Repository: iluwatar/java-design-patterns
Issue: Aggregator (EIP)
Labels: epic: pattern


Issue comments:
Since I've completed Splitter recently I can work now on this one.
Ok @codinghog 

Pull request review comments:

Patch that resolved the issue:
diff --git a/eip-aggregator/README.md b/eip-aggregator/README.md
new file mode 100644
index 000000000000..ec8454f63cef
--- /dev/null
+++ b/eip-aggregator/README.md
@@ -0,0 +1,33 @@
+---
+layout: pattern
+title: EIP Aggregator
+folder: eip-aggregator
+permalink: /patterns/eip-aggregator/
+categories: Enterprise integration
+tags:
+ - Java
+ - Difficulty-Intermittent
+ - Enterprise integration
+---
+
+## Intent
+Sometimes in enterprise systems there is a need to group incoming data in order to process it as a whole. For example
+you may need to gather offers and after defined number of offers has been received you would like to choose the one with
+the best parameters. 
+
+Aggregator allows you to merge messages based on defined criteria and parameters. It gathers original messages, 
+applies aggregation strategy and upon fulfilling given criteria, releasing merged messages.
+ 
+![alt text](./etc/aggregator.gif "Splitter")
+
+## Applicability
+Use the Aggregator pattern when
+
+* You need to combine multiple incoming messages 
+* You want to process grouped data
+
+## Credits
+
+* [Gregor Hohpe, Bobby Woolf - Enterprise Integration Patterns](http://www.enterpriseintegrationpatterns.com/patterns/messaging/Aggregator.html)
+* [Apache Camel - Documentation](http://camel.apache.org/aggregator2.html)
+
diff --git a/eip-aggregator/pom.xml b/eip-aggregator/pom.xml
new file mode 100644
index 000000000000..7467cb3a8069
--- /dev/null
+++ b/eip-aggregator/pom.xml
@@ -0,0 +1,63 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+    The MIT License
+    Copyright (c) 2014-2016 Ilkka Seppälä
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+    The above copyright notice and this permission notice shall be included in
+    all copies or substantial portions of the Software.
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+    THE SOFTWARE.
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>eip-aggregator</artifactId>
+    <parent>
+        <groupId>com.iluwatar</groupId>
+        <artifactId>java-design-patterns</artifactId>
+        <version>1.18.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.apache.camel</groupId>
+            <artifactId>camel-core</artifactId>
+            <version>${camel.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.apache.camel</groupId>
+            <artifactId>camel-spring-boot</artifactId>
+            <version>${camel.version}</version>
+        </dependency>
+
+        <!-- Testing -->
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.apache.camel</groupId>
+            <artifactId>camel-test-spring</artifactId>
+            <version>${camel.version}</version>
+        </dependency>
+
+    </dependencies>
+</project>
\ No newline at end of file
diff --git a/eip-aggregator/src/main/java/com/iluwatar/eip/aggregator/App.java b/eip-aggregator/src/main/java/com/iluwatar/eip/aggregator/App.java
new file mode 100644
index 000000000000..fbff1a28a123
--- /dev/null
+++ b/eip-aggregator/src/main/java/com/iluwatar/eip/aggregator/App.java
@@ -0,0 +1,51 @@
+package com.iluwatar.eip.aggregator;
+
+import org.apache.camel.CamelContext;
+import org.apache.camel.builder.RouteBuilder;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.ConfigurableApplicationContext;
+
+/**
+ * Sometimes in enterprise systems there is a need to group incoming data in order to process it as a whole. For example
+ * you may need to gather offers and after defined number of offers has been received you would like to choose the one
+ * with the best parameters.
+ *
+ * <p>
+ * Aggregator allows you to merge messages based on defined criteria and parameters. It gathers original messages,
+ * applies aggregation strategy and upon fulfilling given criteria, releasing merged messages.
+ * </p>
+ *
+ */
+@SpringBootApplication
+public class App {
+
+  /**
+   * Program entry point. It starts Spring Boot application and using Apache Camel it auto-configures routes.
+   *
+   * @param args command line args
+   */
+  public static void main(String[] args) throws Exception {
+    // Run Spring Boot application and obtain ApplicationContext
+    ConfigurableApplicationContext context = SpringApplication.run(App.class, args);
+
+    // Get CamelContext from ApplicationContext
+    CamelContext camelContext = (CamelContext) context.getBean("camelContext");
+
+    // Add a new routes that will handle endpoints form SplitterRoute class.
+    camelContext.addRoutes(new RouteBuilder() {
+
+      @Override
+      public void configure() throws Exception {
+        from("{{endpoint}}").log("ENDPOINT: ${body}");
+      }
+
+    });
+
+    // Add producer that will send test message to an entry point in WireTapRoute
+    String[] stringArray = {"Test item #1", "Test item #2", "Test item #3"};
+    camelContext.createProducerTemplate().sendBody("{{entry}}", stringArray);
+
+    SpringApplication.exit(context);
+  }
+}
diff --git a/eip-aggregator/src/main/java/com/iluwatar/eip/aggregator/routes/AggregatorRoute.java b/eip-aggregator/src/main/java/com/iluwatar/eip/aggregator/routes/AggregatorRoute.java
new file mode 100644
index 000000000000..5aba0ef27da7
--- /dev/null
+++ b/eip-aggregator/src/main/java/com/iluwatar/eip/aggregator/routes/AggregatorRoute.java
@@ -0,0 +1,38 @@
+package com.iluwatar.eip.aggregator.routes;
+
+import org.apache.camel.builder.RouteBuilder;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Component;
+
+/**
+ * Sample aggregator route definition.
+ *
+ * <p>
+ * It consumes messages out of the <i>direct:entry</i> entry point and forwards them to <i>direct:endpoint</i>.
+ * Route accepts messages containing String as a body, it aggregates the messages based on the settings and forwards
+ * them as CSV to the output chanel.
+ *
+ * Settings for the aggregation are: aggregate until 3 messages are bundled or wait 2000ms before sending bundled
+ * messages further.
+ * </p>
+ *
+ * In this example input/output endpoints names are stored in <i>application.properties</i> file.
+ */
+@Component
+public class AggregatorRoute extends RouteBuilder {
+
+  @Autowired
+  private MessageAggregationStrategy aggregator;
+
+  /**
+   * Configures the route
+   * @throws Exception in case of exception during configuration
+   */
+  @Override
+  public void configure() throws Exception {
+    // Main route
+    from("{{entry}}").aggregate(constant(true), aggregator)
+        .completionSize(3).completionInterval(2000)
+        .to("{{endpoint}}");
+  }
+}
diff --git a/eip-aggregator/src/main/java/com/iluwatar/eip/aggregator/routes/MessageAggregationStrategy.java b/eip-aggregator/src/main/java/com/iluwatar/eip/aggregator/routes/MessageAggregationStrategy.java
new file mode 100644
index 000000000000..a2c90c60921a
--- /dev/null
+++ b/eip-aggregator/src/main/java/com/iluwatar/eip/aggregator/routes/MessageAggregationStrategy.java
@@ -0,0 +1,27 @@
+package com.iluwatar.eip.aggregator.routes;
+
+import org.apache.camel.Exchange;
+import org.apache.camel.processor.aggregate.AggregationStrategy;
+import org.springframework.stereotype.Component;
+
+/**
+ * Aggregation strategy joining bodies of messages. If message is first one <i>oldMessage</i> is null. All changes are
+ * made on IN messages.
+ */
+@Component
+public class MessageAggregationStrategy implements AggregationStrategy {
+
+  @Override
+  public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
+    if (oldExchange == null) {
+      return newExchange;
+    }
+
+    String in1 = (String) oldExchange.getIn().getBody();
+    String in2 = (String) newExchange.getIn().getBody();
+
+    oldExchange.getIn().setBody(in1 + ";" + in2);
+
+    return oldExchange;
+  }
+}
diff --git a/eip-aggregator/src/main/resources/application.properties b/eip-aggregator/src/main/resources/application.properties
new file mode 100644
index 000000000000..cb879e6e270e
--- /dev/null
+++ b/eip-aggregator/src/main/resources/application.properties
@@ -0,0 +1,2 @@
+entry=direct:entry
+endpoint=direct:endpoint
diff --git a/eip-aggregator/src/test/resources/application-test.properties b/eip-aggregator/src/test/resources/application-test.properties
new file mode 100644
index 000000000000..f657ea5a102c
--- /dev/null
+++ b/eip-aggregator/src/test/resources/application-test.properties
@@ -0,0 +1,2 @@
+entry=direct:entry
+endpoint=mock:endpoint
diff --git a/pom.xml b/pom.xml
index 0c03909de269..2d84d50643bb 100644
--- a/pom.xml
+++ b/pom.xml
@@ -149,6 +149,7 @@
         <module>partial-response</module>
         <module>eip-wire-tap</module>
         <module>eip-splitter</module>
+        <module>eip-aggregator</module>
     </modules>
 
     <dependencyManagement>


Test patch:
diff --git a/eip-aggregator/src/test/java/com/iluwatar/eip/aggregator/AppTest.java b/eip-aggregator/src/test/java/com/iluwatar/eip/aggregator/AppTest.java
new file mode 100644
index 000000000000..5eee0986f02f
--- /dev/null
+++ b/eip-aggregator/src/test/java/com/iluwatar/eip/aggregator/AppTest.java
@@ -0,0 +1,15 @@
+package com.iluwatar.eip.aggregator;
+
+import org.junit.Test;
+
+/**
+ * Test for App class
+ */
+public class AppTest {
+
+  @Test
+  public void testMain() throws Exception {
+    String[] args = {};
+    App.main(args);
+  }
+}
diff --git a/eip-aggregator/src/test/java/com/iluwatar/eip/aggregator/routes/AggregatorRouteTest.java b/eip-aggregator/src/test/java/com/iluwatar/eip/aggregator/routes/AggregatorRouteTest.java
new file mode 100644
index 000000000000..449c4aad0f01
--- /dev/null
+++ b/eip-aggregator/src/test/java/com/iluwatar/eip/aggregator/routes/AggregatorRouteTest.java
@@ -0,0 +1,62 @@
+package com.iluwatar.eip.aggregator.routes;
+
+import org.apache.camel.EndpointInject;
+import org.apache.camel.ProducerTemplate;
+import org.apache.camel.component.mock.MockEndpoint;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.test.SpringApplicationConfiguration;
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Test class for <i>AggregatorRoute</i>.
+ * <p>
+ * In order for it to work we have to mock endpoints we want to read/write to. To mock those we need to substitute
+ * original endpoint names to mocks.
+ * </p>
+ */
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringApplicationConfiguration(classes = AggregatorRouteTest.class)
+@ActiveProfiles("test")
+@EnableAutoConfiguration
+@ComponentScan
+public class AggregatorRouteTest {
+
+  @EndpointInject(uri = "{{entry}}")
+  private ProducerTemplate entry;
+
+  @EndpointInject(uri = "{{endpoint}}")
+  private MockEndpoint endpoint;
+
+  /**
+   * Test if endpoint receives three separate messages.
+   * @throws Exception in case of en exception during the test
+   */
+  @Test
+  @DirtiesContext
+  public void testSplitter() throws Exception {
+
+    // Three items in one entry message
+    entry.sendBody("TEST1");
+    entry.sendBody("TEST2");
+    entry.sendBody("TEST3");
+    entry.sendBody("TEST4");
+    entry.sendBody("TEST5");
+
+    // Endpoint should have three different messages in the end order of the messages is not important
+    endpoint.expectedMessageCount(2);
+    endpoint.assertIsSatisfied();
+
+    String body = (String) endpoint.getReceivedExchanges().get(0).getIn().getBody();
+    assertEquals(3, body.split(";").length);
+
+    String body2 = (String) endpoint.getReceivedExchanges().get(1).getIn().getBody();
+    assertEquals(2, body2.split(";").length);
+  }
+}
diff --git a/eip-aggregator/src/test/java/com/iluwatar/eip/aggregator/routes/MessageAggregationStrategyTest.java b/eip-aggregator/src/test/java/com/iluwatar/eip/aggregator/routes/MessageAggregationStrategyTest.java
new file mode 100644
index 000000000000..f4685e334851
--- /dev/null
+++ b/eip-aggregator/src/test/java/com/iluwatar/eip/aggregator/routes/MessageAggregationStrategyTest.java
@@ -0,0 +1,42 @@
+package com.iluwatar.eip.aggregator.routes;
+
+import org.apache.camel.CamelContext;
+import org.apache.camel.Exchange;
+import org.apache.camel.impl.DefaultExchange;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Tests MessageAggregationStrategy
+ */
+public class MessageAggregationStrategyTest {
+
+  @Test
+  public void testAggregate() {
+    MessageAggregationStrategy mas = new MessageAggregationStrategy();
+    Exchange oldExchange = new DefaultExchange((CamelContext) null);
+    oldExchange.getIn().setBody("TEST1");
+
+    Exchange newExchange = new DefaultExchange((CamelContext) null);
+    newExchange.getIn().setBody("TEST2");
+
+    Exchange output = mas.aggregate(oldExchange, newExchange);
+    String outputBody = (String) output.getIn().getBody();
+    assertEquals("TEST1;TEST2", outputBody);
+  }
+
+  @Test
+  public void testAggregateOldNull() {
+    MessageAggregationStrategy mas = new MessageAggregationStrategy();
+
+    Exchange newExchange = new DefaultExchange((CamelContext) null);
+    newExchange.getIn().setBody("TEST2");
+
+    Exchange output = mas.aggregate(null, newExchange);
+    String outputBody = (String) output.getIn().getBody();
+
+    assertEquals(newExchange, output);
+    assertEquals("TEST2", outputBody);
+  }
+}