Exception Management
Last updated
Last updated
The BoxLang language also provides you with a traditional approach to deal with error handling at the code block level. This is usually a trio of constructs:
try
: The try block allows you to demarcate the code to test if it fails or passes ()
catch
: The catch block is executed when the try block fails ()
finally
: The finally block executes no matter if the try fails or passes. It is guaranteed to always execute. ()
Basically, a try and catch statement attempts some code. If the code fails, BoxLang will do whatever is in the exception to try to handle it without breaking. Of course, many different types of exceptions can occur, which should sometimes be handled in a different manner than the others.
The catch construct can take an any
or a custom exception type declared by the BoxLang engine, Java code or custom exceptions within your code. This is a great way to be able to intercept for specific exception types and address them differently.
Custom exception types are defined by you the programmer and they can also be intercepted via their defined name. Let's say that the exception type is "InvalidInteger
" then you can listen to it like this:
The throw()
function or tag has several attributes:
Type : A custom or BoxLang core type
Message : Describes the exception event
Detail : A detailed description of the event
errorCode : A custom error code
extendedInfo : Custom extended information to send in the exception, can be anything
object : Mutually exclusive with the other attributes, usually another exception object or a raw Java exception type.
for a list of native exceptions thrown by the BoxLang Core Runtime. Modules and additional runtimes may also contribute their own native exceptions.
Now that you have seen how to listen to exceptions, let's discover the throw
construct used to throw a developer-specific exception. ()
The rethrow
construct allows you to well, rethrow
the active exception by preserving all of the exception information and types. Usually you use rethrow
within a catch block after you have done some type of operations on the incoming exception. ()