spring-integration Getting started with spring-integration

Remarks

Versions

Generic Inbound and Outbound Channel Adapter

Channel adapter is one of message endpoints in Spring Integration. It is used for unidirectional message flow. There are two types of channel adapter:

Inbound Adapter: input side of the channel. Listen or actively read message.

Outbound Adapter: output side of the channel. Send message to Java class or external system or protocol.

• Source code.

  public class Application {
      static class MessageProducer {
          public String produce() {
              String[] array = {"first line!", "second line!", "third line!"};
              return array[new Random().nextInt(3)];
          }
      }
  
      static class MessageConsumer {
          public void consume(String message) {
              System.out.println(message);
          }
      }
  
      public static void main(String[] args) {
          new ClassPathXmlApplicationContext("classpath:spring/integration/stackoverflow/ioadapter/ioadapter.xml");
      }
  }
   

• XML-style Configuration file:

  <?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.xsd">
      <int:channel id="channel"/>
      <int:inbound-channel-adapter id="inAdapter" channel="channel" method="produce">
          <bean class="spring.integration.stackoverflow.ioadapter.Application$MessageProducer"/>
          <int:poller fixed-rate="1000"/>
      </int:inbound-channel-adapter>
      <int:outbound-channel-adapter id="outAdapter" channel="channel" method="consume">
          <bean class="spring.integration.stackoverflow.ioadapter.Application$MessageConsumer"/>
      </int:outbound-channel-adapter>
  </beans>
   

• Message Flow

  • inAdapter : an inbound channel adapter. Invoke Application$MessageProducer.produce method every 1 second (<int:poller fixed-rate="1000"/> ) and send the returned string as message to the channel channel .
  • channel : channel to transfer message.
  • outAdapter : an outbound channel adapter. Once message reached on channel channel , this adapter will receive the message and then send it to Application$MessageConsumer.consume method which print the message on the console.
  • So you can observe that these random choose string will displayed on the console every 1 second.

Installation or Setup

The best way to get started using Spring-Integration in your project is with a dependency management system, like gradle.

dependencies {
    compile 'org.springframework.integration:spring-integration-core:4.3.5.RELEASE'
}
 

Below is a very simple example using the gateway, service-activator message endpoints.

//these annotations will enable Spring integration and scan for components
@Configuration
@EnableIntegration
@IntegrationComponentScan
public class Application {
    //a channel has two ends, this Messaging Gateway is acting as input from one side of inChannel
    @MessagingGateway
    interface Greeting {
        @Gateway(requestChannel = "inChannel")
        String greet(String name);
    }

    @Component
    static class HelloMessageProvider {
        //a service activator act as a handler when message is received from inChannel, in this example, it is acting as the handler on the output side of inChannel
        @ServiceActivator(inputChannel = "inChannel")
        public String sayHello(String name) {
            return "Hi, " + name;
        }
    }

    @Bean
    MessageChannel inChannel() {
        return new DirectChannel();
    }

    public static void main(String[] args) {
        ApplicationContext context = new AnnotationConfigApplicationContext(Application.class);
        Greeting greeting = context.getBean(Greeting.class);
        //greeting.greet() send a message to the channel, which trigger service activitor to process the incoming message
        System.out.println(greeting.greet("Spring Integration!"));
    }
}
 

It will display the string Hi, Spring Integration! in the console.

Of course, Spring Integration also provides xml-style configuration. For the above example, you can write such following xml configuration file.

<?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.xsd">
    <int:gateway default-request-channel="inChannel"
                 service-interface="spring.integration.stackoverflow.getstarted.Application$Greeting"/>
    <int:channel id="inChannel"/>
    <int:service-activator input-channel="inChannel" method="sayHello">
        <bean class="spring.integration.stackoverflow.getstarted.Application$HelloMessageProvider"/>
    </int:service-activator>
</beans>
 

To run the application using the xml config file, you should change the code new AnnotationConfigApplicationContext(Application.class) in Application class to new ClassPathXmlApplicationContext("classpath:getstarted.xml") . And run this application again, you can see the same output.

Simple Echo Excample with Spring-Integration-Stream

Java code:

public class StdioApplication {
    public static void main(String[] args) {
        new ClassPathXmlApplicationContext("classpath:spring/integration/stackoverflow/stdio/stdio.xml");
    }
}
 

Xml config file

<?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:int-stream="http://www.springframework.org/schema/integration/stream"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/integration/stream
       http://www.springframework.org/schema/integration/stream/spring-integration-stream.xsd
       http://www.springframework.org/schema/integration
       http://www.springframework.org/schema/integration/spring-integration.xsd">
    <int:channel id="channel"/>
    <int-stream:stdin-channel-adapter id="stdin" channel="channel">
        <int:poller fixed-rate="1000"/>
    </int-stream:stdin-channel-adapter>
    <int-stream:stdout-channel-adapter id="stdout" channel="channel"/>
</beans>
 

This is a echo example. When you run this Java application, you can input some string and then it will be displayed on the console.