Code generation on the Java VM - Montreal - 2019-11-05

Montreal Java User Group
November 5, 2019

#Java
#Scala
#Kotlin
#JavaPoet

Transcript

1. Génération de code sur la Java VM Sean Sullivan Montreal Java User Group 5 Novembre 2019
2. About me
4. Voorhees Computing Center
6. Java, 23 years Scala, 8 years Kotlin, 1 year
7. génération de code sur la JVM Java Kotlin Scala
8. Why code generation?
9. less boilerplate more consistency Why code generation?
10. class names parameter names method names exception names Consistency error handling logging JSON serialization network I/O
11. Code generation is not a new idea
12. 2001: Apache Axis
13. wsdl2java August 2001
14. 2003: Apache XmlBeans
15. September 2003 SchemaCodeGenerator
16. The most common use case for source code generation…
17. generating client libraries for REST API’s
18. bytecode source code Two kinds of code generation
19. génération de code sur la JVM Bytecode generation
20. Bytecode generators produce Java class definitions
21. ByteBuddy ObjectWeb ASM cglib Bytecode libraries Javassist Commons BCEL AspectJ
22. Spring Framework
23. cglib spring-core
24. cglib spring-beans
25. Micronaut framework
26. “Unlike Spring which relies exclusively on runtime reflection and proxies, Micronaut uses compile time data to implement dependency injection” micronaut https://docs.micronaut.io/latest/guide/ioc.html
27. “This goal is achieved through the use of Java’s annotation processors" micronaut https://docs.micronaut.io/latest/guide/index.html
28. micronaut https://github.com/micronaut-projects/micronaut-core Annotation processors
29. micronaut ObjectWeb ASM https://github.com/micronaut-projects/micronaut-core
30. Mockito
31. mockito 2.x ByteBuddy https://github.com/mockito/mockito
32. “Mockito switched from CGLIB to the great library ByteBuddy to make mocks” https://github.com/mockito/mockito/wiki/What%27s-new-in-Mockito-2 mockito 2.x
33. Datadog Java agent
34. Datadog Java agent ByteBuddy https://github.com/DataDog/dd-trace-java
35. How can I implement a custom Java agent?
36. Java agent example https://github.com/sullis/java-lang-instrument-example/
37. Java agent example “premain” method https://github.com/sullis/java-lang-instrument-example/
38. Java agent example https://github.com/sullis/java-lang-instrument-example/ ByteBuddy AgentBuilder
39. génération de code sur la JVM Source code generation
40. java.lang.StringBuilder java.io.StringWriter Source generation
41. javapoet CodeModel jdeparser2 javaparser Source generation
42. kotlinpoet kastree Source generation
43. scalameta treehugger.scala Source generation
44. JavaPoet
45. JavaPoet https://github.com/square/javapoet
46. package com.example.helloworld; public final class HelloWorld { public static void main(String[] args) { System.out.println("Hello, JavaPoet!"); } } JavaPoet
47. import com.squareup.javapoet.*; MethodSpec main = MethodSpec.methodBuilder("main") .addModifiers(Modifier.PUBLIC, Modifier.STATIC) .returns(void.class) .addParameter(String[].class, "args") .addStatement("$T.out.println($S)", System.class, "Hello, JavaPoet!") .build(); TypeSpec helloWorld = TypeSpec.classBuilder("HelloWorld") .addModifiers(Modifier.PUBLIC, Modifier.FINAL) .addMethod(main) .build(); JavaFile javaFile = JavaFile.builder("com.example.helloworld", helloWorld) .build(); javaFile.writeTo(System.out); JavaPoet
48. AWS SDK for Java v2
49. AWS SDK for Java v2 “To provide SDK support for the many services that AWS owns, the AWS SDKs make extensive use of code generation” https://aws.amazon.com/blogs/developer/aws-sdk-for-java-2-x-released/
50. AWS SDK for Java v2
51. JavaPoet AWS SDK for Java v2
52. Dagger
53. “Dagger 2 is the first to implement the full stack with generated code” Dagger 2.x “Dependency injection frameworks have existed for years with a whole variety of APIs for configuring and injecting” https://dagger.dev/users-guide.html
54. Dagger 2.x https://dagger.dev/users-guide.html
55. JavaPoet Dagger 2.x
56. REST API code generators apibuilder project guardrail project openapi-generator
57. ApiBuilder project
58. https://www.apibuilder.io/ ApiBuilder
59. https://github.com/apicollective/apibuilder-generator/ ApiBuilder
60. ApiBuilder demo
61. Guardrail project
62. https://guardrail.dev/ Guardrail
63. https://github.com/twilio/guardrail Guardrail
64. https://github.com/twilio/guardrail Guardrail: Scala ScalaMeta
65. https://github.com/twilio/guardrail Guardrail: Java JavaParser
66. Guardrail demo
67. openapi-generator project
68. openapi-generator demo
69. Final thoughts code generation is a powerful technique use a code generator to generate client libraries contribute to open source projects
70. génération de code sur la JVM Questions?
71. The End