Barrier Error Handling

basic/barrier/README.md

@@ -1,8 +1,9 @@
 Barrier Sample
 ==============
 
-This example demonstrates the use of a process barrier component to suspend a thread until some asynchronous operation 
-completes. It uses an **HTTP Inbound Gateway**, splits the request, sends the splits to rabbitmq and then waits for
+This example demonstrates the use of a process barrier component to suspend a thread until some asynchronous operation
+completes. The first example uses an **HTTP Inbound Gateway**, splits the request, sends the splits to rabbitmq and then
+waits for
 the publisher confirms. Finally, the results are returned to the caller.
 
 The sample is a Spring Boot application that loads 2 contexts:
@@ -35,10 +36,38 @@ This will package the application and run it using the [Gradle Application Plugi
 In STS (Eclipse), go to package **org.springframework.integration.samples.barrier**, right-click **Application** and select **Run as** --> **Java Application** (or Spring Boot Application).
 
 ### Output
-  
+
 The gateway (**client**) initiates a simple request posting "A,B,C" to the **server** and the **server** responds with the results.
 You should see the following output from the server:
-   
+
     ++++++++++++ Replied with: Result: A: ack=true, B: ack=true, C: ack=true ++++++++++++
 
+The second example uses a simple gateway to launch some asynchronous tasks and waits for those tasks to complete.
 
+It shows how you might return an exception to the caller if one or more of those tasks fail.
+
+An aggregator is used to aggregate the results; if there are no errors, the results are returned; if one or more
+errors occurred, an exception is sent to release the barrier; this is thrown to the caller and has all the consolidated
+results in a property.
+
+You can run this example from an IDE, such as STS using the technique above; in this case, the class is
+**ErrorHandlingApplication** in the **org.springframework.integration.samples.barrier** package.
+
+It sends a list of integers to the flow:
+
+    [2, 0, 2, 0, 2]
+
+The zeros should fail and in stderr you should see the results:
+
+    ConsolidatedResultsException
+    [results=
+    [5
+    org.springframework.integration.transformer.MessageTransformationException:
+      Failed to transform Message; nested exception is org.springframework.messaging.MessageHandlingException:
+      Expression evaluation failed: 10 / payload; nested exception is java.lang.ArithmeticException: / by zero
+    5
+    org.springframework.integration.transformer.MessageTransformationException:
+      Failed to transform Message; nested exception is org.springframework.messaging.MessageHandlingException:
+      Expression evaluation failed: 10 / payload; nested exception is java.lang.ArithmeticException: / by zero
+    5]
+    ]

basic/barrier/src/main/java/org/springframework/integration/samples/barrier2/Aggregator.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2015 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.integration.samples.barrier2;
+
+import java.util.Collection;
+
+import org.springframework.messaging.MessagingException;
+
+/**
+ * @author Gary Russell
+ * @since 4.2
+ *
+ */
+public class Aggregator {
+
+	public Object aggregate(Collection<Object> results) {
+		for (Object o : results) {
+			if (o instanceof MessagingException) {
+				return new ConsolidatedResultsException(results);
+			}
+		}
+		return results;
+	}
+
+	@SuppressWarnings("serial")
+	public static class ConsolidatedResultsException extends RuntimeException {
+
+		private final Collection<Object> results;
+
+		public ConsolidatedResultsException(Collection<Object> results) {
+			this.results = results;
+		}
+
+		public Collection<Object> getResults() {
+			return results;
+		}
+
+		@Override
+		public String toString() {
+			return "ConsolidatedResultsException\n[results=\n" + results.toString().replaceAll(", ", "\n") + "\n]";
+		}
+
+	}
+
+}

basic/barrier/src/main/java/org/springframework/integration/samples/barrier2/ErrorHandlingApplication.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright 2015 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.integration.samples.barrier2;
+
+import java.util.Arrays;
+
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.context.ConfigurableApplicationContext;
+import org.springframework.context.annotation.ImportResource;
+
+/**
+ * @author Gary Russell
+ * @since 4.2
+ */
+@SpringBootApplication
+@ImportResource("/META-INF/spring/integration/errorhandling-context.xml")
+public class ErrorHandlingApplication {
+
+	public static void main(String[] args) throws Exception {
+		ConfigurableApplicationContext test = new SpringApplicationBuilder(ErrorHandlingApplication.class)
+				.web(false)
+				.run(args);
+		Gateway gateway = test.getBean(Gateway.class);
+		try {
+			gateway.process(Arrays.asList(2, 0, 2, 0, 2), "foo");
+		}
+		catch (Exception e) {
+			System.err.println(e.toString());
+		}
+		test.close();
+	}
+
+}

basic/barrier/src/main/java/org/springframework/integration/samples/barrier2/Gateway.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2015 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.integration.samples.barrier2;
+
+import java.util.Collection;
+
+/**
+ * @author Gary Russell
+ * @since 4.2
+ *
+ */
+public interface Gateway {
+
+	public void process(Collection<Integer> numbers, String correlationId);
+
+}

basic/barrier/src/main/resources/META-INF/spring/integration/errorhandling-context.xml

@@ -0,0 +1,59 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://www.springframework.org/schema/beans"
+	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xmlns:int="http://www.springframework.org/schema/integration"
+	xmlns:rabbit="http://www.springframework.org/schema/rabbit"
+	xmlns:task="http://www.springframework.org/schema/task"
+	xsi:schemaLocation="http://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-4.2.xsd
+		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
+		http://www.springframework.org/schema/rabbit http://www.springframework.org/schema/rabbit/spring-rabbit.xsd
+		http://www.springframework.org/schema/integration http://www.springframework.org/schema/integration/spring-integration.xsd">
+
+	<int:gateway default-request-channel="processChannel"
+				service-interface="org.springframework.integration.samples.barrier2.Gateway"
+				default-payload-expression="#args[0]">
+		<int:default-header name="barrierCorrelation" expression="#args[1]" />
+	</int:gateway>
+
+	<int:publish-subscribe-channel id="processChannel" />
+
+	<int:splitter input-channel="processChannel" output-channel="process" order="1" />
+
+	<int:channel id="process">
+		<int:queue />
+	</int:channel>
+
+	<int:chain input-channel="process" output-channel="aggregatorChannel">
+		<int:transformer expression="10 / payload" /> <!-- exception on 0 payloads -->
+		<int:poller fixed-delay="1000" error-channel="errors" task-executor="exec" />
+	</int:chain>
+
+	<task:executor id="exec"/>
+
+	<!-- Suspend the calling thread until the aggregation is complete -->
+
+	<int:barrier id="barrier" input-channel="processChannel" order="2"
+		correlation-strategy-expression="headers['barrierCorrelation']"
+		timeout="10000" />
+
+	<!-- Aggregate the results and send the result to the barrier release channel -->
+
+	<int:aggregator input-channel="aggregatorChannel" output-channel="release">
+		<bean class="org.springframework.integration.samples.barrier2.Aggregator" />
+	</int:aggregator>
+
+	<int:channel id="release" />
+
+	<int:outbound-channel-adapter channel="release" ref="barrier.handler" method="trigger" />
+
+	<!-- Error flow; send exceptions to the aggregator; restore the correlation data from the failedMessage -->
+
+	<int:chain input-channel="errors" output-channel="aggregatorChannel">
+		<int:header-enricher>
+			<int:correlation-id expression="payload.failedMessage.headers.correlationId" />
+			<int:header name="sequenceSize" expression="payload.failedMessage.headers.sequenceSize" />
+			<int:header name="sequenceNumber" expression="payload.failedMessage.headers.sequenceNumber" />
+		</int:header-enricher>
+	</int:chain>
+
+</beans>