Grails 3 and Java 9/10/11

March 29, 2018

Oracle has announced they will be drastically speeding up their JDK releases – one every 6 months with no overlapping public support.

Java 9 was the first in this accelerated release cycle. While these JDK releases come quick, they end just as quickly. As you’re reading this JDK 9 is already end of life(EOL) and JDK 10 was just released (which will be EOL in 6 months.) JDK 11 will be the first long term support (LTS) release of the JDK.

With all this news, there has been some confusion about what will support what when and how people should be planning for in regards to Java releases. I’ll provide a few facts (and a few of my opinions) on what this means to you as a Grails developer.

Let’s start by answering a few concrete questions.

Will Grails 3 build on JDK 9+?

Grails 3.3.x is based on Spring-Boot 1.5. Spring-Boot 1.5 does not and will not support building in JDK 9+.

Spring Boot 2 is the first version to support Java 9 (Java 8 is also supported). If you are using 1.5 and wish to use Java 9 you should upgrade to 2.0 as we have no plans to support Java 9 on Spring Boot 1.5.x.

That’s definitive – you won’t be building Grails 3 apps in anything but JDK7/8 (and that’s ok, keep reading!)

Will Grails 3 run on JDK9+?

This is a much different question -

The answer is yes – Groovy runs (with a few warnings). You will need to add jaxb explicitly to your CLI or in your dependencies – but it will run. If you use other 3rd party libraries though you will need to validate they will run on JDK9+ as well.

This is great news for user’s environments where you are not able control your runtime and are forced to run on a newer JDK.

If I’m on JDK8 how long will it be supported?

Oracle JDK8 will receive pubic updates through January 2019 – which is cutting it quite close. Oracle plans no overlapping publicly supported binaries giving no breathing room for developers.

My recommendation is to switch to OpenJDK 8 which will be supported until October 2020 or pay Oracle for support. If you run on any PaaS such as AWS Elastic Beanstalk you’ve already been running on OpenJDK (sdkman makes it easy to setup OpenJDK on your workstation as well.)

When can I use Java 9/10/11 with Grails?

Spring-Boot 2 was just recently released (March 2018.) The Grails team is already working on Grails 4 based off it. Quarter 4 of this year (2018) is the targeted release.

Now for a few of my opinions.

Grails builds on top of many projects such as Spring-Boot, Hibernate, Gradle, etc. All of these projects must support the latest JDK before Grails can. This IMO is a good thing – it means many compatibility issues and bug fixes can be worked out before we start using it.

What should we do for now?

  • Spring-Boot 1.5 line is still being actively developed and Grails will continue to use it.

  • If you are using Oracles JDK 8 switch to OpenJDK 8 for security updates or pay Oracle for extended support.

  • Continue to build on JDK 8 and you should be fine running on JDK 10/11 if you need to.

  • Don’t adopt sort term support (STS) or end of life JDK’s such as 9/10

  • Stick to LTS JDK releases such as 8 and 11.


The release of JDK11 (LTS) and Grails 4 will be around the same time - 2018 Q4 – which is really not that far off. Grails 3.3+ and Spring-Boot 1.5+ are still great choices for building new apps on.

I use Grails so I don’t have to worry about these compatibility issues – I get a nice package of things that are recent and work together. I’ll be happy to let this JDK madness shake out before I get in the middle of it – I have features to ship to users rather than worry about JDK’s that are only supported for 6 months.