SDKMAN

One good thing that I discovered as a side-effect of building on these chapters was the SDKMAN (not sure if it should be all capital case?). This is very nice tool if you're on a Mac like I am. It allows you to manage "current version of use" for lots of different SDK:s, such as the Java SDK.

I've been using AdoptOpenJDK for quite some time, both personally in the code of this showcase as well as professionally with my customers. Now that we are going to play around with another SKD/Runtime, GraalVM, it's nice if we can just swap in between work and play so to speak. SDKMAN gives us that opportunity.

To learn how to install SDKMAN on other platforms that Mac refer to the SDKMAN website: https://sdkman.io. If you don't run a Linux based system at all I'm afraid you won't be able to use SDKMAN, you'll have to install the GraalVM-stuff as per their instruction (see below for links).

Installing SDKMAN is very simple on a Mac, just type the following in your console:

curl -s "https://get.sdkman.io" | bash

It'll do its thing for a while and then its there. You may need to start a new console for changes to take effect. Now you can execute SDKMAN commands using the sdk command in your console. Let's try. We are interested in Java in this showcase so let's list the supported Java SDK:s.

sdk list java

This should give you a long list of Java SDK:s. If you didn't have SDKMAN installed prior to this tutorial you'll notice that according to SDKMAN you do not have ANY Java SDK installed. Most likely you do, but SDKMAN unfortunately doesn't detect Java installation made by other tools. This would be a nice improvement of course to be able to import any such. But never mind, we can "reinstall" it using SDKMAN anyway.

Install AdoptOpenJDK

Let's install the latest AdoptOpenJDK for Java 11 since that's the one I've been using quite a lot before for other showcases. Use the identifier found in the list and choose 11.0.7.hs-adpt.

Note that when you run this the "latest" version may have been updated. You should be able to use whatever is latest as long as it is Java 11.

sdk install java 11.0.7.hs-adpt

After this, if you run java -version in your console, you should see something similar to this:

openjdk version "11.0.7" 2020-04-14
OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.7+10)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.7+10, mixed mode)

If you had Java installed and did a run of that command before installation you would most likely have seen something else. Run a sdk list java again and you'll see that now it is installed and also in "Use".

================================================================================
 Vendor        | Use | Version      | Dist    | Status     | Identifier
--------------------------------------------------------------------------------
...
...
AdoptOpenJDK   | >>> | 11.0.7.hs    | adpt    | installed  | 11.0.7.hs-adpt
...
...

The "Use" is sort of the key thing with SDKMAN.

Install GraalVM

We know by now that this showcase is about GraalVM so let's use SDKMAN to install that as well. You'll find it in the list and be sure to pick one for Java 11. You'll know by the ending of the identifier, it should be r11.

sdk install java 20.1.0.r11-grl

When the installation is done SDKMAN will ask you if you want to use this as default. You can select Y. Now run the sdk list java again and you'll see that AdoptOpenJDK is no longer marked with "Use", it's been taken over by GraalVM, but they are both installed. Run a java -version to confirm that your console is now bound to use GraalVM. You should see something similar to this:

openjdk version "11.0.7" 2020-04-14
OpenJDK Runtime Environment GraalVM CE 20.1.0 (build 11.0.7+10-jvmci-20.1-b02)
OpenJDK 64-Bit Server VM GraalVM CE 20.1.0 (build 11.0.7+10-jvmci-20.1-b02, mixed mode, sharing)

The good thing with SDKMAN is that it is super easy to switch between these two, just type sdk use java 11.0.7.hs-adpt and you're back to AdoptOpenJDK. You can confirm by listing and by checking your Java version in the console.

Ok nice, but I opened a new console and then I was back to GraalVM? What the hell have you done to my computer?

• Ok relax, you can change default by typing sdk default java 11.0.7.hs-adpt. Then, unless you say something, your consoles will use your default.

Installing GraalVM native image support

It's nice to have the GraalVM SDK and runtime at hand of course but after all it's just another Java variant. It's not a huge difference to AdoptOpenJDK. Don't know if it's even an improvement really?

The key thing with GraalVM is that we can use it to build binary executables. NOT byte-code, binary pre-compiled machine code. This will essentially turn your Java application into something similar to a compiled C-program. That's where the performance increase is. You can find details about GraalVM at https://www.graalvm.org/getting-started/.

But wait?

Doesn't that mean that we can't run our Java application anywhere anymore?

• Yeah, you can forget about the compile-once-run-anywhere completely. That's gone! The result is gonna be an executable that runs on Linux.

So if you build applications that are to be distributed to various platforms then GraalVM probably isn't for you. At least not the native-image thing.

After all, most of us don't build applications like that anymore, we develop API:s used by Javascript clients, and those API:s consist of services very very often deployed on Linux machines for instance in a Cloud. So... we really don't need compile-once-run-anywhere do we?

Install native-image

To install the GraalVM native-image support your console need to be using the GraalVM SDK, use SDKMAN to switch to it if necessary. Then type:

gu install native-image

The console should throw out something like this and then not complain in the end:

Downloading: Component catalog from www.graalvm.org
Processing Component: Native Image
Downloading: Component native-image: Native Image  from github.com
Installing new component: Native Image (org.graalvm.native-image, version 20.1.0)

Continue to build the application

Now you are all set up to start building the application!