What is the principle behind the implementation of Spri…

The implementation principle of Spring annotation mainly involves two aspects: scanning annotations and handling annotations.

1. Annotation scanning: Spring utilizes the reflection mechanism to scan for annotations on classes and methods. With Java’s reflection mechanism, metadata information of classes such as class name, method name, field name, and annotations on classes and methods can be accessed.
2. Annotation processing: Spring uses annotation processors to parse and handle annotations. An annotation processor is a special class that implements the annotation processor interface defined by the Spring framework. The annotation processor will execute corresponding logic based on the definition and usage of the annotation. For example, for the @Controller annotation, the annotation processor will instantiate the class marked with this annotation as a Controller object and register it with the Spring container; for the @Autowired annotation, the annotation processor will automatically inject the required Bean objects.

In general, the implementation principle of Spring annotations is to scan annotations on classes and methods through reflection, and then parse and process them using annotation processors. This approach allows developers to easily implement common functionalities such as dependency injection and transaction management through simple annotations, thereby improving the readability and flexibility of the code.