Welcome!

Java IoT Authors: Jason Bloomberg, Liz McMillan, Elizabeth White, Pat Romanski, Stackify Blog

Related Topics: Java IoT

Java IoT: Article

Extending Rich GUI Clients with Jython

Implementing a solution

Allowing extensibility of a rich Java GUI is a daunting task. Each user may require slightly different functionality - this one wants to be able to import data from an Excel spreadsheet, and another wants to generate custom XML reports of particular artifacts in the application. You want to make every user happy, but you very rapidly see yourself with multiple code branches trying to satisfy those custom requirements - every Java developer's configuration management nightmare.

Not only is it undesirable to dirty the code base with customer-specific functionality, but you don't want to derail the core development team with continual disruptions for customer requests for simple enhancements to the GUI; it would be much more effective for the customer to be able to add all the functionality that is needed.

At Unicorn Solutions (www.unicorn.com), we developed a Scripting Extension Framework, developed in Jython and XML, that allows non-Java developers to easily enhance our out-of-the-box Swing-based application with custom, rich GUI features. This has greatly increased the extensibility of the Unicorn System, our platform for enterprise metadata management and semantic enterprise information management.

This article is aimed at both developers who are struggling with the task of multiple requests to customize their rich Java client for different customers, and developers who have an interest in Jython and examples of how it integrates with Java applications. It covers the requirements for the framework, and details the design and implementation of the Scripting Extension Framework with sample code. It covers both the usage of XML descriptors for extensions as well as how to call the Jython Interpreter from Java. It will give the target audience in-depth knowledge on how to implement a similar solution in any similar application.

Introduction - Flexing the Inflexible Application Release day has finally arrived - the full-featured Swing application that you've been developing for the past two years is finally going out to the customers on time. The problems start when each customer wants slightly different enhancements, most of which you'd rather not incorporate into the main product. The type of features that a customer might want could range from a simple "Find and Replace" feature, to any of the following customer-specific features (see Figure 1):

  • Batch loading of data from external legacy sources (flat file, Excel)
  • Verification procedures on custom data
  • Wizards for automating custom tasks
  • Generation of reports in different file formats (CSV, XML, or Excel)
  • Automated processes to update data
If this isn't bad enough as it is, it has become apparent that the customer is not going to stop with those requests but will continue to bombard you with enhancement and utility-feature requests for the long-term future.

The traditional ways of addressing such requirements range from releasing a different version of the product for each customer to providing code-hooks that the customer can code against to add the required functionality.

Releasing a different version of the product to each customer is a Configuration Manager's biggest nightmare - the task of maintaining multiple branches of the same release, together with tracking which features are in which version, is an error-prone process that is very expensive on resources. Not only that, but the amount of R&D development time to work on non-generic customer enhancements can be a big drain on resources, both in development and testing.

Providing code-hooks are generally very limiting in the breadth of functionality that can be exposed, and, generally, most custom enhancements can't be fully implemented in this framework.

Making the Application Flexible
Before getting down to making your rich GUI application flexible, we need to understand what it means to be flexible and what we'd like to see from the framework that provides this flexibility.

  1. Low levels of programming skills to develop extensions. Already at Unicorn, there are several customers writing their own extensions with minimal support required from R&D.
  2. The extensions should be developed in an easy-to-learn scripting language that integrates well with the main product.
  3. Customer should be able to create simple GUI dialogs for their enhancements that control user-input, display reports visually, etc.
  4. Seamless integration with core product features. It should not be obvious to users of the customized application which features are part of the core product and which have been developed as custom enhancements.
  5. Ease of deployment - it should be easy for developers of the custom features to deploy these features to the core product. Complicated build processes should be totally avoided.
  6. Customer extensions should be guaranteed to be compatible with future versions of the core product.
The Scripting Framework
In order to answer the above list of requirements to create a flexible rich GUI, at Unicorn we developed a full-fledged scripting framework, allowing in-house developers at customer sites to to create all the extensions that were required. The Scripting Framework consists of a controller that connects all deployed extensions to the application at runtime. Each extension consists of a descriptor, written in XML, that contains relevant information about the extension; for example, display name, input parameters, and a pointer to the script that contains the execution logic of the script.

The Scripting Framework is needed to adopt a programming language. It was decided to use a language that could tightly interact with Java programs, and there were obvious advantages to an interpreted language for ease of development of scripts. This naturally led to the choice of Jython as the language for the Scripting Framework.

Jython
Jython is an implementation of the high-level, dynamic, object-oriented language Python written in 100% Pure Java, and seamlessly integrated with the Java platform. It thus allows you to run Python on any Java platform. In addition to allowing the use of regular Python syntax, it is also possible to create Java objects and call methods on them within a regular Python expression.

Jython is freely available for both commercial and non-commercial use and is distributed with source code. Jython is complementary to Java and is especially suited for the following tasks:

  • Embedded scripting: Java programmers can add the Jython libraries to their system to allow end users to write simple or complicated scripts that add functionality to the application.
  • Rapid application development: Jython programs are typically 2-10X shorter than the equivalent Java program. This translates directly to increased programmer productivity. The seamless interaction between Python and Java allows developers to freely mix the two languages both during development and in shipping products.
  • Dynamic compilation to Java byte codes: Leads to the highest possible performance without sacrificing interactivity.
  • Ability to extend existing Java classes in Jython: Allows the effective use of abstract classes.
The Python language combines remarkable power with very clear syntax. It also supports a full object-oriented programming model, making it a natural fit for Java's OO design.

Let's look at the steps needed to develop an extension, and how extensions are loaded and executed.

Extension Descriptor
The extension descriptor contains instructions on how the executable script should be bound to the application at runtime. The descriptor contains the following information:

  • Display name of the extension.
  • Informal description of the extension.
  • Optional hotkey for the convenient quick launch of the extension.
  • Menu/Toolbar location information - the extension developer can decide where the extension will appear in menus/toobars.
  • Instructions for displaying a rich GUI input dialog - this will typically hold a list of parameters, each describing a single piece of input that the user of the extension can enter at runtime, which will subsequently be passed to the script. Each parameter holds the following information:
    - Internal identifier for input parameter
    - Display name of parameter
    - Type of parameter. This can be simple types such as string, password, number, boolean, string list, or this could also be application-specific objects like Employee, Address, or Company.
  • A pointer to the location of the Jython script to be executed.
It's clear that each extension descriptor contains all of the instructions required for extending the application with the extension, including providing the user with a high-usability user interface for accessing the extension.

We chose XML as the file format for the extension descriptor for several reasons. XML is a popular format for expressing information in a structured manner - parsers and validation tools are readily available. Also, by choosing XML, we are able to validate all descriptors against the XML Schema, which allows for catching badly structured descriptors at an early stage. By publishing the XML Schemas to extension developers, we are also providing the developers with a very handy tool to help create syntactically correct descriptors.

More Stories By Hayden Marchant

Hayden Marchant is a Software Engineer in the Information Integration Solutions group at IBM. He has 10 years of experience in software engineering. Hayden has a 1st class honors BA in mathematics from Cambridge University, England, and is a Sun Certified Programmer.

Comments (2)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@ThingsExpo Stories
SYS-CON Events announced today that DXWorldExpo has been named “Global Sponsor” of SYS-CON's 21st International Cloud Expo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Digital Transformation is the key issue driving the global enterprise IT business. Digital Transformation is most prominent among Global 2000 enterprises and government institutions.
Elon Musk is among the notable industry figures who worries about the power of AI to destroy rather than help society. Mark Zuckerberg, on the other hand, embraces all that is going on. AI is most powerful when deployed across the vast networks being built for Internets of Things in the manufacturing, transportation and logistics, retail, healthcare, government and other sectors. Is AI transforming IoT for the good or the bad? Do we need to worry about its potential destructive power? Or will we...
SYS-CON Events announced today that Daiya Industry will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Daiya Industry specializes in orthotic support systems and assistive devices with pneumatic artificial muscles in order to contribute to an extended healthy life expectancy. For more information, please visit https://www.daiyak...
SYS-CON Events announced today that SIGMA Corporation will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. uLaser flow inspection device from the Japanese top share to Global Standard! Then, make the best use of data to flip to next page. For more information, visit http://www.sigma-k.co.jp/en/.
SYS-CON Events announced today that B2Cloud will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. B2Cloud specializes in IoT devices for preventive and predictive maintenance in any kind of equipment retrieving data like Energy consumption, working time, temperature, humidity, pressure, etc.
SYS-CON Events announced today that Interface Corporation will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Interface Corporation is a company developing, manufacturing and marketing high quality and wide variety of industrial computers and interface modules such as PCIs and PCI express. For more information, visit http://www.i...
SYS-CON Events announced today that Massive Networks, that helps your business operate seamlessly with fast, reliable, and secure internet and network solutions, has been named "Exhibitor" of SYS-CON's 21st International Cloud Expo ®, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. As a premier telecommunications provider, Massive Networks is headquartered out of Louisville, Colorado. With years of experience under their belt, their team of...
SYS-CON Events announced today that NetApp has been named “Bronze Sponsor” of SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. NetApp is the data authority for hybrid cloud. NetApp provides a full range of hybrid cloud data services that simplify management of applications and data across cloud and on-premises environments to accelerate digital transformation. Together with their partners, NetApp em...
SYS-CON Events announced today that Mobile Create USA will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Mobile Create USA Inc. is an MVNO-based business model that uses portable communication devices and cellular-based infrastructure in the development, sales, operation and mobile communications systems incorporating GPS capabi...
SYS-CON Events announced today that Nihon Micron will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Nihon Micron Co., Ltd. strives for technological innovation to establish high-density, high-precision processing technology for providing printed circuit board and metal mount RFID tags used for communication devices. For more inf...
SYS-CON Events announced today that N3N will exhibit at SYS-CON's @ThingsExpo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. N3N’s solutions increase the effectiveness of operations and control centers, increase the value of IoT investments, and facilitate real-time operational decision making. N3N enables operations teams with a four dimensional digital “big board” that consolidates real-time live video feeds alongside IoT sensor data a...
SYS-CON Events announced today that Suzuki Inc. will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Suzuki Inc. is a semiconductor-related business, including sales of consuming parts, parts repair, and maintenance for semiconductor manufacturing machines, etc. It is also a health care business providing experimental research for...
While some developers care passionately about how data centers and clouds are architected, for most, it is only the end result that matters. To the majority of companies, technology exists to solve a business problem, and only delivers value when it is solving that problem. 2017 brings the mainstream adoption of containers for production workloads. In his session at 21st Cloud Expo, Ben McCormack, VP of Operations at Evernote, will discuss how data centers of the future will be managed, how th...
SYS-CON Events announced today that Ryobi Systems will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Ryobi Systems Co., Ltd., as an information service company, specialized in business support for local governments and medical industry. We are challenging to achive the precision farming with AI. For more information, visit http:...
SYS-CON Events announced today that MIRAI Inc. will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. MIRAI Inc. are IT consultants from the public sector whose mission is to solve social issues by technology and innovation and to create a meaningful future for people.
SYS-CON Events announced today that mruby Forum will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. mruby is the lightweight implementation of the Ruby language. We introduce mruby and the mruby IoT framework that enhances development productivity. For more information, visit http://forum.mruby.org/.
SYS-CON Events announced today that Fusic will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Fusic Co. provides mocks as virtual IoT devices. You can customize mocks, and get any amount of data at any time in your test. For more information, visit https://fusic.co.jp/english/.
In his session at @ThingsExpo, Greg Gorman is the Director, IoT Developer Ecosystem, Watson IoT, will provide a short tutorial on Node-RED, a Node.js-based programming tool for wiring together hardware devices, APIs and online services in new and interesting ways. It provides a browser-based editor that makes it easy to wire together flows using a wide range of nodes in the palette that can be deployed to its runtime in a single-click. There is a large library of contributed nodes that help so...
SYS-CON Events announced today that Enroute Lab will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Enroute Lab is an industrial design, research and development company of unmanned robotic vehicle system. For more information, please visit http://elab.co.jp/.
Agile has finally jumped the technology shark, expanding outside the software world. Enterprises are now increasingly adopting Agile practices across their organizations in order to successfully navigate the disruptive waters that threaten to drown them. In our quest for establishing change as a core competency in our organizations, this business-centric notion of Agile is an essential component of Agile Digital Transformation. In the years since the publication of the Agile Manifesto, the conn...