如何使用自定义注释在Spring Boot中隐藏带注释的字段？

Question

I have created custom annotations that I add to my Java class fields. When I create object of that class, I want my custom annotated fields to have value: null or "" or "customAnnotation" For example:

@Entity
public class User implements Serializable{

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "address_id")
private Long id;

@MyCustomAnnotation
private String firstname;

private String lastname;
....

And when I create the object somewhere in the project:

User user = new User();
user.setFirstname("John");
user.setLastname("Smith");

I want it to be:

String firstname = user.getFirstname() // firstname is "" or null
String lastname = user.getLastname()   // lastname is "Smith"

How to create method that will find all annotated fields in all classes in the project and do the same for all of them? Where to store this method? I am working on the Maven, Spring Boot project.

Answer 1

At some point in your code you will have to implement something like this:

Class<User> obj = User.class;

if (obj.isAnnotationPresent(MyCustomAnnotation.class)) {
  //your business logic
}

Sensible places for something like this would be either immediately when creating users, when getting users (for whatever reason the annotation is being used) or at an interval in a timed routine.

edit: See this tutorial: https://www.mkyong.com/java/java-custom-annotations-example/