package com.infomorrow.webroot; import java.util.List; import com.mongodb.BasicDBObject; import com.mongodb.DB; import com.mongodb.DBCollection; import com.mongodb.DBCursor; import com.mongodb.DBObject; import com.mongodb.MongoClient; public class test_mongodb {     public static void  main(String args[]) throws Exception {         MongoClient        mongoClient = new MongoClient( "127.0.0.1" , 27017 );//建立连接         DB get_db_credit = mongoClient.getDB("credit_2");//数据库名         DBCollection collection = get_db_credit.getCollection("report");//集合名，对应mysql中的表名         BasicDBObject filter_dbobject = new BasicDBObject();         //建立查询条件,如果还有其他条件，类似的写即可         // 如:version=3,filter_dbobject.put("version", 3),mongod区分String 和 Integer类型，所以要小心"3"!=3         filter_dbobject.put("user_id", "10065716153075");         //下面执行查询，设置limit,只要10条数据,排序(类mysql orderby) 再建一个BasicDBObject即可，－1表示倒序         DBCursor cursor = collection.find(filter_dbobject).limit(10).sort(new BasicDBObject("create_time",-1));         //把结果集输出成list类型         List<DBObject> list = cursor.toArray();         System.out.println(list.size());//list的长度         System.err.println(cursor.count());//计算结果的数量，类似于(mysql count()函数),不受limit的影响                 //遍历结果集         while(cursor.hasNext()) {             System.out.println(cursor.next());         }     } }