messagelisteneradapter.java

spring api 源代码

	/**
	 * Spring {@link SessionAwareMessageListener} entry point.
	 * <p>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.
	 * @param message the incoming JMS message
	 * @param session the JMS session to operate on
	 * @throws JMSException if thrown by JMS API methods
	 */
	public void onMessage(Message message, Session session) throws JMSException {
		Object convertedMessage = extractMessage(message);
		String methodName = getListenerMethodName(message, convertedMessage);

		if (methodName == null) {
			Object delegate = getDelegate();
			if (delegate != this) {
				if (delegate instanceof SessionAwareMessageListener) {
					if (session != null) {
						((SessionAwareMessageListener) delegate).onMessage(message, session);
						return;
					}
					else if (!(delegate instanceof MessageListener)) {
						throw new javax.jms.IllegalStateException("MessageListenerAdapter cannot handle a " +
								"SessionAwareMessageListener delegate if it hasn't been invoked with a Session itself");
					}
				}
				if (delegate instanceof MessageListener) {
					((MessageListener) delegate).onMessage(message);
					return;
				}
			}
			throw new javax.jms.IllegalStateException("No default listener method specified: " +
					"Either specify a non-null value for the 'defaultListenerMethod' property or " +
					"override the 'getListenerMethodName' method.");
		}

		Object[] listenerArguments = buildListenerArguments(convertedMessage);
		Object result = invokeListenerMethod(methodName, listenerArguments);
		if (result != null) {
			handleResult(result, message, session);
		}
		else {
			logger.debug("No result object given - no result to handle");
		}
	}


    /**
	 * Initialize the default implementations for the adapter's strategies.
	 * @see #setMessageConverter
	 * @see org.springframework.jms.support.converter.SimpleMessageConverter
	 */
	protected void initDefaultStrategies() {
		setMessageConverter(new SimpleMessageConverter());
	}

    /**
	 * Handle the given exception that arose during listener execution.
	 * The default implementation logs the exception at error level.
	 * <p>This method only applies when used as standard JMS {@link MessageListener}.
	 * In case of the Spring {@link SessionAwareMessageListener} mechanism,
	 * exceptions get handled by the caller instead.
	 * @param ex the exception to handle
	 * @see #onMessage(javax.jms.Message)
	 */
	protected void handleListenerException(Throwable ex) {
		logger.error("Listener execution failed", ex);
	}

	/**
	 * Extract the message body from the given JMS message.
	 * @param message the JMS <code>Message</code>
	 * @return the content of the message, to be passed into the
	 * listener method as argument
	 * @throws JMSException if thrown by JMS API methods
	 */
	protected Object extractMessage(Message message) throws JMSException {
		MessageConverter converter = getMessageConverter();
		if (converter != null) {
			return converter.fromMessage(message);
		}
		return message;
	}

	/**
	 * Determine the name of the listener method that is supposed to
	 * handle the given message.
	 * <p>The default implementation simply returns the configured
	 * default listener method, if any.
	 * @param originalMessage the JMS request message
	 * @param extractedMessage the converted JMS request message,
	 * to be passed into the listener method as argument
	 * @return the name of the listener method (never <code>null</code>)
	 * @throws JMSException if thrown by JMS API methods
	 * @see #setDefaultListenerMethod
	 */
	protected String getListenerMethodName(Message originalMessage, Object extractedMessage) throws JMSException {
		return getDefaultListenerMethod();
	}

	/**
	 * 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.
	 * <p>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 <i>single</i> method argument, even if it is an array, with the target
	 * method having a corresponding single argument of the array's type declared.
	 * <p>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.
	 * @param extractedMessage the content of the message
	 * @return the array of arguments to be passed into the
	 * listener method (each element of the array corresponding
	 * to a distinct method argument)
	 */
	protected Object[] buildListenerArguments(Object extractedMessage) {
		return new Object[] {extractedMessage};
	}

	/**
	 * Invoke the specified listener method.
	 * @param methodName the name of the listener method
	 * @param arguments the message arguments to be passed in
	 * @return the result returned from the listener method
	 * @throws JMSException if thrown by JMS API methods
	 * @see #getListenerMethodName
	 * @see #buildListenerArguments
	 */
	protected Object invokeListenerMethod(String methodName, Object[] arguments) throws JMSException {
		try {
			MethodInvoker methodInvoker = new MethodInvoker();
			methodInvoker.setTargetObject(getDelegate());
			methodInvoker.setTargetMethod(methodName);
			methodInvoker.setArguments(arguments);
			methodInvoker.prepare();
			return methodInvoker.invoke();
		}
		catch (InvocationTargetException ex) {
			throw new ListenerExecutionFailedException(
					"Listener method '" + methodName + "' threw exception", ex.getTargetException());
		}
		catch (Throwable ex) {
			throw new ListenerExecutionFailedException("Failed to invoke target method '" + methodName +
					"' with arguments " + ObjectUtils.nullSafeToString(arguments), ex);
		}
	}


	/**
	 * Handle the given result object returned from the listener method,
	 * sending a response message back.
	 * @param result the result object to handle (never <code>null</code>)
	 * @param request the original request message
	 * @param session the JMS Session to operate on (may be <code>null</code>)
	 * @throws JMSException if thrown by JMS API methods
	 * @see #buildMessage
	 * @see #postProcessResponse
	 * @see #getResponseDestination
	 * @see #sendResponse
	 */
	protected void handleResult(Object result, Message request, Session session) throws JMSException {
		if (session != null) {
			if (logger.isDebugEnabled()) {
				logger.debug("Listener method returned result [" + result +
						"] - generating response message for it");
			}
			Message response = buildMessage(session, result);
			postProcessResponse(request, response);
			Destination destination = getResponseDestination(request, response, session);
			sendResponse(session, destination,  response);
		}
		else {
			if (logger.isWarnEnabled()) {
				logger.warn("Listener method returned result [" + result +
						"]: not generating response message for it because of no JMS Session given");
			}
		}
	}

	/**
	 * Build a JMS message to be sent as response based on the given result object.
	 * @param session the JMS Session to operate on
	 * @param result the content of the message, as returned from the listener method
	 * @return the JMS <code>Message</code> (never <code>null</code>)
	 * @throws JMSException if thrown by JMS API methods
	 * @see #setMessageConverter
	 */
	protected Message buildMessage(Session session, Object result) throws JMSException {
		MessageConverter converter = getMessageConverter();
		if (converter != null) {
			return converter.toMessage(result, session);
		}
		else {
			if (!(result instanceof Message)) {
				throw new MessageConversionException(
						"No MessageConverter specified - cannot handle message [" + result + "]");
			}
			return (Message) result;
		}
	}

	/**
	 * Post-process the given response message before it will be sent.
	 * <p>The default implementation sets the response's correlation id
	 * to the request message's correlation id.
	 * @param request the original incoming JMS message
	 * @param response the outgoing JMS message about to be sent
	 * @throws JMSException if thrown by JMS API methods
	 * @see javax.jms.Message#setJMSCorrelationID
	 */
	protected void postProcessResponse(Message request, Message response) throws JMSException {
		response.setJMSCorrelationID(request.getJMSCorrelationID());
	}

	/**
	 * Determine a response destination for the given message.
	 * <p>The default implementation first checks the JMS Reply-To
	 * {@link Destination} of the supplied request; if that is not <code>null</code>
	 * it is returned; if it is <code>null</code>, then the configured
	 * {@link #resolveDefaultResponseDestination default response destination}
	 * is returned; if this too is <code>null</code>, then an
	 * {@link InvalidDestinationException} is thrown.
	 * @param request the original incoming JMS message
	 * @param response the outgoing JMS message about to be sent
	 * @param session the JMS Session to operate on
	 * @return the response destination (never <code>null</code>)
	 * @throws JMSException if thrown by JMS API methods
	 * @throws InvalidDestinationException if no {@link Destination} can be determined
	 * @see #setDefaultResponseDestination
	 * @see javax.jms.Message#getJMSReplyTo()
	 */
	protected Destination getResponseDestination(Message request, Message response, Session session)
			throws JMSException {

		Destination replyTo = request.getJMSReplyTo();
		if (replyTo == null) {
			replyTo = resolveDefaultResponseDestination(session);
			if (replyTo == null) {
				throw new InvalidDestinationException("Cannot determine response destination: " +
						"Request message does not contain reply-to destination, and no default response destination set.");
			}
		}
		return replyTo;
	}

	/**
	 * Resolve the default response destination into a JMS {@link Destination}, using this
	 * accessor's {@link DestinationResolver} in case of a destination name.
	 * @return the located {@link Destination}
	 * @throws javax.jms.JMSException if resolution failed
	 * @see #setDefaultResponseDestination
	 * @see #setDefaultResponseQueueName
	 * @see #setDefaultResponseTopicName
	 * @see #setDestinationResolver
	 */
	protected Destination resolveDefaultResponseDestination(Session session) throws JMSException {
		if (this.defaultResponseDestination instanceof Destination) {
			return (Destination) this.defaultResponseDestination;
		}
		if (this.defaultResponseDestination instanceof DestinationNameHolder) {
			DestinationNameHolder nameHolder = (DestinationNameHolder) this.defaultResponseDestination;
			return getDestinationResolver().resolveDestinationName(session, nameHolder.name, nameHolder.isTopic);
		}
		return null;
	}

	/**
	 * Send the given response message to the given destination.
	 * @param response the JMS message to send
	 * @param destination the JMS destination to send to
	 * @param session the JMS session to operate on
	 * @throws JMSException if thrown by JMS API methods
	 * @see #postProcessProducer
	 * @see javax.jms.Session#createProducer
	 * @see javax.jms.MessageProducer#send
	 */
	protected void sendResponse(Session session, Destination destination, Message response) throws JMSException {
		MessageProducer producer = session.createProducer(destination);
		try {
			postProcessProducer(producer, response);
			producer.send(response);
		}
		finally {
			JmsUtils.closeMessageProducer(producer);
		}
	}

	/**
	 * Post-process the given message producer before using it to send the response.
	 * <p>The default implementation is empty.
	 * @param producer the JMS message producer that will be used to send the message
	 * @param response the outgoing JMS message about to be sent
	 * @throws JMSException if thrown by JMS API methods
	 */
	protected void postProcessProducer(MessageProducer producer, Message response) throws JMSException {
	}


	/**
	 * Internal class combining a destination name
	 * and its target destination type (queue or topic).
	 */
	private static class DestinationNameHolder {

		public final String name;

		public final boolean isTopic;

		public DestinationNameHolder(String name, boolean isTopic) {
			this.name = name;
			this.isTopic = isTopic;
		}
	}

}