java 注解的属性

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD,ElementType.TYPE})
public @interface ItcastAnnotation {
	
	//注解的属性
	String color() default "bule";
	
	//当属性 为 value 时 ,并且只有该属性没有默认值时  可简单写成 ("xxx")
	String value();
	
	//数组类型的属性
	int[] arrayAttr() default {1,3,5};
	
	//枚举类型属性
	DayEnum day() default DayEnum.MONDAY;
	
	//注解类型属性
	MetaAnnotation annotationAttr() default @MetaAnnotation("lh");
}

public class ItcastProxyClass {

	/**
	 * 如果数组属性只有一个值，可省略{}
	 * 
	 * @param args
	 */
	@ItcastAnnotation(color = "red", value = "abc",arrayAttr=2)
	public static void main(String[] args) {
		
		boolean present = SelfAnnotationTest.class.isAnnotationPresent(ItcastAnnotation.class);
		if(present) {
			
			ItcastAnnotation annotation = SelfAnnotationTest.class.getAnnotation(ItcastAnnotation.class);
			
			System.out.println(annotation.color());
			System.out.println(annotation.value());
			System.out.println(annotation.arrayAttr().length);
			System.out.println(annotation.day().next(DayEnum.MONDAY));
			System.out.println(annotation.annotationAttr().value());
			
		}
	}
}

@ItcastAnnotation(value="abc",arrayAttr= {1,2,3})
public class SelfAnnotationTest {
	
}

public @interface MetaAnnotation {
	String value();
}

public enum DayEnum {
	MONDAY,
	SUNDAY;
	
	public DayEnum next(DayEnum day) {
		if(day == MONDAY) {
			return SUNDAY;
		}else {
			return MONDAY;
		}
	}
}