JAVA进阶-注解

注解元数据分为4部分分别为Target,Documented,Inherited,Retention:

/**
 * 	@author Lean  @date:2014-10-13  
 */
@Target(ElementType.METHOD)
public @interface WorkInProgress {}

/**
 * 	@author Lean  @date:2014-10-13  
 */
public class AnnotationSample {
	
	//当在字段中使用时:The annotation @WorkInProgress is disallowed for this location
	//@WorkInProgress
	private int age;
	
	@WorkInProgress
	public static boolean doSomeThing() {
		// TODO Auto-generated method stub
		return false;
	}
	
}

/**
 * 	@author Lean  @date:2014-10-13  
 */
@WorkInProgress
public class AnnotationSample {
	
	private int age;
	
	@WorkInProgress
	public static boolean doSomeThing() {
		// TODO Auto-generated method stub
		return false;
	}
	
	public static void main(String[] args) {
		AnnotationSample obj=new AnnotationSample();
		Class clazz=obj.getClass();
		WorkInProgress progress=(WorkInProgress) clazz.getAnnotation(WorkInProgress.class);
		System.out.println(clazz.getName());
		if (clazz.isAnnotationPresent(WorkInProgress.class)) {
			System.out.println("class Annotationed WorkInProgress!");
		}
		Method[] methods=clazz.getMethods();
		for (Method method : methods) {
			if (method.isAnnotationPresent(WorkInProgress.class)) {
				System.out.println("method Annotationed WorkInProgress!");
			}	
		}
	}
	
}


@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD,ElementType.TYPE})
@interface WorkInProgress {}

Documented>为加入注解的类书写文档,编译执行后执行javadoc的dos命令.就可以在该命令行

/**
 * 	@author Lean  @date:2014-10-13  
 */
@WorkInProgress
public class AnnotationSample {
	
	public static void main(String[] args) throws IllegalAccessException {
		AnnotationSample obj=new AnnotationSample();
		Class clazz=obj.getClass();
		if (clazz.isAnnotationPresent(WorkInProgress.class)) {
			System.out.println("class Annotationed WorkInProgress!");
		}
		Class childClass=AnnotationChildClass.class;
		if (childClass.isAnnotationPresent(WorkInProgress.class)) {
			System.out.println("child class Annotationed WorkInProgress!");
		}
		
	}
	
}


@Inherited
@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD,ElementType.TYPE})
@interface WorkInProgress {}


class AnnotationChildClass extends AnnotationSample{
	
}