Spring Passing a plain POJO to AnnotationConfigApplicationContext creates a Singleton/Prototype bean

Steps to reproduce

Scenario 1: : Singleton beans 1. Create a Java Pojo

public class Reader {

    public Reader() {

    }
}

1. Create AnnotationConfigApplicationContext by supplying Pojo class like below

public class Application {

    public static void main(String[] args) {

        try(var context = new AnnotationConfigApplicationContext(Reader.class, JLabel.class)) {

        System.out.println("Get singleton reader bean: "+context.getBean("reader").hashCode());
        System.out.println("Get singleton reader bean: "+context.getBean("reader").hashCode());
        System.out.println("Get singleton reader bean: "+context.getBean("reader").hashCode());
        System.out.println("Get singleton reader bean: "+context.getBean("reader").hashCode());


        // Another example on JLABEL class

        System.out.println("Get singleton JLabel bean: "+context.getBean("JLabel").hashCode());

        System.out.println("Get singleton JLabel bean: "+context.getBean("JLabel").hashCode());

        }catch(Exception e) {
            System.err.print(e);
        }
    }

}

Here is a sample output

Get singleton reader bean: 1048855692 Get singleton reader bean: 1048855692 Get singleton reader bean: 1048855692 Get singleton reader bean: 1048855692 Get singleton jlabel bean: 2119891622 Get singleton jlabel bean: 2119891622

**Why does AnnotationConfigApplicationContext create a bean from a POJO, this behavior is not mentioned anywhere is document either. Is this the default behavior ? **

Scenario 2: : Configuration class without @Configuration

Another example with a configuration class without @configuration Annotation like below

1. Create a POJO

public class AnotherPojo {

    public AnotherPojo() {

    }
}

1. Create config class without @Configuration.

public class SomeConfiguration {

    @Bean
    public AnotherPojo anothe       context.close();rPojo() {
        return new AnotherPojo();
    }
}

1. Create AnnotationConfigApplicationContext

public class Application {

    public static void main(String[] args) {

        try(var context = new AnnotationConfigApplicationContext(SomeConfiguration.class)) {

        // through config class without @Configuration
        System.out.println("Get singleton anotherPojo through config: "+context.getBean("anotherPojo").hashCode());
        System.out.println("Get singleton anotherPojo through config: "+context.getBean("anotherPojo").hashCode());
        }catch(Exception e) {
            System.err.print(e);
        }

    }

}

This is the output

Get singleton anotherPojo through config: 739973450 Get singleton anotherPojo through config: 739973450

Scenario 3: Prototype bean with only @Scope

1. create a class with only @Scope

@Scope("prototype")

public class Writer {

    public Writer() {
    }

}

1. Create AnnotationConfigApplicationContext

public class Application {
public static void main(String[] args) {

        try (var context = new AnnotationConfigApplicationContext(Writer.class)) {

            System.out.println("Get prototype writer bean: "+context.getBean("writer"));
            System.out.println("Get prototype writer bean: "+context.getBean("writer")
            System.out.println("Get prototype writer bean: "+context.getBean("writer"));
        } catch (Exception e) {
            System.err.print(e);
        }

    }

Here is the sample output:

Get prototype writer bean: org.entitylabs.beans.Writer@44ebcd03 Get prototype writer bean: org.entitylabs.beans.Writer@6356695f Get prototype writer bean: org.entitylabs.beans.Writer@4f18837a

Spring version used : 5.3.12

Also, source code is attachment for all three scenarios

01-singleton-beans-test.zip 02-configuration-bean.zip 03-prototype-beans.zip

Comment From: entitylabs

Spring version used : 5.3.12

Comment From: snicoll

The Javadoc of AnnotationConfigApplicationContext states:

Create a new AnnotationConfigApplicationContext, deriving bean definitions from the given component classes and automatically refreshing the context.

What you call "POJO" (I assume non annotated types) are no different from a service or anything that the context should handle if told so. The second case is what's called lite mode. As for the last one, this is also working as expected, the scope being read from the component like any other stereotype.

Going forward, please ask questions on StackOverflow, as mentioned in the guidelines for contributing, we prefer to use the issue tracker only for bugs and enhancements.