Initial commit of MessageHandlerChain (INT-391).
This commit is contained in:
Mark Fisher
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/*
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* Copyright 2002-2008 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.integration.handler;
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import java.util.List;
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import org.springframework.integration.channel.DirectChannel;
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import org.springframework.integration.context.IntegrationObjectSupport;
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import org.springframework.integration.core.Message;
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import org.springframework.integration.core.MessageChannel;
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import org.springframework.integration.endpoint.EventDrivenConsumer;
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import org.springframework.integration.message.MessageHandler;
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import org.springframework.integration.message.MessageHandlingException;
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import org.springframework.util.Assert;
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/**
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* A composite {@link MessageHandler} implementation that invokes a chain of
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* MessageHandler instances in order.
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*
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* @author Mark Fisher
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*/
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public class MessageHandlerChain extends IntegrationObjectSupport implements MessageHandler {
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private volatile List<MessageHandler> handlers;
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private volatile MessageChannel outputChannel;
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private volatile boolean initialized;
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private final Object initializationMonitor = new Object();
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public void setHandlers(List<MessageHandler> handlers) {
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this.handlers = handlers;
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}
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public void setOutputChannel(MessageChannel outputChannel) {
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this.outputChannel = outputChannel;
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}
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public final void afterPropertiesSet() {
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synchronized (this.initializationMonitor) {
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if (!this.initialized) {
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Assert.notEmpty(this.handlers, "handler list must not be empty");
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this.configureChain();
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this.initialized = true;
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}
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}
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}
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public void handleMessage(Message<?> message) {
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if (!this.initialized) {
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this.afterPropertiesSet();
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}
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this.handlers.get(0).handleMessage(message);
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}
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private void configureChain() {
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DirectChannel channel = null;
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List<MessageHandler> handlers = this.handlers;
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for (int i = 0; i < handlers.size(); i++) {
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boolean first = (i == 0);
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boolean last = (i == handlers.size() - 1);
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MessageHandler handler = handlers.get(i);
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if (!first) {
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EventDrivenConsumer consumer = new EventDrivenConsumer(channel, handler);
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consumer.start();
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}
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if (!last) {
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Assert.isInstanceOf(AbstractReplyProducingMessageHandler.class, handler,
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"All handlers except for the last one in the chain must implement "
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+ AbstractReplyProducingMessageHandler.class.getName());
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channel = new DirectChannel();
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channel.setBeanName("_" + this + ".channel#" + i);
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((AbstractReplyProducingMessageHandler) handler).setOutputChannel(channel);
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}
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else if (handler instanceof AbstractReplyProducingMessageHandler) {
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MessageChannel replyChannel = (this.outputChannel != null) ? this.outputChannel
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: new ReplyForwardingMessageChannel();
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((AbstractReplyProducingMessageHandler) handler).setOutputChannel(replyChannel);
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}
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else {
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Assert.isNull(this.outputChannel,
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"An output channel was provided, but the final handler in the chain is not an "
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+ "instance of [" + AbstractReplyProducingMessageHandler.class.getName() + "]");
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}
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}
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}
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private class ReplyForwardingMessageChannel implements MessageChannel {
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public String getName() {
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return MessageHandlerChain.this.getBeanName();
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}
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public boolean send(Message<?> message) {
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return this.send(message, -1);
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}
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public boolean send(Message<?> message, long timeout) {
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Object replyChannelHeader = message.getHeaders().getReplyChannel();
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if (replyChannelHeader == null) {
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throw new MessageHandlingException(message, "no replyChannel header available");
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}
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MessageChannel replyChannel = null;
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if (replyChannelHeader instanceof MessageChannel) {
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replyChannel = (MessageChannel) replyChannelHeader;
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}
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else if (replyChannelHeader instanceof String) {
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Assert.notNull(getChannelResolver(), "ChannelResolver is required");
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replyChannel = getChannelResolver().resolveChannelName((String) replyChannelHeader);
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}
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else {
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throw new MessageHandlingException(message, "invalid replyChannel type [" + replyChannelHeader.getClass() + "]");
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}
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return (timeout >= 0) ? replyChannel.send(message, timeout) : replyChannel.send(message);
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}
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}
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}
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@@ -0,0 +1,122 @@
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/*
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* Copyright 2002-2008 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.integration.handler;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertNotNull;
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import java.util.ArrayList;
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import java.util.List;
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import org.junit.Test;
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import org.springframework.beans.factory.support.DefaultListableBeanFactory;
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import org.springframework.integration.channel.QueueChannel;
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import org.springframework.integration.core.Message;
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import org.springframework.integration.message.MessageBuilder;
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import org.springframework.integration.message.MessageHandler;
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import org.springframework.integration.message.StringMessage;
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/**
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* @author Mark Fisher
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*/
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public class MessageHandlerChainTests {
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@Test
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public void chainWithOutputChannel() {
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QueueChannel outputChannel = new QueueChannel();
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List<MessageHandler> handlers = new ArrayList<MessageHandler>();
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handlers.add(createHandler(1));
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handlers.add(createHandler(2));
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handlers.add(createHandler(3));
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MessageHandlerChain chain = new MessageHandlerChain();
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chain.setBeanName("testChain");
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chain.setHandlers(handlers);
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chain.setOutputChannel(outputChannel);
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chain.handleMessage(new StringMessage("test"));
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Message<?> reply = outputChannel.receive(0);
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assertNotNull(reply);
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assertEquals("test123", reply.getPayload());
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}
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@Test(expected = IllegalArgumentException.class)
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public void chainWithOutputChannelButLastHandlerDoesNotProduceReplies() {
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QueueChannel outputChannel = new QueueChannel();
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List<MessageHandler> handlers = new ArrayList<MessageHandler>();
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handlers.add(createHandler(1));
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handlers.add(createHandler(2));
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handlers.add(new MessageHandler() {
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public void handleMessage(Message<?> message) {
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}
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});
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MessageHandlerChain chain = new MessageHandlerChain();
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chain.setBeanName("testChain");
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chain.setHandlers(handlers);
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chain.setOutputChannel(outputChannel);
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chain.handleMessage(new StringMessage("test"));
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}
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@Test
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public void chainForwardsToReplyChannel() {
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QueueChannel replyChannel = new QueueChannel();
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List<MessageHandler> handlers = new ArrayList<MessageHandler>();
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handlers.add(createHandler(1));
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handlers.add(createHandler(2));
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handlers.add(createHandler(3));
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MessageHandlerChain chain = new MessageHandlerChain();
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chain.setBeanName("testChain");
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chain.setHandlers(handlers);
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Message<String> message = MessageBuilder.withPayload("test")
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.setReplyChannel(replyChannel).build();
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chain.handleMessage(message);
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Message<?> reply = replyChannel.receive(0);
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assertNotNull(reply);
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assertEquals("test123", reply.getPayload());
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}
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@Test
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public void chainResolvesReplyChannelName() {
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QueueChannel replyChannel = new QueueChannel();
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DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
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beanFactory.registerSingleton("testChannel", replyChannel);
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List<MessageHandler> handlers = new ArrayList<MessageHandler>();
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handlers.add(createHandler(1));
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handlers.add(createHandler(2));
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handlers.add(createHandler(3));
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MessageHandlerChain chain = new MessageHandlerChain();
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chain.setBeanName("testChain");
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chain.setHandlers(handlers);
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chain.setBeanFactory(beanFactory);
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Message<String> message = MessageBuilder.withPayload("test")
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.setReplyChannelName("testChannel").build();
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chain.handleMessage(message);
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Message<?> reply = replyChannel.receive(0);
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assertNotNull(reply);
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assertEquals("test123", reply.getPayload());
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}
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private static MessageHandler createHandler(final int index) {
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return new AbstractReplyProducingMessageHandler() {
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@Override
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protected void handleRequestMessage(Message<?> requestMessage, ReplyMessageHolder replyMessageHolder) {
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replyMessageHolder.set(requestMessage.getPayload().toString() + index);
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}
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};
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}
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}
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