java 类,变量,方法上注解值的获取

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首先定义三个注解类, 分别适用于类,成员变量, 方法

@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)public @interface LeiMode {public int value() default 1;}

@Target(ElementType.FIELD)@Retention(RetentionPolicy.RUNTIME)public @interface FiledMode {public int value() default 1;}

@Target(ElementType.METHOD)@Retention(RetentionPolicy.RUNTIME)public @interface TreahMode {public int value() default 1;}

然后,定义一个类,使用了注解

@LeiMode(5)public class AnnotationDemo {@FiledMode(10)private int itest;@TreahMode()private void test(){}}

1.获取类上的注解值

LeiMode annotation = AnnotationDemo.class.getAnnotation(LeiMode.class);System.out.println(annotation.value());

2.获取所有变量,并获取指定方法上的注解信息

Field[] fields = AnnotationDemo.class.getDeclaredFields();Field field = null;for(Field f : fields){if(f.getName().equals("itest")){field = f;break;}}FiledMode annotation = field.getAnnotation(FiledMode.class);System.out.println(annotation.value());

3.获取指定变量上的注解信息

Field field = AnnotationDemo.class.getDeclaredField("itest");FiledMode annotation = field.getAnnotation(FiledMode.class);System.out.println(annotation.value());

4.获取所有方法,并获取指定方法上的注解信息

Method[] methods = AnnotationDemo.class.getDeclaredMethods(); //可以获取私有方法和公有方法, getMethods() 获取公有方法Method meth = null;for(Method method : methods){if(method.getName().equals("test")){meth = method;break;}}Annotation annotation = meth.getAnnotations()[0];TreahMode mode = (TreahMode) annotation;System.out.println(mode.value());

5.获取指定方法上的注解信息

Method method = AnnotationDemo.class.getDeclaredMethod("test", null);//可以获取私有方法和公有方法System.out.println(method);Annotation[] annotations = method.getAnnotations();Annotation annotation = annotations[0];System.out.println(annotation);TreahMode mode = (TreahMode) annotation;System.out.println(mode.value());

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