driver-legacy/src/main/com/mongodb/DBCollection.java
public void setInternalClass(final String path, final Class<? extends DBObject> aClass) {
        setObjectFactory(objectFactory.update(aClass, asList(path.split("\\."))));
    }
public void setInternalClass(final String path, final Class<? extends DBObject> aClass) {
        setObjectFactory(objectFactory.update(aClass, asList(path.split("\\."))));
    }
Sets the internal class for the given path in the document hierarchy

@param path   the path to map the given Class to
@param aClass the Class to map the given path to