Java 9, ein Über- und Ausblick

Volker Simonis, SAP / volker.simonis@gmail.com

https://simonis.github.io/HackUndSoehne

Wie alles begann..

DEMO

The OpenJDK Project

http://openjdk.java.net/

• Open Source implementation of Java SE
• Licensed under GPLv2 (with Classpath exception)
• Reference implementation for Java 7, 8, 9, ..
• Collaboration space for different implementers:
  • RedHat, SAP, IBM, Google, Intel, Twitter, Azul
• Playground for Java SE related projects:
  • Coin, InvokeDynamic, Lambda, Nashorn, Jigsaw, ...
  • Graal, Panama, Valhalla, Shanandoa, Metropolis, Loom ...

OpenJDK Genealogy

• Everything started with an early development version of JDK 7
  • OpenJDK 6 was a retrofitted JDK 6 port of this version
• IcedTea - a free build harness
  • Initially used to replace non-free parts
  • Add support for additional platforms (Zero, Shark)
  • Additional features (Thermostat, IcedTea-Web, Shenandoah)
  • Base of the OpenJDK packages in most Linux distros
• Today there's a wild zoo of different OpenJDK builds and distributions:
  • Linux distros (IcedTea based?), AdoptOpenJDK, Azul Zulu, Docker, Amazon, ..

• "Commercial" versions of OpenJDK
  • Oracle JDK, SAP JVM, HP JDK, Azul Zing, IBM / Open J9 (only class library)

OpenJDK and the Java™

• You are not allowed to call it Java™ (or Java™ compatible) because:
  • "Java" is a registered trademark
  • You don't get access to the Technology Compatibility Kit (TCK)
• Accessing the TCK requires the signing of the
  OpenJDK Community TCK License Agreement (OCTLA)
  • Only for OpenJDK or "substantially derived" projects
  • OCTLA forbids disclosing TCK information to non-OCTLA licensees
• OCTLA is no trademark license!
• "OpenJDK" can be used according to the "OpenJDK Trademark Notice"

OpenJDK Organization

• Participants: individuals who subscribed to an OpenJDK mailing list
• Contributors: Participants who signed the OCA
• Groups (currently 22)
  • consist of Group Members and a Group Lead
    • Group Members elect new Group Members from Contributors
  • sponsor Projects
• Projects (currently 60)
  • produce artifacts (code, documentation, whole JDK releases)
  • have code repositories, mailing lists and possibly web content
  • consist of Authors, Committers, Reviewers and a Project Lead
    • Project Leads appoint Authors from Contributors
    • Committers elect new Committers from Authors

OpenJDK Infrastructure

• The OpenJDK Homepage
• Too many Mercurial repositories
  • Before jdk10 in fact "forests" of 7 nested sub-repositories
• Way to many mailing lists (currently ~172)
• The JDK Bug System https://bugs.openjdk.java.net
• Code review server http://cr.openjdk.java.net
  • For review requests in Webrev format
  • Must be at least Author to get access
• The OpenJDK Wiki https://wiki.openjdk.java.net
  • Must be a group member to get write access

OpenJDK Tools - Mercurial

• Mercurial is a distributed source control system implemented in Python.
• OpenJDK uses nested sub-repositories (i.e. "forest"):
  • clone them (corba, hotspot, jaxp, jaxws, jdk, langtools, nashorn) manually:

                      
  $ hg clone http:/​/hg.openjdk.java.net/jdk9/dev jdk9-dev
  $ cd jdk9-dev
  $ hg clone http:/​/hg.openjdk.java.net/jdk9/dev/corba
  ...
  $ hg clone http:/​/hg.openjdk.java.net/jdk9/dev/nashorn
                      
                    

  • or use the get_source.sh script which does the same in parallel:

                      
  $ hg clone http:/​/hg.openjdk.java.net/jdk9/dev jdk9-dev
  $ cd jdk9-dev
  $ sh get_source.sh
                      
                    

• Use common/bin/hgforest.sh to execute hg commands in all repositories

OpenJDK Tools - Mercurial

• In jdk10 the "forests" are gone!
  • JEP 296: Consolidate the JDK Forest into a Single Repository
• One fat repo
• Cloning takes longer (not parallelized any more)
• Less confusing for new users

Building the OpenJDK

• Use a Supported Build Platform
• Favor Linux over MacOS X and Windows
• Don't build jdk7 any more :) - since jdk8 the build is configure-based
• jdk8 build instructions are in README-builds.html
• jdk9 build instructions are in common/doc/building.html
• Have a look at the AdoptOpenJDK project
• Use your favorite search engine extensively :)
• Ask on build-dev@openjdk.java.net

Building the OpenJDK

            
$ hg clone http:/​/hg.openjdk.java.net/jdk10/hs/ jdk10-hs
$ cd jdk10-hs
$ bash ./configure --with-native-debug-symbols=external --with-debug-level=slowdebug
configure: Configuration created at Fri Sep 29 00:43:09 CEST 2017.
...
$ make images LOG=debug
...
Start 2017-09-29 00:44:29
End   2017-09-29 01:02:08
00:17:39 TOTAL
$ ./build/linux-x86_64-normal-server-slowdebug/images/jdk/bin/java -version
openjdk version "10-internal"
OpenJDK Runtime Environment (slowdebug build 10-internal+0-adhoc.simonis.jdk10-hs)
OpenJDK 64-Bit Server VM (slowdebug build 10-internal+0-adhoc.simonis.jdk10-hs mixed mode)
            
          

On error use “make images JOBS=1” and take a look at “build.log”

JEP - The JDK Enhancement-Proposal & Roadmap Process

• Collect, review, sort, and record proposals for enhancements to the JDK
• JEP 1: JDK Enhancement-Proposal & Roadmap Process defines the process
• Simpler than a Java Community Process (JCP) Java Specification Request (JSR)
  • Specification changes still require a JSR
• The JEP process is still dominated by Oracle:
  • requires endorsement and funding by Group Leads
  • The OpenJDK Lead (appointed by Oracle) ultimately
    decides which JEPs to include into the Roadmap.
• Still attractive for “implementation enhancements” (i.e. new Ports, GCs, JITs, ..)

JCP - The Java Community Process

• A formalized mechanism for developing Java specifications
• Not an independent standards organization / legal entity
  • A vendor consortium dominated by Oracle
• Membership requires fee for organizations/companies but is free for individuals
• JSR's (Java Specification Requests) for proposing and specifying new technologies:
  • A final JSR provides a free reference implementation and
  • A TCK (Technology Compatibility Kit) for verification
• Currently the JCP specifies three platforms: Java ME, Java SE and Java EE
• JCP is being criticized as being a "rubber stamp organization", but see:
  • Apache vs. Sun on getting access to the TCK
  • JCP EC rejects JSR 376 (Jigsaw)

JAVA 9

JIGSAW DEMO

The future of the Java/OpenJDK

• New six month, release cadence
• Many new projects: Panama, Valhalla, Graal, Loom, Metropolis
• Competition: Open J9

DEMOS