MessageConsumer (Java EE 5 SDK) - Java Platform, Enterprise Edition v5.0 API Specifications
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javax.jms
Interface MessageConsumer
- All Known Subinterfaces:
- QueueReceiver, TopicSubscriber
public interface MessageConsumer
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.
- Version:
- 1.0 - 13 March 1998
- Author:
- Mark Hapner, Rich Burridge
- See Also:
QueueReceiver,TopicSubscriber,Session
| Method Summary | |
|---|---|
void |
close()
Closes the message consumer. |
MessageListener |
getMessageListener()
Gets the message consumer's MessageListener. |
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 |
|---|
getMessageSelector
String getMessageSelector() throws JMSException
- Gets this message consumer's message selector expression.
- Returns:
- this message consumer's message selector, or null if no message selector exists for the message consumer (that is, if the message selector was not set or was set to null or the empty string)
- Throws:
JMSException- if the JMS provider fails to get the message selector due to some internal error.
getMessageListener
MessageListener getMessageListener() throws JMSException
- Gets the message consumer's
MessageListener.- Returns:
- the listener for the message consumer, or null if no listener is set
- Throws:
JMSException- if the JMS provider fails to get the message listener due to some internal error.- See Also:
setMessageListener(javax.jms.MessageListener)
setMessageListener
void setMessageListener(MessageListener listener) throws JMSException
- Sets the message consumer's
MessageListener.Setting the message listener to null is the equivalent of unsetting the message listener for the message consumer.
The effect of calling
MessageConsumer.setMessageListenerwhile messages are being consumed by an existing listener or the consumer is being used to consume messages synchronously is undefined.- Parameters:
listener- the listener to which the messages are to be delivered- Throws:
JMSException- if the JMS provider fails to set the message listener due to some internal error.- See Also:
getMessageListener()
receive
Message receive() throws JMSException
- Receives the next message produced for this message consumer.
This call blocks indefinitely until a message is produced or until this message consumer is closed.
If this
receiveis done within a transaction, the consumer retains the message until the transaction commits.- Returns:
- the next message produced for this message consumer, or null if this message consumer is concurrently closed
- Throws:
JMSException- if the JMS provider fails to receive the next message due to some internal error.
receive
Message receive(long timeout) throws JMSException
- Receives the next message that arrives within the specified
timeout interval.
This call blocks until a message arrives, the timeout expires, or this message consumer is closed. A
timeoutof zero never expires, and the call blocks indefinitely.- Parameters:
timeout- the timeout value (in milliseconds)- Returns:
- the next message produced for this message consumer, or null if the timeout expires or this message consumer is concurrently closed
- Throws:
JMSException- if the JMS provider fails to receive the next message due to some internal error.
receiveNoWait
Message receiveNoWait() throws JMSException
- Receives the next message if one is immediately available.
- Returns:
- the next message produced for this message consumer, or null if one is not available
- Throws:
JMSException- if the JMS provider fails to receive the next message due to some internal error.
close
void close()
throws JMSException
- Closes the message consumer.
Since a provider may allocate some resources on behalf of a
MessageConsumeroutside 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
receiveor message listener in progress has completed. A blocked message consumerreceivecall returns null when this message consumer is closed.- Throws:
JMSException- if the JMS provider fails to close the consumer due to some internal error.
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