Application Development

Panther is a complete three-tier product containing all the client and server components needed in building applications. Clients and servers can reside on different machines connected by a network. The middleware controls communication between client and server components, making it possible for an application's clients to interact with the application's servers.

Panther can work with your choice of the following middleware packages:

• JetNet, Panther's own middleware package.

• Oracle Tuxedo

• MTS, 32 bit Windows only

• WebSphere Application Server

JetNet and Oracle Tuxedo are TP monitor systems using messages and buffers to pass information to and from clients and application servers.

MTS for Windows, one of the deployment options for COM components, controls database connection pooling, transactions and security access for COM component packages.

IBM's WebSphere Application Server deploys Enterprise JavaBeans (EJBs), Java-based components, in a distributed application environment.

This chapter describes:

• What tasks the middleware performs.

• Where the middleware fits into your application.

Using JetNet and Oracle Tuxedo

In JetNet and Oracle Tuxedo applications, the middleware performs the following tasks:

• Establishes client connections to the application. These connections have the option of making use of several client authentication mechanisms. Refer to the client_init command for further information on client initialization and refer to "Client Authentication Functions" for more information on client authentication.

  If you are in the editor, refer to "Opening a Middleware Session in the Editor."

• Forwards service requests to an appropriate server for processing. Making a service call is similar to making a function call, but the function can be executed on a remote machine, and the code making the service call does not need to include any information about the remote machine.

  When no server is immediately available, service requests are queued up for the next available server.

  Service calls can be made either synchronously where further processing is blocked until the reply is received or asynchronously where client processing continues. In the asynchronous case, a reply is received by the client at a later time. Refer to the service_call command for detailed information on service calls.

• Returns data and status to a client following a service request.

• On the client, it can instruct the transaction manager to access the services that will carry out the database requests made by the client.

• Allows client and server agents to send messages to other agents. Refer to the broadcast and notify commands for more information.

• Permits a server to advertise its services to clients. Refer to the advertise command for more information. Servers can also dynamically change their service offerings.

• Automatically restarts servers if they fail, providing the servers have been configured for automatic restart. For more information, refer to "Server Restart Frequency" in JetNet/Oracle Tuxedo Guide.

Opening a Middleware Session in the Editor

In JetNet/Oracle Tuxedo applications, you open a middleware session to connect to a middleware and access the libraries and repositories on the application server. The middleware controls processes and communication between the application's clients and servers. To test an application screen that uses services, you must have a valid middleware connection.

How to Open a Middleware Session

1. Choose FileOpenMiddleware Session. The Connect dialog box appears.
   

   Figure 9-1 Connect to the middleware for a client on a server machine, also called a local or native client.

   For a local client on a server machine, the Connect dialog box has the following fields and specifications:

   • Config File—By default, displays the value of SMRBCONFIG variable. Otherwise, use the Browse button to select your configuration file.

   • Client—Specify client type by name (default is DEVELOPMENT). The client name can be no greater than 31 characters.

   • User—Specify user account (login) name. The user name can be no greater than 31 characters.

   • Password—Specify application password. The password can be no greater than 8 characters.
     

     Figure 9-2 Connect to the middleware for a client not on a server machine, also called a remote client.

     For a client not on a server machine, a remote client, the Connect dialog box has the following fields and specifications:

   • Host Name—By default, displays the value of the SMRBHOST variable. This variable provides the network address of the machines to which the client will connect.

   • Port—By default, displays the value of the SMRBPORT variable. This variable provides the port numbers associated with the machines to which the client will connect.

   • Client—Specify client type by name (default is DEVELOPMENT).

   • User—Specify user account (login) name.

   • Password—Specify application password.

2. Enter the information required in the appropriate fields depending on whether you are a client on a server machine or a PC client.

   If the application requires level-two authentication, then you must enter the application password in the Password field.

   Note: The level of authentication is decided at design time. Thus, a user should be aware of the decided authentication level.

To establish a middleware session programmatically, use the client_init command. For example, this statement opens a client connection and specifies an application password:

client_init PASSWORD appPassword

Refer to client_init for more information.

Using MTS

Since a COM component's entry in the Windows registry also specifies its machine location, the client application uses the same processing to call components on local and remote machines.

MTS is just one of the deployment options. COM components can be deployed using the following technologies:

• COM—Component Object Model. For COM applications, you install the component on each application client.

• DCOM—Distributed COM. For DCOM applications, you install the component on one machine and run a registration program on each application client to point to the component's remote location.

• MTS—Microsoft Transaction Server. For MTS applications, you install the component using the Microsoft Management Console and export an installation file to install and register components on an application client.

For detailed information about deploying COM components, refer to Chapter 5, "Deploying COM Components," in COM/MTS Guide.

Using WebSphere Application Server

In WebSphere Application Server, you deploy EJBs on the WebSphere server machine. Clients in your application can then call methods and set properties on those EJBs. Clients in a Panther application can specify the WebSphere server using the provider_url application property.

For information on setting up Panther software in a WebSphere environment, refer to Chapter 2, "Configuring Machines," in Panther for IBM WebSphere Developer's Studio.