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@ComponentScan

Popularity：252 ℃/2024-08-12 19:14:12

@ComponentScan is an annotation for the Spring Framework that allows developers to specify which package or sub-package under a package Spring should scan for components (such as the@Component、@Service、@Repository(and other annotated labeled classes). By using the@ComponentScanThe developer can automate the registration of these components, enabling them to be managed by the Spring container.

grammatical

@ComponentScan The basic syntax for annotations is as follows:

@ComponentScan(basePackages = "", useDefaultFilters = false, includeFilters = {@Filter(type = , classes = {})}, excludeFilters = {@Filter(type = , classes = {})})

causality

  • basePackages: Used to specify which packages Spring should scan. This property can accept either an array of strings or a dot-separated package path.
  • useDefaultFilters: If set totrue, then the default filter is used, i.e., scanning for all filters with a@Component、@Service、@Repositorycap (a poem)@Controllerannotated class. If set tofalse, then the default filter will not be used.
  • includeFilters: Used to specify which types of classes Spring should include. This property can accept an array of filters, each containing a type and a class. For example.@Filter(type = , classes = {}) Indicates that only scans withMyAnnotationannotated classes.
  • excludeFilters: Used to specify which types of classes Spring should not include. This attribute is similar to theincludeFiltersSimilarly, an array of filters can be accepted.

typical example

The following is an example of how to use the@ComponentScan Examples of:

@SpringBootApplication
@ComponentScan(basePackages = "", useDefaultFilters = false, includeFilters = {@Filter(type = , classes = {})}, excludeFilters = {@Filter(type = , classes = {})})
public class MyApplication {
    public static void main(String[] args) {
        (, args);
    }
}

In this example, Spring will scan thepackage and its subpackages, and only includes packages withMyAnnotationannotation and exclude classes withMyAnnotationannotated classes.

application scenario

  • Automated Component Registration: By@ComponentScanSpring can automatically scan and register classes with specific annotations, thus simplifying the process of component registration.
  • microservices architecture: In a microservice architecture, each service may have multiple modules, each with its own set of components. Using the@ComponentScan Modular development can be achieved by easily defining your own scan path in each module.

caveat

  • @ComponentScan annotation is typically used on the main class of a Spring Boot application so that Spring Boot automatically scans for the package in which the class resides and its subpackages.
  • If you need to scan for a specific module or package, you can set the@ComponentScan annotation is placed on the entry class of that module or package.
  • If you need to exclude certain packages or classes, you can do so by setting theexcludeFiltersattribute to realize it.
    In conclusion.@ComponentScan is an important annotation in the Spring Framework that allows developers to automate the registration of classes with specific annotations, thus simplifying the process of component registration. By using this annotation wisely , you can achieve modular development and microservices architecture .
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