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Contrasting JavaBeans and Enterprise JavaBeans

A Developer's Round Table discussion hosted by Mike Day



Participating Guests: Ken Burgett from the IBM Component Broker beta support team, and Liane Acker, Jim Knutson and David Morrill from the IBM Enterprise Java Beans department.

This group was asked to help us distinguish the basic differences between JavaBeans and Enterprise Java Beans. Here's what they had to say:

Notable Quote: "The whole thrust of this is not so much the capabilities of beans as it is the competitive potential they can provide your business."

"First let's explain what a bean is because both a JavaBean and Server Bean, more commonly known as an Enterprise Java Bean or EJB, have some basic similarities. They are objects or components created with a set of characteristics to do their own specific job, and they have the ability to take on other characteristics from the container on the server in which they currently reside. This enables a bean to behave differently, depending on the specific job and environment where you place it."

"A JavaBean is a component that has interfaces in it or properties associated with it so it can be interrogated by and integrated with other beans that were developed by different people at different times. You can build a bean and tie it together with other beans later at construction time. This provides a way to build something and use it again later; that's the notion of a component. This single application can be deployed stand-alone, within a browser and also as an ActiveX component."

"What makes it different from pure objects is that it has an external interface, called the properties interface which allows a tool to read what the component is supposed to do and hook it up to other beans and plug it into another environment. That's true of JavaBeans and EJBs. JavaBeans are intended to be local to a single process and they are often visible at runtime. This visual component may be a button, list box, graphic or chart, for example, but it is not a requirement."

"An EJB is a non-visual, remote object designed to run on a server and be invoked by clients. You can build an EJB out of multiple, non-visual JavaBeans if you choose. EJBs are intended to live on one machine and be invoked remotely from another machine. They have a deployment descriptor that is intended for the same purpose as JavaBean properties. It is a description about the bean that can be read later by a tool. They are also platform independent. Once a bean is written it can be used on any platform that supports Java and this is true of clients and servers as well."

"In regards to ActiveX, a JavaBean can be deployed as an ActiveX object. A proxy to an EJB can also be an ActiveX object, but an EJB will not be an ActiveX object because ActiveX runs on the desktop. If you really want to do this on a platform dependent, Windows-only platform, then you could have the JavaBean rendered as an ActiveX component."

"Server beans or EJBs are remotely executable components or business objects deployed on the server. They have a protocol that allows them to be accessed remotely and this protocol also allows them to be installed or deployed on a particular server. They have a set of mechanisms that allow them to delegate major qualities of service, security, transactional behavior, concurrancy (the ability to be accessed by more than one client at a time), and persistence (how their state can be saved) to the container in which they are placed on the EJB server. They get their behavior from being installed in a container. Containers provide the different qualities of service so selecting the right EJB server is critical. This is where Component Broker excels."

"The major benefit is that the bean developer can stipulate, when the bean is built, what kind of behavior is needed, but not how it's done. Development is in two parts. You develop the bean and verify that it works with the build tools and you include a deployment descriptor which identifies the kinds of quality of service behaviors needed. In the next step, another person can take that bean and use a deployment tool that reads the EJB deployment descriptor and installs the bean into a container on an enterprise Java server. In this second step, the deployment tool takes some action and this may mean generating codes like state saving codes, putting in transactional hooks, or doing security checks. All this action is generated by the deployment tool. The bean developer and deployer can be different people."

"To state this simply, any platform independent JavaBean can be adapted, through the use of a deployment tool, into a platform specific EJB that has the correct qualities of services available to meet the specific requirements of your existing business systems and applications. This is why an EJB server is so important to integrating your systems, networks and architectures."

"As used in IBM Component Broker, EJBs can be configured as a managed business object. The container they delegate services to is the Component Broker container in which they are installed. The persistence part of an EJB is mapped in what we call the Data or State Object. The EJB server provides different qualities of service for the EJB and choosing the right EJB server may be critical to meeting your complete business requirements. IBM Component Broker is very robust, providing very high levels of functions like workload balancing and support across multiple machines in a server group. It has system management capabilities that go well beyond what the Enterprise Java Server (EJS) specifications call for. Therefore a JavaBean or EJB written to the basic standards can run on Component Broker and gain all that additional value."

"EJBs, as they are generated by a toolset like IBM VisualAge for Java, are server based objects and are intended to be called remotely. They're installed on the EJB server and they get a remote interface to call just as other CORBA remote objects are called."

"For an EJB to work in the Component Broker environment, you can use the Component Broker deployment tool to install it on one or more servers, then add it to the naming server so it can be found universally. Anyone with access to the common naming server can find it, can find the home, and can execute a method on the home, creating an EJB. This is exactly what you do with Component Broker."

"You're probably already using JavaBeans today and don't know it. There are no restrictions to having JavaBeans on your desktop today if you have a Java enabled browser. The web pages you use may have beans as part of an applet. In the very near future, you will interact with JavaBeans as the visual portion of a browser, then those JavaBeans will interface to an EJB on the server. This capability extends to both the Internet and intranets as well."

"In fact, this opens up a tremendous business possibility. Because JavaBeans are platform independent, solution providers in the future will be able to readily market their client-side JavaBeans to a wide audience without having to create or maintain different versions. Then these JavaBeans can be paired with EJBs doing the business functions like ordering, credit card processing, electronic transfers, inventory allocation, shipping, etc. There is a great potential here, and it is the kind of potential Component Broker is designed to deliver."

"Let's take the example of an electronic shopping cart you may see on a catalog shopping web site. Your cart is a JavaBean. You fill it up with items from the catalog shelves and these items are JavaBeans themselves. It is all very visual and user oriented. When you check out, the items in your cart are sent to an EJB on the server which executes the business operations necessary for checking the credit card for authorization and available credit, producing a picking slip or special directions to the shipping department for which items to pull and where to send them - all the activities your business programs are already doing."

"But now we're getting into the unique features and quality of services that are provided by the EJB server and they are not all the same. IBM Component Broker has some very powerful features, for example, scaleability. This lets you deploy EJBs across many types of servers, from small systems to very large networks. So you can start very small, like in a single department if you like deploying on a Java server on a local LAN, knowing the JavaBeans and EJBs you create there can be deployed on a global network whenever you're ready. Then you can test it, get the feel of it, run a pilot, do a prototype, etc. When you're satisfied with it, you can scale it up dramatically by moving it up to a high performance server. You are not constrained by any computer architectural boundaries. It's written in Java and can run on anything where a Java virtual machine is available and any EJS can be used to deploy the object. So you can build on what's convenient today, deploy on what is convenient later and it doesn't have to be the same machine or even the same kind of machine."

"Component Broker supports deploying a business object across multiple servers and EJBs are integrated into Component Broker as business objects and are handled as any other business object. Therefore, the EJBs can connect to the backend system of your choice to do whatever is necessary to meet your business needs. That will become the persistence infrastructure Component Broker provides for the EJB. So you will be able to keep using your current legacy systems and provide them with an e-business interface by utilizing Component Broker as an EJB server."

"The whole thrust of this is not so much the capabilities of beans as it is the competitive potential they can provide your business. Your IT architects and application developers can now focus their attention strictly on your business logic and leave the infrastructure, such as transactions, persistence, and security up to the server. Component Broker provides all that for us, with the object transaction manager, and all the backend access as well. In fact, at JavaOne '98 we are demonstrating the full functionality of EJBs in containers and EJBs as managed objects. If you have the opportunity to attend you will see some of our customers showing and sharing their successes."


Mike Day is a member of IBM's Object Middleware Marketing Team. He conducts round tables that focus on topics of general interest suggested by our readers. Round table guests are selected based on their relative background, experience, or immediate activities in the topic area. If you would like to suggest a topic, write to us at compbrok@us.ibm.com.




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