在上面这篇文章中,当IOService接收消息后,消息被过滤链上的过滤器过滤,从链头到链尾,过程如下:
//消息接收,从链头到链尾-》Iohanlder(这个过程handler处理相关事件)
public void fireMessageReceived(IoSession session, Object message) { Entry head = this.head; callNextMessageReceived(head, session, message); } private void callNextMessageReceived(Entry entry, IoSession session, Object message) { try { entry.getFilter().messageReceived(entry.getNextFilter(), session, message); } catch (Throwable e) { fireExceptionCaught(session, e); } }
private static class TailFilter extends IoFilterAdapter { private static class TailFilter extends IoFilterAdapter { ... public void messageReceived(NextFilter nextFilter, IoSession session, Object message) throws Exception { try { session.getHandler().messageReceived(session, message); } finally { //如果发送消息对象为ByteBuffer,则释放buffer ByteBufferUtil.releaseIfPossible(message); } } ... } }
从上可以看出IoService接收消息后,消息过滤链中的过滤器(协议解码器等)过滤后,最后交给会话handler处理,即IoHandler,今天我们来看一下IoHandler。
/**
* Handles all I/O events fired by MINA.
*
* @author The Apache MINA Project ([email protected])
* @version $Rev$, $Date$
*
* @see IoHandlerAdapter
*/
public interface IoHandler {
/**
* Invoked from an I/O processor thread when a new connection has been created.
* Because this method is supposed to be called from the same thread that
* handles I/O of multiple sessions, please implement this method to perform
* tasks that consumes minimal amount of time such as socket parameter
* and user-defined session attribute initialization.
当一个新的连接创建时,有IO处理器线程调用此方法。由于此方法可以被相同的线程调用,
处理多个会话IO,所以实现此方法时,执行任务时,尽量消耗尽少的时间,比如做一些Socket参数配置,
用户自定义的会话属性
*/
void sessionCreated(IoSession session) throws Exception;
/**
* Invoked when a connection has been opened. This method is invoked after
* {@link #sessionCreated(IoSession)}. The biggest difference from
* {@link #sessionCreated(IoSession)} is that it's invoked from other thread
* than an I/O processor thread once thread modesl is configured properly.
当一个连接打开时调用此方法。此方法在会话创建后调用。与会话创建方法不同的是,
一旦线程模型配置,会话打开被其他线程调用,而不是IO处理器。
*/
void sessionOpened(IoSession session) throws Exception;
/**
* Invoked when a connection is closed.当连接关闭时,调用。
*/
void sessionClosed(IoSession session) throws Exception;
/**
* Invoked with the related {@link IdleStatus} when a connection becomes idle.
* This method is not invoked if the transport type is UDP; it's a known bug,
* and will be fixed in 2.0.
当连接空闲时,sessionIdle方法被相关空闲状态调用。如果传输接口为UDP,此方法不会调用,
这是一个已知的bug,在2.0版本修复
*/
void sessionIdle(IoSession session, IdleStatus status) throws Exception;
/**
* Invoked when any exception is thrown by user {@link IoHandler}
* implementation or by MINA. If cause
is instanceof
* {@link IOException}, MINA will close the connection automatically.
当用户的IO处理器抛出异常时,方法有mina调用。如果异常为IOException,mina将
自动关闭连接。
*/
void exceptionCaught(IoSession session, Throwable cause) throws Exception;
/**
* Invoked when a message is received.接收消息时,调用
*/
void messageReceived(IoSession session, Object message) throws Exception;
/**
* Invoked when a message written by {@link IoSession#write(Object)} is
* sent out.
当消息被Io会话write方法发送出去后,调用
*/
void messageSent(IoSession session, Object message) throws Exception;
}
//IoHandlerAdapter
/** * An abstract adapter class for {@link IoHandler}. You can extend this * class and selectively override required event handler methods only. All * methods do nothing by default. * IoHandlerAdapter为IO处理器的简单实现。你可以扩展此类或重写需要关注的事件处理方法, 默认所有方法什么都不做。 * @author The Apache Directory Project ([email protected]) * @version $Rev$, $Date$ */ public class IoHandlerAdapter implements IoHandler { public void sessionCreated(IoSession session) throws Exception { SessionUtil.initialize(session); } public void sessionOpened(IoSession session) throws Exception { } public void sessionClosed(IoSession session) throws Exception { } public void sessionIdle(IoSession session, IdleStatus status) throws Exception { } public void exceptionCaught(IoSession session, Throwable cause) throws Exception { if (SessionLog.isWarnEnabled(session)) { SessionLog.warn(session, "EXCEPTION, please implement " + getClass().getName() + ".exceptionCaught() for proper handling:", cause); } } public void messageReceived(IoSession session, Object message) throws Exception { } public void messageSent(IoSession session, Object message) throws Exception { } }