Detailed explanation of technical principles of Sundrio :: Annotations :: Transform
Annotations is a characteristic of the Java language, which allows developers to embed metadata information in the code.The Transform framework technology is an annotation -based technology that is used to convert and enhance the code during the compilation period.
The principle of the Transform framework technology is to use the Annotion Processor function, as well as the Java reflex mechanism with the compiler provided by the Java compiler.Developers can customize the annotation and write the corresponding annotation processor to handle these annotations.
First of all, we need to define an annotation to identify code fragments that need to be converted.For example, we can define a @transform annotation:
@Retention(RetentionPolicy.SOURCE)
@Target(ElementType.METHOD)
public @interface Transform {
// Customize the attributes of the annotation
}
Then, we can use the annotation in the code.
public class MyClass {
@Transform
public void processData() {
// Convert code
}
}
Next, we need to write an annotation processor to analyze and processes the @Transform annotation.The annotation processor can be implemented by extending the ABSTRACTPROCESOR class:
@SupportedAnnotationTypes("com.example.Transform")
@SupportedSourceVersion(SourceVersion.RELEASE_8)
public class TransformAnnotationProcessor extends AbstractProcessor {
@Override
public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
for (Element element : roundEnv.getElementsAnnotatedWith(Transform.class)) {
// Treatment of conversion logic
}
return true;
}
}
The annotation processor needs to use the @SupPortedannotationTypes annotation specified to specify the type of annotation to be processed, and @Supportedsourceversion annotation is used to specify the Java version used to specify support.
Finally, we need to use the Javac command during the compilation period to trigger the execution of the annotation processor.You can specify the category name of the annotation processor by using -processor parameters:
javac -processor com.example.TransformAnnotationProcessor MyClass.java
After executing this command, the annotation processor will process the method of @Transform notes in the code, and the conversion and enhancement will be converted as needed.
In summary, the Transform framework technology uses Java's compilation of the annotation processor and reflection mechanism. By customized annotations and the combination of the annotation processor, the function of conversion and enhancement of the code during the compilation period is realized.This technology can help developers write simple, easy -to -maintain code, and improve the performance and scalability of code.
