Explore the working principle of Sundrio :: Annotations :: Transform framework in the Java class library

Sundrio :: Annotations :: Transform is a framework in a Java library to achieve the function of processing and conversion of annotations in the Java program.This article will explore the working principles of Sundrio :: Annotations :: Transform framework, and provide some Java code examples to illustrate its usage. First, we need to understand what annotations are.Note is a metadata in Java, which can encode the structure, behavior or other information in the code in the code.The annotation can be used to provide static inspection of the compiler, processing during runtime or for code generation. The main function of the mainrio :: Annotations :: Transform framework is the annotation of the processing and conversion of the Java program.Below we will introduce its working principles in detail. 1. Generate the annotation processor: When using Sundrio :: Annitations :: Transform framework, we first need to write an annotation processor to process the logic of specified annotations.The annotation processor is a class that realizes javax.annotation.processing.processor interface. It uses javax.annotion.processing.supportedanNotationTypes and javax.annotation.processin through the implementation class. G.SupportedSourceVersion annotation to specify the type and support of the annotations to be processedSource code version. 2. Use the annotation processor processing annotation: Once the annotation processor is created, we can use it in the project to process the annotation.When compiling the Java program, the annotation processor will be automatically triggered. By obtaining the metadata information of the annotation processor, it will be able to find and process the corresponding annotations. 3. Get the annotation information: The annotation processor can obtain the metadata information of the annotation through the reflection mechanism of Java.It can access the member variables, methods, and other attributes on the annotation in order to perform corresponding logical processing. 4. Develop logical processing: Once the annotation processor obtains the annotation information, it can perform the corresponding logical processing.This may include generating new Java code, modifying existing code, or performing any other code conversion and processing operations. Below is a simple example code that shows how to use Sundrio :: Annotations :: Transform framework to create a custom annotation processor and process specified annotations: import javax.annotation.processing.AbstractProcessor; import javax.annotation.processing.ProcessingEnvironment; import javax.annotation.processing.RoundEnvironment; import javax.annotation.processing.SupportedAnnotationTypes; import javax.annotation.processing.SupportedSourceVersion; import javax.lang.model.SourceVersion; import javax.lang.model.element.Element; import javax.lang.model.element.TypeElement; import java.util.Set; @SupportedAnnotationTypes("com.example.MyAnnotation") @SupportedSourceVersion(SourceVersion.RELEASE_8) public class MyAnnotationProcessor extends AbstractProcessor { @Override public synchronized void init(ProcessingEnvironment processingEnv) { super.init(processingEnv); } @Override public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) { // Traversing all the annotation elements for (TypeElement annotation : annotations) { // Find elements that contain specified annotations Set<? extends Element> annotatedElements = roundEnv.getElementsAnnotatedWith(annotation); for (Element element : annotatedElements) { // Treatment of annotation logic System.out.println("Found element with MyAnnotation: " + element); } } return true; } } In the above code, we first created a custom annotationprocessor inherited from ABSTRACTPROCESOR.Specify the type of annotations to be processed by using @SupportedannotationTypes annotation on the annotation processor. This is com.example.myannotation.At the same time, we also use @SupportedSourceVersion to specify the source code version specified. In the process method, we can get elements containing specified annotations and perform corresponding logical processing.Here we simply print out elements containing specified annotations. The above is the working principle of Sundrio :: Annotations :: Transform framework and some Java code examples.By understanding the working principle of this framework, we can more flexibly handle and transform the annotations in the Java program to achieve more efficient development and code generation.