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public interface Session
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 MessageProducer
s.
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_ACKNOWLEDGE
With 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 receive or when the message
listener the session has called to process the message successfully
returns. |
static int |
CLIENT_ACKNOWLEDGE
With this acknowledgment mode, the client acknowledges a consumed message by calling the message's acknowledge method. |
static int |
DUPS_OK_ACKNOWLEDGE
This acknowledgment mode instructs the session to lazily acknowledge the delivery of messages. |
static int |
SESSION_TRANSACTED
This value is returned from the method getAcknowledgeMode if 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 QueueBrowser object to peek at the messages on
the specified queue. |
QueueBrowser |
createBrowser(Queue queue,
String messageSelector)
Creates a QueueBrowser object to peek at the messages on
the specified queue using a message selector. |
BytesMessage |
createBytesMessage()
Creates a BytesMessage object. |
MessageConsumer |
createConsumer(Destination destination)
Creates a MessageConsumer for the specified destination. |
MessageConsumer |
createConsumer(Destination destination,
String messageSelector)
Creates a MessageConsumer for the specified destination,
using a message selector. |
MessageConsumer |
createConsumer(Destination destination,
String messageSelector,
boolean NoLocal)
Creates MessageConsumer for the specified destination, using a
message selector. |
TopicSubscriber |
createDurableSubscriber(Topic topic,
String name)
Creates a durable subscriber to the specified topic. |
TopicSubscriber |
createDurableSubscriber(Topic topic,
String name,
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 MapMessage object. |
Message |
createMessage()
Creates a Message object. |
ObjectMessage |
createObjectMessage()
Creates an ObjectMessage object. |
ObjectMessage |
createObjectMessage(Serializable object)
Creates an initialized ObjectMessage object. |
MessageProducer |
createProducer(Destination destination)
Creates a MessageProducer to send messages to the specified
destination. |
Queue |
createQueue(String queueName)
Creates a queue identity given a Queue name. |
StreamMessage |
createStreamMessage()
Creates a StreamMessage object. |
TemporaryQueue |
createTemporaryQueue()
Creates a TemporaryQueue object. |
TemporaryTopic |
createTemporaryTopic()
Creates a TemporaryTopic object. |
TextMessage |
createTextMessage()
Creates a TextMessage object. |
TextMessage |
createTextMessage(String text)
Creates an initialized TextMessage object. |
Topic |
createTopic(String topicName)
Creates a topic identity given a Topic name. |
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(String name)
Unsubscribes a durable subscription that has been created by a client. |
Field Detail |
---|
static final int AUTO_ACKNOWLEDGE
receive
or when the message
listener the session has called to process the message successfully
returns.
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 Valuesstatic final int DUPS_OK_ACKNOWLEDGE
static final int SESSION_TRANSACTED
getAcknowledgeMode
if the session is transacted.
If a Session
is transacted, the acknowledgement mode
is ignored.
Method Detail |
---|
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.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.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.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.ObjectMessage createObjectMessage(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.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.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.TextMessage createTextMessage(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.boolean getTransacted() throws JMSException
JMSException
- if the JMS provider fails to return the
transaction mode due to some internal error.int getAcknowledgeMode() throws JMSException
JMSException
- if the JMS provider fails to return the
acknowledgment mode due to some internal error.Connection.createSession(boolean, int)
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.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.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.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.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
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
,
ServerSession
void run()
run
in interface Runnable
ServerSession
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.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.MessageConsumer createConsumer(Destination destination, 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.MessageConsumer createConsumer(Destination destination, 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.Queue createQueue(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.Topic createTopic(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.TopicSubscriber createDurableSubscriber(Topic topic, 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.TopicSubscriber createDurableSubscriber(Topic topic, String name, 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.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 specifiedQueueBrowser createBrowser(Queue queue, 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.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.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.void unsubscribe(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 2007 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.