Research on the technical principles of JATBRAINS JAVA Annotation's technical principles in the Java class library

JetBrains Java Annotations framework is a technology used to add metad data to Java code. This framework provides developers with a simple and flexible way to expand and customize the Java class library.This article will study the technical principles of Jetbrains Java Annotations framework and provide some Java code examples. ## What is Jetbrains Java Annotations framework? Java Annotations is a way to contain metadata in the Java source code.Metal data is information about program elements (such as classes, methods, fields, etc.), but it will not affect the actual execution of the program.Annotations can be used to write documents, dynamically generate code, and provide additional compilation.JetBrains Java Annotations framework is a framework developed by Jetbrains to simplify and provide more powerful AnnotationS features. ## Jetbrains Java Annotations Framework The core principle of the Jetbrains Java Annotions framework is to define custom annotations using meta -nNOTATION.Metropolitan annotations are an annotation that is used to comment on other annotations.Through meta -annotations, the scope, goals and characteristics of custom annotations can be defined. The JetBrains Java Annotations framework provides some built -in meta -injection, such as `@Retention`,@Target` and`@Repeatable` to define the retaining strategies, goals and repetitiveness of customized annotations.By applying these element annotations to custom annotations, developers can more flexibly control the behavior of custom annotations. In addition to the meta -note, the Jetbrains Java Annotations framework also provides support from the Annitation Processor.Annotation processor is a tool for processing and analyzing annotations.By writing a customized annotation processor, developers can associate annotations with specific behaviors or logic.For example, the annotation processor can be used to generate code and perform additional compilation or generate documents. ## Jetbrains Java Annotations Framework Code Example Below is a simple example, demonstrating how to use Jetbrains Java Annotations framework to create and use custom annotations: import java.lang.annotation.*; @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.TYPE) public @interface MyAnnotation { String value(); } @MyAnnotation("MyClass") public class MyClass { // some code } In the above example, we define a custom annotation named `@myannotation` and apply it to the` MyClass` class.Through the `@RETENTION (RetentionPolicy.runtime)` yuan annotation, we designate the annotation that the annotation is still available at runtime.And the `@Target (Elementtype.type)` yuan annotation specifies the target of the annotation as a class. You can access the annotations and information through reflection at runtime: import java.lang.annotation.*; @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.TYPE) public @interface MyAnnotation { String value(); } @MyAnnotation("MyClass") public class MyClass { public static void main(String[] args) { Class<?> myClass = MyClass.class; MyAnnotation annotation = myClass.getAnnotation(MyAnnotation.class); if (annotation != null) { System.out.println (annotation.value ()); // Output: MyClass } } } In the above example, we use the `Getannotation ()" method to obtain an instance of the `Myannotation" and access the value of the annotation through this instance. ## in conclusion This article studies the technical principles of Jetbrains Java Annotations framework, and provides some Java code examples.JetBrains Java Annotations framework provides developers with a convenient and flexible way to expand and customize the Java class library by using meta -injection and annotation processors.By understanding Jetbrains Java Annotations framework, developers can better use Annotations to improve the readability and scalability of the code.