Consume Linear OData Feeds in PowerBuilder

The CData API Server produces secure feeds of Linear data that you can consume in PowerBuilder DataWindows. The API Server supports the major Web services, including OData, Atom, JSON, HTML, CSV, TSV, and RSS. It also supports the major authentication schemes and SSL.

This article shows how to create a DataWindow that uses the CData API Server to retrieve data.

Set Up the API Server

Follow the steps below to begin producing secure Linear OData services:

Deploy

The API Server runs on your own server. On Windows, you can deploy using the stand-alone server or IIS. On a Java servlet container, drop in the API Server WAR file. See the help documentation for more information and how-tos.

The API Server is also easy to deploy on Microsoft Azure, Amazon EC2, and Heroku.

Connect to Linear

After you deploy the API Server, provide authentication values and other connection properties needed to connect to Linear by clicking Settings -> Connections and adding a new connection in the API Server administration console.

You can authenticate to Linear with a personal API key or with OAuth 2.0. The API key is the simplest option for connecting with your own Linear account.

Authenticating with an API Key

Set the following connection properties:

• AuthScheme: Set this to APIKey.
• APIKey: A Linear personal API key.

To create a personal API key, log in to Linear, open Settings > Security & access > Personal API keys, select New API key, and create it. Copy the key immediately, because Linear shows it only once.

Authenticating with OAuth

OAuth requires a custom OAuth application registered in Linear (Settings > API > OAuth applications), which provides the OAuthClientId and OAuthClientSecret. Two flows are supported:

• Authorization code: Set AuthScheme to OAuth, InitiateOAuth to GETANDREFRESH, and provide OAuthClientId, OAuthClientSecret, and the CallbackURL defined in your application (e.g., http://localhost:33333). The driver opens Linear in your browser so you can grant access.
• Client credentials: Set AuthScheme to OAuthClient and provide OAuthClientId and OAuthClientSecret. This authenticates the application itself, with no browser interaction, and suits machine-to-machine integrations.

By default, the driver requests the read,write scopes. The driver refreshes the access token automatically when it expires.

You can then choose the Linear entities you want to allow the API Server access to by clicking Settings -> Resources.

Additionally, click Settings -> Server and change the following settings for compatibility with PowerBuilder:

• Default Format: Select XML (Atom) in the menu.
• Default Version: Select 2.0 in the menu.

Authorize API Server Users

After determining the OData services you want to produce, authorize users by clicking Settings -> Users. The API Server uses authtoken-based authentication and supports the major authentication schemes. Access can also be restricted based on IP address; by default, only connections to the local machine are allowed. You can authenticate as well as encrypt connections with SSL.

Create a Profile for Linear

Follow the steps below to use the Database Painter tool to create a database profile for the OData API of the API Server. In the Database Painter, you can graphically manipulate data as well as execute SQL queries.

1. Click Tools -> Database Painter.
2. Right-click the OData node and click New Profile.
3. In the Database Profile Setup dialog, enter the following:
   • Profile Name: Enter a user-friendly name for the profile.
   • URI: Enter the URL to the OData endpoint of the API Server. This URL will resemble the one below:

     http://MyServer:8080/api.rsc

   • Supply User Id and Password: Click this option to use HTTP Basic authentication. Note that the API Server also supports Windows authentication.
   • User Id: Enter the name of an user in the API Server.
   • Password: Enter the authtoken of an user in the API Server.
   
4. To view and modify a table, right-click a table and then click Edit Data -> Grid.

Using Linear Data with PowerBuilder Controls

You can use standard PowerBuilder objects to connect to OData feeds and execute queries. The following example shows how to retrieve Linear data into a DataWindow.

You can add the following code to the open method:

SQLCA.DBMS = "ODT"
SQLCA.DBParm = "ConnectString='URI=http://MyServer:8080/api.rsc;UID=MyAPIUser;PWD=MyAuthtoken'";
CONNECT USING SQLCA;
dw_team.SetTransObject(SQLCA);
dw_team.Retrieve();