Package org.springframework.data.redis.listener.adapter

Class MessageListenerAdapter

java.lang.Object
org.springframework.data.redis.listener.adapter.MessageListenerAdapter
All Implemented Interfaces:
InitializingBean, MessageListener
public class MessageListenerAdapter extends Object implements InitializingBean, MessageListener
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 Redis API.

Make sure to call afterPropertiesSet() after setting all the parameters on the adapter.

Note that if the underlying "delegate" is implementing MessageListener, the adapter will delegate to it and allow an invalid method to be specified. However if it is not, the method becomes mandatory. This lenient behavior allows the adapter to be used uniformly across existing listeners and message POJOs.

Modeled as much as possible after the JMS MessageListenerAdapter in Spring Framework.

By default, the content of incoming Redis 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 Data RedisSerializer. By default, the JdkSerializationRedisSerializer will be used. (If you do not want such automatic message conversion taking place, then be sure to set the Serializer to null.)

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. 

 public interface MessageContentsDelegate {
        void handleMessage(String text);

        void handleMessage(byte[] bytes);

        void handleMessage(Person obj);
 }

In addition, the channel or pattern to which a message is sent can be passed in to the method as a second argument of type String: 

 public interface MessageContentsDelegate {
        void handleMessage(String text, String channel);

        void handleMessage(byte[] bytes, String pattern);
 }
For further examples and discussion please do refer to the Spring Data reference documentation which describes this class (and its attendant configuration) in detail. Important: Due to the nature of messages, the default serializer used by the adapter is StringRedisSerializer. If the messages are of a different type, change them accordingly through setSerializer(RedisSerializer).
Author:
Juergen Hoeller, Costin Leau, Greg Turnquist, Thomas Darimont, Christoph Strobl, Mark Paluch

  • Field Details

    • ORIGINAL_DEFAULT_LISTENER_METHOD

      public static final String ORIGINAL_DEFAULT_LISTENER_METHOD
      Out-of-the-box value for the default listener method: "handleMessage".
      See Also:

    • logger

      protected final Log logger
      Logger available to subclasses

  • Constructor Details

  • Method Details

    • setDelegate

      public void setDelegate(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.

      Parameters:
      delegate - delegate object

    • getDelegate

      @Nullable public Object getDelegate()
      Returns the target object to delegate message listening to.
      Returns:
      message listening delegation

    • setDefaultListenerMethod

      public 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. Out-of-the-box value is "handleMessage".
      See Also:

    • getDefaultListenerMethod

      protected String getDefaultListenerMethod()
      Return the name of the default listener method to delegate to.

    • setSerializer

      public void setSerializer(RedisSerializer<?> serializer)
      Set the serializer that will convert incoming raw Redis messages to listener method arguments.

      The default converter is a StringRedisSerializer.

      Parameters:
      serializer -

    • setStringSerializer

      public void setStringSerializer(RedisSerializer<String> serializer)
      Sets the serializer used for converting the channel/pattern to a String.

      The default converter is a StringRedisSerializer.

      Parameters:
      serializer -

    • afterPropertiesSet

      public void afterPropertiesSet()
      Specified by:
      afterPropertiesSet in interface InitializingBean

    • onMessage

      public void onMessage(Message message, @Nullable byte[] pattern)
      Standard Redis MessageListener entry point.

      Delegates the message to the target listener method, with appropriate conversion of the message argument. In case of an exception, the handleListenerException(Throwable) method will be invoked.

      Specified by:
      onMessage in interface MessageListener
      Parameters:
      message - the incoming Redis message
      pattern - pattern matching the channel (if specified) - can be null.
      See Also:

    • initDefaultStrategies

      protected void initDefaultStrategies()
      Initialize the default implementations for the adapter's strategies.
      See Also:

    • handleListenerException

      protected void handleListenerException(Throwable ex)
      Handle the given exception that arose during listener execution. The default implementation logs the exception at error level.
      Parameters:
      ex - the exception to handle

    • extractMessage

      protected Object extractMessage(Message message)
      Extract the message body from the given Redis message.
      Parameters:
      message - the Redis Message
      Returns:
      the content of the message, to be passed into the listener method as argument

    • getListenerMethodName

      protected String getListenerMethodName(Message originalMessage, Object extractedMessage)
      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 Redis request message
      extractedMessage - the converted Redis request message, to be passed into the listener method as argument
      Returns:
      the name of the listener method (never null)
      See Also:

    • invokeListenerMethod

      protected void invokeListenerMethod(String methodName, Object[] arguments)
      Invoke the specified listener method.
      Parameters:
      methodName - the name of the listener method
      arguments - the message arguments to be passed in
      See Also: