Unlike validation errors, which are generated during validation, invalid business state errors must be constructed manually.

In Commerce Engine, an invalid business state error is an Exception which implements the InvalidBusinessStateException interface. Each exception of type InvalidBusinessStateException can contain multiple StructuredErrorMessage objects, indicating why the failure state occurred.

For example, AvalabilityException is a fully constructed invalid business state error:

  public class AvailabilityException extends EpSystemException implements InvalidBusinessStateException {
      private final List<StructuredErrorMessage> structuredErrorMessages;
  
      public AvailabilityException(final String message, final Collection<StructuredErrorMessage> structuredErrorMessages) {
          super(message);
          this.structuredErrorMessages = structuredErrorMessages == null ? emptyList() : ImmutableList.copyOf(structuredErrorMessages);
      }
        
      @Override
      public List<StructuredErrorMessage< getStructuredErrorMessages() {
          return structuredErrorMessages;
      }
        
      @Override
      public String getExceptionMessage() {
          return getMessage();
      }   
  }            

To handle InvalidBusinessStateException and extract its StructuredErrorMessage objects, first convert InvalidBusinessStateException to ExecutionResult in an exception catch block.

Next, as a part of the conversion:

• Extract the StructuredErrorMessage objects from the InvalidBusinessStateException.
• Use Spring's org.springframework.core.convert.ConversionService to convert StructuredErrorMessage objects to Message or LinkedMessage objects consumable by Cortex.
• Construct an ExecutionResult containing the Message or LinkedMessage objects.

The following is an example of converting an InvalidBusinessStateExeption:

  public ExecutionResult<Void> addItemToCart() {
      try {
          cartService.addItemToCart();
          return ExecutionResultFactory.createUpdateOK();
      } catch (AvailabilityException exception) {
          List<Message> messages = exception.getStructuredErrorMessages()
              .stream()
              .map(sem -> conversionService.convert(sem, Message.class))
              .collect(Collectors.toList());
          return ExecutionResultFactory.createStateFailureWithMessages(exception.getMessage(), messages);
      }
  }   

In addition to being consumable by Cortex, converting StructuredErrorMessage objects to Message or LinkedMessage allows these objects to contain information about links.

Inject ConversionService into the JavaBean where the mapping should occur. ConversionService is able to locate the preexisting Spring converter, as it is already properly registered in the Spring Context of Cortex's repository bundle.

To use ConversionService in another OSGi bundle, add the following to the bundle's blueprint.xml configuration file:

  <reference id="conversionService" interface="org.springframework.core.convert.ConversionService"/commerce-legacy/>