Odysseus allows to implement additional constant variables. For this, the developer has to implement the interface IReplacementProvider from the bundle de.uniol.inf.is.odysseus.script.parser. The implementation has to be provided as a service, then. The interface is as follows:

public interface IReplacementProvider {
	public Collection<String> getReplacementKeys();
	public String getReplacementValue( String replacementKey );	
}

The method getReplacementKeys() has to return a collection of keys which the provider wants to offer. This will be called each time before a OdysseusScript-File is executed (so the list of available keys can change during run-time, if needed). The second method getReplacementValue() finally has to return the value for the given key. It is expected that since the provider provides the key, a value non-null is retured. If the second method return null, OdysseusScript uses an empty string (""). The method is called each time the key is used inside one OdysseusScript file.

Example

The developer wants to add the current date as a constant variable. The class could be implemented as follows:

// Example how to add constant variables
// Caution: This class has to be provided as a service!
public class DateReplacementProvider implements IReplacementProvider {
 
	// We provide one key here to get the currentDate in OdysseusScript
	@Override
	public Collection<String> getReplacementKeys() {
		List<String> keys = new ArrayList<String>();
		keys.add("currentDate");
		return keys;
	}
 
	// Each time, "currentDate" is used in one OdysseusScript-File, this
	// method is called
	@Override
	public String getReplacementValue( String replacementKey ) {
		// obsolete since we provide only one key
		if( replacementKey.equalsIgnoreCase("currentDate") ) {
			return new Date().toString();
		}
		
		return "";
	}
}