Java class library technology core Sundrio :: Annotations :: Transform framework principle analysis
Sundrio :: Annotations :: Transform framework principle analysis
introduction:
In Java development, annotations are a mechanism for adding metadata for code elements (classes, methods, fields, etc.).Sundrio :: Annotations :: Transform is a Java -class library technology core, which provides a simple but powerful way to operate and convert the annotation.This article will in -depth analysis of the principles of Sundrio :: Annotations :: Transform, and explain its usage method through the Java code example.
1. Framework Overview:
Sundrio :: Annotations :: Transform framework is an open source item for processing and conversion annotations.It provides a set of APIs for reading, writing and modifying annotations, and supports annotations and conversion operations during compilation and runtime.This framework consists of the following core components:
1.1. AnnotionPropessor: In order to achieve the converting operation of the annotation, Sundrio :: Annotations :: Transform framework provides an AnnotionProcessor interface.Developers can implement the interface and register to the Java compiler or in the environment to perform customized transformation logic in processing annotations.
1.2. Model: Sundrio :: Annotations :: Transform framework to represent the specific structure of the annotation through the Model type.The Model type provides a set of API that allows us to read and modify the metadata of the annotation, such as the name, attributes, and values of the annotation.
1.3. Transformer: The Transformer interface defines the logic of annotation conversion.Developers can realize the interface and realize customized annotation conversion rules as needed.Through the Transformer interface, we can change the structure and content of the annotation during compilation or runtime.
2. Principles analysis:
Sundrio :: Annotations :: Transform framework working principle as follows:
2.1. Note interpretation: When the Java compiler or the environment encounters annotations, the Sundrio :: Annotations :: Transform framework will use the Model API to analyze the annotation as the corresponding Model object.The Model object represents the structure and content of the annotation, which can be used for further analysis and conversion operations.
2.2. Conversion processing: Once the annotation is analyzed as the Model object, the Sundrio :: Annotations :: Transform framework will process the registered AnnotionProcessor for processing.AnnotionProcessor implementation can modify, increase or delete the annotations according to the custom conversion rules.
2.3. Reconstruction: After processing, Sundrio :: Annotations :: Transform framework will generate rewriting annotations based on the processing results.These rewriting annotations can be used during compilation or running to support the modified annotation function.
3. Example code:
The following sample code demonstrates how to use Sundrio :: Annotations :: Transform framework to process and convey the annotation.
@Retention(RetentionPolicy.RUNTIME)
@Transformation(MyAnnotationTransformer.class)
public @interface MyAnnotation {
int value();
String message() default "";
}
public class MyAnnotationTransformer implements Transformer<MyAnnotation> {
@Override
public MyAnnotation transform(MyAnnotation original, Model model) {
int newValue = original.value() + 1;
String newMessage = original.message() + " (transformed)";
return model.createAnnotation(MyAnnotation.class)
.setValue(newValue)
.setMessage(newMessage)
.build();
}
}
public class Main {
public static void main(String[] args) {
MyAnnotation originalAnnotation = new MyAnnotationImpl(42, "Hello");
AnnotationProcessor<MyAnnotation> processor = new AnnotationProcessor<>();
MyAnnotation transformedAnnotation = processor.process(originalAnnotation);
System.out.println("Original annotation: " + originalAnnotation);
System.out.println("Transformed annotation: " + transformedAnnotation);
}
}
In the above code, we define a custom annotation `myannotation`, and add the`@transformation `annotation to it, specify the converter class` myannotationTransFormer`.The converter class implements the `Transformer <Myannotation>` interface, and rewrite the `Transform` method to modify the value of the annotation.In the `Main` class, we use the` AnnotationProcessor` to process and convey the original note.
4 Conclusion:
Sundrio :: Annotations :: Transform framework provides a simple and powerful way to handle and conversion annotations.Through the Model type, AnnotationProcessor and Transformer interfaces, developers can easily read, modify and rewrite annotations.The framework can play a role in compiling and running, providing greater flexibility and control for Java developers.
