IoService Introduction

IoService provides basic I/O Service and manages I/O Sessions within MINA. Its one of the most crucial part of MINA Architecture. The implementing classes of IoService and child interface, are where most of the low level I/O operations are handled.

IoService Mind Map

Let's try to see what are the responsibilities of the IoService and it implementing class AbstractIoService. Let's take a slightly different approach of first using a Mind Map and then jump into the inner working. The Mind Map was created using XMind.


As seen in the previous graphic, The IoService has many responsabilities :

  • sessions management : Creates and deletes sessions, detect idleness.
  • filter chain management : Handles the filtr chain, allowing the user to change the chain on the fly
  • handler invocation : Calls the handler when some new message is received, etc
  • statistics management : Updates the number of messages sent, bytes sent, and many others
  • listeners management : Manages the Listeners a suer can set up
  • communication management : Handles the transmission of data, in both side

All those aspects will be described in the following chapters.

Interface Details

IoService is the base interface for all the IoConnector's and IoAcceptor's that provides I/O services and manages I/O sessions. The interface has all the functions need to perform I/O related operations.

Lets take a deep dive into the various methods in the interface

  • getTransportMetadata()
  • addListener()
  • removeListener()
  • isDisposing()
  • isDisposed()
  • dispose()
  • getHandler()
  • setHandler()
  • getManagedSessions()
  • getManagedSessionCount()
  • getSessionConfig()
  • getFilterChainBuilder()
  • setFilterChainBuilder()
  • getFilterChain()
  • isActive()
  • getActivationTime()
  • broadcast()
  • setSessionDataStructureFactory()
  • getScheduledWriteBytes()
  • getScheduledWriteMessages()
  • getStatistics()


This method returns the Transport meta-data the IoAcceptor or IoConnector is running. The typical details include provider name (nio, apr, rxtx), connection type (connectionless/connection oriented) etc.


Allows to add a IoServiceListener to listen to specific events related to IoService.


Removes specified IoServiceListener attached to this IoService.


This method tells if the service is currently being disposed. As it can take a while, it's useful to know the current status of the service.


This method tells if the service has been disposed. A service will be considered as disposed only when all the resources it has allocated have been released.


This method releases all the resources the service has allocated. As it may take a while, the user should check the service status using the isDisposing() and isDisposed() to know if the service is now disposed completely.

Always call dispose() when you shutdown a service !


Returns the IoHandler associated with the service.


Sets the IoHandler that will be responsible for handling all the events for the service. The handler contains your application logic !


Returns the map of all sessions which are currently managed by this service. A managed session is a session which is added to the service listener. It will be used to process the idle sessions, and other session aspects, depending on the kind of listeners a user adds to a service.


Returns the number of all sessions which are currently managed by this service.


Returns the session configuration.


Returns the Filter chain builder. This is useful if one wants to add some new filter that will be injected when the sessions will be created.


Defines the Filter chain builder to use with the service.


Returns the current default Filter chain for the service.


Tells if the service is active or not.


Returns the time when this service was activated. It returns the last time when this service was activated if the service is not anymore active.


Writes the given message to all the managed sessions.


Sets the IoSessionDataStructureFactory that provides related data structures for a new session created by this service.


Returns the number of bytes scheduled to be written (ie, the bytes stored in memory waiting for the socket to be ready for write).


Returns the number of messages scheduled to be written (ie, the messages stored in memory waiting for the socket to be ready for write).


Returns the IoServiceStatistics object for this service.