2.2 Developing the Application Backend

The application developer is primarily responsible for developing the backend part of the application; in other words, the classes that handle business logic and data.

For the newsletter subscription form, the application developer may create a class called Subscriber to hold the subscriber information:

package com.mycompany.newsservice.models;



public class Subscriber {

    private String emailAddr;

    private String[] subscriptionIds;



    public String getEmailAddr( ) {

        return emailAddr;

    }



    public void setEmailAddr(String emailAddr) {

        this.emailAddr = emailAddr;

    }



    public String[] getSubscriptionIds( ) {

        return subscriptionIds;

    }



    public void setSubscriptionIds(String[] subscriptionIds) {

        this.subscriptionIds = subscriptionIds;

    }

}

The Subscriber class adheres to the JavaBeans method naming conventions—"properties" are defined by methods for getting their values, named get plus the name of the property, and methods for setting their values, named set plus the property name. As you'll see shortly, this makes it easy to use properties of this class as JSF UI component models.

When a subscription is registered or updated, the information must be saved somewhere, likely in a database. The application developer may decide to develop a separate class responsible for this task or put this logic in the Subscriber class. To keep the example simple, we'll add a method that represents this behavior to the Subscriber class. Also, instead of saving the information in a database, we just write it to System.out:

    public void save( ) {

        StringBuffer subscriptions = new StringBuffer( );

        if (subscriptionIds != null) {

            for (int i = 0; i < subscriptionIds.length; i++) {

                subscriptions.append(subscriptionIds[i]).append(" ");

            }

        }

        System.out.println("Subscriber Email Address: " + emailAddress +

            "\nSubscriptions: " + subscriptions);

    }

This is all the backend code we need for this simple application. Note, however, that none of these application classes refer to JSF classes; the same classes could be used with any type of user interface.