Command line example in java

Passing command line arguments in java

1. check the number argument's passed, exit the program with status success when you received insufficient command line arguments.

        if(args.length==0){

            System.out.println("Insufficient Arguments..");

            System.exit(0);

        }

2.  Parse the arguments to Integer from String.

      System.out.print("sum="+Integer.parseInt(arg1)+Integer.parseInt(arg2));

for complete code click here.

How to migrate MongoDB Collection's with PHP?

1. MongoDB is an NOSQL DB which is very faster in fetching the records from huge data, from a cluster of DB' S with sharding.
2. The delete operation is slower when compared to SQL DB' s.

Here I gave an example for Migrating MongoDB Records which all are inserted in last 24 hours.

Step1: Installing PHP MongoDB database driver
           aptitude install php5-mongo

Step2: Global Constants
         
    Create MongoDB Connection Strings
              public static $connString = "mongodb://123.45.67.89:27017";
              public static $connStringL = "mongodb://127.0.0.1:27017";

    DB, Collection Constants
             public static $db="db";
             public static $dbl="db";
             public static $coll_A="A";


Step3: Function to establish a connection with MongoDB
   
    /*to connect with source mongodb*/
    public function connection(){
        return new MongoClient(self::$connString);
    }

    /*to connect with destination mongodb*/
    public function connectionL(){
        return new MongoClient(self::$connStringL);
    }

Step4: Linux date to timestamp which we need to pass in the MongoDB Query
    public function convertDate2TimeStamp($date){
        $timestamp=strtotime(date($date));
        return $timestamp;
    }

Step5: MongoDB Query Construction and get the result in a Cursor

            $Query=(array('tstamp'=> array('$gt' => $start,'$lte' => $end)));
            $cursor=$coll->find($Query);


Step6: Iterating through Cursor

            while(($doc=$cursor->getNext())!=null){
                 try{
                $res=$collL->insert($doc);
/*
                if($res['ok']!=1)
                    error_log("Insert Failed..",3,"/var/log/mongo-cron/mongo.log");

                foreach($doc as $k => $v){
                 echo PHP_EOL.$v;
                  }*/
}catch(Exception $e){
//skipping the errors
}
            }



Complete Program
-----------------------
class mongocron {

    public static $connString = "mongodb://123.45.67.89:27017";
    public static $connStringL = "mongodb://127.0.0.1:27017";

    public static $db="db";
    public static $dbl="db";
    public static $coll_A="A";


    public function connection(){
        return new MongoClient(self::$connString);
    }

    public function connectionL(){
        return new MongoClient(self::$connStringL);
    }

    public function convertDate2TimeStamp($date){
        $timestamp=strtotime(date($date));
        return $timestamp;
    }

    public function migrate_coll_A(){
        try{
            $timestampStart=$this->convertDate2TimeStamp(date('Y-m-d',strtotime("-1 days")));
            $timestampEnd=$timestampStart+(60*60*23.999999);

            $start=new MongoDate($timestampStart);
            $end=new MongoDate($timestampEnd);

    /* Migrating Collection A */

            $conn=$this->connection();
            $db=$conn->selectDB(self::$db);
            $coll=$db->selectCollection(self::$coll_A);
            $Query=(array('tstamp'=> array('$gt' => $start,'$lte' => $end)));
            $cursor=$coll->find($Query);

            $connL=$this->connectionL();
            $dbL=$connL->selectDB(self::$dbl);

            //$collL=$dbL->selectCollection(self::$collectionL.'-'.date('m-Y',strtotime("-1 days")));
            $collL=$dbL->selectCollection(self::$coll_A);

            //  echo PHP_EOL.date('Y-m-d H:i:s',$start);
            //  echo PHP_EOL.date('Y-m-d H:i:s',$end);

            while(($doc=$cursor->getNext())!=null){
                 try{
                $res=$collL->insert($doc);
/*
                if($res['ok']!=1)
                    error_log("Insert Failed..",3,"/var/log/mongo-cron/mongo.log");

                foreach($doc as $k => $v){
                 echo PHP_EOL.$v;
                  }*/
}catch(Exception $e){
//skipping the errors
}
            }

error_log(date('Y/m/d H:i:s').": Records A migrated\n",3,"/var/log/mongo-cron/mongo.log");

        }catch (Exception $e){
            error_log(date('Y/m/d H:i:s').":A:: unknown Exception:".$e->getMessage(). "\n",3,"/var/log/mongo-cron/mongo.log");
        }
    }


$obj = new mongocron();
$obj->migrate_coll_A();
?>