#114 Aggregator pattern; tests; description

eip-aggregator/src/main/java/com/iluwatar/eip/aggregator/App.java

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+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);
+  }
+}

eip-aggregator/src/main/java/com/iluwatar/eip/aggregator/routes/AggregatorRoute.java

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+package com.iluwatar.eip.aggregator.routes;
+
+import org.apache.camel.builder.RouteBuilder;
+import org.apache.camel.processor.aggregate.AggregationStrategy;
+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}}");
+  }
+}

eip-aggregator/src/main/java/com/iluwatar/eip/aggregator/routes/MessageAggregationStrategy.java

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+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;
+  }
+}

eip-aggregator/src/main/resources/application.properties

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+entry=direct:entry
+endpoint=direct:endpoint