ActiveMQ 的连接和会话

要了解 connection 和 session 的概念，可以先从 ConnectionState 和 SessionState 入手：

// 省略部分代码
public class ConnectionState {ConnectionInfo info;private final ConcurrentHashMap<TransactionId, TransactionState> transactions = new ConcurrentHashMap<TransactionId, TransactionState>();private final ConcurrentHashMap<SessionId, SessionState> sessions = new ConcurrentHashMap<SessionId, SessionState>();private final List<DestinationInfo> tempDestinations = Collections.synchronizedList(new ArrayList<DestinationInfo>());private final AtomicBoolean shutdown = new AtomicBoolean(false);private boolean connectionInterruptProcessingComplete = true;private HashMap<ConsumerId, ConsumerInfo> recoveringPullConsumers;public ConnectionState(ConnectionInfo info) {this.info = info;// Add the default session id.addSession(new SessionInfo(info, -1));}
}

从代码可以看出，连接里有事务集合、会话集合、临时队列集合等，这说明：
1. 事务属于一个连接； 2. 会话属于一个连接； 3. 临时队列的生存期是连接的有效期

 

// 省略部分代码
public class SessionState {final SessionInfo info;private final Map<ProducerId, ProducerState> producers = new ConcurrentHashMap<ProducerId, ProducerState>();private final Map<ConsumerId, ConsumerState> consumers = new ConcurrentHashMap<ConsumerId, ConsumerState>();private final AtomicBoolean shutdown = new AtomicBoolean(false);public SessionState(SessionInfo info) {this.info = info;}
}

从上面能看出，producer 和 consumer 是属于某个会话的，producer 和 consumer 都有唯一的 ID 。

 

// 省略部分代码
public class ProducerState {final ProducerInfo info;private TransactionState transactionState;
}public class ConsumerState {        final ConsumerInfo info;
}

ProducerState 和 ConsumerState 只是做了简单的封装。

其中 ConnectionInfo, SessionInfo, ProducerInfo, ConsumerInfo 都是消息类型，均继承自 BaseCommand 接口。