Class Session

A Session object is a single-threaded context for producing and consuming messages.

A session serves several purposes:

• It is a factory for its message producers and consumers.
• It supplies provider-optimized message factories.
• It is a factory for TemporaryTopics and TemporaryQueues.
• It provides a way to create Queue or Topic objects for those clients that need to dynamically manipulate provider-specific destination names.
• It supports a single series of transactions that combine work spanning its producers and consumers into atomic units.
• It defines a serial order for the messages it consumes and the messages it produces.
• It retains messages it consumes until they have been acknowledged.
• It serializes execution of message listeners registered with its message consumers.
• It is a factory for QueueBrowsers.

A session can create and service multiple message producers and consumers.

One typical use is to have a thread block on a synchronous MessageConsumer until a message arrives. The thread may then use one or more of the Session's MessageProducers.

Once a connection has been started, any session with one or more registered message listeners is dedicated to the thread of control that delivers messages to it. It is erroneous for client code to use this session or any of its constituent objects from another thread of control. The only exception to this rule is the use of the session or connection close method.

It should be easy for most clients to partition their work naturally into sessions. This model allows clients to start simply and incrementally add message processing complexity.

The close method is the only session method that can be called while some other session method is being executed in another thread.

A session may be specified as transacted. Each transacted session supports a single series of transactions. Each transaction groups a set of message sends and a set of message receives into an atomic unit of work. In effect, transactions organize a session's input message stream and output message stream into series of atomic units. When a transaction commits, its atomic unit of input is acknowledged and its associated atomic unit of output is sent. If a transaction rollback is done, the transaction's sent messages are destroyed and the session's input is automatically recovered.

The content of a transaction's input and output units is simply those messages that have been produced and consumed within the session's current transaction.

A transaction is completed using either its session's commit method or its session's rollback method. The completion of a session's current transaction automatically begins the next. The result is that a transacted session always has a current transaction within which its work is done.

AUTO_ACKNOWLEDGE

Number AUTO_ACKNOWLEDGE

With this acknowledgment mode, the system processes acknowledgements when the consumer has successfully returned from its message handler.

CLIENT_ACKNOWLEDGE

Number CLIENT_ACKNOWLEDGE

With this acknowledgment mode, the client acknowledges a consumed message by calling the message's acknowledge method. When any message is acknowledgedThe system processes message acknowledgements as if all messages consumed from the channel were acknowledged.

DUPS_OK_ACKNOWLEDGE

Number DUPS_OK_ACKNOWLEDGE

This acknowledgment mode instructs the session to lazily acknowledge the delivery of messages. Some acknowledgements messages may be redelivered with this mode as a tradeoff for faster performance and higher scalability.

SESSION_TRANSACTED

Number SESSION_TRANSACTED

This acknowledgement mode is used for transacted sessions.

Session

Session()

A Session object is a single-threaded context for producing and consuming messages.

A session serves several purposes:

• It is a factory for its message producers and consumers.
• It supplies provider-optimized message factories.
• It is a factory for TemporaryTopics and TemporaryQueues.
• It provides a way to create Queue or Topic objects for those clients that need to dynamically manipulate provider-specific destination names.
• It supports a single series of transactions that combine work spanning its producers and consumers into atomic units.
• It defines a serial order for the messages it consumes and the messages it produces.
• It retains messages it consumes until they have been acknowledged.
• It serializes execution of message listeners registered with its message consumers.
• It is a factory for QueueBrowsers.

A session can create and service multiple message producers and consumers.

One typical use is to have a thread block on a synchronous MessageConsumer until a message arrives. The thread may then use one or more of the Session's MessageProducers.

Once a connection has been started, any session with one or more registered message listeners is dedicated to the thread of control that delivers messages to it. It is erroneous for client code to use this session or any of its constituent objects from another thread of control. The only exception to this rule is the use of the session or connection close method.

It should be easy for most clients to partition their work naturally into sessions. This model allows clients to start simply and incrementally add message processing complexity.

The close method is the only session method that can be called while some other session method is being executed in another thread.

A session may be specified as transacted. Each transacted session supports a single series of transactions. Each transaction groups a set of message sends and a set of message receives into an atomic unit of work. In effect, transactions organize a session's input message stream and output message stream into series of atomic units. When a transaction commits, its atomic unit of input is acknowledged and its associated atomic unit of output is sent. If a transaction rollback is done, the transaction's sent messages are destroyed and the session's input is automatically recovered.

The content of a transaction's input and output units is simply those messages that have been produced and consumed within the session's current transaction.

A transaction is completed using either its session's commit method or its session's rollback method. The completion of a session's current transaction automatically begins the next. The result is that a transacted session always has a current transaction within which its work is done.

close

VoidFuture close(callback)

Closes the session.

Since a provider may allocate some resources on behalf of a session, clients should close the resources when they are not needed.

There is no need to close the producers and consumers of a closed session.

This is an asynchronous call. The call returns immediately, but the operation continues until outstanding message listeners or receives have completed. The optional callback passed to close is called when the session is finally closed.

Closing a transacted session must roll back the transaction in progress.

This method is the only Session method that can be called concurrently.

Invoking any other Session method on a closed session must throw a JMSException.IllegalStateException. Closing a closed session must not throw an exception.

Parameters:
Function callback - the callback to invoke when the close operation has completed.

Returns:
VoidFuture 

Throws:
JMSException if the JMS provider fails to close the session due to some internal error.

commit

VoidFuture commit(callback)

Commits all messages done in this transaction and releases any locks currently held.

This is an asynchronous call. The call returns immediately, but the operation continues until client is notified that the broker has processed the commit or an error has occurred. The optional callback passed to commit is called when the operation has completed with success or an exception.

Parameters:
Function callback - the callback to invoke when the close operation has completed.

Returns:
VoidFuture 

Throws:
JMSException if the JMS provider fails to commit the transaction due to some internal error.
TransactionRolledBackException if the transaction is rolled back due to some internal error during commit.
IllegalStateException if the method is not called by a transacted session.

createBytesMessage

BytesMessage createBytesMessage()

Creates a BytesMessage object. A BytesMessage object is used to send a message containing a stream of uninterpreted bytes.

Returns:
BytesMessage 

Throws:
JMSException if the JMS provider fails to create this message due to some internal error.

createConsumer

MessageConsumer createConsumer(destination, messageSelector)

Creates MessageConsumer for the specified destination.

Since Queue and Topic both inherit from Destination, they can be used in the destination parameter to create a MessageConsumer.

A client uses a MessageConsumer object to receive messages that have been published to a destination.

The messageSelector parameter is optional.

Parameters:
destination - the Destination to access
messageSelector - only messages with properties matching the message selector expression are delivered. A value of null or an empty string indicates that there is no message selector for the message consumer.

Returns:
MessageConsumer 

Throws:
JMSException if the session fails to create a MessageConsumer due to some internal error.
InvalidDestinationException if an invalid destination is specified.
InvalidSelectorException if the message selector is invalid.

createDurableSubscriber

TopicSubscriber createDurableSubscriber(topic, durableName, messageSelector, noLocal)

Creates a durable subscriber to the specified topic, using a message selector and specifying whether messages published by its own connection should be delivered to it.

If a client needs to receive all the messages published on a topic, including the ones published while the subscriber is inactive, it uses a durable TopicSubscriber. The JMS provider retains a record of this durable subscription and insures that all messages from the topic's publishers are retained until they are acknowledged by this durable subscriber or they have expired.

Sessions with durable subscribers must always provide the same client identifier. In addition, each client must specify a name which uniquely identifies (within client identifier) each durable subscription it creates. Only one session at a time can have a TopicSubscriber for a particular durable subscription. An inactive durable subscriber is one that exists but does not currently have a message consumer associated with it.

A client can change an existing durable subscription by creating a durable TopicSubscriber with the same name and a new topic and/or message selector. Changing a durable subscriber is equivalent to unsubscribing (deleting) the old one and creating a new one.

Parameters:
topic - - the non-temporary Topic to subscribe to
durableName - - the name used to identify this subscription
messageSelector - - only messages with properties matching the message selector expression are delivered. A value of null or an empty string indicates that there is no message selector for the message consumer. Optional parameter with null default.
noLocal - - if true, inhibits the delivery of messages published by its own connection. Optional parameter. Default value is false.

Returns:
TopicSubscriber 

Throws:
JMSException if the session fails to create a subscriber due to some internal error.
InvalidDestinationException if an invalid topic is specified.
InvalidSelectorException if the message selector is invalid.

createMapMessage

MapMessage createMapMessage()

Creates a MapMessage object. A MapMessage object is used to send a self-defining set of name-value pairs, where names are String objects and values are primitive values.

Returns:
MapMessage 

Throws:
JMSException if the JMS provider fails to create this message due to some internal error.

createMessage

Message createMessage()

Creates a Message object. The Message interface is the root interface of all JMS messages. A Message object holds all the standard message header information. It can be sent when a message containing only header information is sufficient.

Returns:
Message 

Throws:
JMSException if the JMS provider fails to create this message due to some internal error.

createProducer

MessageProducer createProducer(destination)

Creates a MessageProducer to send messages to the specified destination.

A client uses a MessageProducer object to send messages to a destination. Since Queue and Topic both inherit from Destination, they can be used in the destination parameter to create a MessageProducer object.

Parameters:
destination - the Destination to send to, or null if this is a producer which does not have a specified destination.

Returns:
MessageProducer 

Throws:
JMSException if the session fails to create a MessageProducer due to some internal error.
InvalidDestinationException if an invalid destination is specified.

createQueue

Queue createQueue(queueName)

Creates a queue identity given a Queue name.

This facility is provided where clients need to dynamically manipulate queue identity. It allows the creation of a queue identity with a provider-specific name.

Note that this method is not for creating the physical queue. The physical creation of queues is an administrative task and is not to be initiated by the JMS API. The one exception is the creation of temporary queues, which is accomplished with the createTemporaryQueue method.

Parameters:
queueName - the name of this Queue

Returns:
Queue a Queue with the given name

Throws:
JMSException if the session fails to create a queue due to some internal error.

createTemporaryQueue

TemporaryQueue createTemporaryQueue()

Creates a TemporaryQueue object. Its lifetime will be that of the Connection unless it is deleted earlier.

Returns:
TemporaryQueue a temporary queue identity

Throws:
JMSException if the session fails to create a temporary queue due to some internal error.

createTemporaryTopic

TemporaryTopic createTemporaryTopic()

Creates a TemporaryTopic object. Its lifetime will be that of the Connection unless it is deleted earlier.

Returns:
TemporaryTopic a temporary topic identity

Throws:
JMSException if the session fails to create a temporary topic due to some internal error.

createTextMessage

TextMessage createTextMessage(text)

Creates an initialized TextMessage object. A TextMessage object is used to send a message containing a String.

Parameters:
text - the string used to initialize this message

Returns:
TextMessage 

Throws:
JMSException if the JMS provider fails to create this message due to some internal error.

createTopic

Topic createTopic(topicName)

Creates a topic identity given a Topic name.

This facility is provided where clients need to dynamically manipulate topic identity. This allows the creation of a topic identity with a provider-specific name.

Note that this method is not for creating the physical topic. The physical creation of topics is an administrative task and is not to be initiated by the JMS API. The one exception is the creation of temporary topics, which is accomplished with the createTemporaryTopic method.

Parameters:
topicName - the name of this Topic

Returns:
Topic a Topic with the given name

Throws:
JMSException if the session fails to create a topic due to some internal error.

getAcknowledgeMode

Number getAcknowledgeMode()

Returns the acknowledgement mode of the session. The acknowledgement mode is set at the time that the session is created. If the session is transacted, the acknowledgement mode is ignored.

Returns:
Number If the session is not transacted, returns the current acknowledgement mode for the session. If the session is transacted, returns SESSION_TRANSACTED.

Throws:
JMSException if the JMS provider fails to return the acknowledgment mode due to some internal error.

getMessageListener

MessageListener getMessageListener()

Returns the session's distinguished message listener (optional).

Returns:
MessageListener the message listener associated with this session

Throws:
JMSException if the JMS provider fails to get the message listener due to an internal error.

getTransacted

boolean getTransacted()

Indicates whether the session is in transacted mode.

Returns:
boolean true if the session is in transacted mode

Throws:
JMSException if the JMS provider fails to return the transaction mode due to some internal error.

recover

void recover()

Stops message delivery in this session, and restarts message delivery with the oldest unacknowledged message.

All consumers deliver messages in a serial order. Acknowledging a received message automatically acknowledges all messages that have been delivered to the client.

Restarting a session causes it to take the following actions:

• Stop message delivery
• Mark all messages that might have been delivered but not acknowledged as "redelivered"
• Restart the delivery sequence including all unacknowledged messages that had been previously delivered. Redelivered messages do not have to be delivered in exactly their original delivery order.

Returns:
void 

Throws:
JMSException if the JMS provider fails to stop and restart message delivery due to some internal error.
IllegalStateException if the method is called by a transacted session.

rollback

VoidFuture rollback()

Rolls back any messages done in this transaction and releases any locks currently held.

This is an asynchronous call. The call returns immediately, but the operation continues until the rollback has completed or an error has occurred. The optional callback passed to rollback is called when the operation has completed with success or an exception.

Returns:
VoidFuture 

Throws:
JMSException if the JMS provider fails to roll back the transaction due to some internal error.
IllegalStateException if the method is not called by a transacted session.

setMessageListener

void setMessageListener(listener)

Sets the session's distinguished message listener (optional).

When the distinguished message listener is set, no other form of message receipt in the session can be used; however, all forms of sending messages are still supported.

This is an expert facility not used by regular JMS clients.

Parameters:
Function, MessageListener listener - the message listener to associate with this session

Returns:
void 

Throws:
JMSException if the JMS provider fails to set the message listener due to an internal error.

unsubscribe

void unsubscribe(name)

Unsubscribes a durable subscription that has been created by a client.

This method deletes the state being maintained on behalf of the subscriber by its provider.

It is erroneous for a client to delete a durable subscription while there is an active MessageConsumer or TopicSubscriber for the subscription, or while a consumed message is part of a pending transaction or has not been acknowledged in the session.

Parameters:
String name - the name used to identify this subscription

Returns:
void 

Throws:
JMSException if the session fails to unsubscribe to the durable subscription due to some internal error.
InvalidDestinationException if an invalid subscription name is specified.