|By Dan North||
|March 5, 2004 12:00 AM EST||
The vast majority of Java enterprise applications are architected along the lines of Sun's original PetStore showcase application. Rather than seeing this as a market stall displaying all the J2EE goods on offer, developers took it as a blueprint for enterprise applications. It certainly created a lot of work for Java application developers (as well as systems administrators and systems integrators), but whether most of the applications needed most of the possible layers - including bean-managed persistence and the ubiquitous DAO - is open for question at the very least. This article briefly describes some of the testability shortcomings of the traditional J2EE model and presents some alternatives.
The J2EE Model
With J2EE we are tied to a single logical server in a client/server architecture, and any component such as a servlet or EJB has to be deployed to the server (potentially a time-consuming process) before we know whether it works. This makes it difficult to use test-driven techniques to develop these components. To make a small change to such a component requires a code change, a recompile, and a redeploy. On many commercial application servers this sequence of events takes too long to be repeated as frequently as TDD requires. The developer is encouraged to deploy bigger changes less often, and therefore has a higher risk of introducing errors.
A few patterns alleviate some of this, most notably the Front Controller/Dispatcher pattern. This has a single component (a servlet in the Web container or a stateless session bean in the EJB tier) that dispatches requests to a POJO (Plain Old Java Object). A POJO is much better suited for unit testing - we can simply instantiate it in a known state and then exercise its behavior. From a TDD perspective, this is what makes a framework like WebWork more "agile" than Struts; for instance, the actual components are testable outside of a container.
J2EE encourages us to model a system in terms of components interacting with one another. Instead we can model in terms of services that an application provides or "things that it does." These services can exist on different machines or in different virtual machines on the same host. As long as we have a means of locating a service, we can use it. In terms of testability, this makes life a lot easier for us. A service is simply a class that implements an interface, so we can test its behavior in isolation or in conjunction with other services just by instantiating a service object and calling methods on it.
Service-oriented mechanisms such as SOAP, XML-RPC, or JINI are cleanly separated from the actual services they advertise. Compare this to a session bean, which is tightly coupled to its container: it requires a number of container-specific classes just to function (such as a javax.ejb. SessionContext), and has a whole complex life cycle associated with it. Both of these make testing a session bean a lot more complex - and add greatly to the time it takes to make a change and test it.
So far we have focused on synchronous behavior. The concept of modeling a system in terms of messages or events being produced and consumed asynchronously from queues is very powerful and yet still largely overlooked. Event-driven systems are renowned for their resilience, but they also lend themselves very nicely to a test-driven approach. As with services, an event consumer or listener is typically a Java class that implements an interface. As long as the consumer class is decoupled from the delivery mechanism, we can easily test its behavior. We can model synchronous behavior asynchronously to gain both scalability and testability. A Staged, Event-Driven Architecture (SEDA) simulates synchronous processing by means of a series of stages, each represented by a queue. Thus each stage can be unit-tested and developed separately.
When you're writing an enterprise application in Java, you shouldn't feel constrained to the classic J2EE model. Investigate some of the alternatives; ask lots of questions; and evaluate the costs, benefits, and risks of using a different approach. But most important, as a developer try to find an architecture that enables you to write testable code. Remember, PetStore is a showcase of technologies, not a blueprint.
|Tom 03/10/04 12:44:18 AM EST|
I agree on the statements made here. Personally I use the approach of moving all logic into POJO''s, which have no knowledge of how their functionality is made public. The servlet or EJB or webservice doing that, is just a hand-through taking care of the appropriate protocol.
|Tom 03/10/04 12:43:24 AM EST|
I agree on the statements made here. Personally I use the approach of moving all logic into POJO''s, which have no knowledge of how their functionality is made public. The servlet or EJB or webserver doing that, is just a hand-through taking care data of the appropriate protocol.
SYS-CON Events announced today that Harbinger Systems will exhibit at SYS-CON's 15th International Cloud Expo®, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Harbinger Systems is a global company providing software technology services. Since 1990, Harbinger has developed a strong customer base worldwide. Its customers include software product companies ranging from hi-tech start-ups in Silicon Valley to leading product companies in the US and large in-house IT organizations.
Oct. 30, 2014 06:00 PM EDT Reads: 3,180
The only place to be June 9-11 is Cloud Expo & @ThingsExpo 2015 East at the Javits Center in New York City. Join us there as delegates from all over the world come to listen to and engage with speakers & sponsors from the leading Cloud Computing, IoT & Big Data companies. Cloud Expo & @ThingsExpo are the leading events covering the booming market of Cloud Computing, IoT & Big Data for the enterprise. Speakers from all over the world will be hand-picked for their ability to explore the economic strategies that utility/cloud computing provides. Whether public, private, or in a hybrid form, clo...
Oct. 30, 2014 05:30 PM EDT Reads: 1,224
SYS-CON Events announces a new pavilion on the Cloud Expo floor where WebRTC converges with the Internet of Things. Pavilion will showcase WebRTC and the Internet of Things. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices--computers, smartphones, tablets, and sensors – connected to the Internet by 2020. This number will continue to grow at a rapid pace for the next several decades.
Oct. 30, 2014 05:30 PM EDT Reads: 2,176
SYS-CON Events announced today that Gridstore™, the leader in software-defined storage (SDS) purpose-built for Windows Servers and Hyper-V, will exhibit at SYS-CON's 15th International Cloud Expo®, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Gridstore™ is the leader in software-defined storage purpose built for virtualization that is designed to accelerate applications in virtualized environments. Using its patented Server-Side Virtual Controller™ Technology (SVCT) to eliminate the I/O blender effect and accelerate applications Gridsto...
Oct. 30, 2014 02:00 PM EDT Reads: 2,545
SYS-CON Events announced today that Red Hat, the world's leading provider of open source solutions, will exhibit at Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Red Hat is the world's leading provider of open source software solutions, using a community-powered approach to reliable and high-performing cloud, Linux, middleware, storage and virtualization technologies. Red Hat also offers award-winning support, training, and consulting services. As the connective hub in a global network of enterprises, partners, a...
Oct. 30, 2014 12:15 PM EDT Reads: 2,063
As the Internet of Things unfolds, mobile and wearable devices are blurring the line between physical and digital, integrating ever more closely with our interests, our routines, our daily lives. Contextual computing and smart, sensor-equipped spaces bring the potential to walk through a world that recognizes us and responds accordingly. We become continuous transmitters and receivers of data. In his session at Internet of @ThingsExpo, Andrew Bolwell, Director of Innovation for HP’s Printing and Personal Systems Group, will discuss how key attributes of mobile technology – touch input, senso...
Oct. 30, 2014 12:00 PM EDT Reads: 1,718
The Internet of Things (IoT) is making everything it touches smarter – smart devices, smart cars and smart cities. And lucky us, we’re just beginning to reap the benefits as we work toward a networked society. However, this technology-driven innovation is impacting more than just individuals. The IoT has an environmental impact as well, which brings us to the theme of this month’s #IoTuesday Twitter chat. The ability to remove inefficiencies through connected objects is driving change throughout every sector, including waste management. BigBelly Solar, located just outside of Boston, is trans...
Oct. 30, 2014 11:00 AM EDT Reads: 2,166
Connected devices and the Internet of Things are getting significant momentum in 2014. In his session at Internet of @ThingsExpo, Jim Hunter, Chief Scientist & Technology Evangelist at Greenwave Systems, will examine three key elements that together will drive mass adoption of the IoT before the end of 2015. The first element is the recent advent of robust open source protocols (like AllJoyn and WebRTC) that facilitate M2M communication. The second is broad availability of flexible, cost-effective storage designed to handle the massive surge in back-end data in a world where timely analytics...
Oct. 30, 2014 08:00 AM EDT Reads: 1,561
Internet of @ThingsExpo Silicon Valley announced on Thursday its first 12 all-star speakers and sessions for its upcoming event, which will take place November 4-6, 2014, at the Santa Clara Convention Center in California. @ThingsExpo, the first and largest IoT event in the world, debuted at the Javits Center in New York City in June 10-12, 2014 with over 6,000 delegates attending the conference. Among the first 12 announced world class speakers, IBM will present two highly popular IoT sessions, which will take place November 4-6, 2014 at the Santa Clara Convention Center in Santa Clara, Calif...
Oct. 30, 2014 07:30 AM EDT Reads: 2,261
The Internet of Things (IoT) promises to evolve the way the world does business; however, understanding how to apply it to your company can be a mystery. Most people struggle with understanding the potential business uses or tend to get caught up in the technology, resulting in solutions that fail to meet even minimum business goals. In his session at Internet of @ThingsExpo, Jesse Shiah, CEO / President / Co-Founder of AgilePoint Inc., will show what is needed to leverage the IoT to transform your business. He will discuss opportunities and challenges ahead for the IoT from a market and tec...
Oct. 29, 2014 11:00 PM EDT Reads: 1,523
SYS-CON Events announced today that TeleStax, the main sponsor of Mobicents, will exhibit at Internet of @ThingsExpo, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. TeleStax provides Open Source Communications software and services that facilitate the shift from legacy SS7 based IN networks to IP based LTE and IMS networks hosted on private (on-premise), hybrid or public clouds. TeleStax products include Restcomm, JSLEE, SMSC Gateway, USSD Gateway, SS7 Resource Adaptors, SIP Servlets, Rich Multimedia Services, Presence Services/RCS, Diame...
Oct. 29, 2014 05:00 PM EDT Reads: 1,630
From a software development perspective IoT is about programming "things," about connecting them with each other or integrating them with existing applications. In his session at @ThingsExpo, Yakov Fain, co-founder of Farata Systems and SuranceBay, will show you how small IoT-enabled devices from multiple manufacturers can be integrated into the workflow of an enterprise application. This is a practical demo of building a framework and components in HTML/Java/Mobile technologies to serve as a platform that can integrate new devices as they become available on the market.
Oct. 29, 2014 02:15 PM EDT Reads: 2,063
SYS-CON Events announced today that O'Reilly Media has been named “Media Sponsor” of SYS-CON's 15th International Cloud Expo®, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. O'Reilly Media spreads the knowledge of innovators through its books, online services, magazines, and conferences. Since 1978, O'Reilly Media has been a chronicler and catalyst of cutting-edge development, homing in on the technology trends that really matter and spurring their adoption by amplifying "faint signals" from the alpha geeks who are creating the future. An...
Oct. 29, 2014 01:00 PM EDT Reads: 1,601
The Transparent Cloud-computing Consortium (abbreviation: T-Cloud Consortium) will conduct research activities into changes in the computing model as a result of collaboration between "device" and "cloud" and the creation of new value and markets through organic data processing High speed and high quality networks, and dramatic improvements in computer processing capabilities, have greatly changed the nature of applications and made the storing and processing of data on the network commonplace.
Oct. 29, 2014 10:00 AM EDT Reads: 2,049
SYS-CON Events announced today that Aria Systems, the recurring revenue expert, has been named "Bronze Sponsor" of SYS-CON's 15th International Cloud Expo®, which will take place on November 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Aria Systems helps leading businesses connect their customers with the products and services they love. Industry leaders like Pitney Bowes, Experian, AAA NCNU, VMware, HootSuite and many others choose Aria to power their recurring revenue business and deliver exceptional experiences to their customers.
Oct. 29, 2014 10:00 AM EDT Reads: 2,117
The Internet of Things (IoT) is going to require a new way of thinking and of developing software for speed, security and innovation. This requires IT leaders to balance business as usual while anticipating for the next market and technology trends. Cloud provides the right IT asset portfolio to help today’s IT leaders manage the old and prepare for the new. Today the cloud conversation is evolving from private and public to hybrid. This session will provide use cases and insights to reinforce the value of the network in helping organizations to maximize their company’s cloud experience.
Oct. 29, 2014 09:00 AM EDT Reads: 2,079
As a disruptive technology, Web Real-Time Communication (WebRTC), which is an emerging standard of web communications, is redefining how brands and consumers communicate in real time. The on-going narrative around WebRTC has largely been around incorporating video, audio and chat functions to apps. In his session at Internet of @ThingsExpo, Alex Gouaillard, Founder and CTO of Temasys Communications, will look at a fourth element – data channels – and talk about its potential to move WebRTC beyond browsers and into the Internet of Things.
Oct. 29, 2014 08:00 AM EDT Reads: 1,639
SYS-CON Events announced today that Gigaom Research has been named "Media Sponsor" of SYS-CON's 15th International Cloud Expo®, which will take place on November 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Ashar Baig, Research Director, Cloud, at Gigaom Research, will also lead a Power Panel on the topic "Choosing the Right Cloud Option." Gigaom Research provides timely, in-depth analysis of emerging technologies for individual and corporate subscribers. Gigaom Research's network of 200+ independent analysts provides new content daily that bridges the gap between break...
Oct. 28, 2014 11:45 PM EDT Reads: 1,667
We certainly live in interesting technological times. And no more interesting than the current competing IoT standards for connectivity. Various standards bodies, approaches, and ecosystems are vying for mindshare and positioning for a competitive edge. It is clear that when the dust settles, we will have new protocols, evolved protocols, that will change the way we interact with devices and infrastructure. We will also have evolved web protocols, like HTTP/2, that will be changing the very core of our infrastructures. At the same time, we have old approaches made new again like micro-services...
Oct. 28, 2014 03:00 PM EDT Reads: 1,605
The Industrial Internet revolution is now underway, enabled by connected machines and billions of devices that communicate and collaborate. The massive amounts of Big Data requiring real-time analysis is flooding legacy IT systems and giving way to cloud environments that can handle the unpredictable workloads. Yet many barriers remain until we can fully realize the opportunities and benefits from the convergence of machines and devices with Big Data and the cloud, including interoperability, data security and privacy.
Oct. 28, 2014 12:00 PM EDT Reads: 1,951