Sections in this chapter:

• Configuring Your Environment
• Running Videoapp
• Looking at the Source Files

There are a small number of restrictions on the use of these applications:

• The videoapp application cannot currently be used with the Informix database. The oldvideo application, however, can be used with Informix.
• While these sample applications can be used with ODBC and SQL Server, if the driver on your platform does not support updatable cursors, the applications will not work. For information on which drivers support updatable cursors, see "Supported Database Clients and ODBC Drivers".
• The videoapp application uses cursors that span multiple HTML pages. If your database driver is single-threaded, these cursors may hold locks on the database and prevent other users from accessing it. For information on which database drivers are single-threaded, see the Enterprise Server 3.x Release Notes.

NOTE: Your database server must be up and running before you can create your video database, and you must configure your database server and client as described in Chapter 10, "Configuring Your Database."

Connecting to the Database and Recompiling

For each application, you must change the connect string in the HTML source file, start.htm, to match your database environment. For information on the parameters you use to connect, see "Database Connection Pools"; for even more information, see the description of the connect method in the JavaScript Reference.

For the videoapp application, change this line:

project.sharedConnections.pool = 
   new DbPool ("<Server Type>", "<Server Identifier>", 
      "<User>", "<Password>", "<Database>", 2, false)

database.connect ("INFORMIX", "yourserver", "informix",
   "informix", "lw_video")

Restart the application in the JavaScript Application Manager.

Creating the Database

The first time you run the scripts you might see errors about dropping databases or tables that do not exist. These error messages are normal; you can safely ignore them.

Informix

The SQL files for creating the video database (lw_video) on Informix are in these two directories:

$NSHOME\js\samples\videoapp\ifx 
$NSHOME\js\samples\oldvideo\ifx 

NOTE: Remember that pathnames in this manual are given in NT format if they are for both NT and Unix. On Unix, you would use $NSHOME/js/samples/videoapp/ ifx.

1. On Unix, log in as "informix" user and run the ifx_load.csh shell script for videoapp and for oldvideo.
   On NT, in the Informix Server program group, double-click the Command-Line Utilities icon to open a DOS window, and then run the following commands:

   cd c:\netscape\server\js\samples\videoapp\ifx
   ifx_load.bat

   You can also run the commands from the oldvideo\ifx directory:

2. You can now run the application by making the changes described in "Connecting to the Database and Recompiling".

The SQL files for creating the video database on Oracle are in these two directories:

$NSHOME\js\samples\videoapp\ora
$NSHOME\js\samples\oldvideo\ora

1. On both Unix and NT, start SQL Plus. From the SQL> prompt, enter this command:

   Start $NSHOME\js\samples\videoapp\ora\ora_video.sql

   You can also run the script from the oldvideo directory. This SQL script does not create a new database. Instead, it creates the Oracle tables in the current instance.

2. On Unix, run the ora_load script file to load the video tables with data. On NT, run the ora_load.bat batch file to load the video tables with data. You must edit the appropriate file to connect to your server; the instructions for doing so are in the file.

3. You can now run the application by making the changes described in "Connecting to the Database and Recompiling".

The SQL files for creating the video database on Sybase are in these two directories:

$NSHOME\js\samples\videoapp\syb
$NSHOME\js\samples\oldvideo\syb

1. Run the appropriate script from the command line. On Unix, the script is:

   syb_video.csh userid password

   For example:

   $NSHOME\js\samples\videoapp\syb\syb_load.csh sa

   On NT, the script is:

   syb_load userid password

   For example:

   c:\netscape\server\js\samples\videoapp\syb\syb_load sa

   Alternatively, you can run the script from the oldvideo directory.

2. You can now run the application by making the changes described in "Connecting to the Database and Recompiling".

NOTE: If you have both Sybase and MS SQL Server or DB2 installed on your machine, there is a potential naming confusion. These vendors have utilities with the same name (bcp and isql). When running this script, be certain that your environment variables are set so that you run the correct utility.

The SQL files for creating the video database on MS SQL Server are in these two directories:

$NSHOME\js\samples\videoapp\mss
$NSHOME\js\samples\oldvideo\mss

1. From a DOS prompt, run this batch file:

   mss_load userid password

   For example:

   c:\netscape\server\js\samples\videoapp\mss\mss_load sa

2. You can now run the application by making the changes described in "Connecting to the Database and Recompiling".

NOTE: If you have both MS SQL Server and Sybase or DB2 installed on your machine, there is a potential naming confusion. These vendors have utilities with the same name (bcp and isql). When running this script, be certain that your environment variables are set so that you run the correct utility.

$NSHOME\js\samples\videoapp\db2
$NSHOME\js\samples\oldvideo\db2

1. (Unix only) Your PATH environment variable must include the $DB2PATH/bin, $DB2PATH/misc, and $DB2PATH/adm directories.

2. Before you can run these scripts, you must have installed the DB2 Software Developer's Kit (DB2 SDK).

3. Also, before you can run the script to create the tables, you must edit it to modify some parameters. On Unix, the script is in db2_load.csh; on NT, it is in db2_load.bat. Edit the appropriate db2_load file and modify the following parameters to reflect your environment:
   • <nodename>: node name alias
   • <hostname>: host name of the node where the target database resides
   • <service-name>: service name or instance name from the services file
   • <database-name>: database name
   • <user>: authorized user
   • <password>: user's password

4. Make sure your /etc/services file has entries for your instance or service name if you are creating the database in a remote DB2 server.

5. Run the appropriate version of the script from the DB2 command window. The db2_load script runs the db2_video.sql and import.sql scripts. These subsidiary scripts create the video tables and load them with data from the *.del files. They do not create a new database. Instead, they create the DB2 tables in the local database alias specified in the db2_load script.

NOTE: If you have both DB2 and Sybase or MS SQL Server installed on your machine, there is a potential naming confusion. These vendors have utilities with the same name (bcp and isql). When running this script, be certain that your environment variables are set so that you run the correct utility.

Once you have created the video database and changed the database connection parameters, you can access the application here:

http://server.domain/videoapp

Figure 13.1    Videoapp home page

If you cannot connect to the database, you see an error message. Make sure you have entered the correct database connection parameters, as described in "Connecting to the Database and Recompiling", recompiled, and restarted the application.

The first thing you must do when you're connected is to add a new customer. Until you have done this, there are no customers to use for any of the other activities.

You can use videoapp as a customer or as an administrator. As a customer, you can:

• rent a movie
• show all the movies you currently have rented

• show all movies and who has them rented
• return a video for a customer
• add a new customer entry
• delete a customer entry
• modify a customer entry

Looking at the Source Files

Table 13.1 Primary videoapp source files  

home.htm	The application default page. Has links to pick.htm, status.htm, rentals.htm, customer.htm, and delete.htm. If not connected to the database, this page redirects the client to start.htm.
start.htm	Connects the application to the database, starts a transaction, and then redirects back to home.htm.
abort.htm	Cancels a transaction and begins a new transaction.
save.htm	Commits a transaction and begins a new transaction.
pick.htm	Allows the customer to rent a movie. It contains frames for category.htm, videos.htm, and pickmenu.htm. The category.htm file displays video categories. The videos.htm file displays all videos in selected category, linked to rent.htm to rent a particular video. The pickmenu.htm file displays choices of other pages to visit.
status.htm	Displays the videos the customer currently has rented. If the customer has not selected an ID, redirects to client.htm, which lets the customer select the ID.
rentals.htm	Displays a list of all rented videos. When the administrator clicks on one, it submits the choice to return.htm, which performs the logic to return the video, then redirects back to rentals.htm.
customer.htm	Allows the administrator to add a new customer. Submits form input to add.htm, which performs logic to add a customer, then redirects back to customer.htm.
delete.htm	Allows the administrator to delete a customer. Displays a list of customers with links to remove.htm, which deletes the specified row from the customer table, then redirects back to delete.htm.
modify.htm	Allows the administrator to modify a customer entry. Displays a list of the first five customers with links to modify1.htm and modify2.htm. Those pages update a specific row in the customer table and then redirect back to modify.htm. The modify3.htm file displays additional customers five at a time.

Application Architecture

Connection and Workflow

If not connected, videoapp redirects to start.htm. On this page, it creates a single pool of database connections to be used by all customers, gets a connection for the user, and starts a database transaction for that connection. It then redirects back to home.htm to continue. The user never sees the redirection.

The database transaction started on start.htm stays open until the user explicitly chooses either to save or discard changes, by clicking the Save Changes or Abort Changes button. When the user clicks one of those buttons, save.htm or abort.htm is run. These pages commit or roll back the open transaction and then immediately start another transaction. In this way, the customer's connection always stays open.

Once it has a database connection, videoapp presents the main page to the user. From that page, the user makes various choices, such as renting a movie or adding a new customer. Each of those options involves displaying various pages that contain server-side JavaScript statements. Many of those pages include statements that use the connection to interact with the database, displaying information or making changes to the database.

The first thing you must do when you're connected is to add a new customer. Until you have done this, there are no customers to use for any of the other activities.

Renting a Movie

The category.htm page queries the database for a list of the known categories of movie. It then displays those categories as links in a table in the left frame. If the user clicks one of those links, videoapp displays video.htm in the right frame. There are a few interesting things about the server-side code that accomplishes these tasks. If you look at this page early on, you see these lines:

var userId = unscramble(client.userId)
var bucket = project.sharedConnections.connections[userId]
var connection = bucket.connection

cursor = connection.cursor("select * from categories");

Here is the next interesting set of statements:

<SERVER>
...
while (cursor.next()) {
   catstr = escape(cursor.category)
</SERVER>

<TR><TD><A HREF=`"videos.htm?category=" + catstr` TARGET="myright">
<SERVER>write(cursor.category);</SERVER></A>
</TD>
</TR>
<SERVER>

} // bottom of while loop

<A HREF=`"videos.htm?category=" + catstr` TARGET="myright">

<A HREF="videos.htm?category=Comedy" TARGET="myright">

The videos.htm page can be served either from pick.htm or from category.htm. In the first case, the category property is not set, so the page displays a message requesting the user choose a category. If the category property is set, videos.htm accesses the database to display information about all the movies in that category. This page uses the same technique as category.htm to construct that information and create links to the rent.htm page.

The rent.htm page actually records the rental for the customer. It gets information from the request and then updates a table in the database to reflect the new rental. This page performs the update, but does not commit the change. That doesn't happen until the user chooses Save Changes or Abort Changes.

The pickmenu.htm page simply displays buttons that let you either return to the home page or to the page for adding a new customer.

Modifying videoapp

• Change the assumption that the existence of the sharedConnections array implies that this particular user is connected. You can change start.htm to check whether there is an ID for this user in that array and whether the connection stored in that location is currently valid. See "Sharing an Array of Connection Pools".
• This application never releases connections back to the pool. Consequently, once a small number of users have connected, nobody else can connect. You can modify this in a couple of ways: add a new command that lets the user indicate completion or implement a scheme to cleanup unused connections. See "Retrieving an Idle Connection".

Last Updated: 10/30/97 12:19:43