Getting Started with WebSphere Application Server

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90 Getting Started with WebSphere Application Server Community Edition Figure 5.1 - Community Edition EJBs: The big picture 5.2 Developing EJBs in Community Edition Community Edition includes OpenEJB, an open source EJB container. Since Community Edition is Java EE 5 compatible, you can create EJBs with annotations defined using the EJB 3.0 specification. Annotations are like meta-tags that you can add to your code and apply them to package declarations, type declarations, constructors, methods, fields, parameters, and variables. Annotations do not affect your code directly, but tools can inspect these annotations at compile time or runtime to generate additional constructs. Before using an EJB, define the interface and implementation class first; then, deploy it into Community Edition. Use the following steps to develop an EJB application in Community Edition: 1. Create an EJB in Community Edition 2. Deploy the EJB in Community Edition These steps will be described in more detail in the next sections. 5.2.1 Creating an EJB To create an EJB, you need to:
1. Define local and remote interfaces for the EJB 2. Implement the EJB class 5.2.1.1 Defining local and remote interfaces Chapter 5 – Enterprise Java Beans 91 To avoid code duplication, define a common interface which can then be inherited by both, local and remote interfaces. In an EJB, a local interface is used by an invoker using the same Java Virtual Machine (JVM) while a remote interface is used by an invoker in a different JVM. Following the EJB 3.0 specification, the local interface is annotated with @Local while the remote interface is annotated with @Remote. Listing 5.1 below provides an example of how you can define the business interface of an EJB. In the example, you define a business interface named HelloInterface. package hello; public interface HelloInterface { public void sayHello(); } Listing 5.1 - Defining the business interface of the EJB Listing 5.2 provides an example of how you can define the local interface of the EJB. It inherits the business interface. package hello; import javax.ejb.Local; @Local public interface HelloInterfaceLocal extends HelloInterface {} Listing 5.2 - Defining local interface of the EJB Listing 5.3 provides an example of how you can define the remote interface of the EJB. package hello; import javax.ejb.Remote; @Remote public interface HelloInterfaceRemote extends HelloInterface{} Listing 5.3 - Defining the remote interface of the EJB 5.2.1.2 Implementing the EJB class Now that the interfaces have been defined, you can implement them. In this step, all the methods of the EJB class will be implemented. As defined in the EJB 3.0 specification, @Stateless is used for a stateless EJB, an EJB that is normally short lived and does not maintain the state on behalf of the client. @Stateful is used for a stateful EJB. Listing 5.4 provides an example. package hello; import javax.ejb.Stateless; @Stateless public class HelloEJB implements HelloInterfaceLocal, HelloInterfaceRemote {
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G E T T I N G S T A R T E D W I T H
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Notices This information was develo
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Trademarks IBM, the IBM logo, and i
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3.8 Exercises .....................
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9.3.2 Changing port numbers .......
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13 Preface Keeping your skills curr
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The DB2 on Campus book series 15
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18 Getting Started with WebSphere A
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1 Chapter 1 - Introduction to WebSp
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Introduction to WebSphere Applicati
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PART III - ADMINISTERING COMMUNITY
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A Appendix A - Solutions to review
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B Appendix B - Up and running with
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Appendix B - Up and running with DB
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C Appendix C - Using the sample cod
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