Another approach is to use new conditional annotations. Since plain Spring 4 you can use @Conditional annotation:
@Component("foo")
@Conditional(FooCondition.class)
class Foo {
...
}
and define conditional logic for registering Foo component:
public class FooCondition implements Condition{
@Override
public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
// return [your conditional logic]
}
}
Conditional logic can be based on context, because you have access to bean factory. For Example when "Bar" component is not registered as bean:
return !context.getBeanFactory().containsBean(Bar.class.getSimpleName());
With Spring Boot (should be used for EVERY new Spring project), you can use these conditional annotations:
@ConditionalOnBean@ConditionalOnClass@ConditionalOnExpression@ConditionalOnJava@ConditionalOnMissingBean@ConditionalOnMissingClass@ConditionalOnNotWebApplication@ConditionalOnProperty@ConditionalOnResource@ConditionalOnWebApplicationYou can avoid Condition class creation this way. Refer to Spring Boot docs for more detail.