是否可以将类表示为字段？

Question

I need to retrieve annotation inside a class. Imagine this:

@MyAnnotation(MyClass.class)
public Table myTable;

What I need to do is to initialize a variable inside class Table from a class inside the annotation. The question is, how can I represent Table class as a field in order to retrieve a value from annotation like this:

Field tableField = ? // Here I should somehow cast 'this' to type Field
Class annotationValue = tableField.getAnnotation(MyAnnotation.class).value();

Is it possible to cast a Table class into a Field class somehow?

Answer 1

If you simply want access to the myTable field as a Field object, you would write:

Field tableField = Enclosing.class.getDeclaredField("myTable");

where Enclosing is the name of the class in which the myTable field is declared.

Answer 2

Field tableField = ? // Here I should somehow cast 'this' to type Field

An annotation doesn't depend on "this" , that is an instance of the class, but depends on the the class itself.

The question is, how can I represent Table class as a field in order to retrieve a value from annotation like this:

By reflection.

Suppose you have the class :

public class MyObject{
  @MyAnnotation(MyClass.class)
  public Table myTable;
}

You could retrieve the field in this way :

Field tableField = MyObject.class.getDeclaredField("myTable"); 

And then use the field to retrieve the value associated to the annotation:

Class<?> annotationValue = tableField.getAnnotation(MyAnnotation.class).value();