Dubbo is upgraded from 2.7.3 to 3.0.6. What is the reason for the repeated bean creation error?

[liunancun]

• I have searched the issues of this repository and believe that this is not a duplicate.

Environment

• Dubbo version: 3.0.6
• Operating System version: Window 7
• Java version: jdk8

Steps to reproduce this issue

@Service
public class DemoService {
}

@SpringBootApplication
public class DemoApplication {

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

	@Bean
	public DemoService demoService() {
		return new DemoService();
	}

}

Pls. provide [GitHub address] to reproduce this issue.

Expected Behavior

Started successfully

Actual Behavior

Startup failed

If there is an exception, please attach the exception trace:

2022-03-20 17:13:21.794  INFO 6920 --- [           main] d.s.b.c.e.WelcomeLogoApplicationListener : 

 :: Dubbo Spring Boot (v3.0.6) : https://github.com/apache/dubbo-spring-boot-project
 :: Dubbo (v3.0.6) : https://github.com/apache/dubbo
 :: Discuss group : dev@dubbo.apache.org


  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::       (v2.2.10.RELEASE)

2022-03-20 17:13:21.907  INFO 6920 --- [           main] com.example.demo.DemoApplication         : Starting DemoApplication on QWERTYUIOP-PC with PID 6920 (D:\work\workspace\elasticsearch\demo\target\classes started by liunancun in D:\work\workspace\elasticsearch\demo)
2022-03-20 17:13:21.908  INFO 6920 --- [           main] com.example.demo.DemoApplication         : No active profile set, falling back to default profiles: default
2022-03-20 17:13:22.357  WARN 6920 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.support.BeanDefinitionOverrideException: Invalid bean definition with name 'demoService' defined in com.example.demo.DemoApplication: Cannot register bean definition [Root bean: class [null]; scope=; abstract=false; lazyInit=null; autowireMode=3; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=demoApplication; factoryMethodName=demoService; initMethodName=null; destroyMethodName=(inferred); defined in com.example.demo.DemoApplication] for bean 'demoService': There is already [Generic bean: class [com.example.demo.DemoService]; scope=singleton; abstract=false; lazyInit=null; autowireMode=0; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null; defined in file [D:\work\workspace\elasticsearch\demo\target\classes\com\example\demo\DemoService.class]] bound.
2022-03-20 17:13:22.370  INFO 6920 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2022-03-20 17:13:22.372 ERROR 6920 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

The bean 'demoService', defined in com.example.demo.DemoApplication, could not be registered. A bean with that name has already been defined in file [D:\work\workspace\elasticsearch\demo\target\classes\com\example\demo\DemoService.class] and overriding is disabled.

Action:

Consider renaming one of the beans or enabling overriding by setting spring.main.allow-bean-definition-overriding=true

This is no problem in Dubbo2.7.3 version, I want to know why it will report an error in Dubbo3.0.6 version, what is the reason?

[liunancun]

After testing several times, it was found that it was caused by the version difference of dubbo-spring-boot-starter. The dubbo-spring-boot-starter of version 2.7.3 can be started normally, and the dependency of dubbo-spring-boot-starter is removed or 3.0.6 is introduced. All versions of dubbo-spring-boot-starter fail to start

[kylixs]

@liunancun
Which @Service is used? fully qualified class name?

@Service
public class DemoService {
}

[kylixs]

Description:

The bean 'demoService', defined in com.example.demo.DemoApplication, could not be registered. A bean with that name has already been defined in file [D:\work\workspace\elasticsearch\demo\target\classes\com\example\demo\DemoService.class] and overriding is disabled.

Action:

Consider renaming one of the beans or enabling overriding by setting spring.main.allow-bean-definition-overriding=true

I think it's worked as expected, the error is throw by spring.
The reason why dubbo 2.7.x is no this error, it seems that dubbo 2.7.x set the spring.main.allow-bean-definition-overriding=true automatically, but this setting is removed in dubbo 3.x.
I think dubbo should not change spring settings by default.

[liunancun]

@kylixs I want to confirm whether spring.main.allow-bean-definition-overriding=true is set in dubbo 2.7.x, and where is it set?

[chickenlj]

The reason why dubbo 2.7.x is no this error, it seems that dubbo 2.7.x set the spring.main.allow-bean-definition-overriding=true automatically, but this setting is removed in dubbo 3.x.
I think dubbo should not change spring settings by default.

As explained by @kylixs, setting of spring.main.allow-bean-definition-overriding=true is not a good practice, so we have removed that starting from 3.0. Please try to modify the usage samples above accordingly. Thanks.