Design of a simple Command Interpreter

Question

Hi,
I have a scenario where a client pgm passes a command string to a Command Interpreter. There are several possible commands. The Command Interpreter accepts these command strings and makes API invocations on some other object.
Some Commands would need to return a value, whereas some others do not need to. These results need to be passed back to the client.
What should the Command Interpreter interface look like ?
For isntance, one command could be somethinfg like <getAllCustomers/>.Another command could be like <deleteCustomer name="foo"/>. The former would return a Document of all Customers. The second one does not return a value,but could throw an Exception.
I was thinking of a CommandInterface with a single method named processCommands(String commandXML(. But this would not work if I need to have different types od return values. Moreover, these APIs are more or less unrelated to each other. i.e. different from a Strategy pattern where there is a specific heirarchy/relationship.
Any ideas are welcome.
rgds.
Menon.

Answer 1

1) What should the Command Interpreter interface look like ?I would use the Command Pattern.
http://www.javaworld.com/javaworld/javatips/jw-javatip68-p2.html
You can combine this with the memento pattern.
Here is the interface that i use when implementing the command pattern.
* An Interface for a Command Object
* see Command Pattern [GOF:233]
* @author martin.spamer
* @version 0.1 - 14:08:58
public interface CommandInterface
   *  An Interface for a Command Object
   *  see Command Pattern [GOF:233]
   *  @param java.util.Properties
   *  @return java.util.Properties
  public java.util.Properties execute( java.util.Properties properties)
    throws CommandException ;
2) What is the best way to dispatch the XML requests to different API
invocations on a particulat object. For instance,I use a CommandFactory which I drive with an xml config file.
and drive it something like:
<actions command="CommandString" classname="uk.co...ClassName"/>