public class MessageListenerAdapter extends AbstractAdaptableMessageListener
By default, the content of incoming Rabbit 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 AMQ 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 Rabbit Message and sent to the exchange of
the incoming message with the routingKey that comes from the Rabbit ReplyTo property or via
specified routingKey).
Note: The sending of response messages is only available when using the ChannelAwareMessageListener
entry point (typically through a Spring message listener container). Usage as 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 handle a Message type 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(Message message);
}
This next example illustrates a Message delegate that just consumes the String contents of
Messages. 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
Messages. Notice how the return type of this method is String: This will result in the
configured MessageListenerAdapter sending a Message 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 its attendant XML configuration) in detail.setDelegate(java.lang.Object),
setDefaultListenerMethod(java.lang.String),
AbstractAdaptableMessageListener.setResponseRoutingKey(String),
AbstractAdaptableMessageListener.setMessageConverter(org.springframework.amqp.support.converter.MessageConverter),
SimpleMessageConverter,
ChannelAwareMessageListener,
AbstractMessageListenerContainer.setMessageListener(java.lang.Object)| Modifier and Type | Field and Description |
|---|---|
static String |
ORIGINAL_DEFAULT_LISTENER_METHOD
Out-of-the-box value for the default listener method: "handleMessage".
|
logger| Constructor and Description |
|---|
MessageListenerAdapter()
Create a new
MessageListenerAdapter with default settings. |
MessageListenerAdapter(Object delegate)
Create a new
MessageListenerAdapter for the given delegate. |
MessageListenerAdapter(Object delegate,
MessageConverter messageConverter)
Create a new
MessageListenerAdapter for the given delegate. |
MessageListenerAdapter(Object delegate,
String defaultListenerMethod)
Create a new
MessageListenerAdapter for the given delegate while also
declaring its POJO method. |
| Modifier and Type | Method and Description |
|---|---|
protected Object[] |
buildListenerArguments(Object extractedMessage)
Build an array of arguments to be passed into the target listener method.
|
protected String |
getDefaultListenerMethod() |
protected Object |
getDelegate() |
protected String |
getListenerMethodName(Message originalMessage,
Object extractedMessage)
Determine the name of the listener method that is supposed to handle the given message.
|
protected Object |
invokeListenerMethod(String methodName,
Object[] arguments)
Deprecated.
in favor of
invokeListenerMethod(String, Object[], Message) |
protected Object |
invokeListenerMethod(String methodName,
Object[] arguments,
Message originalMessage)
Invoke the specified listener method.
|
void |
onMessage(Message message,
com.rabbitmq.client.Channel channel)
Spring
ChannelAwareMessageListener entry point. |
void |
setDefaultListenerMethod(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(Object delegate)
Set a target object to delegate message listening to.
|
buildMessage, extractMessage, getMessageConverter, getReceivedExchange, getReplyToAddress, handleListenerException, handleResult, onMessage, postProcessChannel, postProcessResponse, sendResponse, setEncoding, setMandatoryPublish, setMessageConverter, setResponseExchange, setResponseRoutingKeypublic static final String ORIGINAL_DEFAULT_LISTENER_METHOD
public MessageListenerAdapter()
MessageListenerAdapter with default settings.public MessageListenerAdapter(Object delegate)
MessageListenerAdapter for the given delegate.delegate - the delegate objectpublic MessageListenerAdapter(Object delegate, MessageConverter messageConverter)
MessageListenerAdapter for the given delegate.delegate - the delegate objectmessageConverter - the message converter to usepublic MessageListenerAdapter(Object delegate, String defaultListenerMethod)
MessageListenerAdapter for the given delegate while also
declaring its POJO method.delegate - the delegate objectdefaultListenerMethod - name of the POJO method to call upon message receiptpublic void setDelegate(Object delegate)
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.
delegate - The delegate listener or POJO.protected Object getDelegate()
public void setDefaultListenerMethod(String defaultListenerMethod)
"handleMessage".defaultListenerMethod - The name of the default listener method.getListenerMethodName(org.springframework.amqp.core.Message, java.lang.Object)protected String getDefaultListenerMethod()
public void onMessage(Message message, com.rabbitmq.client.Channel channel) throws Exception
ChannelAwareMessageListener 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 Rabbit message and send it back.
message - the incoming Rabbit messagechannel - the Rabbit channel to operate onException - if thrown by Rabbit API methodsprotected String getListenerMethodName(Message originalMessage, Object extractedMessage) throws Exception
The default implementation simply returns the configured default listener method, if any.
originalMessage - the Rabbit request messageextractedMessage - the converted Rabbit request message, to be passed into the listener method as argumentnull)Exception - if thrown by Rabbit API methodssetDefaultListenerMethod(java.lang.String)protected Object[] buildListenerArguments(Object extractedMessage)
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.
extractedMessage - the content of the message@Deprecated protected Object invokeListenerMethod(String methodName, Object[] arguments) throws Exception
invokeListenerMethod(String, Object[], Message)methodName - the name of the listener methodarguments - the message arguments to be passed inException - if thrown by Rabbit API methodsgetListenerMethodName(org.springframework.amqp.core.Message, java.lang.Object),
buildListenerArguments(java.lang.Object)protected Object invokeListenerMethod(String methodName, Object[] arguments, Message originalMessage) throws Exception
methodName - the name of the listener methodarguments - the message arguments to be passed inoriginalMessage - the original messageException - if thrown by Rabbit API methodsgetListenerMethodName(org.springframework.amqp.core.Message, java.lang.Object),
buildListenerArguments(java.lang.Object)