【Java基础】注解

判断指定注解是否存在： boolean annotationPresent = method.isAnnotationPresent(MyAnnotation.class);

---

1.  自定义注解：MyAnnotation

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
    public @interface MyAnnotation {    
}

2、使用：MyAnnotationDemo 

@Deprecated
public class MyAnnotationDemo {
    @MyAnnotation
    public void print()
    {
        System.out.println("call print()");
    }
}

    3. 测试类

public class MyAnnotationDemoTest {
    public static void main(String[] args) throws Exception {
        Class<?> clazz = Class.forName("com.demo.annotation.MyAnnotationDemo");
        printClassInfo(clazz);

        Method[] methods = clazz.getMethods();
        printMethodInfo(clazz, methods);
    }

    private static void printClassInfo(Class<?> clazz) {       for (Annotation annotation : clazz.getAnnotations()) {
            System.out.println("class annotation name: " + annotation.toString());
        }
        
    }

    private static void printMethodInfo(Class<?> clazz, Method[] methods) throws Exception {       for (Method method : methods) {
            // 判断方法是否有指定的注解信息
                         boolean annotationPresent = method.isAnnotationPresent(MyAnnotation.class);
            if (annotationPresent) {
                System.out.println(method.getName());

                // 反射方式调用当前方法
                method.invoke(clazz.getConstructor(null).newInstance(null), null);
                method.invoke(clazz.newInstance(), null);
                for (Annotation annotation : method.getAnnotations()) {
                    System.out.println("method annotation: " + annotation.toString());
                }
            }
        }        
    }
}

    4. 测试结果：

class annotation name: @java.lang.Deprecated()

print
call print()
call print()
method annotation: @com.demo.annotation.MyAnnotation()