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Oracle® Streams Advanced Queuing Java API Reference 10g Release 2 (10.2) B14291-01 |
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A client uses a MessageConsumer
object to receive messages from a destination. A MessageConsumer
object is created by passing a Destination
object to a message-consumer creation method supplied by a session.
MessageConsumer
is the parent interface for all message consumers.
A message consumer can be created with a message selector. A message selector allows the client to restrict the messages delivered to the message consumer to those that match the selector.
A client may either synchronously receive a message consumer's messages or have the consumer asynchronously deliver them as they arrive.
For synchronous receipt, a client can request the next message from a message consumer using one of its receive
methods. There are several variations of receive
that allow a client to poll or wait for the next message.
For asynchronous delivery, a client can register a MessageListener
object with a message consumer. As messages arrive at the message consumer, it delivers them by calling the MessageListener
's onMessage
method.
It is a client programming error for a MessageListener
to throw an exception.
QueueReceiver
, TopicSubscriber
, Session
Method Summary | |
void |
close() Closes the message consumer. |
MessageListener |
getMessageListener() Gets the message consumer's MessageListener . |
java.lang.String |
getMessageSelector() Gets this message consumer's message selector expression. |
Message |
receive() Receives the next message produced for this message consumer. |
Message |
receive(long timeout) Receives the next message that arrives within the specified timeout interval. |
Message |
receiveNoWait() Receives the next message if one is immediately available. |
void |
setMessageListener(MessageListener listener) Sets the message consumer's MessageListener . |
Method Detail |
public java.lang.String getMessageSelector() throws JMSException
JMSException
- if the JMS provider fails to get the message selector due to some internal error.public MessageListener getMessageListener() throws JMSException
MessageListener
.JMSException
- if the JMS provider fails to get the message listener due to some internal error.setMessageListener(javax.jms.MessageListener)
public void setMessageListener(MessageListener listener) throws JMSException
MessageListener
.
Setting the message listener to null is the equivalent of unsetting the message listener for the message consumer.
The effect of calling MessageConsumer.setMessageListener
while messages are being consumed by an existing listener or the consumer is being used to consume messages synchronously is undefined.
listener
- the listener to which the messages are to be deliveredJMSException
- if the JMS provider fails to set the message listener due to some internal error.getMessageListener()
public Message receive() throws JMSException
This call blocks indefinitely until a message is produced or until this message consumer is closed.
If this receive
is done within a transaction, the consumer retains the message until the transaction commits.
JMSException
- if the JMS provider fails to receive the next message due to some internal error.public Message receive(long timeout) throws JMSException
This call blocks until a message arrives, the timeout expires, or this message consumer is closed. A timeout
of zero never expires, and the call blocks indefinitely.
timeout
- the timeout value (in milliseconds)JMSException
- if the JMS provider fails to receive the next message due to some internal error.public Message receiveNoWait() throws JMSException
JMSException
- if the JMS provider fails to receive the next message due to some internal error.public void close() throws JMSException
Since a provider may allocate some resources on behalf of a MessageConsumer
outside the Java virtual machine, clients should close them when they are not needed. Relying on garbage collection to eventually reclaim these resources may not be timely enough.
This call blocks until a receive
or message listener in progress has completed. A blocked message consumer receive
call returns null when this message consumer is closed.
JMSException
- if the JMS provider fails to close the consumer due to some internal error.
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Oracle® Streams Advanced Queuing Java API Reference 10g Release 2 (10.2) B14291-01 |
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