Best way to define error codes/strings in Java?

Question

I am writing a web service in Java, and I am trying to figure out the best way to define error codes and their associated error strings. I need to have a nu

Answer 1

As far as I am concerned, I prefer to externalize the error messages in a properties files. This will be really helpful in case of internationalization of your application (one properties file per language). It is also easier to modify an error message, and it won't need any re-compilation of the Java sources.

On my projects, generally I have an interface that contains errors codes (String or integer, it doesn't care much), which contains the key in the properties files for this error:

public interface ErrorCodes {
    String DATABASE_ERROR = "DATABASE_ERROR";
    String DUPLICATE_USER = "DUPLICATE_USER";
    ...
}

in the properties file:

DATABASE_ERROR=An error occurred in the database.
DUPLICATE_USER=The user already exists.
...

Another problem with your solution is the maintenability: you have only 2 errors, and already 12 lines of code. So imagine your Enumeration file when you will have hundreds of errors to manage!