Java Annotation Facility:
1.a syntax for declaring annotation types
2.a syntax for annotating declarations
3.APIs for reading annotations
4.a class file representation for annotations
5.an annotation processing tool
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Test { }
Annotation Declaration
1.Annotation type declarations are similar to normal interface declarations
2.An at-sign (@) precedes the interface keyword.
3.Each method declaration defines an element of the annotation type.
4.Method declarations must not have any parameters or a throws clause.
5.Return types are restricted to primitives, String, Class, enums, annotations, and arrays of the preceding types.
6.Methods can have default values.
Annotating Declarations
@Test
public static void m5() { }
Annotation Processing Tool
You can write code to process the declarations where declared.
for (Method m : Class.forName(object).getMethods()) {
if (m.isAnnotationPresent(Test.class)) {
Test a = f.getAnnotation(Test.class);
System.out.println(m.getName() +" is annotated with value of " + a.value());
}
}