The king is dead, long live to the new iOS Java king!

When presenting Darwino, I'm often asked the question how do we run Java natively on iOS, or other platforms that are not known to be Java friendly? Well, we started this journey a few years ago, but the landscape of cross platform Java evolved a lot since that. Let me go through the history and explain where we stand now, as a new king has just been proclaimed. If you thing the story is too long, then just go to Multi OS Engine for the answer.

Back to the dark age, the most promising solution was provided by Google, through a transpiler called J2OBJC. Basically, j2objc converts the Java source code to Objective-C source code, that can later be compiled using Apple XCode as any native Objective-C application. Google is successfully using this technology internally for a set of projects, including popular ones like Inbox. With this, along with GWT, they claim that 70% of the code is shared between Android, iOS and the web. This is more than decent, but it has some issues:
  • It works at the source code level, while most of the libraries are currently provided as compiled binaries, through a maven reposioty
  • The runtime libraries (e.g. the set of classes available at runtime, like*,*...) is a small subset of the standard JRE libraries. That limits what you can use in your application. Even if you pay attention to only use the less common denominator, it prevents you from using libraries depending of the missing pieces
  • Objective-C (and Swift) memory management. While Java uses a garbage collector, Objective-C uses references count. I can write a whole article on the pros and cons on each of them, but the fact is that Java memory management does not translate properly to Objective-C, leading to hard-to-debug issues
  • Finally, it does not provide an easy access to the native APIs like Cocoa, or even JNI (which we use for to access SQLite, for example)
Ok, despite the all the great things it carries, j2objc didn't fit with our objective of "write once, run everywhere".

Fortunately, a beta from a new product called RoboVM appeared soon after. It was not a transpiler but a real compiler that generates true native code from the Java classes. It removed most the limitations of j2objc, by bundling the Android runtime class libraries (minus the specific UI classes), giving access to the whole iOS API through a Java-to-native bridge, full support of JNI... With RoboVM, we migrated our existing Android applications to iOS in a few hours.
Another tool, called Migeran, was also emerging with a very similar value proposition. We also moved our apps to Migeran. But, after talking to both teams, we decided to go with RoboVM, mostly because RoboVM was open source (well, partly). By the meantime, Migeran was acquired by Intel to extend their INDE offerings. They called it Multi OS Engine, aka MOE . That reinforced the validity of our choice.

But we knew that RoboVM was also a potential target for an acquisition. And what had to happen happened. Xamarin, the .NET based competitor, acquired it and changed the rules: raised the price up, stopped to deliver to the open source project... Without any inside knowledge of the acquisition terms, I believe that the Xamarin move to Java was not to make the Java community happier, but to awake and fear its main supporter: Microsoft. Which quickly reacted by acquiring Xamarin a couple of months later, and just killed RoboVM. Man, we are orphan!

One of the solution was to restart from the open source version of RoboVM, and contribute enhancements. Actually, there is a team of knowledgeable LibGDX developers that cleaned-up the code (see: and maintains it. That was the best place to start from. We even contributed the maven plug-in, thanks to Jesse. But the effort to make this project an enterprise grade tool is still big. It misses a decent debugger, support of LLVM and a few other things. Despite the value of the people behind it, it lacks the support of a real organization dedicating resources to its development.

But events are often chained. Another long awaited event happened: Intel decided to release MOE as an open source project. More than that, they gave the leadership back to the original creator, Migeran! That's the difference between Intel and Microsoft: instead of just killing and erasing the project, they decided to give it for free to the community. Many thanks to you Intel, you deserve it!

This changed the game for us. Instead of investing in the opensource RoboVM, we decided to move to MOE. The switch was actually easy, as the two tools are close enough. We made sure with Migeran that what we need is part of the platform, for example Eclipse and Maven support. Clearly, this team is great and they got the features in very quickly. As a result, since Darwino 1.5.0, we moved to the latest MOE 1.2.x and it appears to be very stable. We now have the same experience we had with the commercial version of RoboVM, including a full debugger! Yes, you can debug the Java code you deployed to your device.
Moving forward, we'll support whatever comes from Migeran: 1.3 is currently in a beta state, while 2.0 with come with a bunch of great new features. In particular the support of LLVM, latest ART runtime, maybe native windows support... Well the dream comes true.

Last but not the least, we have great relationship with Migeran and in particular its CTO, the mighty Gergely Kis. Man, this guy is really skilled and he knows what he talks about. We had another opportunity to talk face to face last month, as he came to the first Darwino workshop in Germany. It came out that we are very aligned on the vision, so the future looks very promising. We also exchanged on future projects, like bringing a Java based, fully portable ReactNative to mobile devices.

For more information about MOE now and future, Gergely gave us a presentation during the darwino workhop. The slides are now available on slideshare: Slides

If you are a Java developer who'd like to develop for iOS, then MOE is definitively what you're looking for. Start from Multi Os Engine web site, install the studio and enjoy.


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