This sample demonstrates @Singleton and @EJB annotations described in EJB3.1 lite as well as the usage of JSF framework. @Singleton annotation defines a singleton session bean which can be shared across applications and with its states maintained during the application's lifecycle. @EJB annotation shows how to have another session bean injected to your backing beans.
singletonejb-javaee6 application consists of following list of packages and classes.
The list of web application files in the application is depicted in the following.
The web.xml defines the welcome-file of the web application index.html and declares the involvement of JSF framework with a standard servlet Faces Servlet for request processing.
geronimo-web.xml describes information about the project (e.g. module's unique identification, any dependencies) inside the <sys:environment> tag. It is a good idea to give this module some sort of unique identification, so that it can later be referenced by some other deployable application. The path specified in the* <context-root>* tag will be the first segment of the URL used to access this web application. So to access this web application the url will be http://<hostname>:<port>/Singletonejb-javaee6. Geronimo uses Apache MyFaces as JSF implementation and the component is started by default and available server-wide. Therefore you do no have to add the dependency for myFaces component.
index.xhtml uses the standard HTML tag library to render a form for user input and bind the components on the form with the managed beans properties respectively.
AddCalculatorBackBean.java and SubtractCalculatorBackBean.java hold the form data and invoke a singleton session bean SingletonCalculator for the calculation. Also the JSF managed beans use @EJB annotation for bean injection. We can see two references of SingletonCalculator for Add and Subtract beans. Because both backing beans AddCalculatorBackBean and SubtractSingletonCalculatorBackBean refer to the same object identity, each calculation will be preformed on the result from last calculation.
SingletonCalculator.java do the actual calculation. It's a singleton session bean and can only be initialized once for all requests. It will be destroyed only when the application is stopped.
Get the source code
Please refer to Samples General Information for informations on obtaining and building the source for this and other samples.
Build the web application
Once all the sources get checked out the next step is to build singleton-javaee6 sample. It requires Maven 2 or above for building the binaries.
From the <singletonejb-javaee6_home> directory run the following command.
This process will take a couple of minutes. The binaries will be generated in the corresponding target directory .
Deploy the web application
Deploying sample application is pretty straight forward as we are going to use the Geronimo Console.
- Scroll down to Deploy New from the Console->Navigation panel.
- Load singletonejb-javaee6-war-version.war from singletonejb-javaee6-war\target folder in to the Archive input box.
- Press Install button to deploy application in the server.
Test the web application
The application is visible at http://localhost:8080/singleton-javaee6.
Input a value and click Add for calculation.
Click Go to Subtract Calculator and input a value again, then click subtract. You will see the output is based on the result from the previews step.