weblink - exception

Base class

WebInterfaceException

The WebInterfaceException is the base class for exceptions in web interfaces

It requires a status code to set on the response when the error is encountered and a text constant id for a error message to display
When a WebInterfaceException is handled by the web interface framework the status code is set and a body is generated consisting of a json dictionary with an error message in all available languages and optional further details
- This can then be used by an external client to display an error to the user
Subclasses of WebInterfaceException can overwrite the error_translated property to add further information to the body

Methods

Function Parameters Return Value Description

WebInterfaceException.__init__(self, status, error_text_constant, log_id=LogId.NO_LOG_ID)

status: The HTTP status code
error_text_constant: The text constant with the error message

log_id: A logging ID from the LogId enum

Instance

Initializes a new WebInterfaceException element.

Properties

Property

Getter

Setter

Description

WebInterfaceException.error_translated

Implements the python object that should be used as a body in the response.

Returns the text constant with the error message as a dictionary of language: error text by default

Example output when a error occurs

{
    "DE": "Bei der Transformation sind Fehler aufgetreten.", 
    "PT": "Ocorreram erros na transformação.", 
    "EN": "Errors occurred during transformation.", 
    "FR": "Des erreurs se sont produites pendant la transformation.", 
    "details": {
        "date": {
            "error": "java.text.ParseException: Unparseable date: \"19.09.1991\""
        }, 
        "taskUUID": {
            "error": "No task exists with uuid \"bad-uuid\""
        }, 
        "userID": {
            "error": "No user with external id \"bad-user\" exists"
        }
    }
}

JS

Base classes for specific HTTP status code

These classes all set a specific status code on the response when they are raised during the execution of a web interface.

They all share the same __init__ method and require a text constant to be initialized

Function Parameters Return Value

__init__(self, error_text_constant, log_id=LogId.NO_LOG_ID)

error_text_constant: ID of a text constant containing the error message

log_id: Optional ID to use when logging (currently unused)

Instance

Exception Class	HTTP Status Code	Status Code Name
LockedException	423	LOCKED
NotAcceptableException	406	NOT ACCEPTABLE
BadRequestException	400	BAD REQUEST
NotFoundException	404	NOT FOUND
InternalServerErrorException	500	INTERNAL SERVER ERROR
ExpectationFailedException	417	EXPECTATION FAILED
ConflictException	409	CONFLICT

Exception instances for different business usecases

This is a list of exception instances already defined for several typical web interface use cases.

When they are handled by the web framework, the status code and body is set automatically

Exception Class	HTTP Status Code	Description
EntityNotFoundException	404	The current action was cancelled because the specified object doesn't exist
ProjectLockedException	423	The current action was cancelled because the project is locked
TaskLockedException	423	The current action was cancelled because the task is locked
ProjectFinishedException	423	The current action was cancelled because the project is finished
TaskFinishedException	423	The current action was cancelled because the task is finished
ResourceAssignmentFinishedException	423	The current action was cancelled because the resource assignment is finished
InterfaceLockException	423	The current action was cancelled because the booking is already linked to an external system
BookingCancelledException	423	The current action was cancelled because the booking was cancelled
ReleasedException	423	The current action was cancelled because the booking was released
DeadlineException	423	The current action was cancelled because the booking date is before the deadline
ProjectNotActiveException	423	The current action was cancelled because the project is inactive
MaxHoursReachedException	406	The curent action was cancelled because the resource has reached their maximum allowed booking time
FutureReportingException	406	The current action was cancelled because the project does not allow booking into the future
OutsideReportingPeriodException	406	The current action was cancelled because the booking is outside the booking window
NegativeLoadException	400	The current action was cancelled because negative loads are not permitted

Framework Exceptions

These exceptions are raised by the DefaultServiceImplementation and from inside the web interface framework in general

Exception Class	HTTP Status Code	Description
EntityAttributesNotSetException	400	Raised when an error occurs while applying the attributes from the web to a POJO or when the client gives us data for a read only attribute. Contains details with further information.
TransformationException	400	Raised when a error occurs while applying the Transformers on the data. Contains details with further information.
MandatoryAttributesMissingException	400	Raised when a mandatory attribute is missing in a request to the default PUT/POST interface. Contains details with further information.
SuperfluousAttributesInRequestException	400	Raised when superfluous attributes are present in a request to the default PUT/POST interface. Contains details with further information.
InvalidJsonException	400	Raised by `ServiceImplementation.parse_json_text` when the text contains invalid json. Contains details with further information.
SessionNotFoundWebInterfaceException	400	Raised when a server function raises a `server.SessionNotFoundException`
ModuleNotFoundWebInterfaceException	400	Raised when a server function raises a `server.ModuleNotFoundWebInterfaceException`
UnhandledException	500	Raised for all unhandled exceptions. Contains details with the exception. If the web interface is set to debug logging the details also contain the traceback.
EntityNotSavedWithReasonException	500	Raised when a `utilities.PojoSaveFailedException` occurs.
EntityNotDeletedWithReasonException	500	Raised when a `utilities.PojoDeleteFailedException` occurs

Defining custom exceptions

With a custom exception derived from one of the classes above you can easily raise errors from your implementation and have the web framework handle the formatting.

You can overwrite the errors_translated property to define your own representation appropriate for your client

Custom exception example

from customizing.weblink import BadRequestException

class UserNotSyncedException(BadRequestException):
    
    def __init__(self, user):
        self._user = user
        
    @property
    def error_translated(self):
        obj = {'error': 'user-not-synced',
               'user': self._user}

PY

When this exception is raised in an interface, for example during the post method the response will automatically have status code 400 and a body like this:

Example json body

{
    "error": "user-not-synced",
    "user": "R41"
}

JS

This can then be used by the client to display an appropriate error message.