SendToHandlerMethodReturnValueHandler.java

/*
 * Copyright 2013-2014 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.cloud.aws.messaging.listener;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.config.BeanExpressionContext;
import org.springframework.beans.factory.config.BeanExpressionResolver;
import org.springframework.beans.factory.config.ConfigurableBeanFactory;
import org.springframework.core.MethodParameter;
import org.springframework.messaging.Message;
import org.springframework.messaging.core.DestinationResolvingMessageSendingOperations;
import org.springframework.messaging.handler.annotation.SendTo;
import org.springframework.messaging.handler.invocation.HandlerMethodReturnValueHandler;
import org.springframework.util.Assert;

/**
 * @author Alain Sahli
 * @author Agim Emruli
 */
public class SendToHandlerMethodReturnValueHandler implements HandlerMethodReturnValueHandler, BeanFactoryAware {

    private final DestinationResolvingMessageSendingOperations<?> messageTemplate;
    private BeanFactory beanFactory;

    public SendToHandlerMethodReturnValueHandler(DestinationResolvingMessageSendingOperations<?> messageTemplate) {
        this.messageTemplate = messageTemplate;
    }

    @Override
    public boolean supportsReturnType(MethodParameter returnType) {
        return returnType.getMethodAnnotation(SendTo.class) != null;
    }

    @SuppressWarnings("ConstantConditions")
    @Override
    public void handleReturnValue(Object returnValue, MethodParameter returnType, Message<?> message) throws Exception {
        Assert.state(this.messageTemplate != null, "A messageTemplate must be set to handle the return value.");

        if (returnValue != null) {
            if (getDestinationName(returnType) != null) {
                this.messageTemplate.convertAndSend(getDestinationName(returnType), returnValue);
            } else {
                this.messageTemplate.convertAndSend(returnValue);
            }
        }
    }

    private String getDestinationName(MethodParameter returnType) {
        String[] destination = returnType.getMethodAnnotation(SendTo.class).value();
        return destination.length > 0 ? resolveName(destination[0]) : null;
    }

    private String resolveName(String name) {
        if (!(this.beanFactory instanceof ConfigurableBeanFactory)) {
            return name;
        }

        ConfigurableBeanFactory configurableBeanFactory = (ConfigurableBeanFactory) this.beanFactory;

        String placeholdersResolved = configurableBeanFactory.resolveEmbeddedValue(name);
        BeanExpressionResolver exprResolver = configurableBeanFactory.getBeanExpressionResolver();
        if (exprResolver == null) {
            return name;
        }
        Object result = exprResolver.evaluate(placeholdersResolved, new BeanExpressionContext(configurableBeanFactory, null));
        return result != null ? result.toString() : name;
    }

    @Override
    public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
        this.beanFactory = beanFactory;
    }
}