|By Pete Whitney||
|August 10, 2005 12:00 PM EDT||
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...
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:
- Resource wrapping
- Application isolation
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
3 public void
6 Date today = new Date();
7 PersonDAO personDao =
8 new PersonDAO();
9 Collection persons =
11 // Do what needs to be done
12 // to report on those that
13 // have birthdays today.
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
The IoT is changing the way enterprises conduct business. In his session at @ThingsExpo, Eric Hoffman, Vice President at EastBanc Technologies, discuss how businesses can gain an edge over competitors by empowering consumers to take control through IoT. We'll cite examples such as a Washington, D.C.-based sports club that leveraged IoT and the cloud to develop a comprehensive booking system. He'll also highlight how IoT can revitalize and restore outdated business models, making them profitable...
May. 30, 2016 02:00 PM EDT Reads: 3,053
SYS-CON Events announced today that MangoApps will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. MangoApps provides modern company intranets and team collaboration software, allowing workers to stay connected and productive from anywhere in the world and from any device. For more information, please visit https://www.mangoapps.com/.
May. 30, 2016 01:30 PM EDT Reads: 1,128
SYS-CON Events announced today the How to Create Angular 2 Clients for the Cloud Workshop, being held June 7, 2016, in conjunction with 18th Cloud Expo | @ThingsExpo, at the Javits Center in New York, NY. Angular 2 is a complete re-write of the popular framework AngularJS. Programming in Angular 2 is greatly simplified. Now it’s a component-based well-performing framework. The immersive one-day workshop led by Yakov Fain, a Java Champion and a co-founder of the IT consultancy Farata Systems and...
May. 30, 2016 12:00 PM EDT Reads: 4,113
What a difference a year makes. Organizations aren’t just talking about IoT possibilities, it is now baked into their core business strategy. With IoT, billions of devices generating data from different companies on different networks around the globe need to interact. From efficiency to better customer insights to completely new business models, IoT will turn traditional business models upside down. In the new customer-centric age, the key to success is delivering critical services and apps wit...
May. 30, 2016 11:15 AM EDT Reads: 1,343
Join us at Cloud Expo | @ThingsExpo 2016 – June 7-9 at the Javits Center in New York City and November 1-3 at the Santa Clara Convention Center in Santa Clara, CA – and deliver your unique message in a way that is striking and unforgettable by taking advantage of SYS-CON's unmatched high-impact, result-driven event / media packages.
May. 30, 2016 11:00 AM EDT Reads: 2,575
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, will provide an overview of the evolution of the Internet and the Database and the future of their combination – the Blockchain. Andrew Keys is Co-Founder of ConsenSys Enterprise. He comes to ConsenSys Enterprise with capital markets, technology and entrepreneurial experience. Previously, he worked for UBS investment bank in equities analysis. Later, he was responsible for the creation and distribution of life ...
May. 30, 2016 10:45 AM EDT Reads: 2,060
SYS-CON Events announced today that BMC Software has been named "Siver Sponsor" of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2015 at the Javits Center in New York, New York. BMC is a global leader in innovative software solutions that help businesses transform into digital enterprises for the ultimate competitive advantage. BMC Digital Enterprise Management is a set of innovative IT solutions designed to make digital business fast, seamless, and optimized from mainframe to mo...
May. 30, 2016 09:15 AM EDT Reads: 2,386
SYS-CON Events announced today that MobiDev will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. MobiDev is a software company that develops and delivers turn-key mobile apps, websites, web services, and complex software systems for startups and enterprises. Since 2009 it has grown from a small group of passionate engineers and business managers to a full-scale mobile software company with over 200 develope...
May. 30, 2016 09:15 AM EDT Reads: 2,826
As cloud and storage projections continue to rise, the number of organizations moving to the cloud is escalating and it is clear cloud storage is here to stay. However, is it secure? Data is the lifeblood for government entities, countries, cloud service providers and enterprises alike and losing or exposing that data can have disastrous results. There are new concepts for data storage on the horizon that will deliver secure solutions for storing and moving sensitive data around the world. ...
May. 30, 2016 09:00 AM EDT Reads: 1,448
SoftLayer operates a global cloud infrastructure platform built for Internet scale. With a global footprint of data centers and network points of presence, SoftLayer provides infrastructure as a service to leading-edge customers ranging from Web startups to global enterprises. SoftLayer's modular architecture, full-featured API, and sophisticated automation provide unparalleled performance and control. Its flexible unified platform seamlessly spans physical and virtual devices linked via a world...
May. 30, 2016 08:00 AM EDT Reads: 2,394
SYS-CON Events announced today that ContentMX, the marketing technology and services company with a singular mission to increase engagement and drive more conversations for enterprise, channel and SMB technology marketers, has been named “Sponsor & Exhibitor Lounge Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York City, New York. “CloudExpo is a great opportunity to start a conversation with new prospects, but what happens after the...
May. 30, 2016 07:15 AM EDT Reads: 1,418
Companies can harness IoT and predictive analytics to sustain business continuity; predict and manage site performance during emergencies; minimize expensive reactive maintenance; and forecast equipment and maintenance budgets and expenditures. Providing cost-effective, uninterrupted service is challenging, particularly for organizations with geographically dispersed operations.
May. 30, 2016 07:00 AM EDT Reads: 2,272
The IoTs 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, will demonstrate how to move beyond today's coding paradigm and share the must-have mindsets for removing complexity from the development proc...
May. 30, 2016 06:00 AM EDT Reads: 2,015
SYS-CON Events announced today TechTarget has been named “Media Sponsor” of SYS-CON's 18th International Cloud Expo, which will take place on June 7–9, 2016, at the Javits Center in New York City, NY, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. TechTarget is the Web’s leading destination for serious technology buyers researching and making enterprise technology decisions. Its extensive global networ...
May. 30, 2016 05:30 AM EDT Reads: 3,308
SYS-CON Events announced today that Commvault, a global leader in enterprise data protection and information management, has been named “Bronze Sponsor” of SYS-CON's 18th International Cloud Expo, which will take place on June 7–9, 2016, at the Javits Center in New York City, NY, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Commvault is a leading provider of data protection and information management...
May. 30, 2016 04:45 AM EDT Reads: 3,336
The essence of data analysis involves setting up data pipelines that consist of several operations that are chained together – starting from data collection, data quality checks, data integration, data analysis and data visualization (including the setting up of interaction paths in that visualization). In our opinion, the challenges stem from the technology diversity at each stage of the data pipeline as well as the lack of process around the analysis.
May. 30, 2016 03:15 AM EDT Reads: 1,546
Designing IoT applications is complex, but deploying them in a scalable fashion is even more complex. A scalable, API first IaaS cloud is a good start, but in order to understand the various components specific to deploying IoT applications, one needs to understand the architecture of these applications and figure out how to scale these components independently. In his session at @ThingsExpo, Nara Rajagopalan is CEO of Accelerite, will discuss the fundamental architecture of IoT applications, ...
May. 30, 2016 03:00 AM EDT Reads: 1,403
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, wh...
May. 30, 2016 03:00 AM EDT Reads: 2,094
SYS-CON Events announced today that Tintri Inc., a leading producer of VM-aware storage (VAS) for virtualization and cloud environments, will exhibit at the 18th International CloudExpo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, New York, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA.
May. 30, 2016 02:45 AM EDT Reads: 2,543
SYS-CON Events announced today that Alert Logic, Inc., the leading provider of Security-as-a-Service solutions for the cloud, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. Alert Logic, Inc., provides Security-as-a-Service for on-premises, cloud, and hybrid infrastructures, delivering deep security insight and continuous protection for customers at a lower cost than traditional security solutions. Ful...
May. 30, 2016 02:15 AM EDT Reads: 3,037