Java注解

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

/*
 * @Author:darrenqiao
 * */
@Retention(RetentionPolicy.RUNTIME) //存储到运行期
@Target(ElementType.FIELD)  //作用于字段
@Documented //可以被文档化
@Inherited //可以被注解的子类继承
//这里指定自定义注解的作用是检查值是在value为true时确保字段值仅为male和female中的一个
public @interface MyAnnotation {
    boolean value() default true;
}

import java.lang.reflect.Field;

/*
 * @Author:darrenqiao
 * */

//定义使用自定义注解的类
class Person {
    
    @MyAnnotation(value = true)
    public String gender;

    public Person(String gender) {
        super();
        this.gender = gender;
    }
}

//通过反射实现对注解的处理
class CheckAnnotation {
    public static boolean check(Object object) throws IllegalArgumentException, IllegalAccessException {
        Field[] fields = object.getClass().getDeclaredFields();
        for(Field field : fields) {
            String gender = (String) field.get(object);
            return gender.equals("male") || gender.equals("female");
        }
        return false;
    }
}

public class AnnotationTest {
    
    public static void main(String[] args) throws Exception {
        Person p = new Person("male");
        //调用注解进行检查
        System.out.println(CheckAnnotation.check(p));
    }

}