Code Generation idioms with Xtend
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Code Generation Idioms with Holger Schill
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Transcript of Code Generation idioms with Xtend
Code Generation Idioms with
Holger Schill
AST
What is a Code Generator?
Generator Code
What languages are out there…
“Template” written in Java
The default formatting for that…
Template using Velocity
Template using Velocity
// 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
// 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
Template using Velocity
And there are many more…
XpandAcceleo
Jet…
And there are many more…
XpandAcceleo
Jet…
Every whitespace goes into the output
And there are many more…
XpandAcceleo
Jet…
Every whitespace goes into the output
Bad tooling
And there are many more…
XpandAcceleo
…
Every whitespace goes into the output
Interpreted
Bad tooling
Slow
And there are many more…
Jet…
Every whitespace goes into the output
Translates to Java
Bad tooling
Fast
Let’s see what can do for us…
Let’s see what can do for us…It feels a bit like Java
Static Typing
Let’s see what can do for us…
Compiles to Java
Seamless integrationIt feels a bit like Java
Let’s see what can do for us…
But can do more than that…Compiles to Java
It feels a bit like Java
Template Expressions(aka String Concatenation)
GreyspaceShows what makes it in the generated code
Makes readable templates possible
GreyspaceIndentation of call is taken into account
Model Navigation
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
filter
map
fold
sortBy
head
reduce
Build your own! It’s just library!Higher-Order Functions
ExtensionsAdd new API where you need it
Extensions
Extensions
Dynamic Dispatch
Dynamic Dispatch
Dynamic DispatchGenerated Java
Dynamic Dispatch
IDE Support
Extract methodRenameRefactoring
Content AssistQuick Assist
Formatting
Type Hierarchy
Call Hierarchy
Syntax Coloring
Outline
etc…
Debugging
Debugging
Debugging
Debugging
Debugging
Debugging
Modularization
Feature Models?
AOP?
Dependency Injection
’s easy usage
No Engine needed
No ContextObject needed
’s easy usage
No Engine needed
No ContextObject needed
At the end it’s feels like using Java
but better…
Best practices
Write readable and understandable codeShould be self-evident but …
Write readable and understandable codeShould be self-evident but …
Make use of dependency injection
Guice
Use incremental code generators
Use incremental code generatorsFast turnarounds
Use incremental code generatorsFast turnarounds
Just having it run on a server is no option
The m - 1 Problem
BeanBeanObject
Reso
urce
Configuration File
BeanBeanObject
Reso
urce
BeanBeanObject
Reso
urce
ResourceSet
ResourceSet
The m - 1 Problem
BeanBeanObject
Reso
urce
Configuration File
BeanBeanObject
Reso
urce
BeanBeanObject
Reso
urce
It’s worth to think about a merging strategy
Incremental code generators in Xtext// generator APIfragment = generator.GeneratorFragment auto-inject {}
Incremental code generators in Xtext// generator APIfragment = 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(', '))
}}
Incremental code generators in Xtext// generator APIfragment = 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
Incremental code generators in Xtext// generator APIfragment = 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
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