In Scala DMN, Script Engines can use process engine context

AT

• In Scala DMN, Script Engines can use process engine context
• Document breaking changes in migration guide (e.g., when removing interfaces)

Reasoning

• When using JUEL in the legacy DMN Engine, context providers registered in the process engine can be used (optionally via Spring & CDI)
  • Context switch in Process Applications is performed
  • Beans can be resolved
  • By default built-in function mappers are available (this is not the case for Spring & CDI)
• Providing the process engine context with JUEL in the Scala DMN Engine makes migrating from the legacy DMN Engine smooth
• Since FEEL ist the expression language designed for DMN it makes sense to provide process engine context in FEEL and not only for JUEL
• With respect to the high adoption of the Spring Boot Starter it makes sense to provide registered beans in FEEL/JUEL

Status Quo JUEL

• In process engine config ExpressionManager is initialized in initExpressionManager (Spring and CDI have dedicated expression managers)
  • Functions mappers are registered (e.g., currentUser, now, etc.) => not in Spring & CDI
• ExpressionManager is wrapped in ProcessEngineElProvider (implements ElProvider)
• ProcessEngineElProvider is registered in Legacy DMN Engine

Status Quo Script Engines

Script engines that can be used in the legacy DMN Engine can be registered in...

• 1. the Process Engine via ScriptEngineResolver#addScriptEngineFactory
  2. a Process Application (via SPI & via ScriptEngineResolver#addScriptEngineFactory)
  3. a SPI and be resolved via ScriptEngineManager

Solution Ideas

Process Engine context can be used in ...

1. ... FEEL
2. ... JUEL (previous behavior)
3. ... all registered Script Engines

Scope

• Minimum: use context either in JUEL or FEEL
  • Adding JUEL support is probably easier
• Medium: JUEL and FEEL
  • JUEL due to backward compatibility
  • FEEL because it is the default expression language in DMN
• Maximum: context can be used In all possible expression languages

See

• https://docs.google.com/document/d/1fvp2qf75W7VBSFjfHVz3iRN4Ynq349R6qtq3eP62opw/edit#bookmark=id.t3uae3qrvj4f
• https://docs.google.com/document/d/1fvp2qf75W7VBSFjfHVz3iRN4Ynq349R6qtq3eP62opw/edit#bookmark=id.ut2tq226w1p4