Why is Spring Boot loading all xml files when I only specify one?

Question

I have a very basic Spring Boot Application.

There are 2 @SpringBootApplications in the project:

ApplicationA:

package com.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ImportResource;

/**
 * Created on 2/16/16.
 */
@SpringBootApplication
@ImportResource("classpath:run-app-a-context.xml")
public class ApplicationA {

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(ApplicationA.class, args);

        System.out.println(context.getBean("helloA"));
        System.out.println(context.getBean("helloB"));
    }
}

ApplicationB:

package com.example;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.annotation.ImportResource;

/**
 * Created on 2/16/16.
 */
@SpringBootApplication
@ImportResource("classpath:run-app-b-context.xml")
public class ApplicationB {

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(ApplicationB.class, args);

        System.out.println(context.getBean("helloA"));
        System.out.println(context.getBean("helloB"));
    }
}

As you can see, ApplicationA is only supposed to import run-app-a-context.xml and ApplicationB is only supposed to import run-app-b-context.xml. However, this is not what occurs.

If I run ./gradlew bootRun; I get the following output (emphasis added):

./gradlew bootRun
:compileJava UP-TO-DATE
:processResources UP-TO-DATE
:classes UP-TO-DATE
:findMainClass
:bootRun

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.3.1.RELEASE)

2016-02-16 11:42:21.889  INFO 47524 --- [           main] com.example.ApplicationA                 : Starting ApplicationA on LMC with PID 47524 (/Users/IdeaProjects/whyisitloadingeverything/build/classes/main started in /Users/IdeaProjects/whyisitloadingeverything)
2016-02-16 11:42:21.896  INFO 47524 --- [           main] com.example.ApplicationA                 : No active profile set, falling back to default profiles: default
2016-02-16 11:42:21.975  INFO 47524 --- [           main] s.c.a.AnnotationConfigApplicationContext : Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@24a35978: startup date [Tue Feb 16 11:42:21 PST 2016]; root of context hierarchy
2016-02-16 11:42:22.883  INFO 47524 --- [           main] o.s.b.f.xml.XmlBeanDefinitionReader      : Loading XML bean definitions from class path resource [run-app-b-context.xml]
2016-02-16 11:42:23.081  INFO 47524 --- [           main] o.s.b.f.xml.XmlBeanDefinitionReader      : Loading XML bean definitions from class path resource [run-app-a-context.xml]
2016-02-16 11:42:23.255  INFO 47524 --- [           main] o.s.b.f.config.PropertiesFactoryBean     : Loading properties file from URL [jar:file:/Users/.gradle/caches/modules-2/files-2.1/org.springframework.integration/spring-integration-core/4.2.4.RELEASE/4780d5c2b680796844916402816135f0e79f166f/spring-integration-core-4.2.4.RELEASE.jar!/META-INF/spring.integration.default.properties]
2016-02-16 11:42:23.258  INFO 47524 --- [           main] o.s.i.config.IntegrationRegistrar        : No bean named 'integrationHeaderChannelRegistry' has been explicitly defined. Therefore, a default DefaultHeaderChannelRegistry will be created.
2016-02-16 11:42:23.451  INFO 47524 --- [           main] faultConfiguringBeanFactoryPostProcessor : No bean named 'errorChannel' has been explicitly defined. Therefore, a default PublishSubscribeChannel will be created.
2016-02-16 11:42:23.470  INFO 47524 --- [           main] faultConfiguringBeanFactoryPostProcessor : No bean named 'taskScheduler' has been explicitly defined. Therefore, a default ThreadPoolTaskScheduler will be created.
2016-02-16 11:42:24.036  INFO 47524 --- [           main] o.s.b.f.config.PropertiesFactoryBean     : Loading properties file from URL [jar:file:/Users/.gradle/caches/modules-2/files-2.1/org.springframework.integration/spring-integration-core/4.2.4.RELEASE/4780d5c2b680796844916402816135f0e79f166f/spring-integration-core-4.2.4.RELEASE.jar!/META-INF/spring.integration.default.properties]
2016-02-16 11:42:24.100  INFO 47524 --- [           main] o.s.s.c.ThreadPoolTaskScheduler          : Initializing ExecutorService  'taskScheduler'
2016-02-16 11:42:24.226  INFO 47524 --- [           main] o.s.j.e.a.AnnotationMBeanExporter        : Registering beans for JMX exposure on startup
2016-02-16 11:42:24.243  INFO 47524 --- [           main] o.s.c.support.DefaultLifecycleProcessor  : Starting beans in phase 0
2016-02-16 11:42:24.243  INFO 47524 --- [           main] o.s.i.endpoint.EventDrivenConsumer       : Adding {logging-channel-adapter:_org.springframework.integration.errorLogger} as a subscriber to the 'errorChannel' channel
2016-02-16 11:42:24.244  INFO 47524 --- [           main] o.s.i.channel.PublishSubscribeChannel    : Channel 'application.errorChannel' has 1 subscriber(s).
2016-02-16 11:42:24.244  INFO 47524 --- [           main] o.s.i.endpoint.EventDrivenConsumer       : started _org.springframework.integration.errorLogger
2016-02-16 11:42:24.256  INFO 47524 --- [           main] com.example.ApplicationA                 : Started ApplicationA in 2.9 seconds (JVM running for 3.466)
application A
application B
2016-02-16 11:42:24.257  INFO 47524 --- [       Thread-1] s.c.a.AnnotationConfigApplicationContext : Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@24a35978: startup date [Tue Feb 16 11:42:21 PST 2016]; root of context hierarchy
2016-02-16 11:42:24.258  INFO 47524 --- [       Thread-1] o.s.c.support.DefaultLifecycleProcessor  : Stopping beans in phase 0
2016-02-16 11:42:24.259  INFO 47524 --- [       Thread-1] o.s.i.endpoint.EventDrivenConsumer       : Removing {logging-channel-adapter:_org.springframework.integration.errorLogger} as a subscriber to the 'errorChannel' channel
2016-02-16 11:42:24.259  INFO 47524 --- [       Thread-1] o.s.i.channel.PublishSubscribeChannel    : Channel 'application.errorChannel' has 0 subscriber(s).
2016-02-16 11:42:24.259  INFO 47524 --- [       Thread-1] o.s.i.endpoint.EventDrivenConsumer       : stopped _org.springframework.integration.errorLogger
2016-02-16 11:42:24.260  INFO 47524 --- [       Thread-1] o.s.s.c.ThreadPoolTaskScheduler          : Shutting down ExecutorService 'taskScheduler'
2016-02-16 11:42:24.261  INFO 47524 --- [       Thread-1] o.s.j.e.a.AnnotationMBeanExporter        : Unregistering JMX-exposed beans on shutdown

BUILD SUCCESSFUL

Total time: 13.537 secs

I see that both xml context files are being loaded and therefore the beans in both files are added to the Application Context.

Why is Spring/Spring Boot automatically loading all xml configuration files? How do I stop this behavior?

Answer 1

It is because @SpringBootApplication by default includes the @ComponentScan annotation as well as the @Configuration annotation.

The ComponentScan annotation will recursively scan the current package by default if no basePackageClasses() or basePackages() (or its alias value()) is defined. It looks for classes marked with @Configuration, and if it finds one, the beans defined in it will be added to the Application Context.

Since both ApplicationA and ApplicationB are in the same package; when starting ApplicationA, ApplicationB is automatically component-scanned in (and vice-versa when starting ApplicationB).

The fix is to put ApplicationA and ApplicationB in separate packages.