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A feature introduced in CookXml since 2.0 is the ability to handle exceptions. This feature allows developers to intercept these exceptions and deal with them, by logging, suppressing, or generating an error. This tutorial basically teaches how it works inside CookXml.
Installing ExceptionHandler
ExceptionHandler can be set or get on a global basis by calling CookXml.setDefaultExceptionHandler(ExceptionHandler defaultExceptionHandler) and CookXml.getDefaultExceptionHandler (). This default handler is called when individual CookXml objects do not have their ExceptionHandler set.
Individual CookXml ExceptionHandler can be set/get by calling CookXml..setExceptionHandler(ExceptionHandler exceptionHandler) and CookXml.getEceptionHandler (), respectively.
Exceptions Intercepted
The following table shows the major exceptions intercepted in chronological ordering.
| Exception | Description |
|---|---|
| NoCreatorException | This exception is thrown by DecodeEngine when it starts to process a tag and this tag is not found in the tag library. |
| CreatorException | This exception is thrown by DecodeEngine when the creator for the tag is called and an exception is generated. |
| NoAdderException | This exception is generated when DecodeEngine couldn't find an Adder in the tag library for the given parent and child. |
| AdderException | This exception is thrown when an object is added to the parent object. Depending on how the creator for the object sets things up, Adder maybe called before or after the object is fully configured. |
| NoSetterException | This exception is generated when DecodeEngine couldn't find a setter in the tag library for the given tag and attribute. In most CookXml setup though, this exception should never be generated. |
| SetterException | This exception is thrown when a setter is called to set the attribute of the object created. |
| VarLookupException | This exception is thrown when DecodeEngine fails to read/write a variable. |
There are other types of exceptions as well.
| Exception | Description |
|---|---|
| NoDefaultConstructorException | This exception is thrown by DefaultCreator at library setup phase when no default constructor is found for a given class. |
| ConverterException | This exception is thrown whenever a converter fails to convert a string to a type that is usable by the target object. This exception is usually embeded within SetterException. |
Finally, if an exception occurs in CookXml.xmlDecode function, it will not be wrapped around by CookXmlException.
What to Do with the Exception
Well, here is a list of things off the top of my head.
- Ignore it. This is the case when you want CookXml to decode as much as possible.
- Generate a CookXmlException. This is the case when you want CookXml to immediately return upon an error.
- In deciding what to do with an exception, you can create logs, dump the exception to screen, etc.
