Code Generation idioms with Xtend
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The document discusses code generation techniques using template-based tools like Apache Velocity, highlighting how to generate Java classes from templates. It covers the importance of incremental code generation, tooling practices, and integration with frameworks such as Xtext, emphasizing best practices for writing maintainable and understandable code. Additionally, it touches on features like model navigation, dynamic dispatch, and modularization to enhance developer experience.
![Model Navigation
val eClasses = myEPackage.EClassifiers.filter(EClass)
val abstractEClasses = eClasses.filter[isAbstract]
val namesOfAbstractClasses = abstractEClasses.map[name]
val commaSeparatedNamesOfAbstractClasses = namesOfAbstractClasses.join(',')
CommaSeparatedNamesOfAbstractClasses
Model Navigation](https://image.slidesharecdn.com/codegenerationidiomswithxtend-150521083816-lva1-app6892/85/Code-Generation-idioms-with-Xtend-24-320.jpg)
![Incremental code generators in Xtext
// generator API
fragment = generator.GeneratorFragment auto-inject {}
class MyDslGenerator implements IGenerator {
override void doGenerate(Resource resource, IFileSystemAccess fsa) {
// fsa.generateFile('greetings.txt', 'People to greet: ' +
// resource.allContents
// .filter(typeof(Greeting))
// .map[name]
// .join(', '))
}
}](https://image.slidesharecdn.com/codegenerationidiomswithxtend-150521083816-lva1-app6892/85/Code-Generation-idioms-with-Xtend-56-320.jpg)
![Incremental code generators in Xtext
// generator API
fragment = generator.GeneratorFragment auto-inject {}
class MyDslGenerator implements IGenerator {
override void doGenerate(Resource resource, IFileSystemAccess fsa) {
// fsa.generateFile('greetings.txt', 'People to greet: ' +
// resource.allContents
// .filter(typeof(Greeting))
// .map[name]
// .join(', '))
}
}
Customisable mechanism is taking care to
recompile affected resources](https://image.slidesharecdn.com/codegenerationidiomswithxtend-150521083816-lva1-app6892/85/Code-Generation-idioms-with-Xtend-57-320.jpg)
![Incremental code generators in Xtext
// generator API
fragment = generator.GeneratorFragment auto-inject {}
class MyDslGenerator implements IGenerator {
override void doGenerate(Resource resource, IFileSystemAccess fsa) {
// fsa.generateFile('greetings.txt', 'People to greet: ' +
// resource.allContents
// .filter(typeof(Greeting))
// .map[name]
// .join(', '))
}
}
http://www.eclipse.org/Xtext/documentation/
350_continuous_integration.html
Get Maven integration for free](https://image.slidesharecdn.com/codegenerationidiomswithxtend-150521083816-lva1-app6892/85/Code-Generation-idioms-with-Xtend-58-320.jpg)
Code Generation idioms with Xtend
- 1. Code Generation Idioms with Holger Schill
- 2. AST What is a Code Generator? Generator Code
- 3. What languages are out there…
- 4. “Template” written in Java
- 5. The default formatting for that…
- 8. // Generates Java classes source code // by using Apache Velocity GeneratorUtility utility = new GeneratorUtility(); for (int i = 0; i < classes.size(); i++) { VelocityContext context = new VelocityContext(); ClassDescriptor cl = (ClassDescriptor) classes.get(i); context.put("class", cl); context.put("utility", utility); Template template = Velocity.getTemplate(templateFile); BufferedWriter writer = new BufferedWriter(new FileWriter(cl.getName()+”.java”)); template.merge(context, writer); writer.flush(); writer.close(); Template using Velocity
- 9. // Generates Java classes source code // by using Apache Velocity GeneratorUtility utility = new GeneratorUtility(); for (int i = 0; i < classes.size(); i++) { VelocityContext context = new VelocityContext(); ClassDescriptor cl = (ClassDescriptor) classes.get(i); context.put("class", cl); context.put("utility", utility); Template template = Velocity.getTemplate(templateFile); BufferedWriter writer = new BufferedWriter(new FileWriter(cl.getName()+”.java”)); template.merge(context, writer); writer.flush(); writer.close(); Template using Velocity
- 11. And there are many more… Xpand Acceleo Jet …
- 12. And there are many more… Xpand Acceleo Jet … Everywhitespacegoesintotheoutput
- 13. And there are many more… Xpand Acceleo Jet … Everywhitespacegoesintotheoutput Badtooling
- 14. And there are many more… Xpand Acceleo … Everywhitespacegoesintotheoutput Interpreted Badtooling Slow
- 15. And there are many more… Jet … Everywhitespacegoesintotheoutput TranslatestoJava Badtooling Fast
- 16. Let’s see what can do for us…
- 17. Let’s see what can do for us… It feels a bit like Java StaticTyping
- 18. Let’s see what can do for us… Compiles to Java SeamlessintegrationIt feels a bit like Java
- 19. Let’s see what can do for us… But can do more than that… Compiles to Java It feels a bit like Java
- 20. Template Expressions (aka String Concatenation)
- 21. Greyspace Shows what makes it in the generated code Makes readable templates possible
- 22. Greyspace Indentation of call is taken into account
- 23. Model Navigation
- 24. Model Navigation val eClasses = myEPackage.EClassifiers.filter(EClass) val abstractEClasses = eClasses.filter[isAbstract] val namesOfAbstractClasses = abstractEClasses.map[name] val commaSeparatedNamesOfAbstractClasses = namesOfAbstractClasses.join(',') CommaSeparatedNamesOfAbstractClasses Model Navigation
- 25. filter map fold sortBy head reduce Build your own! It’s just library! Higher-Order Functions
- 26. Extensions Add new API where you need it
- 27. Extensions
- 28. Extensions
- 29. Dynamic Dispatch
- 30. Dynamic Dispatch
- 32. Dynamic Dispatch
- 33. IDE Support Extract method RenameRefactoring Content Assist Quick Assist Formatting Type Hierarchy Call Hierarchy Syntax Coloring Outline etc…
- 34. Debugging
- 35. Debugging
- 36. Debugging
- 37. Debugging
- 38. Debugging
- 39. Debugging
- 40. Modularization
- 41. Feature Models?
- 42. AOP?
- 44. ’s easy usage No Engine needed No ContextObject needed
- 45. ’s easy usage No Engine needed No ContextObject needed At the end it’s feels like using Java but better…
- 46. Best practices
- 47. Write readable and understandable code Should be self-evident but …
- 48. Write readable and understandable code Should be self-evident but …
- 49. Make use of dependency injection Guice
- 50. Use incremental code generators
- 51. Use incremental code generators Fast turnarounds
- 52. Use incremental code generators Fast turnarounds Just having it run on a server is no option
- 53. The m - 1 Problem BeanBeanObject Resource Configuration File BeanBeanObject Resource BeanBeanObject Resource ResourceSet
- 54. ResourceSet The m - 1 Problem BeanBeanObject Resource Configuration File BeanBeanObject Resource BeanBeanObject Resource It’s worth to think about a merging strategy
- 55. Incremental code generators in Xtext // generator API fragment = generator.GeneratorFragment auto-inject {}
- 56. Incremental code generators in Xtext // generator API fragment = generator.GeneratorFragment auto-inject {} class MyDslGenerator implements IGenerator { override void doGenerate(Resource resource, IFileSystemAccess fsa) { // fsa.generateFile('greetings.txt', 'People to greet: ' + // resource.allContents // .filter(typeof(Greeting)) // .map[name] // .join(', ')) } }
- 57. Incremental code generators in Xtext // generator API fragment = generator.GeneratorFragment auto-inject {} class MyDslGenerator implements IGenerator { override void doGenerate(Resource resource, IFileSystemAccess fsa) { // fsa.generateFile('greetings.txt', 'People to greet: ' + // resource.allContents // .filter(typeof(Greeting)) // .map[name] // .join(', ')) } } Customisable mechanism is taking care to recompile affected resources
- 58. Incremental code generators in Xtext // generator API fragment = generator.GeneratorFragment auto-inject {} class MyDslGenerator implements IGenerator { override void doGenerate(Resource resource, IFileSystemAccess fsa) { // fsa.generateFile('greetings.txt', 'People to greet: ' + // resource.allContents // .filter(typeof(Greeting)) // .map[name] // .join(', ')) } } http://www.eclipse.org/Xtext/documentation/ 350_continuous_integration.html Get Maven integration for free
- 59. more than just a code-gen language… http://www.xtend-lang.org/
- 60. Questions ?