Multiple @SpringBootApplication Annotation in a Project

Question

In my project created by SpringBoot,

I have added 2 main classes with @SpringBootApplication.

Because if I use STS I can choose one main application when start to debug.

But I found that while SpringDemoApplication is up ,RabbitMQApplication is also running.

Is this specification ? working appropriately?

Here this is sample to reproduce https://github.com/MariMurotani/SpringDemo/tree/6_rabbitMQ

SpringDemoApplication

package demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;

@SpringBootApplication
public class SpringDemoApplication {

public static void main(String[] args) {

        SpringApplication application = new SpringApplication(SpringDemoApplication.class);
        ApplicationContext context = application.run(args);

    }
}

RabbitMQApplication

package demo;

import java.util.Date;

import org.codehaus.jackson.map.ObjectMapper;
import org.springframework.amqp.core.Binding;
import org.springframework.amqp.core.BindingBuilder;
import org.springframework.amqp.core.Queue;
import org.springframework.amqp.core.TopicExchange;
import org.springframework.amqp.rabbit.connection.ConnectionFactory;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;

import demo.configs.Const;
import demo.dto.Mail;

@SpringBootApplication
public class RabbitMQApplication implements CommandLineRunner {

@Autowired
ApplicationContext context;


@Autowired
RabbitTemplate rabbitTemplate;

@Bean
Queue queue() {
    return new Queue(Const.RabbitMQMessageQue, false);
}

@Bean
TopicExchange exchange() {
    return new TopicExchange("spring-boot-exchange");
}

@Bean
Binding binding(Queue queue, TopicExchange exchange) {
    return BindingBuilder.bind(queue).to(exchange).with(Const.RabbitMQMessageQue);
}

@Bean
SimpleMessageListenerContainer container(ConnectionFactory connectionFactory) {
    SimpleMessageListenerContainer container = new SimpleMessageListenerContainer();
    container.setConnectionFactory(connectionFactory);
    container.setQueueNames(Const.RabbitMQMessageQue);
    //container.setMessageListener(listenerAdapter);
    return container;
}

/*
For asyncronized receiving

@Bean
Receiver receiver() {
    return new Receiver();
}

@Bean
MessageListenerAdapter listenerAdapter(Receiver receiver) {
    return new MessageListenerAdapter(receiver, "receiveMessage");
}*/

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

@Override
public void run(String... args) throws Exception {
    System.out.println("Waiting five seconds...");

    while(0 < 1){
        for(int i = 0 ; i < 5 ; i++){
            String object = (String)rabbitTemplate.receiveAndConvert(Const.RabbitMQMessageQue);
            if(object != null){
                try{
                    System.out.println(new Date().toGMTString() + ": " + object);
                    ObjectMapper mapper = new ObjectMapper();
                    Mail mail = mapper.readValue(object, Mail.class);
                    System.out.println(mail.getToAddress() + " , " + mail.getStrContent());
                }catch(Exception e){
                    System.out.println(e.getMessage());
                }
            }
        }
        Thread.sleep(10000);
    }
}
}

Answer 1

The @SpringBootApplication annotation is a shortcut annotation for @Configuration, @EnableAutoConfiguration, and @ComponentScan.

http://docs.spring.io/spring-boot/docs/current/reference/html/using-boot-using-springbootapplication-annotation.html

The default behavior of @ComponentScan is to look for @Configuration and @Component classes within the same package and all sub-packages of the annotated class. Since all your classes are in the same package, when you start any one of them Spring will find the others and treat them like @Configuration classes, and register their beans, etc.

So yes, this is expected behavior given your project setup. Put each @SpringBootApplication class in a separate subpackage if you don't want this to happen for local testing. If this moves beyond a demo at some point you'll probably want to come up with a better setup (subprojects for each @SpringBootApplication perhaps).