Java Platform, Enterprise Edition (Java EE) 8 The Java EE Tutorial

## Main Interface

The main interface allows students and staff to check students in and out, and record when students are outside at the playground.

The following topics are addressed here:

- Java Persistence API Entities Used in the Main Interface

- Enterprise Beans Used in the Main Interface

- WebSocket Endpoint Used in the Main Interface

- Facelets Files Used in the Main Interface

- Helper Classes Used in the Main Interface

- Properties Files

- Deployment Descriptors Used in Duke’s Tutoring

### Java Persistence API Entities Used in the Main Interface

The following entities used in the main interface encapsulate data stored and manipulated by Duke’s Tutoring, and are located in the `dukestutoring.entity` package in the `dukes-tutoring-common` project.

- `Person`: The `Person` entity defines attributes common to students and guardians tracked by the application. These attributes are the person’s name and contact information, including phone numbers and email address. This entity has two subclasses, `Student` and `Guardian`.

- `PersonDetails`: The `PersonDetails` entity is used to store additional data common to all people, such as attributes like pictures and the person’s birthday, which aren’t included in the `Person` entity for performance reasons.

- `Student` and `Guardian`: The `Student` entity stores attributes specific to the students who come to tutoring. This includes information like the student’s grade level and school. The `Guardian` entity’s attributes are specific to the parents or guardians of a `Student`. Students and guardians have a many-to-many relationship. That is, a student may have one or more guardians, and a guardian may have one or more students.

- `Address`: The `Address` entity represents a mailing address and is associated with `Person` entities. Addresses and people have a many-to-one relationship. That is, one person may have many addresses.

- `TutoringSession`: The `TutoringSession` entity represents a particular day at the tutoring center. A particular tutoring session tracks which students attended that day, and which students went to the park.

- `StatusEntry`: The `StatusEntry` entity, which logs when a student’s status changes, is associated with the `TutoringSession` entity. Students' statuses change when they check in to a tutoring session, when they go to the park, and when they check out. The status entry allows the tutoring center staff to track exactly which students attended a tutoring session, when they checked in and out, which students went to the park while they were at the tutoring center, and when they went to and came back from the park.

For information on creating Java Persistence API entities, see Chapter 40, "Introduction to the Java Persistence API." For information on validating entity data, see Validating Persistent Fields and Properties and Chapter 24, "Bean Validation: Advanced Topics."

### Enterprise Beans Used in the Main Interface

The following enterprise beans used in the main interface provide the business logic for Duke’s Tutoring, and are located in the `dukestutoring.ejb` package in the `dukes-tutoring-war` project:

- `ConfigBean` is a singleton session bean used to create the default students when the application is initially deployed, and to create an automatic EJB timer that creates tutoring session entities every weekday.

- `RequestBean` is a stateless session bean containing the business methods for the main interface. The bean also has business methods for retrieving lists of students. These business methods use strongly typed Criteria API queries to retrieve data from the database. `RequestBean` also injects a CDI event instance, `StatusEvent`. This event is fired from the business methods when the status of a student changes.

For information on creating and using enterprise beans, see Enterprise Beans. For information on creating strongly typed Criteria API queries, see Chapter 43, "Using the Criteria API to Create Queries." For information on CDI events, see Using Events in CDI Applications.

### WebSocket Endpoint Used in the Main Interface

The `javaeetutorial.dukestutoring.web.websocket.StatusEndpoint` class is a WebSocket server endpoint that returns students and their status to client endpoints. The `StatusEndpoint.updateStatus` method is a CDI observer method for the `StatusEvent` event. When a student’s status changes in the main interface, a `StatusEvent` is fired. The `updateStatus` observer method is called by the container, and pushes out the status change to all the client endpoints registered with `StatusEndpoint`.

The `index.xhtml` JavaServer Faces page contains JavaScript code to connect to the WebSocket endpoint. The `onMessage` method on this page clicks a JavaServer Faces button, which makes an Ajax request to refresh the table that shows the current status of the students.

For more information on WebSocket endpoints, see Chapter 19, "Java API for WebSocket." For information on CDI events, see Using Events in CDI Applications.

### Facelets Files Used in the Main Interface

The Duke’s Tutoring application uses Facelets to display the user interface, making extensive use of the templating features of Facelets. Facelets, the default display technology for JavaServer Faces technology, consists of XHTML files located in the `_tut-install_/examples/case-studies/dukes-tutoring-war/src/main/webapp/` directory.

The following Facelets files are used in the main interface:

- `template.xhtml`: Template file for the main interface

- `error.xhtml`: Error file if something goes wrong

- `index.xhtml`: Landing page for the main interface

- `park.xhtml`: Page showing who is currently at the park

- `current.xhtml`: Page showing who is currently in today’s tutoring session

- `statusEntries.xhtml`: Page showing the detailed status entry log for today’s session

- `resources/components/allStudentsTable.xhtml`: A composite component for a table displaying all active students

- `resources/components/allInactiveStudentsTable.xhtml`: A composite component for a table displaying all inactive students

- `resources/components/currentSessionTable.xhtml`: A composite component for a table displaying all students in today’s session

- `resources/components/parkTable.xhtml`: A composite component for a table displaying all students currently at the park

- `WEB-INF/includes/mainNav.xhtml`: XHTML fragment for the main interface’s navigation bar

For information on using Facelets, see Chapter 8, "Introduction to Facelets."

### Helper Classes Used in the Main Interface

The following helper classes, found in the `dukes-tutoring-common` project’s `dukestutoring.util` package, are used in the main interface.

- `CalendarUtil`: A class that provides a method to strip the unnecessary time data from `java.util.Calendar` instances.

- `Email`: A custom Bean Validation annotation class for validating email addresses in the `Person` entity.

- `StatusType`: An enumerated type defining the different statuses that a student can have. Possible values are `IN`, `OUT`, and `PARK`. `StatusType` is used throughout the application, including in the `StatusEntry` entity, and throughout the main interface. `StatusType` also defines a `toString` method that returns a localized translation of the status based on the locale.

### Properties Files

The strings used in the main interface are encapsulated into resource bundles to allow the display of localized strings in multiple locales. Each of the properties files has locale-specific files appended with locale codes, containing the translated strings for each locale. For example, `Messages_es.properties` contains the localized strings for Spanish locales.

The `dukes-tutoring-common` project has the following resource bundle under `src/main/resources/`.

- `javaeetutorial/dukestutoring/util/StatusMessages.properties`: Strings for each of the status types defined in the `StatusType` enumerated type for the default locale. Each supported locale has a property file of the form `StatusMessages_`locale prefix`.properties` containing the localized strings. For example, the strings for Spanish-speaking locales are located in `StatusMessages_es.properties`.

The `dukes-tutoring-war` project has the following resource bundles under `src/main/resources/`.

- `ValidationMessages.properties`: Strings for the default locale used by the Bean Validation runtime to display validation messages. This file must be named `ValidationMessages.properties` and located in the default package as required by the Bean Validation specification. Each supported locale has a property file of the form `ValidationMessages_`locale prefix`.properties` containing the localized strings. For example, the strings for German-speaking locales are located in `ValidationMessages_de.properties`.

- `javaeetutorial/dukestutoring/web/messages/Messages.properties`: Strings for the default locale for the main and administration Facelets interface. Each supported locale has a property file of the form `Messages_`locale prefix`.properties` containing the localized strings. For example, the strings for simplified Chinese-speaking locales are located in `Messages_zh.properties`.

For information on localizing web applications, see Registering Application Messages.

### Deployment Descriptors Used in Duke’s Tutoring

Duke’s Tutoring uses these deployment descriptors in the `src/main/webapp/WEB-INF` directory of the `dukes-tutoring-war` project:

- `faces-config.xml`: The JavaServer Faces configuration file

- `glassfish-web.xml`: The configuration file specific to GlassFish Server, which defines security role mapping

- `web.xml`: The web application configuration file

Duke’s Tutoring also uses the following deployment descriptor in the `src/main/resources/META-INF` directory of the `dukes-tutoring-common` project:

- `persistence.xml`: The Java Persistence API configuration file

No enterprise bean deployment descriptor is used in Duke’s Tutoring. Annotations in the enterprise bean class files are used for the configuration of enterprise beans in this application.

Copyright © 2017, Oracle and/or its affiliates. All rights reserved.