Architecture of the Example Applications

The example applications consist of four main components: DukesAgeResource, a JAX-RS RESTful web service; DukesBirthdayBean, an enterprise bean; FirstcupUser, a Java Persistence API entity; and firstcup-war, a web application created with JavaServer Faces Facelets technology.

Figure 3-1 Architecture of the First Cup Example Applications

Architecture of First Cup example applications.

DukesAgeResource is a JAX-RS resource that calculates the age of Duke, the Java mascot. Duke was born May 23, 1995, when the first demo of Java technology was publicly released.

DukesBirthdayBean is a local, no-interface view stateless session bean that calculates the difference between the user’s age and Duke’s age and stores the user-submitted data in a Java Persistence API entity.

FirstcupUser is a Java Persistence API entity that represents a particular user’s birthday. It is stored in an Apache Derby table and managed by the DukesBirthdayBean business methods.

The firstcup-war web application is a JavaServer Faces Facelets application that accesses DukesAgeResource to display Duke’s age, reads in a date provided by the user, accesses DukesBirthdayBean to calculate who is older, and then displays the difference in years between the user and Duke and the average age difference of all users.

The firstcup-war web application consists of the following:

greeting.xhtml: A Facelets-enabled XHTML page, which is a page that uses the JavaServer Faces Facelets tag libraries. Users can type their birth date in a field and submit it for comparison against Duke’s birth date.
response.xhtml: A Facelets-enabled XHTML page that tells the user whether he or she is older or younger than Duke, based on the date the user entered in the greeting.xhtml page, and displays the average age difference of all users.
DukesBDay.java: A CDI managed bean that defines properties to hold the user’s birth date, uses the JAX-RS Client API to get Duke’s current age from the DukesAgeResource web service, and calculates the age difference between the user and Duke from the enterprise bean.
web.xml: The web application’s deployment descriptor, which is used to configure certain aspects of a web application when it is installed. In this case, it is used to provide a mapping to the application’s FacesServlet instance, which accepts incoming requests, passes them to the life cycle for processing, and initializes resources. It also specifies greeting.xhtml as the welcome file for the application.
WebMessages.properties and WebMessages_es.properties: Java programming language properties files that contain the localized strings used in greeting.xhtml and response.xhtml. By default, the English language strings in WebMessages.properties are used, but Spanish language strings are also provided in WebMessages_es.properties.
DukesBirthdayBean.java: as described above, the enterprise bean packaged within the firstcup-war application. DukesBirthdayBean calculates the difference between the user’s birthday and Duke’s birthday.

Tiers in the Example Applications

The example applications have a web tier component (the firstcup-war web client), three business tier components (the DukesAgeResource web service, the FirstcupUser entity, and the DukesBirthdayBean enterprise bean), and an enterprise information system (EIS) tier (the data in the Apache Derby database table). The user’s web browser is the client tier component, as it accesses the rest of the application through the web tier.

Jakarta EE Technologies Used in the Example Applications

The DukesAgeResource web service is a JAX-RS resource. The DukesBirthdayBean enterprise bean is a stateless session bean. The FirstcupUser entity is a Java Persistence API entity. The DukesBDay CDI managed bean uses the JAX-RS client API to access the DukesAgeResource web service. The firstcup-war web client is a JavaServer Faces application that runs in the web container of the Java EE server.