Create Web-Based Tool Using RESTful API, JSON, and JavaScript

This example shows how to create a web application that calculates the price of a bond from a simple formula. It uses the MATLAB^® Production Server™ RESTful API and JSON Representation of MATLAB Data Types to depict an end-to-end workflow of using MATLAB Production Server. You run this example by entering the following known values into a web interface:

• Face value (or value of bond at maturity) — M

• Coupon payment — C

• Number of payments — N

• Interest rate — i

The application calculates price (P) based on the following equation:

P = C * ( (1 - (1 + i)^-N) / i ) + M * (1 + i)^-N

Use the sliders in the web application to price different bonds.

Step 1: Write MATLAB Code

Write the following code in MATLAB to price bonds. Save the code using the filename pricecalc.m.

function price = pricecalc(face_value, coupon_payment,...
                           interest_rate, num_payments)
    M = face_value;
    C = coupon_payment;
    N = num_payments;
    i = interest_rate;
    
    price = C * ( (1 - (1 + i)^-N) / i ) + M * (1 + i)^-N;

Step 2: Create a Deployable Archive with the Production Server Archive Compiler App

To create the deployable archive for this example:

1. On the Apps tab, select Production Server Archive Compiler.

2. In the Exported Functions field, add pricecalc.m.

3. Rename the archive to BondTools.

4. Click Package.

The generated deployable archive, BondTools.ctf is located in the output folder of the project.

Step 3: Place the Deployable Archive on a Server

1. Download the MATLAB Runtime, if needed, at https://www.mathworks.com/products/compiler/mcr. For more information, see Supported MATLAB Runtime Versions for MATLAB Production Server.

2. Create a server using mps-new. For more information, see Create Server Instance Using Command Line. If you have not already setup your server environment, see mps-setup for more information.

3. If you have not already done so, specify the location of MATLAB Runtime to the server by editing the server configuration file main_config and specifying a path for --mcr-root. See Server Configuration Properties for details.

4. Start the server using mps-start, and verify it is running with mps-status.

5. Copy the BondTools.ctf file to the auto_deploy folder on the server for hosting.

Step 4: Enable Cross-Origin Resource Sharing (CORS) on the Server

Enable Cross-Origin Resource Sharing (CORS) by editing the server configuration file, main_config and specifying the list of domain origins from which requests can be made to the server. For example, setting the cors-allowed-origins option to --cors-allowed-origins * allows requests from any domain to access the server. See cors-allowed-origins and Server Configuration Properties for details.

Step 5: Write JavaScript Code using the RESTful API and JSON

Write the following JavaScript^® code using the RESTful API and JSON Representation of MATLAB Data Types as a guide. Save this code as a JavaScript file named calculatePrice.js.

Code:

 calculatePrice.js

//calculatePrice.js : JavaScript code to calculate the price of a bond.
        function calculatePrice() 
        {
            var cp = parseFloat(document.getElementById('coupon_payment_value').value);
            var np = parseFloat(document.getElementById('num_payments_value').value);
            var ir = parseFloat(document.getElementById('interest_rate_value').value);
            var vm = parseFloat(document.getElementById('facevalue_value').value);

            // A new XMLHttpRequest object
            var request = new XMLHttpRequest();
            //Use MPS RESTful API to specify URL
            var url = "http://localhost:9910/BondTools/pricecalc";
            
            //Use MPS RESTful API to specify params using JSON
            var params = { "nargout":1,
                           "rhs": [vm, cp, ir, np] };

            document.getElementById("request").innerHTML = "URL: " + url + "<br>"
                    + "Method: POST <br>" + "Data:" + JSON.stringify(params);

            request.open("POST", url);

            //Use MPS RESTful API to set Content-Type
            request.setRequestHeader("Content-Type", "application/json");

            request.onload = function()
            {   //Use MPS RESTful API to check HTTP Status
                if (request.status == 200) 
                {
                    // Deserialization: Converting text back into JSON object
                    // Response from server is deserialized 
                    var result = JSON.parse(request.responseText);
					
                    //Use MPS RESTful API to retrieve response in "lhs"
                    if('lhs' in result)
                    {  document.getElementById("error").innerHTML = "" ;
                       document.getElementById("price_of_bond_value").innerHTML = "Bond Price: " + result.lhs[0].mwdata; }
                    else { document.getElementById("error").innerHTML = "Error: " + result.error.message; }
                }
                else { document.getElementById("error").innerHTML = "Error:" + request.statusText; }
                document.getElementById("response").innerHTML = "Status: " + request.status + "<br>"
                        + "Status message: " + request.statusText + "<br>" +
                        "Response text: " + request.responseText;
            }
            //Serialization: Converting JSON object to text prior to sending request
            request.send(JSON.stringify(params)); 
        }

        //Get value from slider element of "document" using its ID and update the value field
        //The "document" interface represent any web page loaded in the browser and
        //serves as an entry point into the web page's content.
        function printValue(sliderID, valueID) {
            var x = document.getElementById(valueID);
            var y = document.getElementById(sliderID);
            x.value = y.value;
        }
        //Execute JavaScript and calculate price of bond when slider is moved
        function updatePrice(sliderID, valueID) {
            printValue(sliderID, valueID);
            calculatePrice();
        }

Step 6: Embed JavaScript within HTML Code

Embed the JavaScript from the previous step within the following HTML code by using the following syntax:

<script src="calculatePrice.js" type="text/javascript"></script>

Save this code as an HTML file named bptool.html.

Code:

 bptool.html

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head lang="en">
    <meta charset="UTF-8">
    <title>Bond Pricing Tool</title>
</head>
<body>
    <!-- Embed the JavaScript code here by referencing calculatePrice.js -->
    <script src="calculatePrice.js" type="text/javascript"></script>
    <script>
        //Helper Code: Execute JavaScript immediately after the page has been loaded
        window.onload = function() {
            printValue('coupon_payment_slider', 'coupon_payment_value');
            printValue('num_payments_slider', 'num_payments_value');
            printValue('interest_rate_slider', 'interest_rate_value');
            printValue('facevalue_slider', 'facevalue_value');
            calculatePrice();
        }
    </script>
    <h1><a>Bond Pricing Tool</a></h1>
    <h2></h2>
    This example shows an application that calculates a bond price from a simple formula.<p>
    You run this example by entering the following known values into a simple graphical interface:<p>
      <ul>
        <li>Face Value (or value of bond at maturity) - M</li>
        <li>Coupon payment - C</li>
        <li>Number of payments - N</li>
        <li>Interest rate - i</li>
      </ul>
      The application calculates price (P) based on the following equation:<p>
      P = C * ( (1 - (1 + i)^-N) / i ) + M * (1 + i)^-N<p>
      <hr>
      <h3>M: Face Value </h3>
      <input id="facevalue_value" type="number" maxlength="4" oninput="updatePrice('facevalue_value', 'facevalue_slider')"/>
      <input type="range" id="facevalue_slider" value="0" min="0" max="10000" onchange="updatePrice('facevalue_slider', 'facevalue_value')"/>

      <h3>C: Coupon Payment </h3>
      <input id="coupon_payment_value" type="number" maxlength="4" oninput="updatePrice('coupon_payment_value', 'coupon_payment_slider')" />
      <input type="range" id="coupon_payment_slider" value="0" min="0" max="1000" onchange="updatePrice('coupon_payment_slider', 'coupon_payment_value')"/>
            
      <h3>N: Number of payments  </h3>
      <input id="num_payments_value" type="number" maxlength="4" oninput="updatePrice('num_payments_value', 'num_payments_slider')"/>
      <input type="range" id="num_payments_slider" value="0" min="0" max="1000" onchange="updatePrice('num_payments_slider', 'num_payments_value')"/>
      
      <h3>i: Interest rate </h3>
      <input id="interest_rate_value" type="number" maxlength="4" step="0.01" oninput="updatePrice('interest_rate_value', 'interest_rate_slider')"/>
      <input type="range" id="interest_rate_slider" value="0" min="0" max="1" step="0.01" onchange="updatePrice('interest_rate_slider', 'interest_rate_value')"/>

    <h2>BOND PRICE</h2>
    <p id="price_of_bond_value" style="font-weight: bold">
    <p id="error" style="color:red">

    <hr>
    <h3>Request to MPS Server</h3>
    <p id="request">
    
    <h3>Response from MPS Server</h3>
    <p id="response">
    <hr>
</body>
</html>

Step 7: Run Example

Confirm that the server with the deployed MATLAB function is running. Open the HTML file bptool.html in a web browser. The default bond price is NaN because no values have been entered as yet. Try the following values to price a bond:

• Face Value = $1000

• Coupon Payment = $100

• Number of payments = 5

• Interest rate = 0.08 (Corresponds to 8%)

The resulting bond price is $1079.85.

Use the sliders in the tool to price different bonds. Varying the interest rate results in the most dramatic change in the price of the bond.