Hello,
I am Anagha Mudigonda, Graduate Student Polytechnic
University New York.
I shall be implementing In-Protocol framework and Fast
FAIL as a part of Google SOC and
subsequent to that I am willing to own the in-protocol
handler framework.
Here is the design I am convinced with after 3
iterations. I have considered all
the requirements discussed in mailing list (especially
that of Danny, Noel, Stefano and Soren)
The framework contains classes- CommandHandler,
SMTPSession, SMTPProtocolHandler, SMTPOutputStream and
SMTPInputStream
A new XML configuration is also included.
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http://football.fantasysports.yahoo.comI am Anagha Mudigonda, Graduate Student Polytechnic University New York.
I shall be implementing In-Protocol framework and Fast FAIL as a part of Google
SOC and
subsequent to that I am willing to own the in-protocol handler framework.
Here is the design I am convinced with after 3 iterations. I have considered
all
the requirements discussed in mailing list (especially that of Danny, Noel,
Stefano and Soren)
The framework contains classes- CommandHandler, SMTPSession,
SMTPProtocolHandler, SMTPOutputStream and SMTPInputStream
A new XML configuration is also included.
class CommandHandler
--------------------
Came up with a broad definition a commandHandler class
A Commandhandler class
1. registers to handle a command ( may process or validate the command
arguments)
2. Registers to handler message (validate message or modify message header or
body)
interface CommandHandler
{
void init(String configStr);
void processCommand(String cmdString);
void setSMTPSession(SMTPSession session);
void processMessage(Mail Obj);
}
There can be more than one command handler registered for a command.
CommandHandlers can be registered to validate commands, modify message.
CommandHandler's *process* methods can trigger events like message start ,
message end and message abort
and session end, session abort.
class SMTPSession
-----------------
The SMTP protocol session maintains the state information and ensures that
the commands are executed in proper order. Also it provides controlled
access to I/O streams.
The SMTP session can be in one of the 4 states:
1. SESSION_START ( as soon as the client connects to server)
2. SESSION_END ( as soon as the client Sends QUIT command or closes connection)
3. MESSAGE_START ( as soon as the client issues MAIL FROM command)
4. MESSAGE_END ( as soon as the client sends message after DATA command)
class SMTPSession
{
//Write Response
void WriteResponse(String respString);
//Register commandhandlers to command
void registerCommandHandler(String cmdPrefix, CommandHandler cmdHandler);
//Register commandhandlers to handle Message
void registerMessageHandler(CommandHandler cmdHandler);
//Command sequence handling
void addCommandSequenceMap(string command, String[] predecessorCmds, string
failMessage); //
bool isCommandAllowed(String cmdString);
//State information
String getSender();
String[] getRecepients();
String setSender(String sender);
String addRecepient(String recepient);
String addRecepient(String[] recepients);
String removeRecepient(String[] recepient);
String removeRecepient(String recepient);
//Message state modifier
void startMessage();
void endMessage();
void abortMessage();
//Message state modifier
void endSession();
void startSession();
void abortSession();
int getState(); //SESSION_START, SESSION_END, MESSAGE_BEGIN, MESSAGE_END
void reset();
SMTPInputStream getInputStream(); // object with no permission to close stream
SMTPOutputStream getOutputStream(); // Output stream object with no permission
to close stream
}
SMTPSession is per connection and is accessible to all commandhandlers.
If a command handler needs to modify the message, it registers with SMTPSession
object.
And SMTPsession object registers after the message is received passes the
message to
all the registered commandhandlers for processing.
class SMTPProtocolHandler
-------------------------
implements the SMTPSession object.
class SMTPProtocolHandler implements SMTPSession
{
//load all handlers and configure these
//configure the command sequence
//wait for SMTP connection
//Create session state object
//check if the command is allowed else respond with the failure message
//then loop thru the command handlers registered with the command and process
the command
//When Message end is triggered, call all the handlers registered for the
message
}
XML Configuration
-----------------
<smtpserver enabled="true">
<!-- port 25 is the well-known/IANA registered port for SMTP -->
<port>25</port>
<!-- NEW CONFIGURATION -->
<Protocolhandler class="org.apache.james.SMTPHandler">
<Session class=org.apache.james.SMTPSession>
<command name="MAIL" commandSequence="HELO,EHLO"/>
<command name="RCPT" commandSequence="RCPT"/>
<event sessionStartCommand=""/>
<event sessionEndCommand="QUIT"/>
<event MessageBeginCommand="MAIL"/>
<event MessageEndCommand="DATA"/>
</Session>
<!-- registers with Protocol handler to handle "MAIL" command -->
<CommandHandler class="org.apache.james.MAILCommandHandler">
config..
</CommandHandler>
<!-- registers with protocol handler to handler "MAIL" command
also registers with protocol handler to handle Message
(SPFhandler adds a SPF details into Message header)
-->
<CommandHandler name="MAIL" class="SPFHandler">
config...
</CommandHandler>
<CommandHandler name="org.apache.james.RCPTCommandHandler">
config
</CommandHandler>
<CommandHandler name="RecepientValidator">
config
</CommandHandler>
</protocolhandler>
</smtpserver>
Extending the framework
-----------------------
The framework can be extended in many ways
1. New commands can be added (for eg: STARTTLS)
Add new command handlers and modifiying the config to include new command
sequence.
2. New Validations (SPF validation)
Add a new command handler.
3. Message Extensions
Replace default command handler with a custom one.
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