Welcome!

Java IoT Authors: Stackify Blog, Yeshim Deniz, Pat Romanski, Matt Lonstine, Glenda Sims

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
DX World EXPO, LLC, a Lighthouse Point, Florida-based startup trade show producer and the creator of "DXWorldEXPO® - Digital Transformation Conference & Expo" has announced its executive management team. The team is headed by Levent Selamoglu, who has been named CEO. "Now is the time for a truly global DX event, to bring together the leading minds from the technology world in a conversation about Digital Transformation," he said in making the announcement.
"Space Monkey by Vivent Smart Home is a product that is a distributed cloud-based edge storage network. Vivent Smart Home, our parent company, is a smart home provider that places a lot of hard drives across homes in North America," explained JT Olds, Director of Engineering, and Brandon Crowfeather, Product Manager, at Vivint Smart Home, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that Conference Guru has been named “Media Sponsor” of the 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. A valuable conference experience generates new contacts, sales leads, potential strategic partners and potential investors; helps gather competitive intelligence and even provides inspiration for new products and services. Conference Guru works with conference organizers to pass great deals to gre...
The Internet of Things will challenge the status quo of how IT and development organizations operate. Or will it? Certainly the fog layer of IoT requires special insights about data ontology, security and transactional integrity. But the developmental challenges are the same: People, Process and Platform. In his session at @ThingsExpo, Craig Sproule, CEO of Metavine, demonstrated how to move beyond today's coding paradigm and shared the must-have mindsets for removing complexity from the develop...
In his Opening Keynote at 21st Cloud Expo, John Considine, General Manager of IBM Cloud Infrastructure, led attendees through the exciting evolution of the cloud. He looked at this major disruption from the perspective of technology, business models, and what this means for enterprises of all sizes. John Considine is General Manager of Cloud Infrastructure Services at IBM. In that role he is responsible for leading IBM’s public cloud infrastructure including strategy, development, and offering m...
"Evatronix provides design services to companies that need to integrate the IoT technology in their products but they don't necessarily have the expertise, knowledge and design team to do so," explained Adam Morawiec, VP of Business Development at Evatronix, in this SYS-CON.tv interview at @ThingsExpo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. In his session at @BigDataExpo, Jack Norris, Senior Vice President, Data and Applications at MapR Technologies, reviewed best practices to ...
Widespread fragmentation is stalling the growth of the IIoT and making it difficult for partners to work together. The number of software platforms, apps, hardware and connectivity standards is creating paralysis among businesses that are afraid of being locked into a solution. EdgeX Foundry is unifying the community around a common IoT edge framework and an ecosystem of interoperable components.
Large industrial manufacturing organizations are adopting the agile principles of cloud software companies. The industrial manufacturing development process has not scaled over time. Now that design CAD teams are geographically distributed, centralizing their work is key. With large multi-gigabyte projects, outdated tools have stifled industrial team agility, time-to-market milestones, and impacted P&L stakeholders.
"Akvelon is a software development company and we also provide consultancy services to folks who are looking to scale or accelerate their engineering roadmaps," explained Jeremiah Mothersell, Marketing Manager at Akvelon, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
"IBM is really all in on blockchain. We take a look at sort of the history of blockchain ledger technologies. It started out with bitcoin, Ethereum, and IBM evaluated these particular blockchain technologies and found they were anonymous and permissionless and that many companies were looking for permissioned blockchain," stated René Bostic, Technical VP of the IBM Cloud Unit in North America, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Conventi...
In his session at 21st Cloud Expo, Carl J. Levine, Senior Technical Evangelist for NS1, will objectively discuss how DNS is used to solve Digital Transformation challenges in large SaaS applications, CDNs, AdTech platforms, and other demanding use cases. Carl J. Levine is the Senior Technical Evangelist for NS1. A veteran of the Internet Infrastructure space, he has over a decade of experience with startups, networking protocols and Internet infrastructure, combined with the unique ability to it...
22nd International Cloud Expo, taking place June 5-7, 2018, at the Javits Center in New York City, NY, and co-located with the 1st DXWorld Expo will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud ...
"Cloud Academy is an enterprise training platform for the cloud, specifically public clouds. We offer guided learning experiences on AWS, Azure, Google Cloud and all the surrounding methodologies and technologies that you need to know and your teams need to know in order to leverage the full benefits of the cloud," explained Alex Brower, VP of Marketing at Cloud Academy, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clar...
Gemini is Yahoo’s native and search advertising platform. To ensure the quality of a complex distributed system that spans multiple products and components and across various desktop websites and mobile app and web experiences – both Yahoo owned and operated and third-party syndication (supply), with complex interaction with more than a billion users and numerous advertisers globally (demand) – it becomes imperative to automate a set of end-to-end tests 24x7 to detect bugs and regression. In th...
"MobiDev is a software development company and we do complex, custom software development for everybody from entrepreneurs to large enterprises," explained Alan Winters, U.S. Head of Business Development at MobiDev, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
Coca-Cola’s Google powered digital signage system lays the groundwork for a more valuable connection between Coke and its customers. Digital signs pair software with high-resolution displays so that a message can be changed instantly based on what the operator wants to communicate or sell. In their Day 3 Keynote at 21st Cloud Expo, Greg Chambers, Global Group Director, Digital Innovation, Coca-Cola, and Vidya Nagarajan, a Senior Product Manager at Google, discussed how from store operations and ...
"There's plenty of bandwidth out there but it's never in the right place. So what Cedexis does is uses data to work out the best pathways to get data from the origin to the person who wants to get it," explained Simon Jones, Evangelist and Head of Marketing at Cedexis, in this SYS-CON.tv interview at 21st Cloud Expo, held Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA.
SYS-CON Events announced today that CrowdReviews.com has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5–7, 2018, at the Javits Center in New York City, NY. CrowdReviews.com is a transparent online platform for determining which products and services are the best based on the opinion of the crowd. The crowd consists of Internet users that have experienced products and services first-hand and have an interest in letting other potential buye...
SYS-CON Events announced today that Telecom Reseller has been named “Media Sponsor” of SYS-CON's 22nd International Cloud Expo, which will take place on June 5-7, 2018, at the Javits Center in New York, NY. Telecom Reseller reports on Unified Communications, UCaaS, BPaaS for enterprise and SMBs. They report extensively on both customer premises based solutions such as IP-PBX as well as cloud based and hosted platforms.