Welcome!

Java IoT Authors: Pat Romanski, Zakia Bouachraoui, Elizabeth White, Liz McMillan, Yeshim Deniz

Related Topics: Java IoT

Java IoT: Article

Spring and Java EE 5 (PART 1)

Simplicity and power combined

Register for Real-World Java Seminar

The Java Platform, Enterprise Edition, or Java EE, is the most popular middleware platform for developing and deploying enterprise applications. Java EE offers developers a choice of vendors, portability, scalability, and robustness. However, it has been criticized for its complexity and its need for a lot of redundant and procedural code. In addition, lightweight frameworks such as Spring and scripting platforms such as Ruby on Rails have emerged to challenge the platform's supremacy in the middleware world.

In response, the Java Community Process has made great efforts to simplify the developer's life with Java EE's latest incarnation: Java EE 5. Innovations such as radically simplified models for Enterprise JavaBeans (EJB) and Web services have changed how enterprise applications are built using Java EE 5 technologies. Combining the robustness of the Java EE platform with lightweight frameworks such as Spring further enables developers to rapidly develop portable, maintainable enterprise applications.

In this two-part series, I will discuss how Java EE 5 simplifies enterprise application development, then uncover how you can utilize the Spring Framework to fill the gaps left by Java EE 5.

Simplified Programming Model with Java EE 5
Java EE 5 radically simplifies the development of enterprise applications by:

  • Adopting a plain old Java object (POJO) programming standard and setting intelligent defaults for EJB components
  • Eliminating the need for deployment descriptors and using Java metadata annotations for deployment settings instead
  • Introducing a simplified POJO persistence model similar to Oracle TopLink and JBoss Hibernate
  • Using dependency injection instead of the Java Naming and Directory Interface (JNDI) to locate resources and EJB components

Let's briefly examine these changes.

Simplified Persistence
Most developers who used the EJB 2 container-managed persistence were disappointed with its complexity and performance. As a result, POJO persistence frameworks such as Hibernate and TopLink became popular, compelling the Java Community Process to standardize a persistence API for the Java platform on a POJO persistence model.

If you've used an object-relational (O/R) mapping framework to build the persistence tier of your application, you'll notice that each framework provides three facilities:

  • A declarative way to perform O/R mapping. This method, called O/R mapping metadata, lets you map an object to one or more database tables. Most O/R frameworks use XML for storing O/R mapping metadata.
  • An API to manipulate entities (for example, to perform create, read, update, and delete - or CRUD - operations). The API lets you persist, retrieve, update, or remove objects. Based on the use of the API and the O/R mapping metadata, the O/R framework performs database operations on your behalf. The API shields you from writing Java Database Connectivity (JDBC) or SQL code to persist your domain objects.
  • A query language to retrieve objects. This is one of the most important aspects of persistence because improper SQL statements may slow down your database. A query language also protects your applications from being cluttered with proprietary SQL, and lets you retrieve entities or objects without writing SQL SELECT statements.

The EJB 3 Java Persistence API (JPA) standardizes the use of persistence for the Java platform by providing a standard mechanism for O/R mapping, an EntityManager API to perform CRUD operations, and a way to extend the EJB query language (EJB-QL) to retrieve entities.

Introducing JPA Entities
An entity is a lightweight domain object - a plain old Java object that you want to persist in a relational database. Like any POJO, an entity may be either an abstract or a concrete class, and it can extend another POJO. You can use the @javax.persistence.Entity annotation to mark a POJO to be an entity, as shown in Listing 1.

(The code examples that follow are taken from my recently published book, EJB 3 in Action, published by Manning Publications.)

I've used annotations to define the mapping of entities to tables; you can also use XML. It's worth mentioning that JPA provides support for rich domain modeling capabilities such as inheritance, and polymorphism. JPA supports several inheritance mapping strategies: single table, joined subclass, and table per class. Unlike EJB 2 container-managed persistence (CMP), JPA is simple and supports automatic generation of primary keys.

Now that you've seen an entity, let's examine how you can manipulate entities by using the EntityManager API.

The EntityManager API
The javax.persistence.EntityManager manages entity lifecycles and exposes several methods to perform CRUD operations on entities. JPA supports two types of EntityManager: container-managed and application-managed. The application-managed EntityManager is really useful when using JPA outside a container. Let's look at an example of using a container-managed EntityManager to manage an entity.

You can use the persist() method to save an instance of entity. For example, if you want to persist an instance of Bid, use the following code:

@PersistenceContext(unitName="actionBazaar")
private EntityManager em;
...
Bid bid = new Bid();
bid.setItem(item);
bid.setBidder(bidder);
bid.setBidPrice(price);
em.persist(bid);

Now that you have a sense of how easy it is to use the persistence feature of EJB 3, we'll examine how EJB 3 simplifies the development of business components.

Simplified EJB 3 Components
EJB 2 was one of the primary technologies responsible for the complexities that have plagued enterprise Java development. Some detractors ridiculed it as a "fat elephant" for its heavyweight nature. It required a lot of redundant code, even to build a simple "HelloWorld" EJB.

EJB 3 simplifies development by adopting the POJO programming model, and simplifies usage of EJB and resources by using dependency injection. It also depends heavily on intelligent defaults and makes the deployment descriptor optional.

Listing 2 provides an example of a simple stateless EJB 3 session bean with a remote interface. In this example, PlaceBidBean is a simple POJO class that implements a regular Java interface - or a plain old Java interface (POJI). The @javax.ejb.Remote converts the POJI to a remote interface and @javax.ejb.Stateless converts the POJO to a stateless EJB.

You can use @Stateful and @MessageDriven annotations to define stateful and message-driven beans, respectively.

More Stories By Debu Panda

Debu Panda is a Director of Product Management at Oracle Corporation. He is lead author of the EJB 3 in Action (Manning Publications) and Middleware Management (Packt). He has more than 20 years of experience in the IT industry and has published numerous articles on enterprise Java technologies and has presented at many conferences. Debu maintains an active blog on enterprise Java at http://debupanda.blogspot.com.

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.


IoT & Smart Cities Stories
The challenges of aggregating data from consumer-oriented devices, such as wearable technologies and smart thermostats, are fairly well-understood. However, there are a new set of challenges for IoT devices that generate megabytes or gigabytes of data per second. Certainly, the infrastructure will have to change, as those volumes of data will likely overwhelm the available bandwidth for aggregating the data into a central repository. Ochandarena discusses a whole new way to think about your next...
DXWorldEXPO LLC announced today that Big Data Federation to Exhibit at the 22nd International CloudEXPO, colocated with DevOpsSUMMIT and DXWorldEXPO, November 12-13, 2018 in New York City. Big Data Federation, Inc. develops and applies artificial intelligence to predict financial and economic events that matter. The company uncovers patterns and precise drivers of performance and outcomes with the aid of machine-learning algorithms, big data, and fundamental analysis. Their products are deployed...
Dynatrace is an application performance management software company with products for the information technology departments and digital business owners of medium and large businesses. Building the Future of Monitoring with Artificial Intelligence. Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more busine...
All in Mobile is a place where we continually maximize their impact by fostering understanding, empathy, insights, creativity and joy. They believe that a truly useful and desirable mobile app doesn't need the brightest idea or the most advanced technology. A great product begins with understanding people. It's easy to think that customers will love your app, but can you justify it? They make sure your final app is something that users truly want and need. The only way to do this is by ...
CloudEXPO | DevOpsSUMMIT | DXWorldEXPO are the world's most influential, independent events where Cloud Computing was coined and where technology buyers and vendors meet to experience and discuss the big picture of Digital Transformation and all of the strategies, tactics, and tools they need to realize their goals. Sponsors of DXWorldEXPO | CloudEXPO benefit from unmatched branding, profile building and lead generation opportunities.
Digital Transformation and Disruption, Amazon Style - What You Can Learn. Chris Kocher is a co-founder of Grey Heron, a management and strategic marketing consulting firm. He has 25+ years in both strategic and hands-on operating experience helping executives and investors build revenues and shareholder value. He has consulted with over 130 companies on innovating with new business models, product strategies and monetization. Chris has held management positions at HP and Symantec in addition to ...
Cell networks have the advantage of long-range communications, reaching an estimated 90% of the world. But cell networks such as 2G, 3G and LTE consume lots of power and were designed for connecting people. They are not optimized for low- or battery-powered devices or for IoT applications with infrequently transmitted data. Cell IoT modules that support narrow-band IoT and 4G cell networks will enable cell connectivity, device management, and app enablement for low-power wide-area network IoT. B...
The hierarchical architecture that distributes "compute" within the network specially at the edge can enable new services by harnessing emerging technologies. But Edge-Compute comes at increased cost that needs to be managed and potentially augmented by creative architecture solutions as there will always a catching-up with the capacity demands. Processing power in smartphones has enhanced YoY and there is increasingly spare compute capacity that can be potentially pooled. Uber has successfully ...
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...
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, its about the data consumed and generated. The devices are tools, mechanisms, conduits. This paper discusses the considerations when dealing with the...