Jakarta First Cup

The client tier consists of application clients that access a Jakarta EE server and that are usually located on a different machine from the server. The clients make requests to the server. The server processes the requests and returns a response back to the client. Many different types of applications can be Jakarta EE clients, and they are not always, or even often, Java applications. Clients can be a web browser, a standalone application, or other servers, and they run on a different machine from the Jakarta EE server.

The web tier consists of components that handle the interaction between clients and the business tier. Its primary tasks are the following:

Table 2-1 lists some of the main Jakarta EE technologies that are used in the web tier in Jakarta EE applications.

Table 2-1 Web-Tier Jakarta EE Technologies

The business tier consists of components that provide the business logic for an application. Business logic is code that provides functionality to a particular business domain, like the financial industry, or an e-commerce site. In a properly designed enterprise application, the core functionality exists in the business tier components.

The following Jakarta EE technologies are among those that are used in the business tier in Jakarta EE applications:

The enterprise information systems (EIS) tier consists of database servers, enterprise resource planning systems, and other legacy data sources, like mainframes. These resources typically are located on a separate machine from the Jakarta EE server, and are accessed by components on the business tier.

The following Jakarta EE technologies are used to access the EIS tier in Jakarta EE applications:

Maven archetypes are templates that create the structure of a particular application. There are two archetypes included in the example, dukes-age-archetype and firstcup-war-archetype. These archetypes create Jakarta EE 8 web applications that you will then edit and deploy.

Before you can create applications based on the archetypes, you must first install the archetypes and supporting projects to your local Maven repository by following these steps:

The required projects, including the archetypes, will be built.

The DukesAgeResource class is a JAX-RS resource class that responds to HTTP GET requests and returns a String representing the age of Duke at the time of the request.

The basic DukesAgeResource resource class is generated from the dukes-age-archetype Maven archetype. This class is annotated with the javax.ws.rs.Path annotation, which specifies the URL suffix to which the resource will respond. The DukesAgeResource class has a single method, getText, annotated with the javax.ws.rs.GET and javax.ws.rs.Produces annotations. The @GET annotation marks the method as a responder to HTTP GET requests, and @Produces specifies the MIME-type of the response sent back from getText to clients. In this case, the MIME-type is text/plain.

In NetBeans IDE, create a new web project using the dukes-age-archetype Maven archetype.

Create the Project in NetBeans IDE 

The dukes-age-archetype archetype creates the structure of the JAX-RS endpoint application, including:

After you create the basic application structure with the archetype, you will configure how the application will run, implement the functionality of the resource class, and then deploy the application.

Configure the dukes-age Web Application

Set the default URL that is brought up in a web browser when you run dukes-age.

Implement the getText Method

Add code to DukesAgeResource.getText that calculates Duke’s age at the time of the request. To do this, use the java.util.Calendar and java.util.GregorianCalendar classes to create an object representing the date May 23, 1995, Duke’s birthday. Then create another Calendar object representing today’s date, and subtract today’s year from Duke’s birth year. If today’s date falls before May 23, subtract a year from this result. Then return the result as a String representation.

Follow these steps to start GlassFish Server and Apache Derby.

Build dukes-age.war, the JAX-RS web application, and deploy it to your GlassFish Server instance.

In the Projects tab, right-click dukes-age and select Run.

After dukes-age.war deploys successfully to GlassFish Server, a web browser will load the URL of the DukesAgeResource path, and you’ll see the returned String representing Duke’s age.

At this point, you’ve successfully created, deployed, and run your first Jakarta EE application. Now you will create a web application that uses this web service data.

Now modify the getAge method of DukesBDay to call the dukes-age web service using the JAX-RS Client API. This will retrieve Duke’s current age, so it can be compared to the user’s age.

Now modify the processBirthday method to get the difference in age between the user’s age and Duke’s age from the DukesBirthdayBean EJB, set the absAgeDiff variable to the absolute value of the age difference, and set a result string that will forward the user to the display page.

A JavaServer Faces resource library is a collection of user-created components collected in a standard location in a web application. Resource libraries are identified according to a resource identifier, a string that represents a particular resource within a web application. Resources can be packaged either at the root of the web application or on the web application’s classpath.

A resource packaged in the web application root must be in a subdirectory of a resources directory at the web application root.

A resource packaged in the web application classpath must be in a subdirectory of the META-INF/resources directory within a web application.

Resource identifiers are unique strings that conform to the following format:

Elements of the resource identifier in brackets ([]) are optional. A resource name, identifying a particular resource (a file or a graphic, for example), is required. In firstcup-war, a resource library with the name components is packaged in the web application root, and this library contains one resource, a file called inputDate.xhtml. The resource identifier for this resource is therefore components/inputDate.xhtml, and it is located in the web application root at resources/components/inputDate.xhtml.

A composite component is a set of user-defined JavaServerFaces and Facelets components located in a resource. In firstcup-war, the inputDate.xhtml resource, located in the components resource library, is a composite component that contains tags for reading in a date the user enters in a form. Composite components consist of an interface definition and an implementation.

The interface definition is specified with the <cc:interface> tag to define which attributes are exposed to pages that use the composite component. Attributes are identified with the <cc:attribute> tag.

The inputDate.xhtml interface definition is as follows. It defines a single attribute, date, that must be specified in pages that use the inputDate composite component.

The implementation of the composite component is specified with the <cc:implementation> tag. The tags within the <cc:implementation> are the actual component tags that will be added to pages that use the composite component. They can be any HTML render kit, JavaServer Faces, or Facelets tags. The #{cc.attrs.attribute-name} expression is used to get the value of the specified attribute from the page or component that is using the composite component.

The implementation of the inputDate composite component is as follows. An HTML input text component will store the entered text into the date attribute, accessed by the #{cc.attrs.date} expression. A JavaServer Faces convertDateTime component will convert the entered text to a date with the form of MM/dd/yyyy (04/13/2014, for example).

If there’s an error with the input of the inputText component, the form submission is unsuccessful, and a warning message is displayed. The message output is specified by the <h:message> tag, which is connected to the inputText component that has the id getdate.

Modify the inputDate composite component in the components resource library.

The firstcup-war web application interface has two XHTML files. The greeting.xhtml file displays Duke’s current age and the form where the user can enter a birthday. The response.xhtml file displays the age difference between the user and Duke.

The greeting.xhtml file contains several pieces of the firstcup-war application detailed previously. It uses the localized strings contained in WebMessages.properties and WebMessages_es.properties. It uses the DukesBDay managed bean to call both the DukesAgeResource JAX-RS web service and the DukesBirthdayBean enterprise bean. It uses the inputDate composite component to create the input for the user to enter a birthday.

Here’s the content of the greeting.xhtml file.

The greeting.xhtml file uses the HTML RenderKit and the components resource library tag libraries. The components tag library has a prefix of fc, and is used to specify the inputDate composite component in the form below. The <fc:inputDate id="userBirthday" date="#{dukesBDay.yourBD}" /> tag has the required date attribute, and it stores the value in the yourBD property in the DukesBDay managed bean by using the EL expression #{dukesBDay.yourBD}.

The localized strings are referenced by the EL expressions #{bundle.property-name}. For example, the <h:outputText value="#{bundle.Welcome}"/> tag will display the following string in English locales:

The <h:commandButton> tag creates a Submit button and specifies that a successful submission should render the response.xhtml file by setting the action attribute to #{dukesBDay.processBirthday}. The processBirthday method returns the value "/response.xhtml". The action attribute is used to define navigation rules for forms in Facelets pages.

The response.xhtml file displays the age difference between the user and Duke and the average age difference of all users so far. Different strings are displayed based on whether the user is the same age, younger, or older than Duke. The text can be displayed or not based on the conditions specified by the rendered attribute of the <h:outputText> tag. The conditions used in the rendered attribute are Expression Language (EL) alternatives to the Java programming language conditional operators to allow XML parsing of the XHTML file.

Table 4-1 Conditional Operator EL Language Alternatives

Here’s the content of the response.xhtml file.

For example, the #{bundle.SameAge} string is displayed if the user and Duke have the same birthday, as specified by the condition #{dukesBDay.ageDiff == 0} in the rendered attribute. That is, the following string is displayed when the ageDiff property of DukesBDay equals 0:

The form also contains a <h:commandButton> tag that creates a Back button, which directs the user back to the greeting.xhtml page, as specified in the action attribute.

Add the form that provides the user interface for displaying Duke’s age and specifying the user’s birthday.

Add a form that displays the age difference between Duke and the user, displays the average age difference of all users, and allows the user to navigate back to greeting.xhtml.