[kcdc 2021] Java 17’s Project Panama Newbies

This post is my live blog from KCDC. For more, see the 2021 KCDC live blog TOC

Speaker: Carl Dea (Azul)

Twitter: @carldea

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Foojay.io has more

JEP 412 – Foreign Access API

  • https://openjdk.java.net/jeps/412 – ties together other JEPs
  • incubator module. Third incubabor
  • in making for at teast 6 years

Problems with old way

  • Communicating with required wrapper code and distributing a .ddl
  • Have to do a lo of work yourself to interfaces with C

URLs

  • jdk.java.net/panama
  • https://github.com/openjdk/panama-foreign
  • panama-dev@openjdk.java.net
  • https://foojay.io/today/project-panama-for-newbies-part-1/
  • https://foojay.io/today/project-panama-for-newbies-part-2/
  • https://foojay.io/today/project-panama-for-newbies-part-3/
  • https://github.com/carldea/panama4newbies

Using

  • java -version. Make sure says 17-panama. (Not part of main JDK)
  • jextract -h to get help
  • jextract will generate Java code for you by looking at C header file
  • Most important options
    • -I (capital Eye) – include file path
    • -d – destination for generate files
    • -l (lowercase ell) – specify a library
    • -t – target package
  • Must add incubator module and enable native access flag to run
  • Can call C methods from Java by importing them
  • Java wil hande the memory allocation/cleanup based on scope

Include

  • Copies file and puts in this file.
  • Not like import where it a reference

My take

This is a topic I knew nothing about. (Or forgot what I had known.) It was really cool to see!

Setting java aliases with zshell on Mac

When I’m working on different versions of Java, I set up a bunch of aliases so I can run commands quickly and compare differences. I recently upgraded my Mac and accepted the default shell as zshell instead of bash. (This change was made a long time ago but I didn’t upgrade for a long time because I didn’t want to incur the risk of being without my computer when everything was closed for the pandemic.)

Since I needed to move this from .bash_profile to .zshenv, I took the opportunity to shed a lot of them. I now have just Java 11 and Java 17 that I am using for comparisons. (LTS to LTS).

My .zshenv now contains this. (Yes, I know I should have patched Java 11, but alas.) I ran “source .zshenv” and am good to go.

Now I can run java11 JeanneTest.java and java17 JeanneTest.java to easily compare differences.

alias javac17=/Library/Java/JavaVirtualMachines/jdk-17-ea.jdk/Contents/Home/bin/javac
alias java17=/Library/Java/JavaVirtualMachines/jdk-17-ea.jdk/Contents/Home/bin/java
alias jar17=/Library/Java/JavaVirtualMachines/jdk-17-ea.jdk/Contents/Home/bin/jar
alias javac11=/Library/Java/JavaVirtualMachines/jdk-11.0.11.jdk/Contents/Home/bin/javac
alias java11=/Library/Java/JavaVirtualMachines/jdk-11.0.11.jdk/Contents/Home/bin/java
alias jar11=/Library/Java/JavaVirtualMachines/jdk-11.0.11.jdk/Contents/Home/bin/jar
alias jshell11=/Library/Java/JavaVirtualMachines/jdk-11.0..jdk/Contents/Home/bin/jshell
alias jdeps11=/Library/Java/JavaVirtualMachines/jdk-11.0.11.jdk/Contents/Home/bin/jdeps
alias jmod11=/Library/Java/JavaVirtualMachines/jdk-11.0.11.jdk/Contents/Home/bin/jmod

export JAVA_HOME="/Library/Java/JavaVirtualMachines/jdk-17-ea.jdk/Contents/Home"