如何从Java中的子代为最终的静态变量赋值？

Question

Suppose we have a hierarchy like this:

class Parent {
  public static final String BASE_NAME = "parent";
  public static final String X_URL = BASE_NAME + "/x";
  public static final String Y_URL = BASE_NAME + "/y";
}

class ChildA extends Parent {
  public static final String BASE_NAME = "childA";
  public static final String X_URL = BASE_NAME + "/x";
  public static final String Y_URL = BASE_NAME + "/y";

  @RequestMapping(value= X_URL)
  public String renderXPage(){...}
}

as you can see the X_URL and Y_URL are repeating both in parent and child, if the child can feed in its own BASE_NAME to the parent, we can eliminate redundant repetition of those constants and then we can use them for the annotation value. How to do this in Java ?

Answer 1

There is no way to reliable achieve this.

You can have @RequestMapping annotation on class and put base part of URL there.

Example:

@RequestMapping("ChildA")
class ChildA {
  @RequestMapping(value= "x")
  public String renderXPage(){...}
}

renderXPage will handle "ChildA/x" URL.

Answer 2

Using the solution of @talex I came up with this neat solution:

public interface CommonRelativeUrls {
  String X_URL = "/x";
  String Y_URL = "/y";
}

public interface Entities {
  String CLASS_A = "class-a";
  String CLASS_B = "class-b";
  ...
}

@RequestMapping(value = Entities.CLASS_A)
public class ClassA implements CommonRelativeUrls {
  @RequestMapping(value= X_URL)
  public String renderXPage(){...}
}