Implement Error handling

When implementing domain logic, there are three types of errors which can happen and need to be handled:

Business errors which can occur if business conditions are not met, but are expected to happen
Validation errors
General errors (all others)

Throw business errors

For every modelled business error, the SDK offers functionality to throw it.

Within the implementation file of a service, command or agent the following code can be used to throw a business error:

throw this.factory.error.nsacrnm.MyBusinessError();

Every error thrown in an implementation file should be handled latest in the errorHandler method of the API operation.

Handle errors

In the implementation file of a service, command, agent and operation error instance check can be done by using isInstanceOf functionality, thus enable to code handling logic for different error instances.

Handling business errors

To safely handle a business error that was modelled in the Solution Designer use the following code:

try {
  // call a service which might throw a business error
  await this.services.nsacrnm.ServiceIdentifier(input);
} catch (e) {
  // check whether the error matches any of the errors modelled in Solution Designer      
  if (this.isInstanceOf.businessError.ns1.NoBalanceAvailable(e)) {
    // now can handle this specific business error
  }

  if (this.isInstanceOf.error.ValidationError(e)) {
    // now can handle this validation error
  }

  if (this.isInstanceOf.businessError.ns2.NoCustomerFound(e)) {
    // now can handle this specific business error
  }
}

Handling general errors

These are the general errors that can occur. To safely handle an error, use the following code:

try {
  // execute some logic
} catch (e) {

  // check whether the validation of an entity (used as input or instance) fails
  if (this.isInstanceOf.error.ValidationError(e)) {
    // now can handle this validation error
  }
  
  // check for a child of abstract BusinessError
  if (this.isInstanceOf.error.BusinessError(e)) {
    // now can handle this Business error
  }

  // check whether an  action (e.g. a command) is not currently available
  if (this.isInstanceOf.error.ActionNotAvailableError(e)) {
    // now can handle this ActionNotAvailable error
  }

  // check whether an aggregate is found in the datastore
  if (this.isInstanceOf.error.AggregateNotFound(e)) {
    // now can handle this AggregateNotFound error
  }

  // check whether an external request (i.e. this.util.request) caused an error
  if (this.isInstanceOf.error.ExternalRequestError(e)) {
    // now can handle this ExternalRequest error
  }
  
  // check whether an internal request caused an error
  if (this.isInstanceOf.error.InternalRequestError(e)) {
    // now can handle this InternalRequest error
  }

  // check for GeneralError
  if (this.isInstanceOf.error.GeneralError(e)) {
    // now can handle this general error
  }
}

Warning:

The hierarchy of error consists of GeneralError, ValidationError and BusinessError, where ValidationError and BusinessError extend GeneralError.