Bind Live Presto Data in Wijmo FlexGrid with CData API Server

Wijmo FlexGrid is a lightweight, high-performance JavaScript datagrid for creating responsive, interactive data applications.

With the CData API Server and the Presto Connector (or any of the 350+ available connectors), you can quickly create APIs that expose live data from multiple sources, using industry standards like OData and Swagger for seamless integration with client-side and server-side controls in Wijmo's FlexGrid.

In this article, we'll use the Wijmo FlexGrid JavaScript components to build a simple HTML page that lets you select tables and columns from Presto and display the data.

Let's get started!

Prerequisites

1. CData API Server: Download a free trial here.
2. Wijmo FlexGrid: No downloads are required for this example, but you can sign up for a free trial here.
3. An active Presto account with access to your data.

Overview

Here's a quick overview of the steps we'll follow:

1. Install the CData API Server, configure a connection to Presto, and expose OData endpoints.
2. Bind Wijmo Grid to the live OData feed for real-time data access and interaction.

Getting Started

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Step 1: Install the CData API Server and Add a Connection to Presto

1.1 Install the API Server

If you haven't already, download an installer for your machine from the CData API Server page. Follow the installation instructions to complete the setup.

Once installed, you can start the server in the following ways:

• Windows: CData API Server runs as a service by default. Make sure the service is running, then open http://hostname:port (e.g., http://localhost:8080/) in your browser to access the API Server admin console.
• Linux/Mac: You can run the server manually or as a service. To start it manually, navigate to the installation directory and run java -jar apiserver.jar.
• Alternatively, run service.sh with root privileges to set up API Server as a Linux system service.

1.2 Enable CORS

When your Wijmo Grid application and the CData API Server are hosted on different domains, CORS (Cross-Origin Resource Sharing) must be enabled. To enable CORS in the API Server:

1. Go to Settings and click the icon to edit CORS settings.
2. Enable Cross-Origin Resource Sharing (CORS).
3. Enable Allow all domains without '*' to accept any origin.
4. In Access-Control-Allow-Origin, enter your Presto origin domain, or use * to allow all domains (suitable for public APIs).
5. Enable Access-Control-Allow-Credentials to allow cookies and auth headers.
6. In Access-Control-Allow-Methods, enter GET, PUT, POST, OPTIONS.
7. In Access-Control-Allow-Headers, enter Authorization, Content-Type.
8. Set Access-Control-Max-Age (default: 3600 seconds).
9. Click Save.

1.3 Add a Presto Connection in the API Server

1. Go to Settings and click Add Connection in the top-right.
2. Select Presto. If it's not visible, toggle off Only Installed to view all connectors.
3. Click Install Connector to auto-install. For a manual setup, choose Manual Install and upload the obtained ZIP file.
4. Once installed, click Presto to configure connection settings.

Set the Server and Port connection properties to connect, in addition to any authentication properties that may be required.

To enable TLS/SSL, set UseSSL to true.

Authenticating with LDAP

In order to authenticate with LDAP, set the following connection properties:

• AuthScheme: Set this to LDAP.
• User: The username being authenticated with in LDAP.
• Password: The password associated with the User you are authenticating against LDAP with.

Authenticating with Kerberos

In order to authenticate with KERBEROS, set the following connection properties:

• AuthScheme: Set this to KERBEROS.
• KerberosKDC: The Kerberos Key Distribution Center (KDC) service used to authenticate the user.
• KerberosRealm: The Kerberos Realm used to authenticate the user with.
• KerberosSPN: The Service Principal Name for the Kerberos Domain Controller.
• KerberosKeytabFile: The Keytab file containing your pairs of Kerberos principals and encrypted keys.
• User: The user who is authenticating to Kerberos.
• Password: The password used to authenticate to Kerberos.
5. Click Save & Test to validate and complete the connection setup.

1.4 Add and Configure Users

To allow secure access to the created OData endpoints, create and configure Users in the API Server.

1. Go to Users from the navigation pane, then click Add User.
2. Set a Username and Password.
3. Select a Role: Select Admin for full access and Query for limited access.
4. Define user Privileges (GET, POST, PUT, DELETE, etc.).
5. Click Add User to save.

Once a user is added, an Authtoken is automatically generated. This token can be used in API requests as a secure authentication method instead of a password.

You can also refresh the Authtoken, disable it, or set expiration rules (e.g., number of days until expiry) by enabling the Token Expiration option in the user settings.

1.5 Add Tables for the Endpoint

To make data from Presto accessible in Wijmo Grid via OData, you need to expose your desired tables through the API Server. Here's how:

1. In the API Server, go to API and click Add Table.
2. Select the Presto connection and click Next.
3. Choose the tables you want to expose and click Confirm.

1.6 Access the Endpoints in Wijmo FlexGrid

Now that your API is configured, Wijmo FlexGrid can connect to the OData endpoints to display live data. Below are the URL formats for OData endpoints that you can use:

These OData endpoints are now ready to be directly consumed in Wijmo FlexGrid using the URL. Since Wijmo FlexGrid supports OData, you can easily bind live data from Presto and create dynamic, interactive grids.

The CData API Server supports full OData filtering capabilities. For custom queries and filtered visualizations, you can append standard OData query parameters like $select, $filter, $orderby, $top, and $skip to your requests.

Step 2: Build the Simple Wijmo Grid

You've got the CData API Server up and running now with consumable OData endpoints from your Presto data. Now let's build a simple Wijmo FlexGrid that lets you select tables and columns and view your data.

1. Get the CData API Endpoint URL by logging into your CData API Server. Go to API from the left navigation, then click View Endpoints at the top-right.
2. Copy the URL (e.g., http://localhost:8080/api.rsc).

3. Create a new HTML file and give it a name (e.g., Wijmo-Grid.html).
4. Paste the following code into your HTML file.
5. Update the following placeholder values at the start of the script section:
• yourUsername: Replace with your CData API Server username.
• yourPassword: Replace with your CData API Server password.
• Your_CData_API_Server_URL: Replace with the full API endpoint URL you copied earlier.
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>Wijmo Grid with CData API Server</title> <!-- Wijmo styles --> <link href="https://cdn.mescius.com/wijmo/5.latest/styles/wijmo.min.css" rel="stylesheet" /> <!-- Wijmo core and controls --> <script src="https://cdn.mescius.com/wijmo/5.latest/controls/wijmo.min.js"></script> <script src="https://cdn.mescius.com/wijmo/5.latest/controls/wijmo.grid.min.js"></script> <script src="https://cdn.mescius.com/wijmo/5.latest/controls/wijmo.input.min.js"></script> <script src="https://cdn.mescius.com/wijmo/5.latest/controls/wijmo.odata.min.js"></script> <style> body { font-family: Arial, sans-serif; margin: 20px; } h1 { color: #00A0FF; text-align: center; } #selectors { display: flex; flex-wrap: wrap; gap: 15px; justify-content: center; align-items: flex-start; margin-bottom: 20px; } .select-group { display: flex; flex-direction: column; min-width: 200px; } label { font-weight: bold; margin-bottom: 5px; color: #00A0FF; } select, button { padding: 6px; font-size: 14px; border: 1px solid #00A0FF; border-radius: 4px; } button { background: #00A0FF; color: white; cursor: pointer; height: 40px; margin-top: 24px; } #columnsContainer { display: flex; flex-direction: column; gap: 5px; max-height: 150px; overflow-y: auto; border: 1px solid #00A0FF; padding: 8px; border-radius: 4px; } #theGrid { margin-top: 20px; border: 2px solid #00A0FF; height: 500px; } .wj-header { background: #00A0FF !important; color: white !important; font-weight: bold; } </style> </head> <body> <h1>Simple Wijmo Grid with CData API Server</h1> <div id="selectors"> <div class="select-group"> <label for="tableSelect">Select Table</label> <select id="tableSelect"></select> </div> <div class="select-group"> <label>Select Columns</label> <div id="columnsContainer"></div> </div> <div> <button onclick="loadGrid()">Load Grid</button> </div> </div> <div id="theGrid"></div> <script> const username = 'yourUsername'; const password = 'yourPassword'; const authHeader = 'Basic ' + btoa(username + ':' + password); const serviceUrl = 'Your_CData_API_Server_URL'; fetch(serviceUrl + '/$metadata', { headers: { Authorization: authHeader } }) .then(res => res.text()) .then(text => { const parser = new DOMParser(); const xml = parser.parseFromString(text, 'application/xml'); const tables = [...xml.getElementsByTagName('EntityType')]; const select = document.getElementById('tableSelect'); tables.forEach(t => { const name = t.getAttribute('Name'); const option = document.createElement('option'); option.value = name; option.textContent = name; select.appendChild(option); }); loadColumns(); // load columns for the first table }); document.getElementById('tableSelect').addEventListener('change', loadColumns); function loadColumns() { const table = document.getElementById('tableSelect').value; fetch(serviceUrl + '/$metadata', { headers: { Authorization: authHeader } }) .then(res => res.text()) .then(text => { const parser = new DOMParser(); const xml = parser.parseFromString(text, 'application/xml'); const entity = [...xml.getElementsByTagName('EntityType')].find(t => t.getAttribute('Name') === table); const columns = [...entity.getElementsByTagName('Property')]; const container = document.getElementById('columnsContainer'); container.innerHTML = ''; columns.forEach(col => { const name = col.getAttribute('Name'); const div = document.createElement('div'); div.innerHTML = `<label><input type="checkbox" value="${name}" checked> ${name}</label>`; container.appendChild(div); }); }); } function loadGrid() { const table = document.getElementById('tableSelect').value; const selectedCols = [...document.querySelectorAll('#columnsContainer input:checked')].map(i => i.value); const odata = new wijmo.odata.ODataCollectionView(serviceUrl, table, { requestHeaders: { Authorization: authHeader } }); const grid = new wijmo.grid.FlexGrid('#theGrid', { itemsSource: odata, autoGenerateColumns: false, columns: selectedCols.map(col => ({ binding: col, header: col })), selectionMode: 'CellRange', allowSorting: true }); } </script> </body> </html>
6. Open the HTML file in your browser.
7. Your browser should display the Wijmo FlexGrid. You can select a table and columns to display your data.

It's that simple. You can build even more complex applications and grids with Wijmo FlexGrid and the CData API Server by connecting to live data from Presto.

Check out the various frameworks supported by Wijmo at https://developer.mescius.com/wijmo.

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