On runtime, code can cause an error that halts the execution and potentially terminate the execution unexpectedly. Typically, this can occur on user input, when the user input is unexpected (for example, while the code expects a Decimal value and the user enters a value with letters). Exception handling enables you to deal with such situations and handle the thrown exception gracefully.

To handle an exception, use the try-catch construct on the code.

Also, you can decide that a particular expression should produce an exception. To throw an exception, use the error() function from the Standard Library.

Throwing Exceptions

The error() function throws an error with an error code. The error code is a String parameter of the construct.

error(<errorcode>)

Example:

error("InvalidISBNFormat")

If an error exception is not caught and handled, the execution terminates. The error can be caught and handled by a try-catch block.

Important: Error throwing functions are part of the Standard Library. Refer to the Standard Library Reference for further information.

Catching Exceptions

To catch and handle error exceptions produced by throw or by null function parameters which must not be null without interrupting the execution, use the try-catch statement block on the code which might cause an exception:

try <expression>
    catch <error_code>, ... -> <handle_expression_1>;
      handle_expression_2;
      ...
end

If the catch statement takes null, any error is caught.

Note: To get the error code and message of the error, use the getErrorCode() and getErrorMessage() functions in the catch:
try 
  createModelInstance(
    synchronous -> true,
    model -> getModel("childProcess","1.0"),
    properties-> ["Triggered by" -> thisModelInstance().id.toString()]
  )
  catch null, "error" -> log("Error: " + getErrorCode() + getErrorMessage(), ERROR_LEVEL)
end

Example:

try getCode()
  catch "Invalid ISBN format", "Invalid ISSN format" -> "Code value is not valid."
end

Example: Catching any error code

try executeFunction()
  catch null -> "Code value is not valid."
end

Note that the block returns an object, which you can cast as appropriate:

try val.toDecimal()
catch null -> "not decimal" as String

Built-in Errors

The Expression Language makes use of the errors with the following error codes:

Error	Description (occurrence circumstances)
AmbiguousNameError	The provided name cannot be resolved to a unique entity.
ArithmeticError	An operand in an arithmetic operation cannot be processed.
BinaryDataError	Binary data cannot be retrieved (for example, from database).
DoesNotExistError	The entity does not exist.
FormatError	The format of an argument is incorrect (for example, on casting of a String).
IncompatibleTypeError	The type of processed value is incorrect (typically on casting or assigning).
IncorrectPathname	The string with the path in invalid.
MergeEvaluationError	Evaluation context created by a View Model cannot be merged.
ModelInstantiationError	Instantiation of a model failed.
ModelInterpretationError	Model cannot be interpreted.
NoExternalRecordProvider	The resource with the requested external record is not available.
NoSuchPropertyError	The record property does not exist.
NullParameterError	A mandatory parameter has the `null` value.
OutOfBoundsError	The collection element does not exist.
OptimisticLockConflictException	Saving changes to record instance failed since the underlying versioned record instance was changed.
ReadOnlyAccessError	The system attempted to write to a read-only object.
RecordNotFound	The record instance does not exist.
ReferenceNotFound	Dereferencing failure (Referenced value was not found.)
SendingError	Error sending failed.
SendingSignalError	Signal sending failed.
WrongSizeError*	The size of a value is incorrect (for example, a String being cast to a map).