Overriding the default exception handling
By default, the DataBlade® API stops the current statement when the statement generates a database runtime error and continues execution when the statement generates a database warning.
About this task
To override the default exception handling, you must take the following actions:
Procedure
- Write a callback function that handles the MI_Exception
event.To handle an MI_Exception event, you can write either of the following types of callback functions:
- Exception callback, which executes only when the MI_Exception event occurs
- All-events callback, which executes when many events occur and can include handling for the MI_Exception event
Within a callback, the DataBlade® API function mi_error_level() returns the exception level for the database server exception. You can also use mi_error_sql_state(), mi_error_sqlcode(), and mi_errmsg() to get more details about the database server exception from its error descriptor.
- Register the callback that handles the MI_Exception event
in the DataBlade®
API module
that needs the exception handling.
Use the mi_register_callback() function to register callback functions. After you register a callback that handles the MI_Exception event, the DataBlade® API invokes this callback instead of performing its default exception handling for the event.
Results
A database server exception triggers an exception callback only if the DataBlade® API module has registered (and enabled) a callback that handles the MI_Exception event. The way that your DataBlade® API module handles a database server exception depends on whether the DataBlade® API module is a UDR or a client LIBMI application.