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A Session object is a single-threaded context for producing and consuming 
 messages. Although it may allocate provider resources outside the Java 
 virtual machine (JVM), it is considered a lightweight JMS object.
 
A session serves several purposes:
TemporaryTopics and 
        TemporaryQueues. 
   Queue or Topic
      objects for those clients that need to dynamically manipulate 
      provider-specific destination names.
   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.
 
If a client desires to have one thread produce messages while others consume them, the client should use a separate session for its producing thread.
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 as their need for concurrency grows.
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.  
 
The Java Transaction Service (JTS) or some other transaction monitor may 
 be used to combine a session's transaction with transactions on other 
 resources (databases, other JMS sessions, etc.). Since Java distributed 
 transactions are controlled via the Java Transaction API (JTA), use of the 
 session's commit and rollback methods in 
 this context is prohibited.
 
The JMS API does not require support for JTA; however, it does define how a provider supplies this support.
Although it is also possible for a JMS client to handle distributed transactions directly, it is unlikely that many JMS clients will do this. Support for JTA in the JMS API is targeted at systems vendors who will be integrating the JMS API into their application server products.
QueueSession, 
TopicSession, 
XASession| Field Summary | |
| static int | AUTO_ACKNOWLEDGEWith this acknowledgment mode, the session automatically acknowledges a client's receipt of a message either when the session has successfully returned from a call to receiveor when the message 
 listener the session has called to process the message successfully 
 returns. | 
| static int | CLIENT_ACKNOWLEDGEWith this acknowledgment mode, the client acknowledges a consumed message by calling the message's acknowledgemethod. | 
| static int | DUPS_OK_ACKNOWLEDGEThis acknowledgment mode instructs the session to lazily acknowledge the delivery of messages. | 
| static int | SESSION_TRANSACTEDThis value is returned from the method getAcknowledgeModeif the session is transacted. | 
| Method Summary | |
|  void | close()Closes the session. | 
|  void | commit()Commits all messages done in this transaction and releases any locks currently held. | 
|  QueueBrowser | createBrowser(Queue queue)Creates a QueueBrowserobject to peek at the messages on 
 the specified queue. | 
|  QueueBrowser | createBrowser(Queue queue,
              java.lang.String messageSelector)Creates a QueueBrowserobject to peek at the messages on 
 the specified queue using a message selector. | 
|  BytesMessage | createBytesMessage()Creates a BytesMessageobject. | 
|  MessageConsumer | createConsumer(Destination destination)Creates a MessageConsumerfor the specified destination. | 
|  MessageConsumer | createConsumer(Destination destination,
               java.lang.String messageSelector)Creates a MessageConsumerfor the specified destination, 
 using a message selector. | 
|  MessageConsumer | createConsumer(Destination destination,
               java.lang.String messageSelector,
               boolean NoLocal)Creates MessageConsumerfor the specified destination, using a
 message selector. | 
|  TopicSubscriber | createDurableSubscriber(Topic topic,
                        java.lang.String name)Creates a durable subscriber to the specified topic. | 
|  TopicSubscriber | createDurableSubscriber(Topic topic,
                        java.lang.String name,
                        java.lang.String messageSelector,
                        boolean 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. | 
|  MapMessage | createMapMessage()Creates a MapMessageobject. | 
|  Message | createMessage()Creates a Messageobject. | 
|  ObjectMessage | createObjectMessage()Creates an ObjectMessageobject. | 
|  ObjectMessage | createObjectMessage(java.io.Serializable object)Creates an initialized ObjectMessageobject. | 
|  MessageProducer | createProducer(Destination destination)Creates a MessageProducerto send messages to the specified 
 destination. | 
|  Queue | createQueue(java.lang.String queueName)Creates a queue identity given a Queuename. | 
|  StreamMessage | createStreamMessage()Creates a StreamMessageobject. | 
|  TemporaryQueue | createTemporaryQueue()Creates a TemporaryQueueobject. | 
|  TemporaryTopic | createTemporaryTopic()Creates a TemporaryTopicobject. | 
|  TextMessage | createTextMessage()Creates a TextMessageobject. | 
|  TextMessage | createTextMessage(java.lang.String text)Creates an initialized TextMessageobject. | 
|  Topic | createTopic(java.lang.String topicName)Creates a topic identity given a Topicname. | 
|  int | getAcknowledgeMode()Returns the acknowledgement mode of the session. | 
|  MessageListener | getMessageListener()Returns the session's distinguished message listener (optional). | 
|  boolean | getTransacted()Indicates whether the session is in transacted mode. | 
|  void | recover()Stops message delivery in this session, and restarts message delivery with the oldest unacknowledged message. | 
|  void | rollback()Rolls back any messages done in this transaction and releases any locks currently held. | 
|  void | run()Optional operation, intended to be used only by Application Servers, not by ordinary JMS clients. | 
|  void | setMessageListener(MessageListener listener)Sets the session's distinguished message listener (optional). | 
|  void | unsubscribe(java.lang.String name)Unsubscribes a durable subscription that has been created by a client. | 
| Field Detail | 
public static final int AUTO_ACKNOWLEDGE
receive or when the message 
 listener the session has called to process the message successfully 
 returns.
public static final int CLIENT_ACKNOWLEDGE
acknowledge method. 
 Acknowledging a consumed message acknowledges all messages that the 
 session has consumed.
 When client acknowledgment mode is used, a client may build up a large number of unacknowledged messages while attempting to process them. A JMS provider should provide administrators with a way to limit client overrun so that clients are not driven to resource exhaustion and ensuing failure when some resource they are using is temporarily blocked.
Message.acknowledge(), 
Constant Field Valuespublic static final int DUPS_OK_ACKNOWLEDGE
public static final int SESSION_TRANSACTED
getAcknowledgeMode if the session is transacted.
 If a Session is transacted, the acknowledgement mode
 is ignored.
| Method Detail | 
public BytesMessage createBytesMessage()
                                throws JMSException
BytesMessage object. A BytesMessage 
 object is used to send a message containing a stream of uninterpreted 
 bytes.
JMSException - if the JMS provider fails to create this message
                         due to some internal error.
public MapMessage createMapMessage()
                            throws JMSException
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 
 in the Java programming language.
JMSException - if the JMS provider fails to create this message
                         due to some internal error.
public Message createMessage()
                      throws JMSException
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.
JMSException - if the JMS provider fails to create this message
                         due to some internal error.
public ObjectMessage createObjectMessage()
                                  throws JMSException
ObjectMessage object. An 
 ObjectMessage object is used to send a message 
 that contains a serializable Java object.
JMSException - if the JMS provider fails to create this message
                         due to some internal error.
public ObjectMessage createObjectMessage(java.io.Serializable object)
                                  throws JMSException
ObjectMessage object. An 
 ObjectMessage object is used 
 to send a message that contains a serializable Java object.
object - the object to use to initialize this message
JMSException - if the JMS provider fails to create this message
                         due to some internal error.
public StreamMessage createStreamMessage()
                                  throws JMSException
StreamMessage object. A 
 StreamMessage object is used to send a 
 self-defining stream of primitive values in the Java programming 
 language.
JMSException - if the JMS provider fails to create this message
                         due to some internal error.
public TextMessage createTextMessage()
                              throws JMSException
TextMessage object. A TextMessage 
 object is used to send a message containing a String
 object.
JMSException - if the JMS provider fails to create this message
                         due to some internal error.
public TextMessage createTextMessage(java.lang.String text)
                              throws JMSException
TextMessage object. A 
 TextMessage object is used to send 
 a message containing a String.
text - the string used to initialize this message
JMSException - if the JMS provider fails to create this message
                         due to some internal error.
public boolean getTransacted()
                      throws JMSException
JMSException - if the JMS provider fails to return the 
                         transaction mode due to some internal error.
public int getAcknowledgeMode()
                       throws JMSException
JMSException - if the JMS provider fails to return the 
                         acknowledgment mode due to some internal error.Connection.createSession(boolean, int)
public void commit()
            throws JMSException
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.
public void rollback()
              throws JMSException
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.
public void close()
           throws JMSException
Since a provider may allocate some resources on behalf of a session outside the JVM, clients should close the resources when they are not needed. Relying on garbage collection to eventually reclaim these resources may not be timely enough.
There is no need to close the producers and consumers of a closed session.
 This call will block until a receive call or message 
 listener in progress has completed. A blocked message consumer
 receive call returns null when this session 
 is 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.
JMSException - if the JMS provider fails to close the
                         session due to some internal error.
public void recover()
             throws JMSException
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:
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.
public MessageListener getMessageListener()
                                   throws JMSException
JMSException - if the JMS provider fails to get the message 
                         listener due to an internal error.setMessageListener(javax.jms.MessageListener), 
ServerSessionPool, 
ServerSession
public void setMessageListener(MessageListener listener)
                        throws JMSException
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.
listener - the message listener to associate with this session
JMSException - if the JMS provider fails to set the message 
                         listener due to an internal error.getMessageListener(), 
ServerSessionPool, 
ServerSessionpublic void run()
run in interface java.lang.RunnableServerSession
public MessageProducer createProducer(Destination destination)
                               throws JMSException
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.
destination - the Destination to send to, 
 or null if this is a producer which does not have a specified 
 destination.
JMSException - if the session fails to create a MessageProducer
                         due to some internal error.
InvalidDestinationException - if an invalid destination
 is specified.
public MessageConsumer createConsumer(Destination destination)
                               throws JMSException
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.
destination - the Destination to access.
JMSException - if the session fails to create a consumer
                         due to some internal error.
InvalidDestinationException - if an invalid destination 
                         is specified.
public MessageConsumer createConsumer(Destination destination,
                                      java.lang.String messageSelector)
                               throws JMSException
MessageConsumer for the specified destination, 
 using a message selector. 
 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 sent to a destination.
destination - the Destination to accessmessageSelector - 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.
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.
public MessageConsumer createConsumer(Destination destination,
                                      java.lang.String messageSelector,
                                      boolean NoLocal)
                               throws JMSException
MessageConsumer for the specified destination, using a
 message selector. This method can specify whether messages published by 
 its own connection should be delivered to it, if the destination is a 
 topic. 
 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. 
               
 
In some cases, a connection may both publish and subscribe to a 
 topic. The consumer NoLocal attribute allows a consumer
 to inhibit the delivery of messages published by its own connection.
 The default value for this attribute is False. The noLocal 
 value must be supported by destinations that are topics.
destination - the Destination to accessmessageSelector - 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.NoLocal - - if true, and the destination is a topic,
                   inhibits the delivery of messages published
                   by its own connection.  The behavior for
                   NoLocal is 
                   not specified if the destination is a queue.
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.
public Queue createQueue(java.lang.String queueName)
                  throws JMSException
Queue name.
 This facility is provided for the rare cases where clients need to dynamically manipulate queue identity. It allows the creation of a queue identity with a provider-specific name. Clients that depend on this ability are not portable.
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.
queueName - the name of this Queue
Queue with the given name
JMSException - if the session fails to create a queue
                         due to some internal error.
public Topic createTopic(java.lang.String topicName)
                  throws JMSException
Topic name.
 This facility is provided for the rare cases where clients need to dynamically manipulate topic identity. This allows the creation of a topic identity with a provider-specific name. Clients that depend on this ability are not portable.
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.
topicName - the name of this Topic
Topic with the given name
JMSException - if the session fails to create a topic
                         due to some internal error.
public TopicSubscriber createDurableSubscriber(Topic topic,
                                               java.lang.String name)
                                        throws JMSException
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 that 
 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.
 
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.
 
In some cases, a connection may both publish and subscribe to a 
 topic. The subscriber NoLocal attribute allows a subscriber
 to inhibit the delivery of messages published by its own connection.
 The default value for this attribute is false.
topic - the non-temporary Topic to subscribe toname - the name used to identify this subscription
JMSException - if the session fails to create a subscriber
                         due to some internal error.
InvalidDestinationException - if an invalid topic is specified.
public TopicSubscriber createDurableSubscriber(Topic topic,
                                               java.lang.String name,
                                               java.lang.String messageSelector,
                                               boolean noLocal)
                                        throws JMSException
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.
topic - the non-temporary Topic to subscribe toname - the name used to identify this subscriptionmessageSelector - 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.noLocal - if set, inhibits the delivery of messages published
 by its own connection
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.
public QueueBrowser createBrowser(Queue queue)
                           throws JMSException
QueueBrowser object to peek at the messages on 
 the specified queue.
queue - the queue to access
JMSException - if the session fails to create a browser
                         due to some internal error.
InvalidDestinationException - if an invalid destination
                         is specified
public QueueBrowser createBrowser(Queue queue,
                                  java.lang.String messageSelector)
                           throws JMSException
QueueBrowser object to peek at the messages on 
 the specified queue using a message selector.
queue - the queue to accessmessageSelector - 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.
JMSException - if the session fails to create a browser
                         due to some internal error.
InvalidDestinationException - if an invalid destination
                         is specified
InvalidSelectorException - if the message selector is invalid.
public TemporaryQueue createTemporaryQueue()
                                    throws JMSException
TemporaryQueue object. Its lifetime will be that 
 of the Connection unless it is deleted earlier.
JMSException - if the session fails to create a temporary queue
                         due to some internal error.
public TemporaryTopic createTemporaryTopic()
                                    throws JMSException
TemporaryTopic object. Its lifetime will be that 
 of the Connection unless it is deleted earlier.
JMSException - if the session fails to create a temporary
                         topic due to some internal error.
public void unsubscribe(java.lang.String name)
                 throws JMSException
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.
name - the name used to identify this subscription
JMSException - if the session fails to unsubscribe to the 
                         durable subscription due to some internal error.
InvalidDestinationException - if an invalid subscription name
                                        is specified.| 
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Copyright 2003 Sun Microsystems, Inc. All rights reserved.