涉及的产品

云数据库 MongoDB，通用型 2核4GB

简介：

  Java代码  
   
 

package com.iminido.nosql;
import com.iminido.ssdb.HMap;
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBObject;
import com.mongodb.MapReduceCommand;
import com.mongodb.MapReduceOutput;
import com.mongodb.WriteConcern;
import java.net.UnknownHostException;
/**
*
* @author JadeLuo
*/
public class NoSqlDb extends Mdb {
static DB db = null;
public static void main(String[] args) {
// NoSqlDb.insert("collectionName", "{\"_id\":\"id1\",\"key\":\"value\"}");
// NoSqlDb.save("collectionName", HMap.init().add("_id", "550cd6d7f21296bf9dc51bb9").add("key", "222"));
// NoSqlDb.save("collectionName", HMap.init().add("_id", "550cd6d7f21296bf9dc51bb9").add("key", "222"));
System.out.print(NoSqlDb.query("collectionName"));
NoSqlDb.remove("collectionName");
System.out.print(NoSqlDb.query("collectionName"));
// initCollection2("msg", "temp2").insert(new BasicDBObject().append("k", "vv"), WriteConcern.FSYNCED);
// System.out.print( initCollection2("msg", "temp2").find().toArray());
}
public static void mapReduce() throws UnknownHostException{
// Mongo mongo = new Mongo("localhost", 27017);
// DB db = mongo.getDB("zhongsou_ad");
/***
* book1 = {name : "Understanding JAVA", pages : 100}
* book2 = {name : "Understanding JSON", pages : 200}
* db.books.save(book1)
* db.books.save(book2)
* book = {name : "Understanding XML", pages : 300}
* db.books.save(book)
* book = {name : "Understanding Web Services", pages : 400}
* db.books.save(book)
* book = {name : "Understanding Axis2", pages : 150}
* db.books.save(book)
*
var map = function() {
var category;
if ( this.pages >= 250 )
category = 'Big Books';
else
category = "Small Books";
emit(category, {name: this.name});
};
var reduce = function(key, values) {
var sum = 0;
values.forEach(function(doc) {
sum += 1;
});
return {books: sum};
};
var count = db.books.mapReduce(map, reduce, {out: "book_results"});
*/
try {
DBCollection books = db.getCollection("books");
BasicDBObject book = new BasicDBObject();
book.put("name", "Understanding JAVA");
book.put("pages", 100);
books.insert(book);
book = new BasicDBObject();
book.put("name", "Understanding JSON");
book.put("pages", 200);
books.insert(book);
book = new BasicDBObject();
book.put("name", "Understanding XML");
book.put("pages", 300);
books.insert(book);
book = new BasicDBObject();
book.put("name", "Understanding Web Services");
book.put("pages", 400);
books.insert(book);
book = new BasicDBObject();
book.put("name", "Understanding Axis2");
book.put("pages", 150);
books.insert(book);
String map = "function() { "+
"var category; " +
"if ( this.pages >= 250 ) "+
"category = 'Big Books'; " +
"else " +
"category = 'Small Books'; "+
"emit(category, {name: this.name});}";
String reduce = "function(key, values) { " +
"var sum = 0; " +
"values.forEach(function(doc) { " +
"sum += 1; "+
"}); " +
"return {books: sum};} ";
MapReduceCommand cmd = new MapReduceCommand(books, map, reduce,
null, MapReduceCommand.OutputType.INLINE, null);
MapReduceOutput out = books.mapReduce(cmd);
for (DBObject o : out.results()) {
System.out.println(o.toString());
}
} catch (Exception e) {
e.printStackTrace();
}
}
//public class NoSqlDb extends Squ{
// public DBCollection getDBCollection(String db, String collect) {
// String host = Const.MONGODB_HOST;// 主机名
// int port = Const.MONGODB_PORT;// 端口
// MongoClient mg = null;
// try {
// mg = new MongoClient(host, port);
// } catch (UnknownHostException ex) {
// Logger.getLogger(NoSqlDb.class.getName()).log(Level.SEVERE, null, ex);
// }
// DBCollection clg = mg.getDB(db).getCollection(collect);
// return clg;
// }
}

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Mongodb MapReduce

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