Spring Integration — Demo

In this exmple, we’ll see the basics of Spring Integration

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-demo</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <packaging>jar</packaging>

   <name>spring-integration-demo</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>

CustomGateway.java

package com.oreilly.demo;

public interface CustomGateway {
   public void print(String message);
}

PrintService.java

package com.oreilly.demo;

public class PrintService {

   public void print(String message){
      System.out.println(message);
   }
}

ReverseService.java

package com.oreilly.demo;

public class ReverseService {

   public void reverse(String message){
      System.out.println(new StringBuilder(message).reverse().toString());
   }
}

MainApp.java

package com.oreilly.demo;

import org.springframework.beans.factory.annotation.Autowired;
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;

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

   @Autowired
   private CustomGateway gateway;

   public static void main(String[] args) {
      SpringApplication.run(SpringIntegrationDemoApplication.class, args);
   }

   @Override
   public void run(ApplicationArguments arg0) throws Exception {
      gateway.print("Hello World");
   }
}

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">

   <!-- Endpoint -->  
   <int:gateway service-interface="com.oreilly.demo.CustomGateway" default-request-channel="inputChannel">
      <int:method name="print"/> 
   </int:gateway>

   <!-- Channel -->
   <int:channel id="inputChannel"/>

   <!-- Endpoint -->  
   <!--<int:service-activator ref="reverseService" input-channel="inputChannel" method="reverse"/>-->
   <int:service-activator ref="printService" input-channel="inputChannel" method="print" />

   <bean id="printService" class="com.oreilly.demo.PrintService"/>
   <bean id="reverseService" class="com.oreilly.demo.ReverseService"/>
</beans>

output —

2021–12–12 20:05:21.005 INFO 21976 — — [ main] o.s.i.gateway.GatewayProxyFactoryBean : started bean ‘customGateway’
2021–12–12 20:05:21.011 INFO 21976 — — [ main] c.o.d.SpringIntegrationDemoApplication : Started SpringIntegrationDemoApplication in 1.07 seconds (JVM running for 1.808)
2021–12–12 20:05:21.011 INFO 21976 — — [ main] o.s.i.h.s.MessagingMethodInvokerHelper : Overriding default instance of MessageHandlerMethodFactory with provided one.
Hello World
2021–12–12 20:05:21.011 INFO 21976 — — [ionShutdownHook] ProxyFactoryBean$MethodInvocationGateway : stopped bean ‘customGateway#print(String)’
2021–12–12 20:05:21.011 INFO 21976 — — [ionShutdownHook] o.s.i.gateway.GatewayProxyFactoryBean : stopped bean ‘customGateway’