Getting Started-2-Tier

This tutorial gives an overview of two-tier and web application development, and offers a general methodology for enhanced client/server application development. Whether you are new to Panther software or are already a Panther user, a novice or experienced programmer, you can build this mini-application to learn about Panther's application development process. You can also can use the tutorial's examples, principles, code, and concepts as a template for your own applications.

About this Tutorial

The tutorial is organized into four modules plus a wrap-up and is designed to be followed in sequence. Each module begins with an introduction that describes the basic concepts to be learned in it and what you can expect to accomplish on completion. Each module has two or more lessons, for a total of 12 lessons.

You start by setting up the client/server environment. In practice, a system administrator would probably set this up for the development team—the intent here is for you to become familiar with the process of setting up a development environment.

After the environment is set up, you start building an application that, on completion, consists of three screens that can be used to view and update video distributors and their orders.

The tutorial uses a JDB database, provided with the distribution, that contains distributor and order data. It also accesses a tutorial library, which contains the client screens and JPL modules that are used in the lessons.

Accessing the Tutorial Lessons

You can click on any of the lessons in the following figure to access that lesson.

About Each Module

The lessons in Module 1 show how to set up the Panther environment to develop an application and to run a client-server application on the web. Typically, a system administrator sets up the web server environment for the development team. The purpose of this module is to acquaint you with this process.

The first lesson introduces you to the Panther development environment. In the second lesson, you set up a Panther web application server.

In the process of setting up the environment, you are introduced to the following concepts:

• Setup Variables—Panther applications depend on a number of setup variables. These describe the operating environment—for example, the layout of your system and the terminal you are using. They also point to the Panther software installation and specific setup files, and other files required by the application such as libraries. Setup files can also store variables that control the behavior of a Panther application and how users interact with it—for example, message display, cursor behavior, and numeric format.

• Web Setup Manager—The graphical Web Setup Manager guides you through the settings needed to configure your web application server.

Module 2: Creating and Testing Screens

Module 2 contains five lessons that lay the groundwork for your application—one that implements the functions used to view and update a list of video distributors and their orders. In these lessons, you perform these tasks:

• Create a repository and populate it with imported database objects from the vidsales database provided with the tutorial.

• Use the screen wizard to create a screen that displays information about the distributors and their orders.

• Test the behavior of your screen.

• Assign properties to the screen objects, and enhance the screen to query the database using those properties.
  

When you complete the lessons in this module, you will have a client screen that lets you query the database for specific distributors. In the process of creating the screen, you are introduced to the following concepts:

• The use of a repository for storing database-derived objects used in your application allows the screen wizard to build screens.

• The screen wizard guides you through the process of creating screens, prompting you for basic design information that it uses to build fully functional screens.

• Test mode allows you to test screen attributes and logic, including data validation, database interactions, and client/server connections. In test mode, your client screen appears and behaves as it would in the final application.

• The transaction manager knows about the interaction between database tables and columns from information retrieved from the database during the import process. It automatically builds the appropriate SQL statements, keeps track of data changes, and knows when to activate or deactivate specific widgets on the client screen.

• Each object in your repository has a set of properties that define its visual and behavioral attributes, as well as database definitions if the object was derived from a database. These properties can be used as the basis of a query on the database.

Module 3: Connecting the Screens

Module 3 consists of four lessons that show you how to improve the appearance, capabilities, and flow of your application. In these lessons, you:

• Enhance a client screen by allowing users to search for distributors by name or ID.

• Apply global and local changes to application objects.

• Write several JPL procedures to send and receive data between screens and to and from the database.

• Add other capabilities, such as double-click events, to the user interface.

When you have completed the lessons in this module, you will have a second screen, which you will use to query the database for distributors using either their name or ID, and to invoke the screen you created in Module 2.

In Lesson 9, you add JPL procedures to your screens. These procedures are provided in tutorstd.lib, and their contents are described in the lesson. If you have additional questions about the code, you can refer to the comments in the actual JPL procedure, since the comments are not included in the lesson text.

In the process of creating the query screen, you will be introduced to the following concepts:

• The editor provides a graphical environment for enhancing screens that were previously created with the screen wizard, allowing you to alter the size, position, properties, and so forth, of both the screens and the objects contained in them.

• The inheritance link between a repository and application objects allows you to use the repository to update the client screens by propagating changes from parent objects in the repository to objects in your application screens.

• JPL procedures can be attached to screens and widgets to perform such functions as sending or receiving data between screens, performing error handling, and providing the transaction manager with additional instructions for handling database transactions.

• A variety of ways exist to enhance the usability of your application, such as implementing double-click events, having commands or procedures executed only under certain conditions, and so forth.

Module 4: Extending the Application

Module 4 consists of two lessons that guide you through the process of adding a third screen to your application. The screen and an order entry interface are created using the screen wizard. It allows the user to add a new order and update existing ones for a selected video distributor.

In the process of developing this portion of the application, you will be introduced to the following concepts:

• Using the screen wizard to create selection screens—pick lists that display acceptable database values for a field. Selection screens are helpful when you need to add a new record to the database.

• Calculating data from database values. You will extend the use of the database by adding a virtual column to a table view and thereby include the widget in the automated SQL generation.

• Including a virtual widget in a table view also allows the transaction manager to apply the same styles to the widget as to the other widgets belonging to the table view.

• Deleting a single detail record on a master-detail screen, instead of deleting the master and all of its detail records.

• Implementing a validation procedure on the client screen that recalculates totals when an update, delete, or insert operation is indicated.

Hints for Completing the Tutorial

• This tutorial is meant to be completed sequentially—each lesson builds on the results of the previous one. If you jump ahead, you might not have the data or screens you need to perform the tasks being covered in that lesson.

• When you are done using the application—at the end of the day or if you want to continue the tutorial later—remember to shut down the web application. When you want to resume, make sure you're in the appropriate directory, set up the environment by applying the setup file (in UNIX), and restart the web application.

Before You Start

Before you start the tutorial, be aware of the following requirements:

• Know the directory and path name where Panther software is installed.

• Set up the Panther client to run either on a UNIX workstation or under Windows; instructions are given for both platforms. Illustrations represent the Windows version.

• If you run the client under Windows, make sure the Panther Samples\Tutorial directory is installed on your PC.

• To set up a web application server (Lesson 2), you need to have a web browser installed on your PC. You also need to find out the location of your HTTP server and its program directory (CGI, NSAPI, or ISAPI).

  If you do not have an HTTP server, you can skip Lesson 2. Follow the instructions for testing the screens in GUI.

For more information on configuring systems to run the tutorial, refer to Appendix A, "Setting Up the Tutorial."

Starting the Tutorial From the Beginning

If you have already started the tutorial, and wish to start it over from the first lesson, delete the files from the tutorial working directory, proltut, and copy the files over from the tutorial directory, tutorial. Both directories are in the samples directory of the Panther software installation.

For More Information...

As you progress through the tutorial or after you complete it, you might have questions about a specific area of Panther. Listed below are places you can look for more information.