What is the best way to organize queue in R/3?

Question

Hi,
I'm in a middle of a project, where I should implement queue in order to sync data between 2 systems - r/3 and legasy one. I have few user exits (or bussiness events), which could be rised concurently in time, and I need only 1 instance of the sync module to run at a time. Well, I know the technique to prevent a program from running in multiple processes, and I have an idea how to organize a queue (my idea is to use transparent table to track actions which should be sync-ed), but there allways are some 'bottlenecks' that should be considered in such an implementation.
That's why it might be of great help if someone could share his/her knowledge on this topic or point me to the right paper/docu, if available.
I just don't want to reinvent the wheel, if possible
Many thanks in advance.
Regards,
Ivaylo Mutafchiev
SAP BC Consultant - ABAP developer
Varna Bussiness Services Ltd.

Answer 1

I'm not sure why you don't just invent a generic data structure (e.g., table name, list of column names and aliases of column names) such as:
class QueryMetaData {
  private final String tableName;
  private final String[] columnNames;
  private final String[] columnAliases;
}Read into the above structure from a properties file, database table, etc. You can store meta-data itself in places other than enum constants, particularly if would like to change the meta-data without requiring a new build of your application.
That having been said, WRT to your specific questions:
(1) Finally, from your experience, what is the best way to organize all that stuff?See above
(2) I have heard that smart Java programmer should avoid using the enums by any means. Do you agree?Enums are better than simple constants using int or String or something similar. If there are known, discrete values unlikely to change frequently, I see no issues with an enum. They improve the readability of code, and there are enough syntactic sugar features in the language (switch statements come to mind) to make them appealing.
(3) Generally what will you prefer when creating a constant which has two values: two final Integers or enum?
See above. Enums were introduced (in large part) to do away with storing constants as integers.
- Saish