Weblogic Authors: Yeshim Deniz, Elizabeth White, Michael Meiner, Michael Bushong, Avi Rosenthal

Related Topics: Weblogic

Weblogic: Article

Effective EJB: Make EJBs Work For You

"Java Development is at a Crossroads."

Do we façade? The decision to have a façade as a gateway for your other EJB components should be considered well ahead of time. It cannot be an afterthought. Once the decision has been made to have a façade, you can design the façade to return objects that are aggregations of values. The fine-grained access will be handled by the façade and is effective because it is generally within the container. This way we can reduce the number of round trips to the remote server.

Ok. We façade. But how good is our facade? When designing EJB interfaces the crucial points are that, for the purposes of designing remote interfaces, state should be avoided where possible and remote interfaces should be sufficiently coarse grained. Coarse graining interface design does not necessarily mean bundling all of the methods of your EJB layer inside one façade. Most often it is good to have multiple facades serving as gateways to your EJB components. When designing EJB-based architecture the safest approach is to find a balance between an object-oriented domain model and the procedural remote service layer.

Effective Exception Handling
Exception handling is another of the most muddled areas of EJB development. Exceptions are basically a breakaway from the expected behavior. These breaks are very common in distributed architectures because there are too many heterogeneous environments involved that are all connected by the network. A single network failure can trigger a catastrophe. Handling exceptions in EJB is particularly complex, and EJB involves two types of exceptions. The following are some guidelines for handling exceptions.

  • Refractor Logic out of Exception Handling Blocks. Having application logic inside exception handling code is a bad practice that often leads to code that is difficult to understand, change, and debug. The particular case in EJB programming where logic is deliberately pushed into exception handling code is transaction rollbacks. Rolling back transactions when there is an exception confuses program flow. Also, rolling back a container-managed transaction is not a straightforward task. EJB specification recommends use of EJBContext.setRollBackOnly() instead. Second, transaction rollback during an exception is not always appropriate. Third, transaction rollback falls outside of the transaction implementation. If an application throws an exception when running inside an EJB with notSupported transaction attribute, there is confusion as to whether to roll back the suspended enclosing transaction or not.
  • Don't Swallow Exceptions. Exception logging is an important part of any component design. One of the most common mistakes made by developers is to just print the exception and continue as if nothing has happened. Whenever there is an exception, it is an indication that something has gone wrong. The error could be on part of the container or in your application code itself. Simply logging exceptions without much detail makes debugging very difficult. Java provides an elegant way of logging the complete exception trace. In most cases, the exception trace would provide all of the information that is required to debug a problem. It is also better to have a custom verbose attached to the exception trace to help make understanding the situation easier.
  • Throw the Right Exception. Always. One bad practice in many EJB implementations is the tendency to wrap application exceptions into Container exceptions and throw them at the client. This practice stems from the misconception that the container handles all things for you when you are developing an EJB. However, container exceptions are specialized cases where there is a failure on part of the container, while the application exceptions are a run-time application failure. An example of application exception is invalid credit card number. This should not be wrapped inside a container exception like EJBException. The application exceptions are to be gracefully handled as in any other normal Java class.
  • Look for Hot Potatoes. A hot potato is a particular situation where a MDB repeatedly receives a same message and throws an exception while handling the message. When a JMS server does not receive an acknowledgement for a message delivered to a consumer, the server's only recourse is to resend the message. This sets the stage for repeated delivery of the same message indefinitely when the consumer that is processing the message does not handle an exception condition properly.
When developing MDBs care should be taken to identify potential areas of code that cause the hot potato situation. The solution for this is to break the acknowledgement and message processing into two execution paths. Acknowledge the message immediately once received. When an exception occurs during message processing, you may possibly write the exception to an error queue.

Effective EJB Persistence
The EJB specification addresses the persistence services through a special class of beans called entity beans. Entity beans are aimed at abstracting the domain data model. As such, they represent rows in a database table if the underlying datasource is an RDBMS. Initial specifications sparked a lot of controversy about entity beans and their usage. Henceforth, the persistence API has been rewritten twice in 1.1 and 2.0 specifications.

Because persistence is a fine-grained service it does not fit naturally into the coarse-grained nature of EJB services. This brings in a lot of confusion about how best to use entity beans. Before the decision to use entity beans has been made, a careful evaluation of alternate persistence models is advised. If a decision has been made to use entity beans, the following problems should be carefully considered and evaluated.

Exposing Entity Beans Directly to the Client Through Remote Interfaces
Due to their fine-grained nature, entity beans provide fertile grounds for antipatterns when exposed directly to the client. One of the most popular problems that is likely to be encountered is the n + 1 problem. This means you will require n + 1 remote calls to retrieve n attributes of a business entity. The extra call is to obtain the remote stub from the EJB container. Addressing the same retrieval function through a plain POJO DAO is much easier. All you will require is a JDBC call to retrieve the rows.

A more subtle problem associated with exposing entity beans is the loss of transaction integrity. Consider an entity bean with three mutator methods. Further assume that a client needs to update two columns of the entity represented by two mutator methods in a transaction. How does the client ensure that transaction integrity is maintained between two successive update methods on the entity bean? The only way out is to use a session façade to wrap the entity bean.

Avoid Application Joins
Managing entity relations within the application code will cause serious performance issues. Java is not optimized for database lookups. It is a bad programming practice to emulate application joins inside Java code. Databases use sophisticated technologies to optimize query access plans and consequently minimize the number of data comparisons. For example, the act of looking up for a Person entity when given an address entity within the application does not scale. These types of relations are best expressed in terms of a CMR field (from EJB 2.0). The number of comparisons that an application makes inside a loop construct in an attempt to simulate a relational join will have a severe impact on application performance.

More Stories By Shankar Itchapurapu

Shankar Itchapurapu is a software engineer at Oracle in India. He holds a Master's degree in Computer Applications. You can e-mail Shankar at [email protected]

Comments (3)

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
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...
Nordstrom is transforming the way that they do business and the cloud is the key to enabling speed and hyper personalized customer experiences. In his session at 21st Cloud Expo, Ken Schow, VP of Engineering at Nordstrom, discussed some of the key learnings and common pitfalls of large enterprises moving to the cloud. This includes strategies around choosing a cloud provider(s), architecture, and lessons learned. In addition, he covered some of the best practices for structured team migration an...
Product connectivity goes hand and hand these days with increased use of personal data. New IoT devices are becoming more personalized than ever before. In his session at 22nd Cloud Expo | DXWorld Expo, Nicolas Fierro, CEO of MIMIR Blockchain Solutions, will discuss how in order to protect your data and privacy, IoT applications need to embrace Blockchain technology for a new level of product security never before seen - or needed.
Imagine if you will, a retail floor so densely packed with sensors that they can pick up the movements of insects scurrying across a store aisle. Or a component of a piece of factory equipment so well-instrumented that its digital twin provides resolution down to the micrometer.
In his keynote at 18th Cloud Expo, Andrew Keys, Co-Founder of ConsenSys Enterprise, provided 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 settle...
BnkToTheFuture.com is the largest online investment platform for investing in FinTech, Bitcoin and Blockchain companies. We believe the future of finance looks very different from the past and we aim to invest and provide trading opportunities for qualifying investors that want to build a portfolio in the sector in compliance with international financial regulations.
No hype cycles or predictions of a gazillion things here. IoT is here. You get it. You know your business and have great ideas for a business transformation strategy. What comes next? Time to make it happen. In his session at @ThingsExpo, Jay Mason, an Associate Partner of Analytics, IoT & Cybersecurity at M&S Consulting, presented a step-by-step plan to develop your technology implementation strategy. He also discussed the evaluation of communication standards and IoT messaging protocols, data...
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 ...
In his session at 21st Cloud Expo, Raju Shreewastava, founder of Big Data Trunk, provided a fun and simple way to introduce Machine Leaning to anyone and everyone. He solved a machine learning problem and demonstrated an easy way to be able to do machine learning without even coding. Raju Shreewastava is the founder of Big Data Trunk (www.BigDataTrunk.com), a Big Data Training and consulting firm with offices in the United States. He previously led the data warehouse/business intelligence and B...
"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...
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...
When shopping for a new data processing platform for IoT solutions, many development teams want to be able to test-drive options before making a choice. Yet when evaluating an IoT solution, it’s simply not feasible to do so at scale with physical devices. Building a sensor simulator is the next best choice; however, generating a realistic simulation at very high TPS with ease of configurability is a formidable challenge. When dealing with multiple application or transport protocols, you would be...
Smart cities have the potential to change our lives at so many levels for citizens: less pollution, reduced parking obstacles, better health, education and more energy savings. Real-time data streaming and the Internet of Things (IoT) possess the power to turn this vision into a reality. However, most organizations today are building their data infrastructure to focus solely on addressing immediate business needs vs. a platform capable of quickly adapting emerging technologies to address future ...
We are given a desktop platform with Java 8 or Java 9 installed and seek to find a way to deploy high-performance Java applications that use Java 3D and/or Jogl without having to run an installer. We are subject to the constraint that the applications be signed and deployed so that they can be run in a trusted environment (i.e., outside of the sandbox). Further, we seek to do this in a way that does not depend on bundling a JRE with our applications, as this makes downloads and installations rat...
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.
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.
In this strange new world where more and more power is drawn from business technology, companies are effectively straddling two paths on the road to innovation and transformation into digital enterprises. The first path is the heritage trail – with “legacy” technology forming the background. Here, extant technologies are transformed by core IT teams to provide more API-driven approaches. Legacy systems can restrict companies that are transitioning into digital enterprises. To truly become a lead...
Digital Transformation (DX) is not a "one-size-fits all" strategy. Each organization needs to develop its own unique, long-term DX plan. It must do so by realizing that we now live in a data-driven age, and that technologies such as Cloud Computing, Big Data, the IoT, Cognitive Computing, and Blockchain are only tools. In her general session at 21st Cloud Expo, Rebecca Wanta explained how the strategy must focus on DX and include a commitment from top management to create great IT jobs, monitor ...
"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...
The IoT Will Grow: In what might be the most obvious prediction of the decade, the IoT will continue to expand next year, with more and more devices coming online every single day. What isn’t so obvious about this prediction: where that growth will occur. The retail, healthcare, and industrial/supply chain industries will likely see the greatest growth. Forrester Research has predicted the IoT will become “the backbone” of customer value as it continues to grow. It is no surprise that retail is ...