自定义注解的使用

1. 注解类

@Target({
    ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface MyMessage {
    

    String name() default "sam";

    int num() default 0;

    String desc();

}

2. 实体类

public class AnnotationTest {
    

    @MyMessage(num = 10, desc = "参数a")
     int a;
    
     int b;
    
    @MyMessage(name = "Sam test", desc = "测试方法test")
    public void test(String a) {
    
        System.out.println(a);
    }
    @MyMessage(name = "Sam test", desc = "测试方法test")
    public void  test111(String a,String b){
    
        System.out.println("fdsfdsafa");
    }
}

3. 注解解析类

public class MyMessageProcessor {
    
    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, InvocationTargetException, NoSuchMethodException {
    
// 获取class类
        Class<?> aClass = Class.forName("com.AnnotationTest");
// 获取所有属性
        Field[] declaredFields = aClass.getDeclaredFields();
// 实例化
        AnnotationTest o = (AnnotationTest)aClass.newInstance();
// 便利属性
        for (Field declaredField : declaredFields) {
    
            if(declaredField.isAnnotationPresent(MyMessage.class)){
    
// 得到注解的信息
                MyMessage myMessage = declaredField.getAnnotation(MyMessage.class);
// 获取注解上面的所有值
            System.out.println("name:" + myMessage.name() + " num:" + myMessage.num() + " desc:" + myMessage.desc());
// 如果是私有属性，打破壁垒
               declaredField.setAccessible(true);
// 给属性设置值
                declaredField.set(o,myMessage.num());
            }


        }
        //获取类中的方法
        Method[] methods = aClass.getMethods();
        //遍历方法
        for (Method method : methods) {
    
            //判断方法是否带有MyMessage注解
            if (method.isAnnotationPresent(MyMessage.class)) {
    
                // 获取所有注解 method.getDeclaredAnnotations();
                // 获取MyMessage注解
                MyMessage myMessage = method.getAnnotation(MyMessage.class);
                if (method.getName().equals("test")){
    
// 进行方法的调用 ，注意参数的问题
                    /** * 如果知道方法的名字，可以这样写 * Method test111 = aClass.getMethod("test111", String.class, String.class); * test111.invoke(o,myMessage.name(),myMessage.name()); */
                    method.invoke(o,myMessage.name());
                }

                System.out.println("name:" + myMessage.name() + " num:" + myMessage.num() + " desc:" + myMessage.desc());
            }
        }
    }
}