javax.jms.MessageConsumer Maven / Gradle / Ivy
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package javax.jms;
/** A client uses a {@code MessageConsumer} object to receive messages
* from a destination. A {@code MessageConsumer} object is created by
* passing a {@code Destination} object to a message-consumer creation
* method supplied by a session.
*
* {@code MessageConsumer} is the parent interface for all message
* consumers.
*
*
A {@code 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 {@code MessageConsumer}'s
* messages or have the {@code MessageConsumer} asynchronously deliver them
* as they arrive.
*
* For synchronous receipt, a client can request the next message from a
* {@code MessageConsumer} using one of its {@code receive} methods. There are several
* variations of {@code receive} that allow a client to poll or wait for the next message.
*
* For asynchronous delivery, a client can register a {@code MessageListener} object
* with a {@code MessageConsumer}.
* As messages arrive at the {@code MessageConsumer}, it delivers them by calling
* the {@code MessageListener}'s {@code onMessage} method.
*
* It is a client programming error for a {@code MessageListener} to throw an exception.
*
* @see javax.jms.QueueReceiver
* @see javax.jms.TopicSubscriber
* @see javax.jms.Session
*
* @version JMS 2.0
* @since JMS 1.0
*/
public interface MessageConsumer extends AutoCloseable{
/** Gets this message consumer's message selector expression.
*
* @return 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)
*
* @exception JMSException if the JMS provider fails to get the message
* selector due to some internal error.
*/
String
getMessageSelector() throws JMSException;
/** Gets the {@code MessageConsumer}'s {@code MessageListener}.
*
* This method must not be used in a Java EE web or EJB application.
* Doing so may cause a {@code JMSException} to be thrown though this is not guaranteed.
*
* @return the {@code MessageConsumer}'s {@code MessageListener}, or null if one was not set
*
* @exception JMSException if the JMS provider fails to get the {@code MessageListener}
* for one of the following reasons:
*
* - an internal error has occurred or
*
- this method has been called in a Java EE web or EJB application
* (though it is not guaranteed that an exception is thrown in this case)
*
*
* @see javax.jms.MessageConsumer#setMessageListener(javax.jms.MessageListener)
*/
MessageListener getMessageListener() throws JMSException;
/** Sets the {@code MessageConsumer}'s {@code MessageListener}.
*
* Setting the the {@code MessageListener} to null is the equivalent of
* unsetting the {@code MessageListener} for the {@code MessageConsumer}.
*
* The effect of calling this method
* while messages are being consumed by an existing listener
* or the {@code MessageConsumer} is being used to consume messages synchronously
* is undefined.
*
* This method must not be used in a Java EE web or EJB application.
* Doing so may cause a {@code JMSException} to be thrown though this is not guaranteed.
*
* @param listener the listener to which the messages are to be
* delivered
*
* @exception JMSException if the JMS provider fails to set the {@code MessageConsumer}'s {@code MessageListener}
* for one of the following reasons:
*
* - an internal error has occurred or
*
- this method has been called in a Java EE web or EJB application
* (though it is not guaranteed that an exception is thrown in this case)
*
*
* @see javax.jms.MessageConsumer#getMessageListener()
*/
void setMessageListener(MessageListener listener) 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 {@code receive} is done within a transaction, the
* consumer retains the message until the transaction commits.
*
* @return the next message produced for this message consumer, or
* null if this message consumer is concurrently closed
*
* @exception JMSException if the JMS provider fails to receive the next
* message due to some internal error.
*
*/
Message
receive() 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 {@code timeout} of zero never expires, and the call blocks
* indefinitely.
*
* @param timeout the timeout value (in milliseconds)
*
* @return the next message produced for this message consumer, or
* null if the timeout expires or this message consumer is concurrently
* closed
*
* @exception JMSException if the JMS provider fails to receive the next
* message due to some internal error.
*/
Message
receive(long timeout) throws JMSException;
/** Receives the next message if one is immediately available.
*
* @return the next message produced for this message consumer, or
* null if one is not available
*
* @exception JMSException if the JMS provider fails to receive the next
* message due to some internal error.
*/
Message
receiveNoWait() throws JMSException;
/**
* Closes the message consumer.
*
* Since a provider may allocate some resources on behalf of a
* {@code 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 {@code receive} call in progress on this
* consumer has completed. A blocked {@code 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 {@code onMessage}
* method on its own consumer. After this method returns the
* {@code onMessage} method will be allowed to complete normally.
*
* This method is the only {@code MessageConsumer} method that can be called
* concurrently.
*
* @exception JMSException
* if the JMS provider fails to close the consumer due to
* some internal error.
*/
void close() throws JMSException;
}