OpenJDK Planning to Bring Java to iOS Platform

After the announcement of plugins of Gluon Client that support JavaFX & Java on the iPhone devices, co-founder of Gluon and Java Champion, Johan Vos, starts a mailing list, rebooting the discussion of OpenJDK mobile! Let’s have a look at the news on mobile Java front.

A recent proposal floating in the OpenJDK community seeks to jumpstart Java on iOS. According to Johan Vos-- CTO at mobile developer Gluon-- the plan involves picking up work on the project of OpenJDK Mobile, intended to build the OpenJDK API and classes for iOS and Android.

Recently, Vos posted a bulletin related to these efforts. OpenJDK Mobile aims at providing the same APIs in all the latest versions of the OpenJDK source repository to Android and iOS, leveraging the tools familiar to Java app developers. Though, the main focus is on iOS which has lacked traditional support for Java language. Furthermore, Apple has not allowed the Java Virtual Machine to run on this platform.

About OpenJDK:

Open Java Development Kit also known as OpenJDK is a Free and open-source implementation of Java Platform Standard Edition (Java SE). It is created by the Java Community, OpenJDK, IBM, Oracle Corporation, Red Hat, SAP SE, and Apple Inc, and is used for creating app solutions that are compatible with Mac OS X, OpenIndiana, Linux, and many other platforms.

The OpenJDK project produces a plethora of components. Some important components are the Java Class Library, the virtual machine (HotSpot), and the Java compiler (javac).

The Web Start and web-browser plugin- which form part of Oracle Java- are not included in the OpenJDK. Previously, Sun indicated that they will try to open-source all these components, but neither Oracle nor Sun have done so. The only available Web Start implementations and free plugin as of the year 2016 are those provided by Iced Tea.

OpenJDK planning to allow Java development for Android and iOS device.

• It will be focusing heavily on iOS devices.
• It introduced GraalVM ahead-of-time compiler.

Recently, the Java Community and OpenJDK has proposed an idea of making the Java capable of entering uncharted territory which is iOS. The Java community has shared that they are looking forward to restart their work on the project of OpenJDK Mobile center to make this happen.

But there are some questions that arise here like what made them take this decision and what is the benefit of taking this decision? Let’s uncover the answers here.

This OpenJDK project has introduced a set of APIs in the latest version of the OpenJDK source repository to iOS and Android– giving web app developers an opportunity to use the development tools of Java in the mobile ecosystem.

It has come up with several opportunities like maintaining a seamless communication with the help of server-side cloud, handling UI controls for the client applications, and employing platform-specific APIs in order to produce a native executable for iOS and Android devices eventually.

Although, the main focus of this project is kept over the iOS platform because though initial versions of Android have supported Java for development, there is no such opportunity available in the ecosystem of iOS. It does not provide any traditional support for JVM (Java Virtual Machine), Java, and the entire concept of JIT (Just-in-time) Compilation.

Therefore, in order to make the Java presence active on both of the platforms, the development team has introduced GraalVM ahead-of-time compiler for effective compilation of code at the build time in the iOS platform, which will aid the app developers to easily connect the compiled Java code with the native libraries and make the entire executable for this platform.

It implies that the Java web developers will not invest their time in learning Swift or Objective-C for getting into iOS mobile app development world. By this way, they can employ the cross-platform app development environment of Java for creating iPhone app solutions and leverage competitive advantages.

While bringing the Java for iPhone mobile app devices is the main component of this proposal, the Java community is also planning to introduce obsolete RoboVM tool and Gluons own Eclipse plugin in order to use Java on the Android mobile app devices.

In addition to this, they are planning to release a synchronized fork of OpenJDK master using the Project Skara.

As a whole, this gives a clear indication that the Java community is planning to bring revolutionary changes in their mobile app development economy – both in iOS and Android ecosystem. Therefore, not only for Java app developers, it is a good move for those in iOS and Android app development also. They can tap on new opportunities in the mobile app development industry and leverage higher benefits.

Therefore, if you are also a Java web app developer or someone in the iOS or Android mobile ecosystem, you should keep yourself updated with these announcements pertaining to OpenJDK mobile.

Let’s have a look at the excerpt of the interview with the Java Champion, Johan Vos taken by JAXenter. (word-by-word)

JAXenter: You released the Gluon Client Plug-ins, which allow you to run Java applications on iOS devices. How is this technology possible?

Johan Vos: Apple does not allow apps that generate code while running on a device. Hence, the typical Java VM approach does not work, as this approach uses a compiler to compile bytecode and generate native code while running. However, by compiling the Java bytecode Ahead Of Time (before the app is submitted), the plugins move the compilation phase-out of the runtime, and towards the build time. This requires an AOT compiler (which we use the GraalVM compiler for) and static libraries for both Java and JavaFX, which we build from the OpenJDK and OpenJFX open source code repositories

JAXenter: The blog post for the announcement is called “Java on iOS, for real”. – And indeed, there have been repeated attempts to bring Java to iOS devices. What is the difference between your approach and earlier attempts? Why “for real”?

Johan Vos: Instead of creating something in parallel with the core Java and JavaFX development, we try to improve those crucial projects so that they work on mobile as well. That has a number of advantages: we leverage the great work done in those projects, we  immediately benefit from bug fixes and new features in those projects, and developers really use the same Java on mobile as they are used to use on desktop and server.

It took some time before we had our approach working. GraalVM, OpenJDK and OpenJFX are complex projects, providing lots of functionality. But the integration work is done, and we can now benefit from changes in those 3 upstream projects. Hence, in our approach, it took a long time to get the basics running, but the basics are now stronger than ever before, and maintaining the project, including staying on par with new features in Java, will be much easier than with other approaches.

JAXenter: Java on iOS – why should you do that at all? From your point of view, what are the advantages of such an approach?

Johan Vos: Java is the leading language in many areas, and there is a large number of Java developers working with a large number of frameworks. A Java application written for Windows, works on Mac and Linux as well, without the Java developer having to learn something Mac or Linux specific. An advantage of Java on iOS that all Java developers can now use their existing skills to run applications on iOS devices.

Many companies already have an existing backend written in Java, with a web-based front-end. Those companies are increasingly getting requests to create a mobile front-end as well.

Thanks to Java on mobile, the existing Java teams in those companies can control the development of mobile applications. There will still be the need for graphic designers and UX experts, but with the backend team and the mobile team sharing the same skills and languages, the integration between mobile apps and enterprise infrastructure becomes more smooth and secure.

Security is one of the cornerstones of Java. With an increased interest in privacy and security, it makes sense to use the Java security on mobile, and for communicating between mobile and enterprise.

JAXenter: The Gluon client plug-ins are based on the GraalVM – a technology that is becoming more and more popular. What makes GraalVM currently one of the most exciting projects in the Java ecosystem?

Johan Vos: Looking at performance, the current generation of JIT compilers (e.g. hotspot) does an excellent job at runtime. The codebases are often hard to maintain though, and a compiler written in Java is easier to maintain for Java developers.

Furthermore, Graal with its AOT compiler allows for very fast startup time. This is important in e.g. serverless functions, where the lifetime of the VM is typically shorter than the time needed for the JIT compiler to do its work; but also for consumer apps where a slow startup negatively impacts the user experience.

On top of that, the polyglot characteristics of Graal make it very easy for today’s polyglot development to combine e.g. Java and Python in the same environment and share data structures.

To be clear, Graal is not a replacement for OpenJDK. We also use the core API’s and their implementations, and the syntax of the language that are developed in OpenJDK. OpenJDK provides a top-quality platform, and the duo GraalVM and OpenJDK is the killer combination.

JAXenter: You have worked with the GraalVM team to go the last mile to support iOS devices. What was the collaboration like – what was the biggest challenge?

Johan Vos: The GraalVM team was in the midst of finalizing the first release of the GraalVM Enterprise Edition while we were working on new functionality that was required to make it work with Java 11, JNI, LLVM, AArch64. However, the team has been extremely open, flexible and pragmatic. We tried to stay as close as possible to the master development branch of Graal, while still being able to use experimental new features. Pushing new features upstream requires passing a number of CI tests, and therefore the quality of the existing code can be guaranteed while still allowing new code.

JAXenter: Gluon relies heavily on JavaFX and is actively involved in the OpenJFX project. What has happened in the JavaFX development over the last few months?

Johan Vos: It took awhile for the JavaFX ecosystem to get used to modules and to the faster release cycle. We are now in a much more smooth water, and the JavaFX development is going very well, with a number of contributors working on specific features. One of the most important things that are currently under development in JavaFX, is the integration of third-party native rendering systems with the JavaFX native rendering. A number of developers are currently working on an API that allows doing this, and this will open the door for many projects that require very specific rendering to use JavaFX as well. In general, we try to lower the barriers for projects to use JavaFX.

With Gluon, we are of course working as well on making sure JavaFX works first class on mobile. With the JavaFX 8 family, the code difference between JavaFX for desktop and JavaFX for mobile was pretty large.

For JavaFX 13, the difference is much, much smaller, and we hope to have 0 difference by JavaFX 14.

In general, the focus of OpenJFX is to provide a very solid, mature and flexible base for Java developers to create client applications with a focus on performance and user experience. Rather than providing an extensive set of UI elements, OpenJFX focuses on the foundations, making sure third-party libraries, frameworks, tools, and projects can focus on their specific functionality without worrying about the underlying components.

JAXenter: Back to the Gluon Client Plug-ins themselves – what is the current state of development?

Johan Vos: We have early-access for deployment to MacOS and iOS, with Linux coming very soon. We have samples for the basic HelloWorld and HelloFX, which contains a very basic JavaFX application. This allows developers to experiment with it, and to become used to the approach.

JAXenter: Finally, what are your plans for the future?

Johan Vos: As said, we are only at the starting point now but we are confident we can move fast now. Obviously, we will support more targets (Windows and Android). Also, the developer experience is very important to us. We want to improve the tools, integrate with IDE’s, and make it easy, intuitive and familiar for Java developers to create mobile apps using their favorite tools. Specific for mobile, we’ll work on more integrations with mobile-specific functionality.

We are also continuing to improve our Gluon Mobile and Gluon CloudLink offerings, which allow creating real shiny mobile apps that integrate easily and in a secure way with cloud and backend infrastructure.

Wrapping Up:

Hope this article is able to clear all your doubts related to recent OpenJDK update of Java. No doubt, this new update will increase the demand of Java developers in the market.

I have been working in Xicom Technologies for the last 12 years as a Business Analyst. We have developed and lead several Java based software projects from the conception stage to the final delivery.

We have been closely following the recent software developments in the OpenJDK front and hope that we will build iOS apps soon using Java and OpenJDK.