Welcome!

Java IoT Authors: APM Blog, Stackify Blog, Liz McMillan, William Schmarzo, Elizabeth White

Related Topics: Java IoT, Mobile IoT

Java IoT: Article

Java J2EE Lite with Spring Framework

The combined burden of EJBs and coarse-grained component design has given the term test driven design a new meaning

To further drive this point home, let's assume a physical architecture of a J2EE application that uses the EJB approach. (This by no means is the only possible architecture, but it helps make some important points.) Figure 6 shows Web apps and some EJBs collocated on the same physical machine.

Just because Web apps and EJBs are collocated, three of these runtime services are not needed:

  • The remoting of EJBs is not necessary as Web apps will call EJBs locally.
  • Clustering of EJBs is achieved via replica-aware home and remote stubs. Again, since the caller (Web app) and the called object (EJB) are on the same machine, there is not much sense in using cluster-aware stubs. Note that HttpSession replication for making Web apps cluster-aware is still desirable though.
  • Typically, if EJBs are not remoted, then you wouldn't want to impose security restrictions at the EJB tier.
As for the following runtime services:
  • Caching of entity EJBs in the container, on the other hand, is a valuable benefit that may be considered depending on the use case at hand.
  • Transactions are the most commonly used service provided declaratively by the EJB container. Many developers prefer the declarative use of Container Managed Transactions (CMT) over programmatic transaction management.
  • Persistence is now a separate specification from the EJB specification (JSR-220) and therefore, in future, will not be a direct service of the EJB container. However, it is a valuable service that can save development time, and, in some cases perform better.
We see that just collocating causes some of the services provided by the EJB container to become redundant.

Therefore applications designed using EJBs will have to interject a container every time a service is invoked, even if it doesn't need 90% of the services it offers. In addition, it will be designed coarsely with the EJB's remote interface and bandwidth considerations. Compare this with a Spring-based design where the business classes are first designed, unencumbered by EJB technology, using all the power of OO design like inheritance and coding to interfaces. Once the business design is complete, then infrastructure services are applied to them on an as-needed basis.

However, many times collocation is not a good fit. Sometimes, depending on the use case, EJBs become a desired feature. For example, middle-tier bean caching necessitates the use of entity EJBs and clustering at an EJB level necessitates the use of session EJBs. For these and other reasons, let's look at how to access SLSBs from Spring.

Defining StatelessSessionBeans in the BeanFactory
SLSBs are widely used to provide the service façade in business applications. Sometimes it's not advisable to remove all SLSBs in favor of proxied objects. In fact, the non-invasive nature of Spring makes it a good candidate for phasing in its use. For that reason or other legitimate uses of SLSBs (like third-party SLSBs), it's easy to make Spring managed beans and SLSBs coexist in the same application.

In Listing 17 we will see how an SLSB can be wrapped in a Spring-managed bean that can be retrieved from the BeanFactory. In the listing the orderContext.xml file shows how a Spring-supplied class (SimpleRemoteStatelessSessionProxyFactoryBean) is injected with a jndiName and a JNDI location for telling it where a certain EJB lives.

The second point is the businessInterface property into which OrderService interface is injected. This is different from the EJBRemote interface and is just a Java interface that is also implemented by the POJO manager OrderServiceImpl.

Beyond that, it is business as usual. The SLSB can now be accessed just like any other bean managed by the Spring bean factory by using the handle orderServiceEJBProxy.

At this point, we have demonstrated that Spring can easily straddle an application that uses SLSBs at the service layer and service objects built from scratch using Spring.

Accessing the Bean Factory from a Web App
Now that we have defined services in the bean factory, how do we actually access the instance of those services? Spring provides several generic classes to make this task easier.

The ApplicationContext interface is at the root of the hierarchy of several interfaces whose implementers read the BeanFactory (or factories) into objects accessible by clients. The WebApplicationContext is one such interface for accessing the BeanFactory from a Web app, as shown in Listing 18.

First the web.xml of the Web app has the following lines supplied that tell the ServletContext about Spring's bean factory. The ContextLoaderListener loads up the Bean Factory configuration at Web app startup time. Next, the Order.jsp (that lives in the bundled Web app made2order.war) loads up the context from the ServletContext as shown in Listing 19. orderService and myProxiedServiceWithSeveralInterceptors are instances of singleton services that are defined in the BeanFactory.

Similarly, ClassPathXmlApplicationContext(paths) is another helper class that gets services from the BeanFactory as is used in the JUnit test suite's setup() method (see Listing 20). Note that a new BeanFactory can be swapped in at runtime by placing it in the classpath and destroying the current context.

Testing
Encouraging good testing practices is one of the value propositions of Spring. IoC is a good mechanism to encourage integration testing, whereas coding to interfaces is really what facilitates Unit testing.

In our example, jdbcOrderDAO can be easily replaced by a hibernateOrderDAO for conducting JUnit integration tests from within Eclipse, for example.

Similarly, instead of using a POJO manager implementation of OrderService, you can just as easily replace the implementation with the OrderEJB (which also implements the OrderService interface).

For unit testing on the other hand, EasyMock has been used. The class OrderServiceUnitTest only tests the service implementation by injecting a mock dao into the service layer. Since OrderDAO is an interface, this is easily achieved by casting the MockControl.getMock() method to return an OrderDAO instance. Then, by injecting the mockDAO to the service (setter injection), we can only test the code in the service. EasyMock uses the concept of recording and playback. The exact calls to the mockDAO are recorded first and then the test case is run. EasyMock asserts whether or not the playback is exactly the same as the one recorded.

For more detailed examples, look at the class OrderServiceUnitTest.java.

Because of the simple nature of this application, it certainly doesn't make it a good candidate for an example of test driven design. However, all else being equal, easily testable code will more be more likely to drive design than code that is hard to test.

Where Do We Go from Here
Spring provides an IoC and AOP-based framework to build infrastructure services. Even though we identified some EJB container-based services that are not needed; sometimes, depending on the use case, those services provide value. In those cases, remoting, security, and persistence can be applied to Spring proxy using the same mechanism that was used by transactions or auditing. This allows for open-ended growth where services are applied on an as-needed basis to certain Spring-managed service beans. The sample application does not show these additional features, however, the interested reader can explore Spring supplied support classes for:

  • Remoting using Caucho's Hessian and Burlap protocols
  • Security using Acegi
  • Persistence using Hibernate
There are several Spring classes for other services, which are not mentioned here.

Summary
We have implemented the separation-of-concerns pattern by isolating business code from infrastructure code via method interception and Spring proxies. In addition, using IoC and the convenience of a BeanFactory, we are able to inject different implementations into different service contracts.

By moving to a POJO-based business tier, our design is not encumbered by bandwidth considerations as with EJB design. The design of the applica-tion can be as object-oriented and fine-grained as needed because we are not dealing with issues of multiple inheritance or layering.

We looked at the scalability issues and concluded that we can apply several enterprise-level services on an as-needed basis while still remaining cluster-able at a Web app level.

We looked at testing strategies and showed that coding to interfaces allows for the easy use of third-party testing tools like EasyMock. IoC via interfaces allows for integration testing using a configurable bean factory.

In the end, made2order is easier to maintain because we have removed infrastructure code from our business code. It is easier to test because of ease of configuration using a bean factory approach and coding to interfaces. Last, it performs better compared to an EJB-based solution because we are not interjecting a one-size-fits-all container in our business operations.

References

More Stories By Pankaj Tandon

Pankaj Tandon is a software engineer at Crowncastle. His interests include object-oriented design and development and architecting the software process using open source technologies. He is a Sun Certified Java developer for the Java 2 platform. He lives in Pittsburgh, PA, plays guitar, and mixes music in his spare time.

Comments (6) View Comments

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.


Most Recent Comments
Pankaj Tandon 02/21/06 10:38:18 AM EST

I just realized that if you are here then you have already found the online version of the article.. here is the link to the downloadable artifact then..
http://res.sys-con.com/story/feb06/180377/source.html

Click on "Additional Code II" to get the full webapp+ code.

Pankaj Tandon 02/17/06 05:48:23 PM EST

Hi all,
I have received several emails from folks telling me about this snafu on JDJs part.
The link is there burried somewhere in the JDJ labyrinth.
You can get to it and some performance analysis at:
http://technochord.blogspot.com/2006/02/j2ee-lite-with-spring-framework....

Bob Raker 02/16/06 11:37:12 AM EST

This was a very good article. But, where the hell does one go to download listing 9-20. Thanks.

Rob Moore 02/14/06 12:14:11 PM EST

Is the sample code available?

Thanks,

Rob

SYS-CON Brazil News Desk 02/14/06 09:46:50 AM EST

J2EE applications of late have become weight conscious. The combined burden of EJBs and coarse-grained component design has given the term test driven design a new meaning: technology driven design! Fortunately a host of lightweight solutions are emerging, such as PicoContainer, Spring Framework, Hivemind, Hibernate, Castor, and Webwork. In this article I'll discuss my experience with the Spring Framework and how it can be used to make a J2EE application more maintainable, testable, and better performing.

SYS-CON India News Desk 02/13/06 02:55:13 PM EST

J2EE applications of late have become weight conscious. The combined burden of EJBs and coarse-grained component design has given the term test driven design a new meaning: technology driven design! Fortunately a host of lightweight solutions are emerging, such as PicoContainer, Spring Framework, Hivemind, Hibernate, Castor, and Webwork. In this article I'll discuss my experience with the Spring Framework and how it can be used to make a J2EE application more maintainable, testable, and better performing.

@ThingsExpo Stories
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...
"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.
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.
"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...
"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.
"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.
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...
"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...
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.
"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.
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 ...
It is of utmost importance for the future success of WebRTC to ensure that interoperability is operational between web browsers and any WebRTC-compliant client. To be guaranteed as operational and effective, interoperability must be tested extensively by establishing WebRTC data and media connections between different web browsers running on different devices and operating systems. In his session at WebRTC Summit at @ThingsExpo, Dr. Alex Gouaillard, CEO and Founder of CoSMo Software, presented ...
WebRTC is great technology to build your own communication tools. It will be even more exciting experience it with advanced devices, such as a 360 Camera, 360 microphone, and a depth sensor camera. In his session at @ThingsExpo, Masashi Ganeko, a manager at INFOCOM Corporation, introduced two experimental projects from his team and what they learned from them. "Shotoku Tamago" uses the robot audition software HARK to track speakers in 360 video of a remote party. "Virtual Teleport" uses a multip...
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...
SYS-CON Events announced today that Evatronix 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. Evatronix SA offers comprehensive solutions in the design and implementation of electronic systems, in CAD / CAM deployment, and also is a designer and manufacturer of advanced 3D scanners for professional applications.
Leading companies, from the Global Fortune 500 to the smallest companies, are adopting hybrid cloud as the path to business advantage. Hybrid cloud depends on cloud services and on-premises infrastructure working in unison. Successful implementations require new levels of data mobility, enabled by an automated and seamless flow across on-premises and cloud resources. In his general session at 21st Cloud Expo, Greg Tevis, an IBM Storage Software Technical Strategist and Customer Solution Architec...
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 ...
An increasing number of companies are creating products that combine data with analytical capabilities. Running interactive queries on Big Data requires complex architectures to store and query data effectively, typically involving data streams, an choosing efficient file format/database and multiple independent systems that are tied together through custom-engineered pipelines. In his session at @BigDataExpo at @ThingsExpo, Tomer Levi, a senior software engineer at Intel’s Advanced Analytics gr...
When talking IoT we often focus on the devices, the sensors, the hardware itself. The new smart appliances, the new smart or self-driving cars (which are amalgamations of many ‘things’). When we are looking at the world of IoT, we should take a step back, look at the big picture. What value are these devices providing? IoT is not about the devices, it’s about the data consumed and generated. The devices are tools, mechanisms, conduits. In his session at Internet of Things at Cloud Expo | DXWor...