java怎么通过反射给成员变量添加自定义注解,请写出示例代码和测试用例,注意要用到反射哦.
public class Test {
public String name;
public int age;
}
public class Main {
public static void main(String[] args) throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
// 获取Test类
Class<Test> clazz = Test.class;
// 获取name字段
Field nameField = clazz.getDeclaredField("name");
// 将@MyAnnotation注解添加到name字段
nameField.setAnnotation(MyAnnotation.class.getConstructor(String.class).newInstance("name annotation"));
// 获取age字段
Field ageField = clazz.getDeclaredField("age");
// 将@MyAnnotation注解添加到age字段
ageField.setAnnotation(MyAnnotation.class.getConstructor(String.class).newInstance("age annotation"));
// 测试获取注解
Test test = new Test();
MyAnnotation nameAnnotation = nameField.getAnnotation(MyAnnotation.class);
System.out.println(nameAnnotation.value()); // name annotation
MyAnnotation ageAnnotation = ageField.getAnnotation(MyAnnotation.class);
System.out.println(ageAnnotation.value()); // age annotation
}
}
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
@interface MyAnnotation {
String value();
}