LEARNING MONO

 

Experiments for

Url fileReading,

MySql dbquery

and

Cryptography 

 

R.S.Ramaswamy

( published in DeveloperIQ…Jan-2006)

 

    The C# language has been made available for Linux/Unix platforms through  Mono , an open-source/free project, initiated by Miguel de Icaza and promoted by Novell Netware & IBM.In fact, the Common Language Runtime, the special feature of DotNet platform , originally available for Windows platform only , is now being ported to Linux/Unix environments. The C# compiler in Mono is only the first step in this direction. Just as DotNet framework can be used with VB.net, Java script, J# and Managed C++, the Mono project also hopes to provide these features, ultimately. Thereby, it is claimed that all the platform-independent advantages of Java will be combined with the language-independent common-language-runtime of DotNet and the result will be better than either. That is for the future however.

 

 Right now, only C# is available in Mono. And unlike Java, which can be run in any platform, ( for which a Java interpreter is available) , Mono is available only for Linux/Unix).As it is,  it may be a bit premature to abandon j2ee and jump into the Mono bandwagon too hastily.! Enterprise container is not yet available in Mono and so it will not be suitable for projects which require enterprise-services.

 

 Even DotNet , has not provided independent Enterprise container  and gives only a wrapper for COM+ of legacy fame. It is a tacit admission and may be the reason for Microsoft vigorously promoting XML webservice, because it enables DotNet to make use of EJB!

 

No harm in experimenting and learning C# through Mono, however, to get ready for the promised day of deliverance from 'non-open' software like Java!, (as if  Java source is being kept secret !Actually, it is as open as it can be. It is like an open-access public library where you can access, borrow and use the books without mutilating the books! There are many voices questioning the very rationale of the Mono project and suspecting Corporate shadow-boxing behind the scenes.)

 

    JDK was introduced in Jan 1996 , and C#

came in 2000 & Mono about  2 years back in 2003. No wonder then that C# has taken a number of advanced features from JDK and hence Mono's C# also is very much like JDK.

 

It will be instructive to study C# and Java side-by-side. Sometimes, it would seem that the class naming and API of Java is much more elegant than C#.  For learners who would like to study C# in comparison to Java, the following two books are very useful.

 

   1)Professional DotNet

     for Java Developers with C#

    -by

    Jack Lunn & others

    ( WROX PRESS)

 

   2) C# Programming

      -Burton Harvey

      (WROX PRESS)

 

   We can use Java both in Windows and Linux. Similarly, Mono allows C# to be developed and run in Windows and Linux platforms. Mono for Windows  has been given in DeveloperIQ cd's a number of times. It is a compact zip file compared to the DotNet Framework SDK and installtion is very easy. After installing it , we can get at the  Mono console through the 'start' menu.

    We can then  edit our C#  source code in any folder of our choice and compile and run the programs.

   To compile , the command is:

>mcs   demo.cs

 

   and to run the program,

>mono  demo.exe

 

------------------------------------------

   Let us now begin with a simple example to read an URL file and print the contents in console. We will first see the Java version and then the C# version.

--------------------------------------------

 

import java.io.*;

import java.net.*;

 

class urlfile

{

    public static void main(String args[])

    {

     try

       {

        URL   url = new URL ( args[0]);

        DataInputStream    dis =

        new DataInputStream( url.openStream());

 

        String   s = dis.readLine();      

        while(s   !=   null)

         {

          System.out.println(s);

          s = dis.readLine();

         }

    } catch(Exception e1)

         (System.out.println(""+e1);}

  }

}

===========================================

As usual , we give path:

 g:\sam>

set  PATH=c:\windows\command;d:\jdk1.3\bin

 

 compile and run the program .Let us assume that Apache server has been installed in our system (using PHP-Triad software). We start apache from 'start' menu. Let us place a simple file names.txt in the root folder of Apache. ( c:\apache\htdocs).

To test our program, we run the java program with the argument:

>java urlfile "http://localhost/names.txt"

 

This will show the names.txt file in the console.

-------------------------------------------

 

Let us now write a similar program in C# , compile and test it using MONO.

------------------------------------------

EXPERIMENT-2

------------

Reading an URL file

----------------------

using System;

using System.Net;

using System.IO;

 

using System.Text;  //  Encode.ASCII

 

class urlfile

{

  public static void Main(String[]   args)

  {

   

 

HttpWebRequest       webreq =

                  (HttpWebRequest)

          WebRequest.Create (args[0]);

 

HttpWebResponse        webresp =

(HttpWebResponse)webreq.GetResponse();

 

 

StreamReader        ins =

            new StreamReader

       ( webresp.GetResponseStream(),

                     Encoding.ASCII);

 

    //-----------------------------------

 

    String     s = ins.ReadLine();

 

    while(s  !=  null)

    {

    Console.WriteLine(s);

    s=ins.ReadLine();      

    }

 

  }

}

===========================================

   The code is almost the same as in Java .

 

We can create this file in g:\monodemos folder. Navigate to g:\monodemos folder(through the Mono console obtained from start menu...this is important.If  we access this file from outside the mono console, we won't get the required classpaths).

We can compile and run the program by the procedure mentioned already and we get expected result without any problem.

======================================

 

EXPERIMENT-2

============

Accessing MySql Database

------------------------

 

We now see an example of accessing a MySql Database, through Mono.But before that we see a simple sample for Database access in DotNet Framework SDK.

( let us create a folder 'g:\dnf'.

dnf for DotNet FrameWork Sdk)

 

=======================================

// g:\dnf\accessreader.cs

 

using    System;

using   System.Data.OleDb;

using   System.Data;

 

 

class accessreader

{

   public static void Main(String[]   args)

   {      

 

 String s1=

   "Provider=Microsoft.JET.OLEDB.4.0;

           data    source=e:\\dbdemo.mdb";

//( to be typed in a single line)

// ( leave space between 'data' & 'source')

 

   OleDbConnection     con=

           new     OleDbConnection(s1);

 

   con.Open();

 

 

  

   String   sql=   args[0];

   OleDbCommand      command=

            new OleDbCommand(sql,con);

 

   OleDbDataReader     reader=

               command.ExecuteReader();

 

  

   while(reader.Read())

   {

 Console.WriteLine(reader[0].ToString());

   }  

  

   reader.Close();

 

   con.Close();

  }

}

-------------------------------------------

The above code is meant for DotNet FrameWork SDK.

We can create this file in g:\csharp

and compile by the command:

g:\csharp>csc  dbdemo.cs

 

and run the program by

g:\csharp>dbdemo

------------------------------------------

 

The important part of the code is the String for Provider. In Mono, also the operative part of the code is the same except for the string denoting the Provider for MySql database.

 

=========================================

//  g:\monodemos\monomysql.cs

 

using    System;

 

using   System.Data;

using   ByteFX.Data.MySqlClient;

 

class monomysql

{

 public static void Main(String[]   args)

 {        

      

 String s1 = "Server=localhost;Database=addressbook;";

 

   MySqlConnection     conn=null;

   try

   {

   conn=new MySqlConnection(s1);

   String   sql = args[0];

 

   MySqlCommand command=

       new MySqlCommand(sql,conn);

   conn.Open();

 

   MySqlDataReader    reader=

            command.ExecuteReader();

 

   while(reader.Read())

   {

   Console.WriteLine(reader[0].ToString());

   }

   reader.Close();

   conn.Close();

 

 

   }catch(Exception e1) { }

   }

}

===========================================

 

   It is assumed that readers are quite familiar with ADO.net in DotNet Framework SDK.

 

   Mono installation provides ready-made Data-providers for IBM DB2, MySql,ODBC,Oracle,OLE DB, PostgreSQL,Micrsoft SqlServer and Sybase.

But we must import the required libraries.

In the above case, we have used

ByteFX.Data.MySqlClient;

 

Except that we have changed the provider string and name of the classes, there is very little difference in DotNet Framework code and Mono code!

=======================================

   However, the following points are very important.

 

While compiling, we should give reference to ByteFX.Data

 

We have created the file in :

g:\monodemos\monomysql.cs

 

>mcs  -r:ByteFX.Data  -r:System.Data  monomysql.cs

 

   We get the message ,

compilation succeeeded.

 

After this, we can run the program as:

>mono monomysql.exe  "select * from table1"

 

It is assumed that we have already created the mysql database 'address book' and table1.

 

The mysql database is started from the start menu of php triad.

 

We get correct result.

=======================================

EXPERIMENT-3

Cryptography in C#

------------------

 

  Finally, we will see an example for Encryption and Decryption in C# . Readers can refer to the tutorial on Java Cryptography API's in the December 2005 issue of DeveloperIQ.

   The concept of Secret key  and the various types of algorithms has been covered there. One such algorithm is TripleDES.In this example, we will use that algorithm. The code creates the secret key by TripleDES, and then gets the key and the Initialisation Vector(IV). Using this secret key, it encrypts the given string.

After this, the encrypted message is decrypted and displayed. Readers may compare the code with that of the similar lesson in Java , published in December 2005 issue. The similarity would be striking!

Now for the code..

 

-------------------------------------------// g:\monodemos\keyer.cs

using  System;

using  System.IO;

using  System.Security.Cryptography;

using  System.Text;

 

public class keyer

{

   public static void Main(String[]   args)

   {

 

TripleDESCryptoServiceProvider   provider=

  new    TripleDESCryptoServiceProvider();

 

    provider.GenerateKey();

 

    provider.GenerateIV();  

 

    String a = args[0];

 

   //--------------------------------------

MemoryStream  ms1  = new MemoryStream();

CryptoStream  cs1  = new CryptoStream     (ms1,   provider.CreateEncryptor(),

                   CryptoStreamMode.Write);

 

 cs1.Write

(Encoding.ASCII.GetBytes(a),0,a.Length);

 

    cs1.FlushFinalBlock();

 

    byte[]       secret = ms1.ToArray();

  //----encrypted  data ready!--------

Console.WriteLine("encrypted data ready!");

 

 

MemoryStream    ms2  = new MemoryStream();

 

CryptoStream    cs2  = new CryptoStream

(ms2,provider.CreateDecryptor(),

                 CryptoStreamMode.Write);

 

    cs2.Write(secret,0,secret.Length);

    cs2.FlushFinalBlock();

 

    ms2.Seek(0,SeekOrigin.Begin);

StreamReader      reader =

                   new StreamReader(ms2);

String    original = reader.ReadToEnd();

Console.WriteLine("original got back!");

    Console.WriteLine(original);

 

  }

}

=========================================

 

  After creating the file, we can compile this through the Mono console and run it .

 

g:\monodemos>mcs  keyer.cs

 

g:\monodemos>mono keyer.exe "this is secret!"

 

We will get the console display:

 

encrypted data ready

oroginal got back

this is secret!

--

   In actual practice, we can store the key , vector and encrypted data in files. We then read these from the files and use the same key and vector to decrypt.

=========================================

Suggested Reference book:

 

MONO

-A Developer's notebook

-by Ed Dumbill

-OReilly publication

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