|
Oracle® Streams Advanced Queuing Java API Reference 10g Release 2 (10.2) B14291-01 |
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
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, java.lang.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, java.lang.String messageSelector) Creates a MessageConsumer for the specified destination, using a message selector. |
MessageConsumer |
createConsumer(Destination destination, java.lang.String messageSelector, boolean NoLocal) Creates MessageConsumer for 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 MapMessage object. |
Message |
createMessage() Creates a Message object. |
ObjectMessage |
createObjectMessage() Creates an ObjectMessage object. |
ObjectMessage |
createObjectMessage(java.io.Serializable object) Creates an initialized ObjectMessage object. |
MessageProducer |
createProducer(Destination destination) Creates a MessageProducer to send messages to the specified destination. |
Queue |
createQueue(java.lang.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(java.lang.String text) Creates an initialized TextMessage object. |
Topic |
createTopic(java.lang.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(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 messageJMSException
- 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 messageJMSException
- 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 sessionJMSException
- if the JMS provider fails to set the message listener due to an internal error.getMessageListener()
, ServerSessionPool
, ServerSession
public void run()
run
in interface java.lang.Runnable
ServerSession
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 nameJMSException
- 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 nameJMSException
- 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 subscriptionJMSException
- 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 connectionJMSException
- 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 accessJMSException
- if the session fails to create a browser due to some internal error.InvalidDestinationException
- if an invalid destination is specifiedpublic 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 specifiedInvalidSelectorException
- 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 subscriptionJMSException
- if the session fails to unsubscribe to the durable subscription due to some internal error.InvalidDestinationException
- if an invalid subscription name is specified.
|
Oracle® Streams Advanced Queuing Java API Reference 10g Release 2 (10.2) B14291-01 |
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | |||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |