Exception management system

Introduction

All exceptions that are not catched by your code are handled by the __ErrorHandler class.

Once the __ErrorHandler receives an exception, it perform the following operations:

• Logs the exception (if applicable by settings in the lion.ini file)
• Executes a logic associated to the type of exception (just for exceptions subclassing the __LionException)
• Shows a page with information regarding the exception

Exception model in lion is already integrated with the I18n framework, allowing to define internationalized message

Exception can be declared in xml configuration files and grouped by their semantic (i.e. security exception, configuration exceptions, rendering exceptions and so on).

Last but not the least, the class in charge of rendering the page showing the exception can be customized.

Runtime settings

Lion has some runtime settings regarding how to handle exceptions (defined in /app/lion.ini):

...
 
;Set as no for production environment
DEBUG_MODE = yes
 
;Recommended to set as no for production environment
DISPLAY_EXCEPTIONS = yes
DISPLAY_DEBUG_INFO = yes
 
...
 
;-------------------------------------
; LOGGING DIRECTIVES:
;-------------------------------------
LOG_ENABLED = yes
;log uncatched exceptions:
LOG_EXCEPTIONS = yes
;log additional debug information when exceptions are uncatched:
LOG_DEBUG_INFO = yes
 
...

Being:

• DEBUG_MODE: If debug mode is set to false, the trace of the exception won't be shown in the screen.
• DISPLAY_EXCEPTIONS: This setting allow to show the concrete exception message. Otherwise a general message will be shown for every exception.
• DISPLAY_DEBUG_INFO: This setting allow to show the trace when an exception comes. Note that this setting works just in debug mode. Otherwise it's ignored by Lion.
• LOG_ENABLED: This setting enable the logging. We may turn on this setting in order to also log exceptions.
• LOG_EXCEPTIONS: This setting forces to log every exception. Note that this setting works just if logging is enabled.
• LOG_DEBUG_INFO: This setting log the trace and complementary debug information when an exception is raised. Note that this setting works just if logging is enabled.

The __LionException class

Lion has his own exception hierarchy subclassing the abstract exception class __LionException.
However, Lion does not require to subclass the __LionException by our own exceptions.

Lion error handling system

The error handler brings some advantages:

1. It decouples the usage of a concrete exception class or the other one from our logic, making it transparent to our application. See The Error Table.
2. It eases the internationalization of our exception messages. See Exceptions and I18n.
3. It eases the maintenance of all our exceptions within a single place as well as the assignment of error codes
4. It eases how exceptions are shown to the user in an error page. See The Error Page.