org.springframework.jms.listener.adapter

Class MessageListenerAdapter

java.lang.Object

org.springframework.jms.listener.adapter.AbstractAdaptableMessageListener

org.springframework.jms.listener.adapter.MessageListenerAdapter

All Implemented Interfaces:

SessionAwareMessageListener<Message>, SubscriptionNameProvider

public class MessageListenerAdapter
extends AbstractAdaptableMessageListener
implements SubscriptionNameProvider

Message listener adapter that delegates the handling of messages to target listener methods via reflection, with flexible message type conversion. Allows listener methods to operate on message content types, completely independent from the JMS API.

By default, the content of incoming JMS messages gets extracted before being passed into the target listener method, to let the target method operate on message content types such as String or byte array instead of the raw Message. Message type conversion is delegated to a Spring JMS MessageConverter. By default, a SimpleMessageConverter will be used. (If you do not want such automatic message conversion taking place, then be sure to set the MessageConverter to null.)

If a target listener method returns a non-null object (typically of a message content type such as String or byte array), it will get wrapped in a JMS Message and sent to the response destination (either the JMS "reply-to" destination or a specified default destination).

Note: The sending of response messages is only available when using the SessionAwareMessageListener entry point (typically through a Spring message listener container). Usage as standard JMS MessageListener does not support the generation of response messages.

Find below some examples of method signatures compliant with this adapter class. This first example handles all Message types and gets passed the contents of each Message type as an argument. No Message will be sent back as all of these methods return void.

public interface MessageContentsDelegate {
    void handleMessage(String text);
    void handleMessage(Map map);
    void handleMessage(byte[] bytes);
    void handleMessage(Serializable obj);
 }

This next example handles all Message types and gets passed the actual (raw) Message as an argument. Again, no Message will be sent back as all of these methods return void.

public interface RawMessageDelegate {
    void handleMessage(TextMessage message);
    void handleMessage(MapMessage message);
    void handleMessage(BytesMessage message);
    void handleMessage(ObjectMessage message);
 }

This next example illustrates a Message delegate that just consumes the String contents of TextMessages. Notice also how the name of the Message handling method is different from the original (this will have to be configured in the attandant bean definition). Again, no Message will be sent back as the method returns void.

public interface TextMessageContentDelegate {
    void onMessage(String text);
 }

This final example illustrates a Message delegate that just consumes the String contents of TextMessages. Notice how the return type of this method is String: This will result in the configured MessageListenerAdapter sending a javax.jms.TextMessage in response.

public interface ResponsiveTextMessageContentDelegate {
    String handleMessage(String text);
 }

For further examples and discussion please do refer to the Spring reference documentation which describes this class (and it's attendant XML configuration) in detail.

Since:

2.0

Author:

Juergen Hoeller

See Also:

setDelegate(java.lang.Object), setDefaultListenerMethod(java.lang.String), AbstractAdaptableMessageListener.setDefaultResponseDestination(Destination), AbstractAdaptableMessageListener.setMessageConverter(org.springframework.jms.support.converter.MessageConverter), SimpleMessageConverter, SessionAwareMessageListener, AbstractMessageListenerContainer.setMessageListener(java.lang.Object)

Field Summary

Fields

Modifier and Type	Field and Description
private java.lang.String	defaultListenerMethod
private java.lang.Object	delegate
static java.lang.String	ORIGINAL_DEFAULT_LISTENER_METHOD Out-of-the-box value for the default listener method: "handleMessage".

Fields inherited from class org.springframework.jms.listener.adapter.AbstractAdaptableMessageListener

logger

Constructor Summary

Constructors

Constructor and Description
MessageListenerAdapter() Create a new MessageListenerAdapter with default settings.
MessageListenerAdapter(java.lang.Object delegate) Create a new MessageListenerAdapter for the given delegate.

Method Summary

Modifier and Type	Method and Description
protected java.lang.Object[]	buildListenerArguments(java.lang.Object extractedMessage) Build an array of arguments to be passed into the target listener method.
protected java.lang.String	getDefaultListenerMethod() Return the name of the default listener method to delegate to.
protected java.lang.Object	getDelegate() Return the target object to delegate message listening to.
protected java.lang.String	getListenerMethodName(Message originalMessage, java.lang.Object extractedMessage) Determine the name of the listener method that is supposed to handle the given message.
java.lang.String	getSubscriptionName() Determine the subscription name for this message listener object.
protected java.lang.Object	invokeListenerMethod(java.lang.String methodName, java.lang.Object[] arguments) Invoke the specified listener method.
void	onMessage(Message message, Session session) Spring SessionAwareMessageListener entry point.
void	setDefaultListenerMethod(java.lang.String defaultListenerMethod) Specify the name of the default listener method to delegate to, for the case where no specific listener method has been determined.
void	setDelegate(java.lang.Object delegate) Set a target object to delegate message listening to.

Methods inherited from class org.springframework.jms.listener.adapter.AbstractAdaptableMessageListener

buildMessage, extractMessage, getDestinationResolver, getMessageConverter, getMessagingMessageConverter, getResponseDestination, handleListenerException, handleResult, onMessage, postProcessProducer, postProcessResponse, resolveDefaultResponseDestination, sendResponse, setDefaultResponseDestination, setDefaultResponseQueueName, setDefaultResponseTopicName, setDestinationResolver, setHeaderMapper, setMessageConverter

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ORIGINAL_DEFAULT_LISTENER_METHOD

public static final java.lang.String ORIGINAL_DEFAULT_LISTENER_METHOD

Out-of-the-box value for the default listener method: "handleMessage".

See Also:

Constant Field Values

delegate

private java.lang.Object delegate

defaultListenerMethod

private java.lang.String defaultListenerMethod

Constructor Detail

MessageListenerAdapter

public MessageListenerAdapter()

Create a new MessageListenerAdapter with default settings.

MessageListenerAdapter

public MessageListenerAdapter(java.lang.Object delegate)

Create a new MessageListenerAdapter for the given delegate.

Parameters:

delegate - the delegate object

Method Detail

setDelegate

public void setDelegate(java.lang.Object delegate)

Set a target object to delegate message listening to. Specified listener methods have to be present on this target object.

If no explicit delegate object has been specified, listener methods are expected to present on this adapter instance, that is, on a custom subclass of this adapter, defining listener methods.

getDelegate

protected java.lang.Object getDelegate()

Return the target object to delegate message listening to.

setDefaultListenerMethod

public void setDefaultListenerMethod(java.lang.String defaultListenerMethod)

Specify the name of the default listener method to delegate to, for the case where no specific listener method has been determined. Out-of-the-box value is "handleMessage".

See Also:

getListenerMethodName(Message, java.lang.Object)

getDefaultListenerMethod

protected java.lang.String getDefaultListenerMethod()

Return the name of the default listener method to delegate to.

onMessage

public void onMessage(Message message,
                      Session session)
               throws JMSException

Spring SessionAwareMessageListener entry point.

Delegates the message to the target listener method, with appropriate conversion of the message argument. If the target method returns a non-null object, wrap in a JMS message and send it back.

Specified by:

onMessage in interface SessionAwareMessageListener<Message>

Parameters:

message - the incoming JMS message

session - the JMS session to operate on

Throws:

JMSException - if thrown by JMS API methods

getSubscriptionName

public java.lang.String getSubscriptionName()

Description copied from interface: SubscriptionNameProvider

Determine the subscription name for this message listener object.

Specified by:

getSubscriptionName in interface SubscriptionNameProvider

getListenerMethodName

protected java.lang.String getListenerMethodName(Message originalMessage,
                                                 java.lang.Object extractedMessage)
                                          throws JMSException

Determine the name of the listener method that is supposed to handle the given message.

The default implementation simply returns the configured default listener method, if any.

Parameters:

originalMessage - the JMS request message

extractedMessage - the converted JMS request message, to be passed into the listener method as argument

Returns:

the name of the listener method (never null)

Throws:

JMSException - if thrown by JMS API methods

See Also:

setDefaultListenerMethod(java.lang.String)

buildListenerArguments

protected java.lang.Object[] buildListenerArguments(java.lang.Object extractedMessage)

Build an array of arguments to be passed into the target listener method. Allows for multiple method arguments to be built from a single message object.

The default implementation builds an array with the given message object as sole element. This means that the extracted message will always be passed into a single method argument, even if it is an array, with the target method having a corresponding single argument of the array's type declared.

This can be overridden to treat special message content such as arrays differently, for example passing in each element of the message array as distinct method argument.

Parameters:

extractedMessage - the content of the message

Returns:

the array of arguments to be passed into the listener method (each element of the array corresponding to a distinct method argument)

invokeListenerMethod

protected java.lang.Object invokeListenerMethod(java.lang.String methodName,
                                                java.lang.Object[] arguments)
                                         throws JMSException

Invoke the specified listener method.

Parameters:

methodName - the name of the listener method

arguments - the message arguments to be passed in

Returns:

the result returned from the listener method

Throws:

JMSException - if thrown by JMS API methods

See Also:

getListenerMethodName(Message, java.lang.Object), buildListenerArguments(java.lang.Object)