EclipseCon demo projects for JDT with Javac

This repository hosts the source project and the scenario description to demo JDT with JavacY

Scenario

Prerequisites

Projects need to be available on filesystem

• eclipsecon-demo-jdt-with-javac
• spring-petclinic
• spring-data-jpa
• java-jwt

with mvn verify && mvn clean already run on those.

Demo things working

Basics

Open spring-petclinic in editor/IDE, show features working

• outline view
• control-click navigation
• code completion
• create an edit that causes an error
  • show diagnostic
• show quickfix

Show generated .class files (maybe highlight they're from Javac)

Annotation processing

• Demo a mapstruct annotation processing sample in annotation_processing package
• Highlight the generated .java files (highlight they're from Javac)
• Modify a source file and showcase the generated .java file is updated

Build

• Full Build
  • Open the target/classes/build folder to show the .class files
• Incremental Build
  • Open build/Dto.java and add a new field String role
  • Open the target/classes/build folder to show the updated .class files (Compare the timestamp to see only the affected classes are updated)

Tests and debugging

• Open BasicTest.java
• Put a breakpoint in assert...
• Debug as JUnit Test
• see breakpoints, step into areWeIn2024, value of year on hover... working

Differences with ECJ

• Type inference ( eclipse-jdt/eclipse.jdt.core#494 ): Use TypeInferenceDemo.java
• dots in folder name ( redhat-developer/vscode-java#1406 ): Use DotInFolderNames.java
• Annotation processing (AbortCompilation): https://github.com/spring-projects/spring-data-jpa.git - throw AbortCompilation when handling annotation processing
• JPMS: try importing https://github.com/auth0/java-jwt ; ECJ fails, Javac ?

Showcase introduction a new Java feature

Better recovery/diagnostics in Java 24

• Open javac24isBetter/Test.javac
  • With ECJ: uninteresting messages
  • with Javac (23): crash ☹️, messy diagnostics
  • with Javac 24: no crash but empty -> check log -> add problem mapping -> re-edit => much better!

A new feature

Find a small Java 24 feature already supported by Javac and that we have easily-ish converted to JDT. Then for the presentation, revert this support. Show the feature is missing and reimplement live the support to showcase it's a matter of minutes.