public interface MessageConsumer
extends java.lang.AutoCloseable
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 MessageConsumer
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 MessageConsumer
's messages or have the MessageConsumer
asynchronously deliver them as they arrive.
For synchronous receipt, a client can request the next message from a MessageConsumer
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 MessageConsumer
. As
messages arrive at the MessageConsumer
, 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
Modifier and Type | Method and Description |
---|---|
void |
close()
Closes the message consumer.
|
MessageListener |
getMessageListener()
Gets the
MessageConsumer '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
MessageConsumer 's MessageListener . |
java.lang.String getMessageSelector() throws JMSException
JMSException
- if the Jakarta Messaging provider fails to get the message selector due to some internal error.MessageListener getMessageListener() throws JMSException
MessageConsumer
's MessageListener
.
This method must not be used in a Jakarta EE web or EJB application. Doing so may cause a JMSException
to be
thrown though this is not guaranteed.
MessageConsumer
's MessageListener
, or null if one was not setJMSException
- if the Jakarta Messaging provider fails to get the MessageListener
for one of the following
reasons:
setMessageListener(jakarta.jms.MessageListener)
void setMessageListener(MessageListener listener) throws JMSException
MessageConsumer
's MessageListener
.
Setting the the MessageListener
to null is the equivalent of unsetting the MessageListener
for the
MessageConsumer
.
The effect of calling this method while messages are being consumed by an existing listener or the
MessageConsumer
is being used to consume messages synchronously is undefined.
This method must not be used in a Jakarta EE web or EJB application. Doing so may cause a JMSException
to be
thrown though this is not guaranteed.
listener
- the listener to which the messages are to be deliveredJMSException
- if the Jakarta Messaging provider fails to set the MessageConsumer
's MessageListener
for
one of the following reasons:
getMessageListener()
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 Jakarta Messaging provider fails to receive the next message due to some internal error.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 Jakarta Messaging provider fails to receive the next message due to some internal error.Message receiveNoWait() throws JMSException
JMSException
- if the Jakarta Messaging provider fails to receive the next message due to some internal error.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 will block until a receive
call in progress on this consumer has completed. A blocked
receive
call returns null when this message consumer is closed.
If this method is called whilst a message listener is in progress in another thread then it will block until the message listener has completed.
This method may be called from a message listener's onMessage
method on its own consumer. After this method
returns the onMessage
method will be allowed to complete normally.
This method is the only MessageConsumer
method that can be called concurrently.
close
in interface java.lang.AutoCloseable
JMSException
- if the Jakarta Messaging provider fails to close the consumer due to some internal error.