Module jakarta.messaging

Package jakarta.jms

Interface JMSConsumer

All Superinterfaces:

AutoCloseable

public interface JMSConsumer
extends AutoCloseable

A client using the simplified Jakarta Messaging API introduced for Jakarta Messaging 2.0 uses a JMSConsumer object to receive messages from a queue or topic. A JMSConsumer object may be created either created by passing a Queue or Topic object to one of the createConsumer methods on a JMSContext. or by passing a Topic object to one of the createSharedConsumer or createDurableConsumer methods on a JMSContext.

A JMSConsumer can be created with a message selector. A message selector allows the client to restrict the messages delivered to the JMSConsumer to those that match the selector.

A client may either synchronously receive a JMSConsumer's messages or have the JMSConsumer asynchronously deliver them as they arrive.

For synchronous receipt, a client can request the next message from a JMSConsumer 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 JMSConsumer. As messages arrive at the JMSConsumer, it delivers them by calling the MessageListener 's onMessage method.

It is a client programming error for a MessageListener to throw an exception.

Since:

JMS 2.0

Version:

Jakarta Messaging 2.0

See Also:

• JMSContext

Method Summary

Modifier and Type	Method	Description
void	close()	Closes the JMSConsumer.
MessageListener	getMessageListener()	Gets the JMSConsumer's MessageListener.
String	getMessageSelector()	Gets this JMSConsumer's message selector expression.
Message	receive()	Receives the next message produced for this JMSConsumer.
Message	receive(long timeout)	Receives the next message that arrives within the specified timeout interval.
<T> T	receiveBody(Class<T> c)	Receives the next message produced for this JMSConsumer and returns its body as an object of the specified type.
<T> T	receiveBody(Class<T> c, long timeout)	Receives the next message produced for this JMSConsumer that arrives within the specified timeout period and returns its body as an object of the specified type.
<T> T	receiveBodyNoWait(Class<T> c)	Receives the next message produced for this JMSConsumer if one is immediately available and returns its body as an object of the specified type.
Message	receiveNoWait()	Receives the next message if one is immediately available.
void	setMessageListener(MessageListener listener)	Sets the JMSConsumer's MessageListener.

Method Details

getMessageSelector

String getMessageSelector()

Gets this JMSConsumer's message selector expression.

Returns:

this JMSConsumer's message selector, or null if no message selector exists for the JMSConsumer (that is, if the message selector was not set or was set to null or the empty string)

Throws:

JMSRuntimeException - if the Jakarta Messaging provider fails to get the message selector due to some internal error.

getMessageListener

MessageListener getMessageListener()
                            throws JMSRuntimeException

Gets the JMSConsumer's MessageListener.

This method must not be used in a Jakarta EE web or EJB application. Doing so may cause a JMSRuntimeException to be thrown though this is not guaranteed.

Returns:

the JMSConsumer's MessageListener, or null if one was not set

Throws:

JMSRuntimeException - if the Jakarta Messaging provider fails to get the MessageListener for one of the following reasons:

• an internal error has occurred or
• this method has been called in a Jakarta EE web or EJB application (though it is not guaranteed that an exception is thrown in this case)

See Also:

• setMessageListener(jakarta.jms.MessageListener)

setMessageListener

void setMessageListener(MessageListener listener)
                 throws JMSRuntimeException

Sets the JMSConsumer's MessageListener.

Setting the MessageListener to null is the equivalent of unsetting the MessageListener for the JMSConsumer.

The effect of calling this method while messages are being consumed by an existing listener or the JMSConsumer 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 JMSRuntimeException to be thrown though this is not guaranteed.

Parameters:

listener - the listener to which the messages are to be delivered

Throws:

JMSRuntimeException - if the Jakarta Messaging provider fails to set the JMSConsumer's MessageListener for one of the following reasons:

• an internal error has occurred or
• this method has been called in a Jakarta EE web or EJB application (though it is not guaranteed that an exception is thrown in this case)

See Also:

• getMessageListener()

receive

Message receive()

Receives the next message produced for this JMSConsumer.

This call blocks indefinitely until a message is produced or until this JMSConsumer is closed.

If this receive is done within a transaction, the JMSConsumer retains the message until the transaction commits.

Returns:

the next message produced for this JMSConsumer, or null if this JMSConsumer is concurrently closed

Throws:

JMSRuntimeException - if the Jakarta Messaging provider fails to receive the next message due to some internal error.

receive

Message receive(long timeout)

Receives the next message that arrives within the specified timeout interval.

This call blocks until a message arrives, the timeout expires, or this JMSConsumer is closed. A timeout of zero never expires, and the call blocks indefinitely.

Parameters:

timeout - the timeout value (in milliseconds)

Returns:

the next message produced for this JMSConsumer, or null if the timeout expires or this JMSConsumer is concurrently closed

Throws:

JMSRuntimeException - if the Jakarta Messaging provider fails to receive the next message due to some internal error.

receiveNoWait

Message receiveNoWait()

Receives the next message if one is immediately available.

Returns:

the next message produced for this JMSConsumer, or null if one is not available

Throws:

JMSRuntimeException - if the Jakarta Messaging provider fails to receive the next message due to some internal error.

close

void close()

Closes the JMSConsumer.

Since a provider may allocate some resources on behalf of a JMSConsumer 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 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 JMSConsumer method that can be called concurrently.

Specified by:

close in interface AutoCloseable

Throws:

JMSRuntimeException - if the Jakarta Messaging provider fails to close the consumer due to some internal error.

receiveBody

<T> T receiveBody(Class<T> c)

Receives the next message produced for this JMSConsumer and returns its body as an object of the specified type. This method may be used to receive any type of message except for StreamMessage and Message, so long as the message has a body which is capable of being assigned to the specified type. This means that the specified class or interface must either be the same as, or a superclass or superinterface of, the class of the message body. If the message is not one of the supported types, or its body cannot be assigned to the specified type, or it has no body, then a MessageFormatRuntimeException is thrown.

This method does not give access to the message headers or properties (such as the JMSRedelivered message header field or the JMSXDeliveryCount message property) and should only be used if the application has no need to access them.

This call blocks indefinitely until a message is produced or until this JMSConsumer is closed.

If this method is called within a transaction, the JMSConsumer retains the message until the transaction commits.

The result of this method throwing a MessageFormatRuntimeException depends on the session mode:

• AUTO_ACKNOWLEDGE or DUPS_OK_ACKNOWLEDGE: The Jakarta Messaging provider will behave as if the unsuccessful call to receiveBody had not occurred. The message will be delivered again before any subsequent messages. This is not considered to be redelivery and does not cause the JMSRedelivered message header field to be set or the JMSXDeliveryCount message property to be incremented.
• CLIENT_ACKNOWLEDGE: The Jakarta Messaging provider will behave as if the call to receiveBody had been successful and will not deliver the message again. As with any message that is delivered with a session mode of CLIENT_ACKNOWLEDGE, the message will not be acknowledged until acknowledge is called on the JMSContext. If an application wishes to have the failed message redelivered, it must call recover on the JMSContext. The redelivered message's JMSRedelivered message header field will be set and its JMSXDeliveryCount message property will be incremented.
• Transacted session: The Jakarta Messaging provider will behave as if the call to receiveBody had been successful and will not deliver the message again. As with any message that is delivered in a transacted session, the transaction will remain uncommitted until the transaction is committed or rolled back by the application. If an application wishes to have the failed message redelivered, it must roll back the transaction. The redelivered message's JMSRedelivered message header field will be set and its JMSXDeliveryCount message property will be incremented.

Type Parameters:

T - The type of the message body

Parameters:

c - The type to which the body of the next message should be assigned.
If the next message is expected to be a TextMessage then this should be set to String.class or another class to which a String is assignable.
If the next message is expected to be a ObjectMessage then this should be set to java.io.Serializable.class or another class to which the body is assignable.
If the next message is expected to be a MapMessage then this should be set to java.util.Map.class (or java.lang.Object.class).
If the next message is expected to be a BytesMessage then this should be set to byte[].class (or java.lang.Object.class).

Returns:

the body of the next message produced for this JMSConsumer, or null if this JMSConsumer is concurrently closed

Throws:

MessageFormatRuntimeException -

• if the message is not one of the supported types listed above
• if the message body cannot be assigned to the specified type
• if the message has no body
• if the message is an ObjectMessage and object deserialization fails.

JMSRuntimeException - if the Jakarta Messaging provider fails to receive the next message due to some internal error

receiveBody

<T> T receiveBody(Class<T> c,
 long timeout)

Receives the next message produced for this JMSConsumer that arrives within the specified timeout period and returns its body as an object of the specified type. This method may be used to receive any type of message except for StreamMessage and Message, so long as the message has a body which is capable of being assigned to the specified type. This means that the specified class or interface must either be the same as, or a superclass or superinterface of, the class of the message body. If the message is not one of the supported types, or its body cannot be assigned to the specified type, or it has no body, then a MessageFormatRuntimeException is thrown.

This method does not give access to the message headers or properties (such as the JMSRedelivered message header field or the JMSXDeliveryCount message property) and should only be used if the application has no need to access them.

This call blocks until a message arrives, the timeout expires, or this JMSConsumer is closed. A timeout of zero never expires, and the call blocks indefinitely.

If this method is called within a transaction, the JMSConsumer retains the message until the transaction commits.

The result of this method throwing a MessageFormatRuntimeException depends on the session mode:

• AUTO_ACKNOWLEDGE or DUPS_OK_ACKNOWLEDGE: The Jakarta Messaging provider will behave as if the unsuccessful call to receiveBody had not occurred. The message will be delivered again before any subsequent messages. This is not considered to be redelivery and does not cause the JMSRedelivered message header field to be set or the JMSXDeliveryCount message property to be incremented.
• CLIENT_ACKNOWLEDGE: The Jakarta Messaging provider will behave as if the call to receiveBody had been successful and will not deliver the message again. As with any message that is delivered with a session mode of CLIENT_ACKNOWLEDGE, the message will not be acknowledged until acknowledge is called on the JMSContext. If an application wishes to have the failed message redelivered, it must call recover on the JMSContext. The redelivered message's JMSRedelivered message header field will be set and its JMSXDeliveryCount message property will be incremented.
• Transacted session: The Jakarta Messaging provider will behave as if the call to receiveBody had been successful and will not deliver the message again. As with any message that is delivered in a transacted session, the transaction will remain uncommitted until the transaction is committed or rolled back by the application. If an application wishes to have the failed message redelivered, it must roll back the transaction. The redelivered message's JMSRedelivered message header field will be set and its JMSXDeliveryCount message property will be incremented.

Type Parameters:

T - The message body type

Parameters:

c - The type to which the body of the next message should be assigned.
If the next message is expected to be a TextMessage then this should be set to String.class or another class to which a String is assignable.
If the next message is expected to be a ObjectMessage then this should be set to java.io.Serializable.class or another class to which the body is assignable.
If the next message is expected to be a MapMessage then this should be set to java.util.Map.class (or java.lang.Object.class).
If the next message is expected to be a BytesMessage then this should be set to byte[].class (or java.lang.Object.class).

timeout - The maximum amount of time this method blocks. Zero means blocking indefinitely.

Returns:

the body of the next message produced for this JMSConsumer, or null if the timeout expires or this JMSConsumer is concurrently closed

Throws:

MessageFormatRuntimeException -

• if the message is not one of the supported types listed above
• if the message body cannot be assigned to the specified type
• if the message has no body
• if the message is an ObjectMessage and object deserialization fails.

JMSRuntimeException - if the Jakarta Messaging provider fails to receive the next message due to some internal error

receiveBodyNoWait

<T> T receiveBodyNoWait(Class<T> c)

Receives the next message produced for this JMSConsumer if one is immediately available and returns its body as an object of the specified type. This method may be used to receive any type of message except for StreamMessage and Message, so long as the message has a body which is capable of being assigned to the specified type. This means that the specified class or interface must either be the same as, or a superclass or superinterface of, the class of the message body. If the message is not one of the supported types, or its body cannot be assigned to the specified type, or it has no body, then a MessageFormatRuntimeException is thrown.

This method does not give access to the message headers or properties (such as the JMSRedelivered message header field or the JMSXDeliveryCount message property) and should only be used if the application has no need to access them.

If a message is not immediately available null is returned.

If this method is called within a transaction, the JMSConsumer retains the message until the transaction commits.

The result of this method throwing a MessageFormatRuntimeException depends on the session mode:

• AUTO_ACKNOWLEDGE or DUPS_OK_ACKNOWLEDGE: The Jakarta Messaging provider will behave as if the unsuccessful call to receiveBodyNoWait had not occurred. The message will be delivered again before any subsequent messages. This is not considered to be redelivery and does not cause the JMSRedelivered message header field to be set or the JMSXDeliveryCount message property to be incremented.
• CLIENT_ACKNOWLEDGE: The Jakarta Messaging provider will behave as if the call to receiveBodyNoWait had been successful and will not deliver the message again. As with any message that is delivered with a session mode of CLIENT_ACKNOWLEDGE, the message will not be acknowledged until acknowledge is called on the JMSContext. If an application wishes to have the failed message redelivered, it must call recover on the JMSContext. The redelivered message's JMSRedelivered message header field will be set and its JMSXDeliveryCount message property will be incremented.
• Transacted session: The Jakarta Messaging provider will behave as if the call to receiveBodyNoWait had been successful and will not deliver the message again. As with any message that is delivered in a transacted session, the transaction will remain uncommitted until the transaction is committed or rolled back by the application. If an application wishes to have the failed message redelivered, it must roll back the transaction. The redelivered message's JMSRedelivered message header field will be set and its JMSXDeliveryCount message property will be incremented.

Type Parameters:

T - The type of the message body

Parameters:

c - The type to which the body of the next message should be assigned.
If the next message is expected to be a TextMessage then this should be set to String.class or another class to which a String is assignable.
If the next message is expected to be a ObjectMessage then this should be set to java.io.Serializable.class or another class to which the body is assignable.
If the next message is expected to be a MapMessage then this should be set to java.util.Map.class (or java.lang.Object.class).
If the next message is expected to be a BytesMessage then this should be set to byte[].class (or java.lang.Object.class).

Returns:

the body of the next message produced for this JMSConsumer, or null if one is not immediately available or this JMSConsumer is concurrently closed

Throws:

MessageFormatRuntimeException -

• if the message is not one of the supported types listed above
• if the message body cannot be assigned to the specified type
• if the message has no body
• if the message is an ObjectMessage and object deserialization fails.

JMSRuntimeException - if the Jakarta Messaging provider fails to receive the next message due to some internal error