引言：
前面的文章我们看了Nio处理器，先来回顾一下：
NioProcessor内部有一个选择器Selector，一个可重入读写锁用于控制选择器相关的操作，构造主要是初始化线程执行器和选择器。Nio处理器的选择操作，唤醒等操作，实际通过内部的选择器完成。初始化会话，主要是配置会话通道为非阻塞模式，注册会话通道读事件到选择器。注册新选择器，主要是注册旧选择器的选择key（集合）关联的会话，通道，及通道兴趣事件集到新的选择器；会话时附加在通道选择key的Attachment上。处理器处理会话读写操作，主要是通过会话关联的通道完成。关闭会话主要是关闭会话关联的字节通道和取消会话关联选择key。
今天我们来看一下Io会话的定义：
/**
* A handle which represents connection between two endpoints regardless of
* transport types.
*
* {@link IoSession} provides user-defined attributes. User-defined attributes
* are application-specific data which is associated with a session.
* It often contains objects that represents the state of a higher-level protocol
* and becomes a way to exchange data between filters and handlers.
*
* <h3>Adjusting Transport Type Specific Properties</h3>
* <p>
* You can simply downcast the session to an appropriate subclass.
*
*
* <h3>Thread Safety</h3>
*
* {@link IoSession} is thread-safe. But please note that performing
* more than one {@link #write(Object)} calls at the same time will
* cause the {@link IoFilter#filterWrite(IoFilter.NextFilter, IoSession, IoFilter.WriteRequest)}
* is executed simnutaneously, and therefore you have to make sure the
* {@link IoFilter} implementations you're using are thread-safe, too.
*
*
* @author The Apache Directory Project ([email protected])
* @version $Rev$, $Date$
*/
public interface IoSession {
/**
* Returns the {@link IoService} which provides I/O service to this session.
获取会话关联的IoService
*/
IoService getService();
/**
* Returns the {@link IoServiceConfig} of this session.
获取会话关联的IoService配置
*/
IoServiceConfig getServiceConfig();
/**
* Returns the {@link IoHandler} which handles this session.
获取会话Iohandler
*/
IoHandler getHandler();
/**
* Returns the configuration of this session.
获取会话配置
*/
IoSessionConfig getConfig();
/**
* Returns the filter chain that only affects this session.
获取会话过滤链
*/
IoFilterChain getFilterChain();
/**
* Writes the specified <code>message</code> to remote peer. This
* operation is asynchronous; {@link IoHandler#messageSent(IoSession, Object)}
* will be invoked when the message is actually sent to remote peer.
* You can also wait for the returned {@link WriteFuture} if you want
* to wait for the message actually written.
发送消息给远端的peer。此操作是异步的，当消息实际发送到远端peer时，会调用
IoHandler#messageSent方法法。如果想等待消息实际发送完，可以等待WriteFuture。
*/
WriteFuture write(Object message);
/**
* Closes this session immediately. This operation is asynthronous.
* Wait for the returned {@link CloseFuture} if you want to wait for
* the session actually closed.
立刻关闭会话。此操作为异步的。如果想要等待会话实际完成关闭，可以等待CloseFuture
*/
CloseFuture close();
/**
* Returns an attachment of this session.
* This method is identical with <tt>getAttribute( "" )</tt>.
返回会话附加物
*/
Object getAttachment();
/**
* Sets an attachment of this session.
* This method is identical with <tt>setAttribute( "", attachment )</tt>.
* 设置会话附加物
* @return Old attachment. <tt>null</tt> if it is new.
*/
Object setAttachment(Object attachment);
/**
* Returns the value of user-defined attribute of this session.
* 获取会话属性key对一个的属性值
* @param key the key of the attribute
* @return <tt>null</tt> if there is no attribute with the specified key
*/
Object getAttribute(String key);
/**
* Sets a user-defined attribute.
* 设置会话属性
* @param key the key of the attribute
* @param value the value of the attribute
* @return The old value of the attribute. <tt>null</tt> if it is new.
*/
Object setAttribute(String key, Object value);
/**
* Sets a user defined attribute without a value. This is useful when
* you just want to put a 'mark' attribute. Its value is set to
* {@link Boolean#TRUE}.
* 设置会话无值属性
* @param key the key of the attribute
* @return The old value of the attribute. <tt>null</tt> if it is new.
*/
Object setAttribute(String key);
/**
* Removes a user-defined attribute with the specified key.
* 移除会话属性
* @return The old value of the attribute. <tt>null</tt> if not found.
*/
Object removeAttribute(String key);
/**
* Returns <tt>true</tt> if this session contains the attribute with
* the specified <tt>key</tt>.
判断是否包含属性key
*/
boolean containsAttribute(String key);
/**
* Returns the set of keys of all user-defined attributes.
获取会话所有属性
*/
Set getAttributeKeys();
/**
* Returns transport type of this session.
获取会话transport类型，socket，Datagram，vmpipe
*/
TransportType getTransportType();
/**
* Returns <code>true</code> if this session is connected with remote peer.
会话是否连接
*/
boolean isConnected();
/**
* Returns <code>true</tt> if and only if this session is being closed
* (but not disconnected yet) or is closed.
会话是否关闭
*/
boolean isClosing();
/**
* Returns the {@link CloseFuture} of this session. This method returns
* the same instance whenever user calls it.
获取会话关闭结果
*/
CloseFuture getCloseFuture();
/**
* Returns the socket address of remote peer.
获取会话远端peer地址
*/
SocketAddress getRemoteAddress();
/**
* Returns the socket address of local machine which is associated with this
* session.
获取会话本地地址
*/
SocketAddress getLocalAddress();
/**
* Returns the socket address of the {@link IoService} listens to to manage
* this session. If this session is managed by {@link IoAcceptor}, it
* returns the {@link SocketAddress} which is specified as a parameter of
* {@link IoAcceptor#bind(SocketAddress, IoHandler)}. If this session is
* managed by {@link IoConnector}, this method returns the same address with
* that of {@link #getRemoteAddress()}.
获取IoService监听管理会话的地址。如果会话被IoAcceptor管理，返回的为IoAcceptor#bind(SocketAddress, IoHandler)
的参数地址。如果会话为IoConnector，则返回的远端peer地址。
*/
SocketAddress getServiceAddress();
/**
* Returns idle time for the specified type of idleness in seconds.
返回空闲状态的空闲时间s
*/
int getIdleTime(IdleStatus status);
/**
* Returns idle time for the specified type of idleness in milliseconds.
返回空闲状态的空闲时间ms
*/
long getIdleTimeInMillis(IdleStatus status);
/**
* Sets idle time for the specified type of idleness in seconds.
设置空闲状态的空闲时间
*/
void setIdleTime(IdleStatus status, int idleTime);
/**
* Returns write timeout in seconds.
获取写超时时间s
*/
int getWriteTimeout();
/**
* Returns write timeout in milliseconds.
获取写超时时间ms
*/
long getWriteTimeoutInMillis();
/**
* Sets write timeout in seconds.
设置写超时时间
*/
void setWriteTimeout(int writeTimeout);
/**
* Returns the current {@link TrafficMask} of this session.
返回会话传输状态（读写）
*/
TrafficMask getTrafficMask();
/**
* Sets the {@link TrafficMask} of this session which will result
* the parent {@link IoService} to start to control the traffic
* of this session immediately.
设置会话传输状态，这将引起Io服务，开始控制会话传输
*/
void setTrafficMask(TrafficMask trafficMask);
/**
* A shortcut method for {@link #setTrafficMask(TrafficMask)} that
* suspends read operations for this session.
暂定会话读操作
*/
void suspendRead();
/**
* A shortcut method for {@link #setTrafficMask(TrafficMask)} that
* suspends write operations for this session.
暂定会话写操作
*/
void suspendWrite();
/**
* A shortcut method for {@link #setTrafficMask(TrafficMask)} that
* resumes read operations for this session.
恢复会话读操作
*/
void resumeRead();
/**
* A shortcut method for {@link #setTrafficMask(TrafficMask)} that
* resumes write operations for this session.
恢复会话写操作
*/
void resumeWrite();
/**
* Returns the total number of bytes which were read from this session.
获取从会话读取的字节数
*/
long getReadBytes();
/**
* Returns the total number of bytes which were written to this session.
获取会话写的字节数
*/
long getWrittenBytes();
/**
* Returns the total number of messages which were read and decoded from this session.
获取从会话读取或解码的消息数
*/
long getReadMessages();
/**
* Returns the total number of messages which were written and encoded by this session.
获取会话发送消息和编码消息的数量
*/
long getWrittenMessages();
/**
* Returns the total number of write requests which were written to this session.
获取会话写请求的数量
*/
long getWrittenWriteRequests();
/**
* Returns the number of write requests which are scheduled to be written
* to this session.
获取会话写请求实际被调度的数量，即实际发送数量
*/
int getScheduledWriteRequests();
/**
* Returns the number of bytes which are scheduled to be written to this
* session.
获取会话实际发送字节数
*/
int getScheduledWriteBytes();
/**
* Returns the time in millis when this session is created.
获取会话创建时间
*/
long getCreationTime();
/**
* Returns the time in millis when I/O occurred lastly.
获取会话上一次发送IO操作的时间
*/
long getLastIoTime();
/**
* Returns the time in millis when read operation occurred lastly.
获取会话上一次读操作的时间
*/
long getLastReadTime();
/**
* Returns the time in millis when write operation occurred lastly.
获取会话上一次写操作的时间
*/
long getLastWriteTime();
/**
* Returns <code>true</code> if this session is idle for the specified
* {@link IdleStatus}.
判断会话是否处理空闲状态status
*/
boolean isIdle(IdleStatus status);
/**
* Returns the number of the fired continuous <tt>sessionIdle</tt> events
* for the specified {@link IdleStatus}.
获取会话处于空闲状态status的次数
* <p>
* If <tt>sessionIdle</tt> event is fired first after some time after I/O,
* <tt>idleCount</tt> becomes <tt>1</tt>. <tt>idleCount</tt> resets to
* <tt>0</tt> if any I/O occurs again, otherwise it increases to
* <tt>2</tt> and so on if <tt>sessionIdle</tt> event is fired again without
* any I/O between two (or more) <tt>sessionIdle</tt> events.
*/
int getIdleCount(IdleStatus status);
/**
* Returns the time in millis when the last <tt>sessionIdle</tt> event
* is fired for the specified {@link IdleStatus}.
获取会话上次处于空闲状态status的时间
*/
long getLastIdleTime(IdleStatus status);
}
附：
//TransportType
/**
* Represents network transport types.
* MINA provides three transport types by default:
* [list]
* [*]{@link #SOCKET} - TCP/IP
* [*]{@link #DATAGRAM} - UDP/IP
* <li>{@link #VM_PIPE} - in-VM pipe support (only available in protocol
* layer</li>
* [/list]
* <p>
* You can also create your own transport type. Please refer to
* {@link #TransportType(String[], boolean)}.
*
* @author The Apache Directory Project ([email protected])
* @version $Rev$, $Date$
*/
public final class TransportType implements Serializable {
private static final long serialVersionUID = 3258132470497883447L;
private static final Map name2type = new HashMap();
private final String[] names;
private final transient boolean connectionless;
private final transient Class envelopeType;
/**
* Transport type: TCP/IP (Registry name: <tt>"SOCKET"</tt> or <tt>"TCP"</tt>)
*/
public static final TransportType SOCKET = new TransportType(new String[] {
"SOCKET", "TCP" }, false);
/**
* Transport type: UDP/IP (Registry name: <tt>"DATAGRAM"</tt> or <tt>"UDP"</tt>)
*/
public static final TransportType DATAGRAM = new TransportType(
new String[] { "DATAGRAM", "UDP" }, true);
/**
* Transport type: in-VM pipe (Registry name: <tt>"VM_PIPE"</tt>)
* Please refer to
* [url=../protocol/vmpipe/package-summary.htm]<tt>org.apache.mina.protocol.vmpipe</tt>[/url]
* package.
*/
public static final TransportType VM_PIPE = new TransportType(
new String[] { "VM_PIPE" }, Object.class, false);
...
}
//TrafficMask
/**
* A type-safe mask that is used to control the traffic of {@link IoSession}
* with {@link IoSession#setTrafficMask(TrafficMask)}.
*
* @author The Apache Directory Project ([email protected])
* @version $Rev$, $Date$
*/
public class TrafficMask {
private final int interestOps;
private final String name;
/**
* This mask suspends both reads and writes.
*/
public static final TrafficMask NONE = new TrafficMask(0, "none");
/**
* This mask suspends writes, and resumes reads if reads were suspended.
*/
public static final TrafficMask READ = new TrafficMask(
SelectionKey.OP_READ, "read");
/**
* This mask suspends reads, and resumes writes if writes were suspended.
*/
public static final TrafficMask WRITE = new TrafficMask(
SelectionKey.OP_WRITE, "write");
/**
* This mask resumes both reads and writes if any of them were suspended.
*/
public static final TrafficMask ALL = new TrafficMask(SelectionKey.OP_READ
| SelectionKey.OP_WRITE, "all");
...
}