An object oriented mechanism is disclosed that allows class replacement that is based on a specified processing context by replacing existing configuration data with new configuration data within an existing object oriented program. The configuration data is preferably stored in a data structure external to the class definitions to allow modifying the classes without re-compiling the class code. The configuration data includes multiple entries, where each entry is a key-value pair. The key includes information relating to the processing context, and the value includes information relating to the class that corresponds to the key. When an instance of a class needs to be created, the context information is retrieved, a key is generated from a combination of the class information and the context information, and the context-sensitive key is used to retrieve the corresponding class configuration data from the data structure that specifies a particular class. An object that is an instance of the specified class is then created. By generating a key that is context-specific, configuration data for a class can be scoped to a particular processing context, thereby providing context-based class replacement.