Transforming a 15 year old model-driven application from C++ to Java

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Case Study presented a Code Generation 2012 (http://www.codegeneration.net/cg2012/) on March 28, 2012.

Case Study presented a Code Generation 2012 (http://www.codegeneration.net/cg2012/) on March 28, 2012.

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  • This presentation is tcase study about “Transforming a 15 year old model-driven application from C++ to Java”
  • Let me first give an overview of my presentation.
  • First I will introduce myself. Then I will describe the assignment that this presentation is about Since the assignment was essentially a renovation of an existing application, I will describe how renovation of old applications is done in general. Next I will describe how we applied different strategies in succession as we learned on the job. Finally I will try to draw some lessons from the experience and mention a number of problems that we did not yet find a good solution for.
  • What I learned in those 27 years: - Automated procedures as important as programming skills or architecture - Automated build - Version management - Automated deployment - (Automatic unit testing) - Communication and trust within team Specialties: - Software factories 25+ years - used to be new but now more common - Model-driven code generation 10+ years - Agile Development - eXtreme Programming 10+ years - Scrum 3+ years
  • What was our assignment?
  • A very succesful mortgage application - 185 screens (or parts of screens) - 100 users - regular quarterly releases - sizeable model: 200.000 lines, 10Mb of XMI Using a proprietary model-driven C++ generator written in C++ Several interfaces to external systems, queues Several native Windows DLL's for complicated calculations
  • Implicit metamodel (as far as known) Model in relational tables (DB2) C++ “Class Tree” to load model in memory - analogous to the EMF generated Java API Loader containing the mapping knowledge Hand-written C++ framework - persistence support classes, including lazy loading - user interface support classes Action Language: COOL (Common Object Oriented Language), used everywhere: - methods of objects - actions on UI elements (buttons, fields)
  • Scarce expertise - model-driven techniques in general - this particular modeler/generator in particular - C++ Dependent on outdated C++ compiler and libraries Modeler/generator maintained but not further developed: dead end Difficult to offshore Wanted: a regular Java webapplication No code generator - dependency on proprietary tool - Current developers where quite happy with the tool and productive
  • Start to establish goals for a new application Collect requirements Make specification Implement However: in many cases there is only source code, and if there is more documentation, it is often outdated. How to renovate: - automatic source translation? No idiomatic Java. - Better: reverse engineer specifications and re-implement - Even better (but more difficult): reverse engineer reqs. - End to Goals.
  • But in our case we had specification in the form of an executable (therefore correct) model. 1) Write a new C++ generator to generate Java - Problem: large conceptual gap to bridge: - C++ to Java (fluency in both needed) - Different architecture - On top of model driven skills 2) Use Mod4J as intermediate model - Smaller conceptual gap - Built-in Java architecture - Based on written reference architecture 3) Migrate model to EMF for productivity - Better tools - Better software factory 4) Mod4J incompatibly architecture - fat client ↔ layering - COOL language everywhere - lazy loading
  • Want to use EMF - Need an ecore metamodel - Derive from “Class Tree” - Via Enterprise Architect im/export - Generate an export program - Generate our new application - Loading time: 1,5 second - But initially 25 seconds (!) - Need a HashMap for id's
  • An intermediate model provides a natural place for names
  • Classic client server → modern three tiered layered Lazy loading assumed in de Action Language One Scope with UI scripts and Class Methods
  • Know your tools - EMF is great, but you need the book - Xtext2 for the COOL Parser difficult to integrate - Xtend2, nice but buggy and slow
  • Eclipse is difficult - Working combination of (versions of) plugins - Hard to get rid of the red crosses Continuous integration - Maven ↔ OSGi: two worlds - Solve a similar problem - Different audiences: tool/application builders - But MDCD overlap the two - Eclipse artifacts not automatically in maven repositories.
  • How to maintain the migrated model: - Use EMF tree editor - already quite good - Derive an Xtext grammar from the metamodel - beautify - DSL for “free” - The language is still the same - Familiar for the maintainers

Transcript

  • 1. 1Transforming a 15 year old model-drivenapplication from C++ to JavaEric Jan Malotaux Code Generation 2012, Cambridge, UK 2012-03-28
  • 2. Overview
  • 3. 3 OVERVIEW Who I Am The Assignment Renovating applications The Strategy Lessons Learned Unsolved Problems
  • 4. 4 WHO AM I Eric Jan Malotaux Software Architect with Ordina, ICT service provider in the Netherlands Trained as a musician and musicologist 27 years experience in software development What I learned Automated procedures (software factory) as important as programming skills Communication and trust within a team even more important Specialties – anything that speeds up software development Software factories – automating as much as possible Agile development (extreme programming, Scrum) Model-driven code generation
  • 5. The AssignmentTransforming a 15 year old model-driven application from C++ to Java
  • 6. 6 THE ASSIGNMENT THE APPLICATION A very succesful mortgage application 185 screens 100 users Quarterly releases Sizeable model: 200,000 lines (10Mb) of XMI Using a proprietary model-driven code generator Several interfaces to external systems: queues Several native Windows DLLs for complicated calculations
  • 7. 8 THE ASSIGNMENT THE MODELER/GENERATOR Old, but very complete Model in relational tables (DB2) Modeler written in MS-Access C++ Class Tree to keep model in memory Loader containing mapping (DB → Class Tree) knowledge Hand-written C++ framework, modeled Persistence support classes, including lazy loading User Interface support classes Action Language: COOL (Common Object Oriented Language) Methods on objects Actions on UI elements, like buttons Implicit metamodel (as far as known)
  • 8. 9 THE ASSIGNMENT WHY TRANSFORM? Dependent on outdated C++ compiler and libraries Scarce expertise Model-driven techniques in general The proprietary modeler/generator in particular C++ Modeler/generator maintained, but not further development Doesnt fit in Enterprise Architecture Difficult to offshore Want a mainstream Java web application And no code generator anymore please, thank you very much. No dependency on proprietary tools Current developers where quite happy, though
  • 9. Renovating applications
  • 10. Legacy application Renovated application Goals Goals Requirements update Requirements reverse engineering Specifications update Specifications reverse engineering Implementatio Automatic C++ to Java translation Implementatio n n
  • 11. The Strategy
  • 12. Legacy application Renovated application Goals Requirements FAST FAST Mod4J FAST model C++ C++ C++ extractor model Xtend2 mogram model extractor extractor generator (database) (xmi) (textual DSL) (xmi) Xtend2 Xpand C++ generator C++ generator generator C++ Java implementatio implementatio n n
  • 13. Migrating the (meta)models
  • 14. Old Intermediate New (Enterprise Architect) SQL C++ UML EcoreM3 expressed in Abstract expressed in expressed in expressed in Syntax FAST FAST EA C++ FAST EA ecoreM2 metamodel “Class Tree” import metamodel export Expo metamodel (relational) rt (ecore) gene ra to r expressed in expressed in expressed in (xten d FMA 2) gen FMA FMA e FMA Model FMA exporM1 model gen load e object t r model (database) graph a (xmi) r (C++) t a o t r o s r (xte s n (C+ d + 2 FMA FMAM0 user data ) ) application
  • 15. Ext r a Enterpri se c Legenda t Architect o given r FAST gen FAST manual FAST e EMF “Class metamo toolsmetamo r generato Tree del del a r ” (ecore) generated t o r FMA (xte n FMA FAST model Load/ d model model FM(databas extract 2 (XMI) Java API A e) ) gen e r a FAST t FMA editor o model r (xte n d JNA FMA 2 FMA ) adapters example (Java) (Java) (Java) FAST FAST maven/framewo framewo javac/ rk rk build (C++) (Java)External External (MQ) (MQ) FMA clas clas (JWS/jar FMA ses ses ) data (C++) (Java)
  • 16. Lessons Learned
  • 17. 18 LESSONS LEARNED The value of an explicit metamodel Help in understanding the model Generated export program Generated tree editor Generated model API Basis for a new DSL
  • 18. 19 LESSONS LEARNED Generator architecture Consistent naming Use an intermediate model
  • 19. 20 LESSONS LEARNED Incompatible source/target architecture Layering: classic client → server, modern three-tiered Lazy loading assumed in the COOL Action Language One Action Language for UI and Class Methods
  • 20. 21 LESSONS LEARNED Know your tools Know your tools EMF is a great tool, once you obtain a copy of the EMF book Xtext2, needed for COOL Parser, difficult to integrate Xtend2, nice but still buggy
  • 21. 22 REMAINING UNSOLVED PROBLEMS Eclipse is a hard to tame beast! Working combination of (versions of) plugins Hard to get rid of red crosses Continuous integration Maven ↔ OSGi: two worlds Eclipse artifacts (not) in public maven repositories
  • 22. 23 REMAINING CHALLENGE Maintaining the migrated model Use the EMF-generated tree editor already as good as, or better than, the Access application Derive an Xtext grammar from the metamodel Manual adjustments Have a DSL almost for free Familiar concepts: the metamodel (language) was not changed.
  • 23. 24 www.ordina.nl