Spring multiple @Configuration classes

Question

I am using Spring @Configuration annotation to configure my application.

Currently, I have a single @Configuration class where all my beans are declared. As the number of beans is growing (more than 30), I want to split it in many classes.

Some beans are using common classes (mainly utility classes) :

Foo.class is an utility class Bar.class and Baz.class both use Foo.class

I want to have all Foo, Bar and Baz in three distinct @Configuration classes (respectively Conf1, Conf2 and Conf3)

The problem is that I don't have access to an instance of Conf1 from Conf2 and Conf3 :

Conf1.class

@Configuration 
public class Conf1 {
    @Bean
    public Foo foo() {
        return new Foo();
    }
}

Conf2.class

@Configuration 
public class Conf2 {
    @Bean
    public Bar bar() {
        Bar bar = new Bar();
        bar.setFoo(conf1.foo()); // Not possible !
        return bar;
    }
}

Conf3.class

@Configuration 
public class Conf3 {
    @Bean
    public Baz baz() {
        Baz baz = new Baz();
        baz.setFoo(conf1.foo()); // Not possible !
        return baz;
    }
}

Any idea on how can I solve this issue ?

Answer 1

@Configuration
@Import({ DataSourceConfig.class, TransactionConfig.class })
public class AppConfig extends ConfigurationSupport {
      // bean definitions here can reference bean definitions in DataSourceConfig or TransactionConfig
}

Answer 2

You should be able to autowire them:

@Configuration 
public class Conf2 {
    @Autowired
    Conf1 conf1;
    ...
}

Alternatively, you can autowire beans rather than configurations:

@Configuration 
public class Conf2 {
    @Autowired
    Foo foo;
    ...
}

Answer 3

Spring framework chapter-5 explained it very nicely.

• @ExternalBean : One configuration class may need to reference a bean defined in another configuration class (or in XML, for that matter). The @ExternalBean annotation provides just such a mechanism. When JavaConfig encounters a method annotated as @ExternalBean, it replaces that method definition with a lookup to the enclosing bean factory for a bean with the same name as the method name

• @Import : @Import represents JavaConfig's equivalent of XML configuration's element. One configuration class can import any number of other configuration classes, and their bean definitions will be processed as if locally defined

• ConfigurationSupport : As a convenience, @Configuration classses can extend ConfigurationSupport, primarily in order to facilitate easy lookup of beans from the enclosing BeanFactory / ApplicationContext.