You may have noticed that none of the examples in this chapter show the string or object values passed to the methods being checked to see if they are null or of the wrong type. The reason is that it is not necessary. The client infrastructure guarantees that no method will be called with a null value and that no conversion operation will be invoked for an object that is not compatible with the class returned by the converter plug-in's getDomainClass method. Your custom code need never include any error handling and reporting code for these checks.