springboot-component-scan

Overview of basic features of @ComponentScan

preface

By default in spring boot applications the main package (package where the @SpringBootApplication is defined) is scanned in search of components.

Sometimes we want to scan packages outside the main package.

project description

structure

In this project:

• main package: com.example.springbootcomponentscan
  • inner package: com.example.springbootcomponentscan.insiders1
    • @Component: Insider class
• outside main package: outsiders1
  • @Component: Outsider class

solution

We have two options:

• not type safe

  @ComponentScan(basePackages = {"com.example.springbootcomponentscan", 
          "outsiders1"})
  

  documentation:

  Base packages to scan for annotated components.

  @AliasFor("value")
  String[] basePackages() default {};
  

• type safe

  @ComponentScan(basePackageClasses = {ScanOutsiders1.class,
          SpringbootComponentScanApplication.class})
  

  where ScanOutsiders1.class is a special no-op marker class recommended in documentation:

  Type-safe alternative to basePackages for specifying the packages to scan for annotated components. The package of each class specified will be scanned. Consider creating a special no-op marker class or interface in each package that serves no purpose other than being referenced by this attribute.

  Class<?>[] basePackageClasses() default {};