Spring Integration — Endpoints

In this example, we ‘ll make the use of Endpoint to send the message and Subscribe to it.

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<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>

   <groupId>com.oreilly.integration</groupId>
   <artifactId>spring-integration</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <packaging>jar</packaging>
   <name>spring-integration</name>
   <description>Demo project for Spring Boot</description>

   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>2.6.1</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>

   <properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <java.version>1.8</java.version>
   </properties>

   <dependencies>
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-integration</artifactId>
      </dependency>
      
      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </dependency>
   </dependencies>
   
   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
      </plugins>
   </build>
   

</project>

PrintService.java

package com.oreilly.integration;

import java.util.Map.Entry;

import org.springframework.integration.support.MessageBuilder;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageHeaders;

public class PrintService {

   public Message<?> print(Message<String> message){
      MessageHeaders headers = message.getHeaders();

      for(Entry<String,Object> entry:headers.entrySet()){
         System.out.println("Key >> "+ entry.getKey()+":: Value >> "+ entry.getValue());
      }
      
      System.out.println(message.getPayload());
      return MessageBuilder.withPayload("New Message").build();
   }
}

MainApp.java

package com.oreilly.integration;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.ApplicationArguments;
import org.springframework.boot.ApplicationRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.ImportResource;
import org.springframework.integration.channel.DirectChannel;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageHandler;
import org.springframework.messaging.MessagingException;
import org.springframework.messaging.support.MessageBuilder;

@SpringBootApplication
@Configuration
@ImportResource("integration-context.xml")
public class SpringIntegrationApplication implements ApplicationRunner {

   @Autowired
   @Qualifier("inputChannel")
   private DirectChannel inputChannel;

   @Autowired
   @Qualifier("outputChannel")
   private DirectChannel outputChannel;
   
   public static void main(String[] args) {
      SpringApplication.run(SpringIntegrationApplication.class, args);
   }

   @Override
   public void run(ApplicationArguments arg0) {

      outputChannel.subscribe(new MessageHandler(){

         @Override
         public void handleMessage(Message<?> message) throws MessagingException {
            System.out.println(message.getPayload());
         }
         
      });
      
      Message<String> message = MessageBuilder
            .withPayload("Hello World, from the builder pattern")
            .setHeader("newHeader", "newHeaderValue")
            .build();
      inputChannel.send(message);
   }
}

integration-context.xml

<?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"
   xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
      http://www.springframework.org/schema/integration http://www.springframework.org/schema/integration/spring-integration-4.2.xsd">

   <int:channel id="inputChannel"/>
   <int:channel id="outputChannel"/>

   <bean class="com.oreilly.integration.PrintService" id="printService"/>
   
   <int:service-activator ref="printService"
                     method="print"
                     input-channel="inputChannel"
                     output-channel="outputChannel" />
</beans>

Output —

Key >> newHeader:: Value >> newHeaderValue
Key >> id:: Value >> 6661d579-b524–49d2–7f68–306e342e99ad
Key >> timestamp:: Value >> 1639326484153
Hello World, from the builder pattern
New Message