Understanding Java Meta-Annotations: @Target, @Retention, @Documented, and @Inherited

Java meta‑annotations are annotations that annotate other annotations, allowing developers to define an annotation's retention policy, applicable targets, documentation inclusion, and inheritance behavior.

The four core meta‑annotations are @Retention , @Target , @Documented , and @Inherited , each serving a specific purpose.

@Target

@Target specifies where an annotation can be applied, with possible ElementType values such as TYPE , FIELD , METHOD , PARAMETER , CONSTRUCTOR , LOCAL_VARIABLE , ANNOTATION_TYPE , and PACKAGE .

Example:

import java.lang.annotation.ElementType;
import java.lang.annotation.Target;

@Target({ElementType.TYPE, ElementType.FIELD, ElementType.METHOD})
public @interface MyAnnotation {
    // ...
}

In this example, @Target allows MyAnnotation to be used on classes, fields, and methods.

@Retention

@Retention defines how long the annotation is retained: SOURCE , CLASS , or RUNTIME .

Example:

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
    // ...
}

Here the annotation is retained at runtime and can be accessed via reflection.

@Documented

@Documented indicates that the annotation should appear in generated Javadoc.

Example:

@Documented
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
    // ...
}

This makes the annotation visible in Javadoc.

@Inherited

@Inherited allows the annotation to be inherited by subclasses.

Example:

import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

@Inherited
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {
    // ...
}

Subclasses of a class annotated with @MyAnnotation will inherit the annotation.

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