Interested in how the changes in the Java ecosystem effect you? This talk covers several strategies on how to manage the new JDK release cadence.

1. Dan Heidinga
Eclipse OpenJ9 Project Lead
Interpreter Lead, IBM Runtimes
@danheidinga
DanHeidinga
Migrate early, migrate often!
JDK release cadence strategies
Theresa Mammarella
Eclipse OpenJ9 Software Developer
@t_mammarella
theresa-m

2. 2
Important disclaimers
§ THE INFORMATION CONTAINED IN THIS PRESENTATION IS PROVIDED FOR INFORMATIONAL PURPOSES ONLY.
§ WHILST EFFORTS WERE MADE TO VERIFY THE COMPLETENESS AND ACCURACY OF THE INFORMATION
CONTAINED IN THIS PRESENTATION, IT IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED.
§ ALL PERFORMANCE DATA INCLUDED IN THIS PRESENTATION HAVE BEEN GATHERED IN A CONTROLLED
ENVIRONMENT. YOUR OWN TEST RESULTS MAY VARY BASED ON HARDWARE, SOFTWARE OR
INFRASTRUCTURE DIFFERENCES.
§ ALL DATA INCLUDED IN THIS PRESENTATION ARE MEANT TO BE USED ONLY AS A GUIDE.
§ IN ADDITION, THE INFORMATION CONTAINED IN THIS PRESENTATION IS BASED ON IBM’S CURRENT
PRODUCT PLANS AND STRATEGY, WHICH ARE SUBJECT TO CHANGE BY IBM, WITHOUT NOTICE.
§ IBM AND ITS AFFILIATED COMPANIES SHALL NOT BE RESPONSIBLE FOR ANY DAMAGES ARISING OUT
OF THE USE OF, OR OTHERWISE RELATED TO, THIS PRESENTATION OR ANY OTHER DOCUMENTATION.
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– CREATING ANY WARRANT OR REPRESENTATION FROM IBM, ITS AFFILIATED COMPANIES OR ITS
OR THEIR SUPPLIERS AND/OR LICENSORS

3. https://developer.ibm.com/newsletters/java/
3

4. § The brave new world of Java
§ Always be migrating
§ Continuous migration strategies
4
Outline

5. 5
Historical Java release model
2005 2010 2015 2020 2025
Java 6
Java 7
Java 8
6 years, 4 months
3 years, 9 months
8 years, 6 months

6. Java 9
(09/2017)
Java 10
(03/2018)
Java 11
(09/2018)
Java 12
(03/2019)
Java 17
(09/2021)
6
Brave new world

7. 7
•Author(s): Videoplasty.com
•Man on a Treadmill Cartoon.svg from Wikimedia Commons
•License: Creative Commons Attribution-ShareAlike 4.0

8. Java 9
(09/2017)
Java 10
(03/2018)
Java 11
(09/2018)
Java 12
(03/2019)
Java 17
(09/2021)
8
Brave new world

9. Java 9
(09/2017)
Java 10
(03/2018)
Java 11
(09/2018)
Java 12
(03/2019)
Java 17
(09/2021)
9
6 month release cadence

10. LTS = Long Term Support?
10

11. Java 9
(09/2017)
Java 10
(03/2018)
Java 11
LTS
(09/2018)
Java 12
(03/2019)
Java 17
LTS
(09/2021)
11
LTS: up to the community

12. Prebuilt OpenJDK binaries
adoptopenjdk.net
Docker Hub
hub.docker.com/u/adoptopenjdk
12

13. 13
… bugs will be fixed on a “best effort” basis …
… for higher levels of assurance you should contact commercial
companies offering support …
Support Levels

14. Who to contact?

15. Who to contact?
IBM
Red Hat
Amazon
Oracle
BellSoft
Azul
JClarity
Others?
Everyone! Lots of vendors are
providing support* for OpenJDK builds:
(* List may be incomplete / inaccurate)

16. 16DevNexus 2019 / DOC ID / March, 2019 / ©2019 IBMCorporation
Are you suffering from a large Java
support bill from Oracle?
IBM Runtimes for Business
Enterprise support for open source Java
Security and bug fixes
1-800-CALL-IBM support
Trusted and Secure
25+ years of Java expertise
Performance advantages
66% smaller footprint
100% throughput performance
Migrate your app with no app changes
Save on Cost
Only pay for support for what you need

17. Java 9
(09/2017)
Java 10
(03/2018)
Java 11
LTS
(09/2018)
Java 12
(03/2019)
Java 17
LTS
(09/2021)
17
LTS: up to the community

18. “eat the elephant a bite at a time”
§ The gap between LTS releases is HUGE
§ How can an application keep up?
–Move to a stable base
–Track changes in 6 month pieces
18
Always be migrating

19. “the best time to plant a tree is either 20 years ago or today”
§ Migration 6-7-8 is mostly smooth
§ Java 8 is the oldest stable base you should use, support through 2025*
§ By not upgrading you are leaving performance improvements on the table!
19
Migrate to a stable base: Java 8

20. Major ecosystem changes!
§ Java Platform Module System makes internal APIs inaccessible
§ API elements are deprecated for removal (Java EE, Corba and more)
… And gone in Java 11!
§ Version system has changed, URLClassLoader is replaced, Etc.
20
Track future changes: Java 9

21. Major ecosystem changes!
§ Java Platform Module System makes internal APIs inaccessible
§ API elements are deprecated for removal (Java EE, Corba and more)
… And gone in Java 11!
§ Version system has changed, URLClassLoader is replaced, Etc.
21
Track PAST changes: Java 9

22. @Deprecated
§ Element is dangerous or a better alternative exists, use is discouraged
@Deprecated(since="9")
§ Since(): Release in which API element was deprecated
@Deprecated(since="1.4", forRemoval=true)
§ forRemoval(): Marked true if API element will be removed in a future release
22
JEP 277: Enhanced Deprecation

23. 23
Continuous integration pipeline
Setup
(Java 8)
Build
(Java 8)
Test
(Java 8)

24. § Pay attention to warnings!
§ Fixing them gets you clean on the current release
§ Treat warnings as errors so build will fail if warnings are present
24
javac warnings
javac -Werror

25. 25
Setup
(Java 8)
Build
(Java 8)
Test
(Java 8)
Build
(Java 11)
Setup
(Java 11)
Test
(Java 11)
Continuous migration strategies

26. 26
Continuous migration strategies
Setup Build TestMigration
checks

27. JDEPS = Java Class Dependency Analyzer
§ Java 8+ JDKs
§ Analyzes the dependencies by class or package (default) level
§ Not just for migrating to modularity!
27
jdeps Overview

28. 28
Demo
github.com/theresa-m/migrateearly-demo
hub.docker.com/u/adoptopenjdk

29. docker run --rm -it -v `pwd`/DemoApp/:/DemoApp
adoptopenjdk/openjdk11-openj9
jdeps -jdkinternals /DemoApp/target/DemoApp.jar
29
jdeps docker commandline

30. § Java 9+ JDKs
§ Scans jar/class files to identify deprecated API elements
§ Deprecated elements may cause behavioral issues or be removed
30
jdeprscan Overview

31. 31
Demo
github.com/theresa-m/migrateearly-demo
hub.docker.com/u/adoptopenjdk

32. 32
jdeprscan docker commandline
docker run --rm -it -v `pwd`/DemoApp/:/DemoApp
adoptopenjdk/openjdk11-openj9
jdeprscan --for-removal /DemoApp/target/DemoApp.jar

33. 33
Continuous migration strategies
Setup Build Testjdeps jdeprscan

34. 34
Multi-release JAR files
§ Java 9+ SDKs
§ Enables JAR files to support multiple Java versions
§ Combination of shared and version specific classes
sun.misc.Unsafe to java.lang.invoke.VarHandle

35. 35
Multi-release JAR files
DemoApp.jar
• migrate
• early
• Demo.class
• DemoRunnable.class
• META-INF
• MANIFEST.MF

36. 36
Multi-release JAR files
MultiReleaseDemoApp.jar
• migrate
• early
• Demo.class
• VersionedCode.class
• DemoRunnable.class
• META-INF
• MANIFEST.MF
• versions
• 9
• VersionedCode.class
DemoApp.jar
• migrate
• early
• Demo.class
• DemoRunnable.class
• META-INF
• MANIFEST.MF

37. 37
Demo
github.com/theresa-m/migrateearly-demo
hub.docker.com/u/adoptopenjdk

38. App.jar
test.jar
junit.jar
mokito.jar
jackson.jar
asm-all.jar
Internal_lib.jar
jdbc.jar
some_team.jar
38
Dependencies

39. § Expect to run parallel CI pipelines at least once every 6 months
§ Run jdeps & jdeprscan as part of every build to prevent new regressions
§ Use multi-release jars if no workaround for current and latest versions
§ Beware the dependency graph
39
Strategies

40. § The Java ecosystem is delivering innovation faster than ever before!
§ The free lunch is over. Migrate early, migrate often
§ Even on an LTS, use the JDK tools to prepare for the next migration
40
Key points to take away

41. Thank you!

42. https://adoptopenjdk.net/releases.html?variant=openjdk11&jvmVariant=openj9
https://adoptopenjdk.net/releases.html?variant=openjdk8&jvmVariant=openj9
https://github.com/eclipse/openj9
https://openj9.slack.com/
42