ApacheMina study notes (4)-Session

Session is the core of Apache. every time a client is connected, a new Session is created until the connection is closed. Session is used to save connections and various information. Session is the core of Apache. every time a client is connected, a new Session is created until the connection is closed. Session is used to save connections and various information.

The Session has the following statuses:

Connected : the session has been created and is availableIdle : the session hasn't processed any request for at least a period of time (this period is configurable)Idle for read : no read has actually been made for a period of timeIdle for write : no write has actually been made for a period of timeIdle for both : no read nor write for a period of timeClosing : the session is being closed (the remaining messages are being flushed, cleaning up is not terminated)Closed : The session is now closed, nothing else can be done to revive it.

Indicates the status transition relationship of the Session:

For example, if you want to track how many requests a user sends after a session is established, it can easily store the ing: you only need to create a key and associate it with the value.

...  int counterValue = session.getAttribute( "counter" );  session.setAttribute( "counter", counterValue + 1 );  ...

We use the key/value pair to store attributes in the session. this key/value pair can be read, added, or deleted through the session container.

Define container

As we said, this container is a key/value container, which is a ING by default and can also be defined as other data structures. When a Session is created, we can implement an interface and a factory to create a container. The following code snippet demonstrates how to create a container during Session initialization (you cannot understand it. what does this mean ?)

protected final void initSession(IoSession session,          IoFuture future, IoSessionInitializer sessionInitializer) {      ...      try {          ((AbstractIoSession) session).setAttributeMap(session.getService()                  .getSessionDataStructureFactory().getAttributeMap(session));      } catch (IoSessionInitializationException e) {          throw e;      } catch (Exception e) {          throw new IoSessionInitializationException(                  "Failed to initialize an attributeMap.", e);      }

And here is the factory interface we can implement if we want to define another kind of container:

public interface IoSessionDataStructureFactory {      /**      * Returns an {@link IoSessionAttributeMap} which is going to be associated      * with the specified session.  Please note that the returned      * implementation must be thread-safe.      */       IoSessionAttributeMap getAttributeMap(IoSession session) throws Exception;   }

Filter chain

Each session is associated with a filter chain to process incoming requests or outgoing data. Each session will specify a separate filtering chain. In most cases, we will use many identical filtering chains in the session.

Statistics

Each session also keep a track of records about what has been done for the session :number of bytes received/sentnumber of messages received/sentIdle statusthroughputand many other useful informations.Handler

Finally, it is equally important that a Handler is attached to a Session to process messages of the program. This Handler will also send a packet as a response, as long as the write method is simply called:

...  session.write( 
 
   );  ...
 

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