注解初定义

1.定义

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

@Retention(RetentionPolicy.RUNTIME) //作用时间，是运行时，其他有编译时等
@Target(ElementType.METHOD) //作用的对象，这里是方法，也可以是类和属性，参数
public @interface SampleAnnotation { 
//注解名称是SampleAnnotation，需要用@interface定义注解
//方法
	String value();
}

 2. 使用

public class SampleAnnatationUser {
//这些值会被注解的value方法得到
	@SampleAnnotation("oh my god ,i put a value in it")
	public void use() {
		System.out.println("success,i use");
	}

	public void notUse() {
		System.out.println("fail,i am not use");
	}
}

 3.实现，无反射不注解

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class SampleMain {
	public static void main(String[] args) {
		SampleAnnatationUser sampleAnnatationUser = new SampleAnnatationUser();
		for (Method method : sampleAnnatationUser.getClass().getMethods()) {
			if (method.isAnnotationPresent(SampleAnnotation.class)) {
				try {
					SampleAnnotation  annotation = method.getAnnotation(SampleAnnotation.class);
					System.out.println(annotation.value());
					method.invoke(sampleAnnatationUser, null);
				} catch (IllegalArgumentException e) {
					e.printStackTrace();
				} catch (IllegalAccessException e) {
					e.printStackTrace();
				} catch (InvocationTargetException e) {
					e.printStackTrace();
				}
			}
		}
	}
}

 

 4.结果

oh my god ,i put a value in it
success,i use