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ejb-throws-exception: Handle Exceptions across JARs in an EAR

The ejb-throws-exception quickstart demonstrates how to throw and handle exceptions across JARs in an EAR.

What is it?

The ejb-throws-exception quickstart extends the ejb-in-ear quickstart and demonstrates how to handle exceptions across JARs in an EAR deployed to {productNameFull}. In this quickstart, an EJB in the EJB JAR throws a custom exception. The web application in the client JAR catches the exception and displays it in a nicely formatted message. The EAR contains: JSF WAR, an EJB JAR and a client library JAR containg classes that both the WAR and EJB JAR use.

This example consists of the following Maven projects, each with a shared parent.

Project Description

ejb

This project contains the EJB code and can be built independently to produce the JAR archive.

  • The EJB has a single method sayHello which will take in a String name.

  • If the name is not null or an empty String, it returns Hello <name>.

  • If the name is null or an empty String, it throws a custom GreeterException exception back to the client.

web

This project contains the JSF pages and the CDI managed bean.

  • The CDI Managed Bean, GreeterBean, is bound to the JSF page, index.xhtml.

  • It invokes the GreeterEJB and displays the response back from the EJB.

  • The GreeterBean catches the custom GreeterException exception thrown by GreeterEJB and displays the exception message in the response text on the JSF page.

ear

This project builds the EAR artifact and pulls in the ejb, web, and client artifacts.

ejb-api

This project builds the ejb-api library artifact which is used by the ejb, web, as well as remote client artifacts.

  • This directory contains the EJB interfaces, custom exceptions the EJB throws and any other transfer objects which the EJB may receive or send back to the client.

  • The EJB interfaces, custom exceptions, and other transfer objects are split into a separate JAR, which is packaged in the ear/lib. This allows all sub deployments of the EAR to see the classes of the ejb-api JAR in the classpath. This is also useful for remote clients.

  • The ejb-api JAR can be distributed to a remote client and give the remote clients the classes that are needed to interact with the EJB.

The root pom.xml builds each of the subprojects in the above order and deploys the EAR archive to the server.

The example follows the common "Hello World" pattern, using the following workflow.

  1. A JSF page asks for a user name.

  2. On clicking Say Hello, the value of the Name input text is sent to a managed bean named GreeterBean.

  3. On setting the name, the Greeter invokes the GreeterEJB, which was injected to the managed bean. Notice that the field is annotated with @EJB.

  4. The EJB responds with Hello <name> or throws an exception if the name is empty or null.

  5. The response or exception’s message from invoking the GreeterEJB is stored in a field (response) of the managed bean.

  6. The managed bean is annotated as @RequestScoped, so the same managed bean instance is used only for the request/response.

Access the Application

The application will be running at the following URL http://localhost:8080/{artifactId}/.

Enter a name in the input field Name and click the Say Hello button to see the response.

The Response output text will display the response from the EJB. If the Name input text box is not empty, then the Response output text will display Hello <name> If the Name input text box is empty, then the Response output text will display the message of the exception throw back from the EJB.

For this quickstart, follow the special instructions to build Quickstarts Containing an EAR.

  1. Right-click on the {artifactId}-ear subproject, and choose Run As → Run on Server.

  2. Choose the server and click Finish.

  3. This starts the server, deploys the application, and opens a browser window that accesses the running application.

  4. To undeploy the project, right-click on the {artifactId}-ear project and choose Run As → Maven build. Enter wildfly:undeploy for the Goals and click Run.