How to scan multiple paths using the @ComponentScan annotation?

Question

I'm using Spring 3.1 and bootstrapping an application using the @Configuration and @ComponentScan attributes.

The actual start is done with

new AnnotationConfigApplicationContext(MyRootConfigurationClass.class); 

This Configuration class is annotated with

@Configuration @ComponentScan("com.my.package") public class MyRootConfigurationClass 

and this works fine. However I'd like to be more specific about the packages I scan so I tried.

@Configuration @ComponentScan("com.my.package.first,com.my.package.second") public class MyRootConfigurationClass 

However this fails with errors telling me it can't find components specified using the @Component annotation.

What is the correct way to do what I'm after?

Thanks

Answer 1

@ComponentScan uses string array, like this:

@ComponentScan({"com.my.package.first","com.my.package.second"}) 

When you provide multiple package names in only one string, Spring interprets this as one package name, and thus can't find it.

Answer 2

There is another type-safe alternative to specifying a base-package location as a String. See the API here, but I've also illustrated below:

@ComponentScan(basePackageClasses = {ExampleController.class, ExampleModel.class, ExmapleView.class}) 

Using the basePackageClasses specifier with your class references will tell Spring to scan those packages (just like the mentioned alternatives), but this method is both type-safe and adds IDE support for future refactoring -- a huge plus in my book.

Reading from the API, Spring suggests creating a no-op marker class or interface in each package you wish to scan that serves no other purpose than to be used as a reference for/by this attribute.

IMO, I don't like the marker-classes (but then again, they are pretty much just like the package-info classes) but the type safety, IDE support, and drastically reducing the number of base packages needed to include for this scan is, with out a doubt, a far better option.