Errors handling in web services: Difference between revisions
From MoodleDocs
| Line 15: | Line 15: | ||
All exceptions contain a translated message + debuginfo. | All exceptions contain a translated message + debuginfo. | ||
=== How to handle exception on the client side=== | |||
=== When to send an exception === | |||
=== When to send an exception on the server side === | |||
* DB WRITE functions must rollback when an exception is raised. We usually throw back the exception to the server. | * DB WRITE functions must rollback when an exception is raised. We usually throw back the exception to the server. | ||
* Example: the user does not have appropriate access rights to call the function) | * Example: the user does not have appropriate access rights to call the function) | ||
Revision as of 03:53, 1 May 2012
Exceptions
Format
Exceptions are caught by the server that generate its own error format. For example in REST:
<?xml version="1.0" encoding="UTF-8"?>
<EXCEPTION class="invalid_parameter_exception">
<MESSAGE>Invalid parameter value detected</MESSAGE>
<DEBUGINFO></DEBUGINFO>
</EXCEPTION>
All exceptions contain a translated message + debuginfo.
How to handle exception on the client side
When to send an exception on the server side
- DB WRITE functions must rollback when an exception is raised. We usually throw back the exception to the server.
- Example: the user does not have appropriate access rights to call the function)
Warning messages
Format
/**
* Creates a warnings external_multiple_structure
* @return external_multiple_structure
* @since Moodle 2.3
*/
private static function warnings() {
return new external_multiple_structure(
new external_single_structure( array(
'key' => new external_value(PARAM_ALPHA, 'the key can be matched by the client developer
to find out what kind of error happened and implement a specific behavior against this error.
For example: "userdoesntexist"'),
'debug' => new external_value(PARAM_TEXT, 'a not translated debug message to help the client developer to
know straight away what is the issue'),
'elementsdesc' => new external_value(PARAM_TEXT, 'explaination of the elements. For example:
"elements is an array containing the missing user id"
"elements is a list of failing course id" or
"elements is an array(context, component, area, itemid) - the failing grade" or
"elements is a list of non existing course/category like (courseid1, categoryid1, courseid2, categoryid2...)" '),
'elements' => new external_multiple_structure( new external_value(PARAM_RAW, 'an element can be used
by the client developer implements some automatic code fixing on the client side')),
), 'warning'), 'list of warnings'
);
}
When to send a warning
Most of the time you send warning in get_xxx() functions.
- Example: the user is requesting information for a list of courses and one of those courses in no longer available
