Welcome!

Java IoT Authors: Pat Romanski, Elizabeth White, Liz McMillan, Carmen Gonzalez, Yeshim Deniz

Related Topics: Java IoT

Java IoT: Article

Interface All Boundaries

Providing tangible benefits to your application

Experienced developers know many of the benefits of and motivations for using interface-based design principles. Interfaces provide for polymorphic behavior by hiding the implementation and only exposing the relevant public methods of the implementing class. What may be less appreciated is that the use of interfaces, when applied to an entire application, can provide for application isolation, while at the same time enhancing testing capabilities.

In this article we'll explore the use of interfaces at all application boundaries and gain an appreciation for why we should consider, and possibly even mandate, interface-based design principles at all application boundaries. This mandate should apply even if application requirements or application design do not call for differing behavior behind the interface.

What Is an Application Boundary?
Before we start mandating anything throughout our entire application, it would be helpful to have a better feel for exactly what an application boundary is. Consider any application you write. The application is composed of the classes that you write and the code or resources with which your application interacts. Unless you're writing an "Hello World" application, you will need to access many or all of the following resources:

  • File system, library, server, database...
Although the above list is only a small subset of the many external resources that should be considered application boundary resources, it does convey the essence of the idea. Figure 1 provides a pictorial view of these application boundary resources.

Motivations for Interfaces
While many motivations drive the use of interfaces, it is instructive to describe the core motivations. As one example, consider JDBC, which makes heavy use of interface-based design principles. A ResultSet is an interface; moreover, all JDBC driver vendors must provide an implementation for the ResultSet interface. Application developers simply use the ResultSet, in most instances not knowing or caring how the underlying code is implemented. Application developers code to the ResultSet interface while the actual implementation is usually defined and configured apart from the application code. JDBC is based heavily on interfaces to support the ability to change the driver implementation without impacting the application code. Simply put, portability is the driving factor for JDBC interfaces.

Resource wrapping can be listed as a second motivation for the use of interfaces. The main intent is to support the ability to change the wrapped resource with little to no application code changes. In this sense, the motivations for resource wrapping are very similar to the JDBC example except that most resources are not based on a set of predefined interfaces as JDBC is. By contrast, different resources that deliver the same or similar functionality are not likely to have the same API. As a result, the interface for a changed resource is likely to become more of a façade-based implementation, especially if a resource change is realized.

Other application interfaces are typically chosen for the polymorphic benefits realized by an interface-based design. The application behavior is mandated by either specific requirements or by design recognizing the similarities between two or more subsystems or elements. On the application side, interface-based solutions are nearly always chosen based on required or desired application behavior with polymorphism being the driving motivation.

Lastly, application isolation should be added as another motivation for the use of interfaces. The intent of application isolation is not necessarily to support the future change of a tool or resource, but rather to support the ability to remove the resource dependency from an application. Isolation is often needed during unit testing, but is also beneficial in the early stages of development when the resource in question may not yet be available. Using interfaces at all application boundaries delivers the ability to easily plug in alternative implementations that are not resource dependant. This capability can deliver extensive benefits to a development team by eliminating the constraints imposed by some resource dependencies.

For brevity, the motivations for interface-based design are:

  • Portability
  • Resource wrapping
  • Polymorphism
  • Application isolation
Project Example, Iteration 1
Application isolation is the motivation we'll spend the remainder of this article on. With that thought in mind, let's turn to the impact of external resources on our application code base. For better understanding we'll use the retrieval of a collection of person objects from a database as our core example. In iteration 1 we'll provide an unimproved implementation. This iteration shows a small cut of the code as it might exist without the use of interface-based design principles. Using good design principles we'll encapsulate our database access by using a PersonDAO class (Data Access Object pattern) for all database access. Figure 2 shows the UML for our simplified application.

The PersonDAO class will acquire a database connection and issue queries on behalf of the invoking party, which in this instance is the BusinessFacade class (Façade Pattern). The code below shows a brief implementation of the BusinessFacade class. Note the direct instantiation and use of the PersonDAO class, which immediately ties the BusinessFacade class to the database resources referenced in the PersonDAO class.

1  public class BusinessFacade
2  {
3  public void
4  reportTodaysBirthdays()
5  {
6  Date today = new Date();
7  PersonDAO personDao =
8  new PersonDAO();
9  Collection persons =
10  personDao.getByBirthDate(today);
11  // Do what needs to be done
12  // to report on those that
13  // have birthdays today.
14  }
15  }

Being tied to the database imposes all of the following resource requirements:

  • Existing network connectivity
  • Database server capable of handling the connection request
  • Database schema supporting the Person table
  • Database data from which the query can be fulfilled
It's certainly true that we will be required to be tied to some database at some time during the development phase. However, imposing such a hard dependency for all development unnecessarily hinders other developers working outside the realm of the database. Moreover, the hard dependency can be rather easily avoided with a little forethought and a simple interface!

More Stories By Pete Whitney

Pete Whitney is a Solutions Architect for Cloudera. His primary role at Cloudera is guiding and assisting Cloudera's clients through successful adoption of Cloudera's Enterprise Data Hub and surrounding technologies.

Previously Pete served as VP of Cloud Development for FireScope Inc. In the advertising industry Pete designed and delivered DG Fastchannel’s internet-based advertising distribution architecture. Pete also excelled in other areas including design enhancements in robotic machine vision systems for FSI International Inc. These enhancements included mathematical changes for improved accuracy, improved speed, and automated calibration. He also designed a narrow spectrum light source, and a narrow spectrum band pass camera filter for controlled machine vision imaging.

Pete graduated Cum Laude from the University of Texas at Dallas, and holds a BS in Computer Science. Pete can be contacted via Email at [email protected]

Comments (0)

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
DevOps is often described as a combination of technology and culture. Without both, DevOps isn't complete. However, applying the culture to outdated technology is a recipe for disaster; as response times grow and connections between teams are delayed by technology, the culture will die. A Nutanix Enterprise Cloud has many benefits that provide the needed base for a true DevOps paradigm.
SYS-CON Events announced today that Progress, a global leader in application development, has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Enterprises today are rapidly adopting the cloud, while continuing to retain business-critical/sensitive data inside the firewall. This is creating two separate data silos – one inside the firewall and the other outside the firewall. Cloud ISVs ofte...
Existing Big Data solutions are mainly focused on the discovery and analysis of data. The solutions are scalable and highly available but tedious when swapping in and swapping out occurs in disarray and thrashing takes place. The resolution for thrashing through machine learning algorithms and support nomenclature is through simple techniques. Organizations that have been collecting large customer data are increasingly seeing the need to use the data for swapping in and out and thrashing occurs ...
SYS-CON Events announced today that Outscale, a global pure play Infrastructure as a Service provider and strategic partner of Dassault Systèmes, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Founded in 2010, Outscale simplifies infrastructure complexities and boosts the business agility of its customers. Outscale delivers a secure, reliable and industrial strength solution for its customers, which in...
SYS-CON Events announced today that DivvyCloud will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. DivvyCloud software enables organizations to achieve their cloud computing goals by simplifying and automating security, compliance and cost optimization of public and private cloud infrastructure. Using DivvyCloud, customers can leverage programmatic Bots to identify and remediate common cloud problems in rea...
Amazon started as an online bookseller 20 years ago. Since then, it has evolved into a technology juggernaut that has disrupted multiple markets and industries and touches many aspects of our lives. It is a relentless technology and business model innovator driving disruption throughout numerous ecosystems. Amazon’s AWS revenues alone are approaching $16B a year making it one of the largest IT companies in the world. With dominant offerings in Cloud, IoT, eCommerce, Big Data, AI, Digital Assis...
SYS-CON Events announced today that delaPlex will exhibit at SYS-CON's @CloudExpo, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. delaPlex pioneered Software Development as a Service (SDaaS), which provides scalable resources to build, test, and deploy software. It’s a fast and more reliable way to develop a new product or expand your in-house team.
In order to meet the rapidly changing demands of today’s customers, companies are continually forced to redefine their business strategies in order to meet these needs, stay relevant and continue to see profitable growth. IoT deployment and development is integral in this transformation, and today businesses are increasingly seeing the value of investing their resources into IoT deployments. These technologies are able increase ROI through projects such as connecting supply chains or enabling sm...
SYS-CON Events announced today that Cloudistics, an on-premises cloud computing company, has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Cloudistics delivers a complete public cloud experience with composable on-premises infrastructures to medium and large enterprises. Its software-defined technology natively converges network, storage, compute, virtualization, and management into a ...
New competitors, disruptive technologies, and growing expectations are pushing every business to both adopt and deliver new digital services. This ‘Digital Transformation’ demands rapid delivery and continuous iteration of new competitive services via multiple channels, which in turn demands new service delivery techniques – including DevOps. In this power panel at @DevOpsSummit 20th Cloud Expo, moderated by DevOps Conference Co-Chair Andi Mann, panelists will examine how DevOps helps to meet th...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
Every successful software product evolves from an idea to an enterprise system. Notably, the same way is passed by the product owner's company. In his session at 20th Cloud Expo, Oleg Lola, CEO of MobiDev, will provide a generalized overview of the evolution of a software product, the product owner, the needs that arise at various stages of this process, and the value brought by a software development partner to the product owner as a response to these needs.
SYS-CON Events announced today that A&I Solutions has been named “Bronze Sponsor” of SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Founded in 1999, A&I Solutions is a leading information technology (IT) software and services provider focusing on best-in-class enterprise solutions. By partnering with industry leaders in technology, A&I assures customers high performance levels across all IT environments including: mai...
Most technology leaders, contemporary and from the hardware era, are reshaping their businesses to do software in the hope of capturing value in IoT. Although IoT is relatively new in the market, it has already gone through many promotional terms such as IoE, IoX, SDX, Edge/Fog, Mist Compute, etc. Ultimately, irrespective of the name, it is about deriving value from independent software assets participating in an ecosystem as one comprehensive solution.
SYS-CON Events announced today that EARP will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. "We are a software house, so we perfectly understand challenges that other software houses face in their projects. We can augment a team, that will work with the same standards and processes as our partners' internal teams. Our teams will deliver the same quality within the required time and budget just as our partn...
SYS-CON Events announced today that delaPlex will exhibit at SYS-CON's @ThingsExpo, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. delaPlex pioneered Software Development as a Service (SDaaS), which provides scalable resources to build, test, and deploy software. It’s a fast and more reliable way to develop a new product or expand your in-house team.
SYS-CON Events announced today that Tappest will exhibit MooseFS at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. MooseFS is a breakthrough concept in the storage industry. It allows you to secure stored data with either duplication or erasure coding using any server. The newest – 4.0 version of the software enables users to maintain the redundancy level with even 50% less hard drive space required. The software func...
In his keynote at @ThingsExpo, Chris Matthieu, Director of IoT Engineering at Citrix and co-founder and CTO of Octoblu, focused on building an IoT platform and company. He provided a behind-the-scenes look at Octoblu’s platform, business, and pivots along the way (including the Citrix acquisition of Octoblu).
SYS-CON Events announced today that Outscale will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Outscale's technology makes an automated and adaptable Cloud available to businesses, supporting them in the most complex IT projects while controlling their operational aspects. You boost your IT infrastructure's reactivity, with request responses that only take a few seconds.
SYS-CON Events announced today that Systena America will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Systena Group has been in business for various software development and verification in Japan, US, ASEAN, and China by utilizing the knowledge we gained from all types of device development for various industries including smartphones (Android/iOS), wireless communication, security technology and IoT serv...