Code generation on the Java VM 2022-04-19

Code generation on the Java VM
Portland Java User Group
April 19, 2022

#java
#scala
#kotlin

Transcript

1. Code generation on the Java VM Sean Sullivan Portland Java User Group 2022-04-19
2. Code generation Java Kotlin Scala
3. Why code generation?
4. less boilerplate more consistency Why code generation?
5. class names parameter names method names exception names Consistency error handling logging JSON serialization network I/O
6. Code generation is not a new idea
7. 2001: Apache Axis
8. wsdl2java August 2001
9. 2003: Apache XmlBeans
10. September 2003 SchemaCodeGenerator
11. The most common use case for source code generation…
12. generating client libraries for REST API’s
13. Code generation Source code generation
14. java.lang.StringBuilder java.io.StringWriter Source generation
15. javapoet javaparser jdeparser2 CodeModel Source generation
16. kotlinpoet kotlinx-ast kastree Source generation
17. scalameta treehugger.scala Source generation
18. JavaPoet
19. JavaPoet https://github.com/square/javapoet
20. package com.example.helloworld; public final class HelloWorld { public static void main(String[] args) { System.out.println("Hello, JavaPoet!"); } } JavaPoet
21. 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 method builder class builder fi le builder
22. AWS SDK for Java v2
23. 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/
24. AWS SDK for Java v2
25. JavaPoet AWS SDK for Java v2
26. Dagger
27. “Dagger 2 is the fi rst 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 con fi guring and injecting” https://dagger.dev/users-guide.html
28. Dagger 2.x https://dagger.dev/users-guide.html
29. JavaPoet Dagger 2.x
30. REST API code generators apibuilder project guardrail project openapi-generator
31. ApiBuilder project
32. https://www.apibuilder.io/ ApiBuilder
33. ApiBuilder
35. ApiBuilder demo
36. Guardrail project
37. https://guardrail.dev/ Guardrail
38. https://github.com/guardrail-dev/guardrail Guardrail
39. https://github.com/guardrail-dev/guardrail Guardrail: Scala ScalaMeta
40. https://github.com/guardrail-dev/guardrail Guardrail: Java JavaParser
41. Guardrail example
42. guardrail-maven-plugin <plugin> <groupId>dev.guardrail</groupId> <artifactId>guardrail-maven-plugin</artifactId> <version>0.70.0</version> <executions> … </executions> </plugin>
43. guardrail-maven-plugin <con fi guration> <language>java</language> <kind>client</kind> <framework>dropwizard</framework> <specPath>${project.basedir}/src/main/openapi/petstore.json</specPath> <packageName>com.example.clients.petstore</packageName> </con fi guration> Java client
44. guardrail-maven-plugin
45. openapi-generator project
46. openapi-generator
47. openapi-generator
48. openapi-generator
49. openapi-generator uses Mustache templates
51. Mustache
52. Mustache template
53. Eclipse Collections
54. Eclipse Collections uses code generation
56. Why does Eclipse Collections use code generation?
57. Primitive collections
59. StringTemplate library
60. .stg fi les
67. String File
68. Bonus Round
69. Strange Loop 2021
70. OpenRewrite
71. Final thoughts code generation is a powerful technique use a code generator to generate client libraries contribute to open source projects
72. Code generation Questions?
73. The End