jQuery Captcha Plugin: The Contact Form Code Example

Click on the link below that matches your BotDetect CAPTCHA jQuery Plugin usage scenario:

First Time Here?

The jQuery CAPTCHA Integration Guide is the best place to start!

..............................................................

jQuery-based Frontend and the web API with MVC Core 1/2 on Backend

This is a partial walk-through of the example source code. It is not meant to replace a proper step-by-step guide. If you are new to BotDetect, skip it for now; and do start your first jQuery captcha integration by following our step-by-step jQuery CAPTCHA Integration Guide.

Introduction

This contact form jQuery captcha example shows the code required to display and validate captchas in a contact form of the application with a jQuery frontend and a web API with MVC Core 1/2 backend.

Download the BotDetect ASP.NET CAPTCHA Component and run this example

Within this page, the root folder of the extracted archive is referred as the <BDC-DIR>.

This example is in the <BDC-DIR>/core-on-core/examples/s_api-captcha-jquery-webapi_mvccore2/ folder; and contains the following files:

Frontend: contact.html

The wwwroot/contact.html source file does the following:

  • Loads the BotDetect CAPTCHA jQuery Plugin into the page
  • Displays the captcha and user-input markups on the page
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>BotDetect jQuery CAPTCHA Examples</title>
  <link href="styles/styles.css" type="text/css" rel="stylesheet">
</head>
<body>
    <header>
        <div class="header-content"><h1>BotDetect jQuery CAPTCHA Examples</h1></div>
    </header>

    <nav>
      <ul class="nav">
        <li><a href="basic.html">Basic Example</a></li>
        <li><a href="contact.html" class="active">Contact Example</a></li>
      </ul>
    </nav>

    <section id="main-content">
        <form id="contactForm" method="POST">
            <div id="form-messages"></div>

            <label>
                <span>Name:</span>
                <input type="text" id="name" name="name">
            </label>
            <div class="error name"></div>


            <label>
                <span>Email</span>
                <input type="email" id="email" name="email" >
            </label>
            <div class="error email"></div>


            <label>
                <span>Subject:</span>
                <input type="text" id="subject" name="subject">
            </label>
            <div class="error subject"></div>


            <label>
                <span>Message:</span>
                <textarea id="message" name="message"></textarea>
            </label>
            <div class="error message"></div>


            <!-- captcha challenge: placeholder -->
            <div id="botdetect-captcha" data-captchastylename="jqueryFormCaptcha"></div>

            <label>
                <span>Retype the characters from the picture:</span>
                <!-- captcha code: user-input textbox -->
                <input 
                    type="text" 
                    id="userCaptchaInput" 
                >
            </label>

            <button type="submit" id="submitButton" class="btn btn-primary">Send</button>
        </form>
    </section>
    
    <script src="node_modules/jquery/jquery.min.js"></script>
    <script src="node_modules/jquery-captcha/dist/jquery-captcha.min.js"></script>
    <script src="js/contact.js"></script>
</body>
</html>

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Frontend: contact.js

The wwwroot/js/contact.js source file does the following:

  • Sets the captchaEndpoint property to point to the captcha endpoint path on backend
  • Loads the captcha challenges from backend
  • Sends the post request with the captcha id and the user entered captcha code to backend
  • Processes the captcha validation results:
    • when the captcha validation fails -- it reloads captcha and displays an error message
    • when the captcha validation succeeds -- it executes by the captcha protected action
$(function () {

    // create the frontend captcha instance in the DOM.ready event-handler;
    // and set the captchaEndpoint property to point to 
    // the captcha endpoint path on your app's backend
    var captcha = $('#botdetect-captcha').captcha({
        captchaEndpoint: 'simple-captcha-endpoint.ashx'
    });

    // the validation-error messages for the form's data-input fields
    var errorMessages = {
        name: 'Name must be at least 3 chars long!',
        email: 'Email is invalid!',
        subject: 'Subject must be at least 10 chars long!',
        message: 'Message must be at least 10 chars long!'
    };

    // the global variables that hold the validation-status flags of the form's data-input fields;
    // those validation-status flags will be checked on form submit
    var isNameValid = false,
        isEmailValid = false,
        isSubjectValid = false,
        isMessageValid = false;

    function validateName() {
        var name = $('#name').val();
        isNameValid = (name.length >= 3);
        if (isNameValid) {
            $('.name').text('');
        } else {
            $('.name').text(errorMessages.name);
        }
    }

    function validateEmail() {
        var email = $('#email').val();
        var emailRegEx = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
        isEmailValid = emailRegEx.test(email);
        if (isEmailValid) {
            $('.email').text('');
        } else {
            $('.email').text(errorMessages.email);
        }
    }

    function validateSubject() {
        var subject = $('#subject').val();
        isSubjectValid = (subject.length >= 10);
        if (isSubjectValid) {
            $('.subject').text('');
        } else {
            $('.subject').text(errorMessages.subject);
        }
    }

    function validateMessage() {
        var message = $('#message').val();
        isMessageValid = (message.length >= 10);
        if (isMessageValid) {
            $('.message').text('');
        } else {
            $('.message').text(errorMessages.message);
        }
    }

    // validate the form's data-input fields on blur event
    $('#name').blur(validateName);
    $('#email').blur(validateEmail);
    $('#subject').blur(validateSubject);
    $('#message').blur(validateMessage);

    // process the contact form on submit event
    $('#contactForm').submit(function (event) {

        if (isNameValid && isEmailValid && isSubjectValid && isMessageValid) {
            
            // get the user-entered captcha code value to be validated at the backend side
            var userEnteredCaptchaCode = captcha.getUserEnteredCaptchaCode();

            // get the id of a captcha instance that the user tried to solve
            var captchaId = captcha.getCaptchaId();

            var postData = {
                name: $('#name').val(),
                email: $('#email').val(),
                subject: $('#subject').val(),
                message: $('#message').val(),
                // add the user-entered captcha code value to the post data
                userEnteredCaptchaCode: userEnteredCaptchaCode,
                // add the id of a captcha instance to the post data
                captchaId: captchaId
            };

            // post both the form-data and captcha data to the backend
            $.ajax({
                method: 'POST',
                url: 'api/contact-captcha',
                data: JSON.stringify(postData),
                contentType: "application/json",
                success: function (response) {
                    if (response.success == false) {
                        // captcha validation failed; show the error message
                        $('#form-messages')
                            .removeClass()
                            .addClass('alert alert-error')
                            .text(response.errors.userEnteredCaptchaCode);
                        // call the captcha.reloadImage()
                        // in order to generate a new captcha challenge
                        captcha.reloadImage();
                    } else {
                        // captcha validation succeeded; proceed with the workflow
                        window.location.replace('notify_page/contact_success_notify.html');
                    }
                },
                error: function (error) {
                    throw new Error(error);
                }
            });

        } else {
            $('#form-messages')
                .removeClass()
                .addClass('alert alert-error')
                .text('Please enter valid values.');
        }

        event.preventDefault();
    });
});

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Backend: appsettings.json

The appsettings.json source file contains the following:

  • BotDetect configuration section that defines the CaptchaEndpointPath path
{
  "Logging": {
    "IncludeScopes": false,
    "LogLevel": {
      "Default": "Warning"
    }
  },
  "BotDetect": {
    "CaptchaEndpointPath": "simple-captcha-endpoint.ashx"
  }
}

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Backend: Startup.cs

The Startup.cs source file does the following:

  • Configures the application pipeline to use SimpleCaptcha middleware
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;

using BotDetect.Web;
using BotDetect.Web.Http;

namespace jQueryWebAPIwithMVC6CaptchaExample
{
    public class Startup
    {
        public Startup(IHostingEnvironment env)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", optional: false, reloadOnChange: true)
                .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
                .AddEnvironmentVariables();
            Configuration = builder.Build();
        }

        public IConfigurationRoot Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            // You can omit the next line on .NET Core 2.0 or higher
            services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

            services.AddMemoryCache(); // Adds a default in-memory 
                                       // implementation of 
                                       // IDistributedCache

            // Add framework services.
            services.AddMvc();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            loggerFactory.AddConsole(Configuration.GetSection("Logging"));
            loggerFactory.AddDebug();

            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            // Serve my app-specific default file, if present.
            DefaultFilesOptions options = new DefaultFilesOptions();
            options.DefaultFileNames.Clear();
            options.DefaultFileNames.Add("basic.html");
            app.UseDefaultFiles(options);
            app.UseStaticFiles();

            // Configure the application pipeline to use SimpleCaptcha middleware
            app.UseSimpleCaptcha(Configuration.GetSection("BotDetect"));

            app.UseMvc();
        }
    }
}

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Backend: botdetect.xml

The botdetect.xml source file contains the following:

  • Captcha style definitions consisting of:
    • The name of a captcha style
    • The ID of an <input> element in which user enters captcha codes
    • Other option settings -- the captcha code length in this particular case
<?xml version="1.0" encoding="UTF-8"?>
<botdetect xmlns="https://captcha.com/schema/net"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="https://captcha.com/schema/net 
     https://captcha.com/schema/net/botdetect-4.4.2.xsd">

  <captchaStyles>
    <captchaStyle>
      <name>jqueryFormCaptcha</name>
      <userInputID>userCaptchaInput</userInputID>
      <codeLength>4-6</codeLength>
    </captchaStyle>
  </captchaStyles>
</botdetect>

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Backend: ContactApiController.cs

The Controllers/ContactApiController.cs source file does the following:

  • Extracts the userEnteredCaptchaCode and captchaId values posted from the frontend
  • Validates captchas by calling the Validate(userEnteredCaptchaCode, captchaId) method
  • Returns the json-formatted captcha validation results to frontend
using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;
using System.Text.RegularExpressions;

using BotDetect.Web;

namespace jQueryWebAPIwithMVC6CaptchaExample.Controllers
{
    [Route("api/contact-captcha")]
    public class ContactApiController : Controller
    {
        [HttpPost]
        public IActionResult Post([FromBody] Models.ContactFormModel data)
        {
            string name = data.Name;
            string email = data.Email;
            string subject = data.Subject;
            string message = data.Message;

            string userEnteredCaptchaCode = data.UserEnteredCaptchaCode;
            string captchaId = data.CaptchaId;

            // validate the form data
            Dictionary<string, string> errors = new Dictionary<string, string>();

            if (!IsValidName(name))
            {
                errors.Add("name", "Name must be at least 3 chars long!");
            }

            if (!IsValidEmail(email))
            {
                errors.Add("email", "Email is invalid!");
            }

            if (!IsValidSubject(subject))
            {
                errors.Add("subject", "Subject must be at least 10 chars long!");
            }

            if (!IsValidMessage(message))
            {
                errors.Add("message", "Message must be at least 10 chars long!");
            }

            // validate the user entered captcha code
            if (!IsCaptchaCorrect(userEnteredCaptchaCode, captchaId))
            {
                errors.Add("userEnteredCaptchaCode", "CAPTCHA validation failed!");
                // TODO: consider logging the attempt
            }

            bool isErrorsEmpty = errors.Count > 0 ? false : true;

            if (isErrorsEmpty)
            {
                // TODO: all validations succeeded; execute the protected action
                // (send email, write to database, etc...)
            }

            // create an object that stores the validation result
            Dictionary<string, object> validationResult = new Dictionary<string, object>();
            validationResult.Add("success", isErrorsEmpty);
            validationResult.Add("errors", errors);

            // return the json string with the validation result to the frontend
            return Json(validationResult);
        }

        // the captcha validation function
        private bool IsCaptchaCorrect(string userEnteredCaptchaCode, string captchaId)
        {
            // create a captcha instance to be used for the captcha validation
            SimpleCaptcha captcha = new SimpleCaptcha();
            // execute the captcha validation
            return captcha.Validate(userEnteredCaptchaCode, captchaId);
        }

        private bool IsValidName(string name)
        {
            if (name == null)
            {
                return false;
            }

            return (name.Length >= 3);
        }

        private bool IsValidEmail(string email)
        {
            if (email == null)
            {
                return false;
            }
            Regex regex = new Regex(@"^[\w-_\.+]*[\w-_\.]\@([\w]+\.)+[\w]+[\w]$");
            Match match = regex.Match(email);

            return match.Success;
        }

        private bool IsValidSubject(string subject)
        {
            if (subject == null)
            {
                return false;
            }

            return (subject.Length > 9) && (subject.Length < 255);
        }

        private bool IsValidMessage(string message)
        {
            if (message == null)
            {
                return false;
            }

            return (message.Length > 9) && (message.Length < 255);
        }
    }
}

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jQuery-based Frontend and the Legacy ASP.NET Web-API 2 on Backend

This is a partial walk-through of the example source code. It is not meant to replace a proper step-by-step guide. If you are new to BotDetect, skip it for now; and do start your first jQuery captcha integration by following our step-by-step jQuery CAPTCHA Integration Guide.

Introduction

This contact form jQuery captcha example shows the code required to display and validate captchas in a contact form of the application with a jQuery frontend and a legacy ASP.NET Web-API 2 backend.

Download the BotDetect ASP.NET CAPTCHA Component and run this example

Within this page, the root folder of the extracted archive is referred as the <BDC-DIR>.

This example is in the <BDC-DIR>/lgcy-on-lgcy/examples/s_api-captcha-jquery-webapi2/csharp/ folder; and contains the following files:

Frontend: contact.html

The contact.html source file does the following:

  • Loads the BotDetect CAPTCHA jQuery Plugin into the page
  • Displays the captcha and user-input markups on the page
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>BotDetect jQuery CAPTCHA Examples</title>
  <link href="styles/styles.css" type="text/css" rel="stylesheet">
</head>
<body>
    <header>
        <div class="header-content"><h1>BotDetect jQuery CAPTCHA Examples</h1></div>
    </header>

    <nav>
      <ul class="nav">
        <li><a href="basic.html">Basic Example</a></li>
        <li><a href="contact.html" class="active">Contact Example</a></li>
      </ul>
    </nav>

    <section id="main-content">
        <form id="contactForm" method="POST">
            <div id="form-messages"></div>

            <label>
                <span>Name:</span>
                <input type="text" id="name" name="name">
            </label>
            <div class="error name"></div>


            <label>
                <span>Email</span>
                <input type="email" id="email" name="email" >
            </label>
            <div class="error email"></div>


            <label>
                <span>Subject:</span>
                <input type="text" id="subject" name="subject">
            </label>
            <div class="error subject"></div>


            <label>
                <span>Message:</span>
                <textarea id="message" name="message"></textarea>
            </label>
            <div class="error message"></div>


            <!-- captcha challenge: placeholder -->
            <div id="botdetect-captcha" data-captchastylename="jqueryFormCaptcha"></div>

            <label>
                <span>Retype the characters from the picture:</span>
                <!-- captcha code: user-input textbox -->
                <input 
                    type="text" 
                    id="userCaptchaInput" 
                >
            </label>

            <button type="submit" id="submitButton" class="btn btn-primary">Send</button>
        </form>
    </section>
    
    <script src="node_modules/jquery/jquery.min.js"></script>
    <script src="node_modules/jquery-captcha/dist/jquery-captcha.min.js"></script>
    <script src="js/contact.js"></script>
</body>
</html>

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Frontend: contact.js

The js/contact.js source file does the following:

  • Sets the captchaEndpoint property to point to the captcha endpoint path on backend
  • Loads the captcha challenges from backend
  • Sends the post request with the captcha id and the user entered captcha code to backend
  • Processes the captcha validation results:
    • when the captcha validation fails -- it reloads captcha and displays an error message
    • when the captcha validation succeeds -- it executes by the captcha protected action
$(function () {

    // create the frontend captcha instance in the DOM.ready event-handler;
    // and set the captchaEndpoint property to point to 
    // the captcha endpoint path on your app's backend
    var captcha = $('#botdetect-captcha').captcha({
        captchaEndpoint: 'simple-captcha-endpoint.ashx'
    });

    // the validation-error messages for the form's data-input fields
    var errorMessages = {
        name: 'Name must be at least 3 chars long!',
        email: 'Email is invalid!',
        subject: 'Subject must be at least 10 chars long!',
        message: 'Message must be at least 10 chars long!'
    };

    // the global variables that hold the validation-status flags of the form's data-input fields;
    // those validation-status flags will be checked on form submit
    var isNameValid = false,
        isEmailValid = false,
        isSubjectValid = false,
        isMessageValid = false;

    function validateName() {
        var name = $('#name').val();
        isNameValid = (name.length >= 3);
        if (isNameValid) {
            $('.name').text('');
        } else {
            $('.name').text(errorMessages.name);
        }
    }

    function validateEmail() {
        var email = $('#email').val();
        var emailRegEx = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
        isEmailValid = emailRegEx.test(email);
        if (isEmailValid) {
            $('.email').text('');
        } else {
            $('.email').text(errorMessages.email);
        }
    }

    function validateSubject() {
        var subject = $('#subject').val();
        isSubjectValid = (subject.length >= 10);
        if (isSubjectValid) {
            $('.subject').text('');
        } else {
            $('.subject').text(errorMessages.subject);
        }
    }

    function validateMessage() {
        var message = $('#message').val();
        isMessageValid = (message.length >= 10);
        if (isMessageValid) {
            $('.message').text('');
        } else {
            $('.message').text(errorMessages.message);
        }
    }

    // validate the form's data-input fields on blur event
    $('#name').blur(validateName);
    $('#email').blur(validateEmail);
    $('#subject').blur(validateSubject);
    $('#message').blur(validateMessage);

    // process the contact form on submit event
    $('#contactForm').submit(function (event) {

        if (isNameValid && isEmailValid && isSubjectValid && isMessageValid) {
            
            // get the user-entered captcha code value to be validated at the backend side
            var userEnteredCaptchaCode = captcha.getUserEnteredCaptchaCode();

            // get the id of a captcha instance that the user tried to solve
            var captchaId = captcha.getCaptchaId();

            var postData = {
                name: $('#name').val(),
                email: $('#email').val(),
                subject: $('#subject').val(),
                message: $('#message').val(),
                // add the user-entered captcha code value to the post data
                userEnteredCaptchaCode: userEnteredCaptchaCode,
                // add the id of a captcha instance to the post data
                captchaId: captchaId
            };

            // post both the form-data and captcha data to the backend
            $.ajax({
                method: 'POST',
                url: 'api/webapi/contact',
                data: JSON.stringify(postData),
                contentType: "application/json",
                success: function (response) {
                    if (response.success == false) {
                        // captcha validation failed; show the error message
                        $('#form-messages')
                            .removeClass()
                            .addClass('alert alert-error')
                            .text(response.errors.userEnteredCaptchaCode);
                        // call the captcha.reloadImage()
                        // in order to generate a new captcha challenge
                        captcha.reloadImage();
                    } else {
                        // captcha validation succeeded; proceed with the workflow
                        window.location.replace('notify_page/contact_success_notify.html');
                    }
                },
                error: function (error) {
                    throw new Error(error);
                }
            });

        } else {
            $('#form-messages')
                .removeClass()
                .addClass('alert alert-error')
                .text('Please enter valid values.');
        }

        event.preventDefault();
    });
});

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Backend: web.config

The web.config source file does the following:

  • Registers the simple-captcha-endpoint.ashx path
  • Maps it to the BotDetect.Web.SimpleCaptchaHandler
<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <appSettings></appSettings>
  <system.web>
    <compilation debug="false" targetFramework="4.5"/>
    <httpRuntime targetFramework="4.5"/>
    <httpHandlers>
      <!-- Register the HttpHandler used for BotDetect Captcha requests -->
      <add verb="GET" path="simple-captcha-endpoint.ashx"
	   type="BotDetect.Web.SimpleCaptchaHandler, BotDetect"/>
    </httpHandlers>
  </system.web>
  <system.webServer>
    <validation validateIntegratedModeConfiguration="false"/>
    <handlers>
      <!-- Register the HttpHandler used for BotDetect Captcha requests (IIS 7.0+) -->
      <remove name="BotDetectCaptchaHandler"/>
      <add name="BotDetectCaptchaHandler" preCondition="integratedMode" 
	   verb="GET" path="simple-captcha-endpoint.ashx"
	   type="BotDetect.Web.SimpleCaptchaHandler, BotDetect"/>
    </handlers>
    <defaultDocument>
      <files>
        <clear />
        <add value="basic.html"/>
      </files>
    </defaultDocument>
  </system.webServer>
</configuration>

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Backend: botdetect.xml

The botdetect.xml source file contains the following:

  • Captcha style definitions consisting of:
    • The name of a captcha style
    • The ID of an <input> element in which user enters captcha codes
    • Other option settings -- the captcha code length in this particular case
<?xml version="1.0" encoding="UTF-8"?>
<botdetect xmlns="https://captcha.com/schema/net"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="https://captcha.com/schema/net
            https://captcha.com/schema/net/botdetect-4.4.2.xsd">

    <captchaStyles>
        <captchaStyle>
            <name>jqueryFormCaptcha</name>
            <userInputID>userCaptchaInput</userInputID>
            <codeLength>4-6</codeLength>
        </captchaStyle>
    </captchaStyles>
</botdetect>

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Backend: WebApiController.cs

The Backend/Controllers/WebApiController.cs source file does the following:

  • Extracts the userEnteredCaptchaCode and captchaId values posted from the frontend
  • Validates captchas by calling the Validate(userEnteredCaptchaCode, captchaId) method
  • Returns the json-formatted captcha validation results to frontend
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System.Web.Http;
using jQueryWebAPICaptchaExampleCSharp.Backend.Models;

using BotDetect.Web;

namespace jQueryWebAPICaptchaExampleCSharp.Backend.Controllers
{
    public class WebApiController : ApiController
    {
        // POST api/webapi/contact
        public IHttpActionResult Contact([FromBody]CaptchaContactModel data)
        {
            string name = data.Name;
            string email = data.Email;
            string subject = data.Subject;
            string message = data.Message;

            string userEnteredCaptchaCode = data.UserEnteredCaptchaCode;
            string captchaId = data.CaptchaId;

            // validate the form data
            Dictionary<string, string> errors = new Dictionary<string, string>();

            if (!IsValidName(name))
            {
                errors.Add("name", "Name must be at least 3 chars long!");
            }

            if (!IsValidEmail(email))
            {
                errors.Add("email", "Email is invalid!");
            }

            if (!IsValidSubject(subject))
            {
                errors.Add("subject", "Subject must be at least 10 chars long!");
            }

            if (!IsValidMessage(message))
            {
                errors.Add("message", "Message must be at least 10 chars long!");
            }

            // validate the user entered captcha code
            if (!IsCaptchaCorrect(userEnteredCaptchaCode, captchaId))
            {
                errors.Add("userEnteredCaptchaCode", "CAPTCHA validation failed!");
                // TODO: consider logging the attempt
            }

            bool isErrorsEmpty = errors.Count <= 0;

            if (isErrorsEmpty)
            {
                // TODO: all validations succeeded; execute the protected action
                // (send email, write to database, etc...)
            }

            // create an object that stores the validation result
            Dictionary<string, object> validationResult = new Dictionary<string, object>();
            validationResult.Add("success", isErrorsEmpty);
            validationResult.Add("errors", errors);

            // return the json string with the validation result to the frontend
            return Ok(validationResult);
        }

        // the captcha validation function
        private bool IsCaptchaCorrect(string userEnteredCaptchaCode, string captchaId)
        {
            // create a captcha instance to be used for the captcha validation
            SimpleCaptcha captcha = new SimpleCaptcha();
            // execute the captcha validation
            return captcha.Validate(userEnteredCaptchaCode, captchaId);
        }

        private bool IsValidName(string name)
        {
            if (name == null)
            {
                return false;
            }

            return (name.Length >= 3);
        }

        private bool IsValidEmail(string email)
        {
            if (email == null)
            {
                return false;
            }
            Regex regex = new Regex("^[\\w-_\\.+]*[\\w-_\\.]\\@([\\w]+\\.)+[\\w]+[\\w]$");
            Match match = regex.Match(email);

            return match.Success;
        }

        private bool IsValidSubject(string subject)
        {
            if (subject == null)
            {
                return false;
            }

            return (subject.Length > 9) && (subject.Length < 255);
        }

        private bool IsValidMessage(string message)
        {
            if (message == null)
            {
                return false;
            }

            return (message.Length > 9) && (message.Length < 255);
        }
    }

    public class CaptchaContactModel
    {
        [JsonProperty("name")]
        public string Name { get; set; }

        [JsonProperty("email")]
        public string Email { get; set; }

        [JsonProperty("subject")]
        public string Subject { get; set; }

        [JsonProperty("message")]
        public string Message { get; set; }

        [JsonProperty("captchaId")]
        public string CaptchaId { get; set; }

        [JsonProperty("userEnteredCaptchaCode")]
        public string UserEnteredCaptchaCode { get; set; }
    }
}

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..............................................................

jQuery-based Frontend and the Legacy ASP.NET Generic Handler on Backend

This is a partial walk-through of the example source code. It is not meant to replace a proper step-by-step guide. If you are new to BotDetect, skip it for now; and do start your first jQuery captcha integration by following our step-by-step jQuery CAPTCHA Integration Guide.

Introduction

This contact form jQuery captcha example shows the code required to display and validate captchas in a contact form of the application with a jQuery frontend and a legacy ASP.NET Generic Handler backend.

Download the BotDetect ASP.NET CAPTCHA Component and run this example

Within this page, the root folder of the extracted archive is referred as the <BDC-DIR>.

This example is in the <BDC-DIR>/lgcy-on-lgcy/examples/s_api-captcha-jquery-generic_handler/csharp/ folder; and contains the following files:

Frontend: contact.html

The contact.html source file does the following:

  • Loads the BotDetect CAPTCHA jQuery Plugin into the page
  • Displays the captcha and user-input markups on the page
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>BotDetect jQuery CAPTCHA Examples</title>
  <link href="styles/styles.css" type="text/css" rel="stylesheet">
</head>
<body>
    <header>
        <div class="header-content"><h1>BotDetect jQuery CAPTCHA Examples</h1></div>
    </header>

    <nav>
      <ul class="nav">
        <li><a href="basic.html">Basic Example</a></li>
        <li><a href="contact.html" class="active">Contact Example</a></li>
      </ul>
    </nav>

    <section id="main-content">
        <form id="contactForm" method="POST">
            <div id="form-messages"></div>

            <label>
                <span>Name:</span>
                <input type="text" id="name" name="name">
            </label>
            <div class="error name"></div>


            <label>
                <span>Email</span>
                <input type="email" id="email" name="email" >
            </label>
            <div class="error email"></div>


            <label>
                <span>Subject:</span>
                <input type="text" id="subject" name="subject">
            </label>
            <div class="error subject"></div>


            <label>
                <span>Message:</span>
                <textarea id="message" name="message"></textarea>
            </label>
            <div class="error message"></div>


            <!-- captcha challenge: placeholder -->
            <div id="botdetect-captcha" data-captchastylename="jqueryFormCaptcha"></div>

            <label>
                <span>Retype the characters from the picture:</span>
                <!-- captcha code: user-input textbox -->
                <input 
                    type="text" 
                    id="userCaptchaInput" 
                >
            </label>

            <button type="submit" id="submitButton" class="btn btn-primary">Send</button>
        </form>
    </section>
    
    <script src="node_modules/jquery/jquery.min.js"></script>
    <script src="node_modules/jquery-captcha/dist/jquery-captcha.min.js"></script>
    <script src="js/contact.js"></script>
</body>
</html>

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Frontend: contact.js

The js/contact.js source file does the following:

  • Sets the captchaEndpoint property to point to the captcha endpoint path on backend
  • Loads the captcha challenges from backend
  • Sends the post request with the captcha id and the user entered captcha code to backend
  • Processes the captcha validation results:
    • when the captcha validation fails -- it reloads captcha and displays an error message
    • when the captcha validation succeeds -- it executes by the captcha protected action
$(function () {

    // create the frontend captcha instance in the DOM.ready event-handler;
    // and set the captchaEndpoint property to point to 
    // the captcha endpoint path on your app's backend
    var captcha = $('#botdetect-captcha').captcha({
        captchaEndpoint: 'simple-captcha-endpoint.ashx'
    });

    // the validation-error messages for the form's data-input fields
    var errorMessages = {
        name: 'Name must be at least 3 chars long!',
        email: 'Email is invalid!',
        subject: 'Subject must be at least 10 chars long!',
        message: 'Message must be at least 10 chars long!'
    };

    // the global variables that hold the validation-status flags of the form's data-input fields;
    // those validation-status flags will be checked on form submit
    var isNameValid = false,
        isEmailValid = false,
        isSubjectValid = false,
        isMessageValid = false;

    function validateName() {
        var name = $('#name').val();
        isNameValid = (name.length >= 3);
        if (isNameValid) {
            $('.name').text('');
        } else {
            $('.name').text(errorMessages.name);
        }
    }

    function validateEmail() {
        var email = $('#email').val();
        var emailRegEx = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
        isEmailValid = emailRegEx.test(email);
        if (isEmailValid) {
            $('.email').text('');
        } else {
            $('.email').text(errorMessages.email);
        }
    }

    function validateSubject() {
        var subject = $('#subject').val();
        isSubjectValid = (subject.length >= 10);
        if (isSubjectValid) {
            $('.subject').text('');
        } else {
            $('.subject').text(errorMessages.subject);
        }
    }

    function validateMessage() {
        var message = $('#message').val();
        isMessageValid = (message.length >= 10);
        if (isMessageValid) {
            $('.message').text('');
        } else {
            $('.message').text(errorMessages.message);
        }
    }

    // validate the form's data-input fields on blur event
    $('#name').blur(validateName);
    $('#email').blur(validateEmail);
    $('#subject').blur(validateSubject);
    $('#message').blur(validateMessage);

    // process the contact form on submit event
    $('#contactForm').submit(function (event) {

        if (isNameValid && isEmailValid && isSubjectValid && isMessageValid) {
            
            // get the user-entered captcha code value to be validated at the backend side
            var userEnteredCaptchaCode = captcha.getUserEnteredCaptchaCode();

            // get the id of a captcha instance that the user tried to solve
            var captchaId = captcha.getCaptchaId();

            var postData = {
                name: $('#name').val(),
                email: $('#email').val(),
                subject: $('#subject').val(),
                message: $('#message').val(),
                // add the user-entered captcha code value to the post data
                userEnteredCaptchaCode: userEnteredCaptchaCode,
                // add the id of a captcha instance to the post data
                captchaId: captchaId
            };

            // post both the form-data and captcha data to the backend
            $.ajax({
                method: 'POST',
                url: 'form/ContactHandler.ashx',
                dataType: 'json',
                contentType: 'application/json',
                data: JSON.stringify(postData),
                success: function (response) {
                    if (response.success == false) {
                        // captcha validation failed; show the error message
                        $('#form-messages')
                            .removeClass()
                            .addClass('alert alert-error')
                            .text(response.errors.userEnteredCaptchaCode);
                        // call the captcha.reloadImage()
                        // in order to generate a new captcha challenge
                        captcha.reloadImage();
                    } else {
                        // captcha validation succeeded; proceed with the workflow
                        window.location.replace('notify_page/contact_success_notify.html');
                    }
                },
                error: function (error) {
                    throw new Error(error);
                }
            });

        } else {
            $('#form-messages')
                .removeClass()
                .addClass('alert alert-error')
                .text('Please enter valid values.');
        }

        event.preventDefault();
    });
});

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Backend: web.config

The web.config source file does the following:

  • Registers the simple-captcha-endpoint.ashx path
  • Maps it to the BotDetect.Web.SimpleCaptchaHandler
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
  <system.web>
    <compilation debug="true" targetFramework="4.5"/>
    <httpRuntime targetFramework="4.5"/>
    <httpHandlers>
      <!-- Register the HttpHandler used for BotDetect Captcha requests -->
      <add verb="GET" path="simple-captcha-endpoint.ashx"
           type="BotDetect.Web.SimpleCaptchaHandler, BotDetect"/>
    </httpHandlers>
  </system.web>
  <system.webServer>
    <validation validateIntegratedModeConfiguration="false" />
    <handlers>
      <!-- Register the HttpHandler used for BotDetect Captcha requests (IIS 7.0+) -->
      <remove name="BotDetectCaptchaHandler"/>
      <add name="BotDetectCaptchaHandler" preCondition="integratedMode"
           verb="GET" path="simple-captcha-endpoint.ashx"
           type="BotDetect.Web.SimpleCaptchaHandler, BotDetect"/>
    </handlers>
    <defaultDocument>
      <files>
        <clear />
        <add value="basic.html"/>
      </files>
    </defaultDocument>
  </system.webServer>
</configuration>

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Backend: botdetect.xml

The botdetect.xml source file contains the following:

  • Captcha style definitions consisting of:
    • The name of a captcha style
    • The ID of an <input> element in which user enters captcha codes
    • Other option settings -- the captcha code length in this particular case
<?xml version="1.0" encoding="UTF-8"?>
<botdetect xmlns="https://captcha.com/schema/net"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="https://captcha.com/schema/net
            https://captcha.com/schema/net/botdetect-4.4.2.xsd">

    <captchaStyles>
        <captchaStyle>
            <name>jqueryFormCaptcha</name>
            <userInputID>userCaptchaInput</userInputID>
            <codeLength>4-6</codeLength>
        </captchaStyle>
    </captchaStyles>
</botdetect>

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Backend: ContactHandler.ashx

The form/ContactHandler.ashx source file does the following:

  • Extracts the userEnteredCaptchaCode and captchaId values posted from the frontend
  • Validates captchas by calling the Validate(userEnteredCaptchaCode, captchaId) method
  • Returns the json-formatted captcha validation results to frontend
<%@ WebHandler Language="C#" Class="ContactHandler" %>

using System;
using System.Web;
using System.IO;
using Newtonsoft.Json;
using System.Collections.Generic;
using System.Text.RegularExpressions;

using BotDetect.Web;

public class ContactHandler : IHttpHandler
{
    public void ProcessRequest (HttpContext context)
    {
        if (HttpContext.Current.Request.HttpMethod == "POST")
        {
            string dataJson = new StreamReader(context.Request.InputStream).ReadToEnd();

            Dictionary<string, string> formDataObj = new Dictionary<string, string>();
            formDataObj = JsonConvert.DeserializeObject<Dictionary<string, string>>(dataJson);

            string name = formDataObj["name"];
            string email = formDataObj["email"];
            string subject = formDataObj["subject"];
            string message = formDataObj["message"];

            string userEnteredCaptchaCode = formDataObj["userEnteredCaptchaCode"];
            string captchaId = formDataObj["captchaId"];

            // validate the form data
            Dictionary<string, string> errors = new Dictionary<string, string>();

            if (!IsValidName(name))
            {
                errors.Add("name", "Name must be at least 3 chars long!");
            }

            if (!IsValidEmail(email))
            {
                errors.Add("email", "Email is invalid!");
            }

            if (!IsValidSubject(subject))
            {
                errors.Add("subject", "Subject must be at least 10 chars long!");
            }

            if (!IsValidMessage(message))
            {
                errors.Add("message", "Message must be at least 10 chars long!");
            }

            // validate the user entered captcha code
            if (!IsCaptchaCorrect(userEnteredCaptchaCode, captchaId))
            {
                errors.Add("userEnteredCaptchaCode", "CAPTCHA validation failed!");
                // TODO: consider logging the attempt
            }

            bool isErrorsEmpty = (errors.Count > 0) ? false : true;

            if (isErrorsEmpty)
            {
                // TODO: all validations succeeded; execute the protected action
                // (send email, write to database, etc...)
            }

            // create an object that stores the validation result
            Dictionary<string, object> validationResult = new Dictionary<string, object>();
            validationResult.Add("success", isErrorsEmpty);
            validationResult.Add("errors", errors);

            // return the json string with the validation result to the frontend
            context.Response.ContentType = "application/json; charset=utf-8";
            context.Response.Write(JsonConvert.SerializeObject(validationResult));
        }
        else
        {
            context.Response.ContentType = "text/plain";
            context.Response.Write("Only HTTP POST requests are allowed.");
        }
    }

    // the captcha validation function
    private bool IsCaptchaCorrect(string userEnteredCaptchaCode, string captchaId)
    {
        // create a captcha instance to be used for the captcha validation
        SimpleCaptcha captcha = new SimpleCaptcha();
        // execute the captcha validation
        return captcha.Validate(userEnteredCaptchaCode, captchaId);
    }

    private bool IsValidName(string name)
    {
        if (name == null)
        {
            return false;
        }

        return (name.Length >= 3);
    }

    private bool IsValidEmail(string email)
    {
        if (email == null)
        {
            return false;
        }
        Regex regex = new Regex("^[\\w-_\\.+]*[\\w-_\\.]\\@([\\w]+\\.)+[\\w]+[\\w]$");
        Match match = regex.Match(email);

        return match.Success;
    }

    private bool IsValidSubject(string subject)
    {
        if (subject == null)
        {
            return false;
        }

        return (subject.Length > 9) && (subject.Length < 255);
    }

    private bool IsValidMessage(string message)
    {
        if (message == null)
        {
            return false;
        }

        return (message.Length > 9) && (message.Length < 255);
    }

    public bool IsReusable
    {
        get
        {
            return false;
        }
    }
}

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..............................................................

jQuery-based Frontend and the Java Servlet on Backend

This is a partial walk-through of the example source code. It is not meant to replace a proper step-by-step guide. If you are new to BotDetect, skip it for now; and do start your first jQuery captcha integration by following our step-by-step jQuery CAPTCHA Integration Guide.

Introduction

This contact form jQuery captcha example shows the code required to display and validate captchas in a contact form of the application with a jQuery frontend and a Java Servlet backend.

Download the BotDetect Java CAPTCHA Library archive and run this example

Within this page, the root folder of the extracted archive is referred as the <BDC-DIR>.

This example is in the <BDC-DIR>/examples/s_api-captcha-jquery-servlet/ folder; and contains the following files:

Frontend: contact.html

The src/main/webapp/contact.html source file does the following:

  • Loads the BotDetect CAPTCHA jQuery Plugin into the page
  • Displays the captcha and user-input markups on the page
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>BotDetect jQuery CAPTCHA Examples</title>
  <link href="styles/styles.css" type="text/css" rel="stylesheet">
</head>
<body>
    <header>
        <div class="header-content"><h1>BotDetect jQuery CAPTCHA Examples</h1></div>
    </header>

    <nav>
      <ul class="nav">
        <li><a href="basic.html">Basic Example</a></li>
        <li><a href="contact.html" class="active">Contact Example</a></li>
      </ul>
    </nav>

    <section id="main-content">
        <form id="contactForm" method="POST">
            <div id="form-messages"></div>

            <label>
                <span>Name:</span>
                <input type="text" id="name" name="name">
            </label>
            <div class="error name"></div>


            <label>
                <span>Email</span>
                <input type="email" id="email" name="email" >
            </label>
            <div class="error email"></div>


            <label>
                <span>Subject:</span>
                <input type="text" id="subject" name="subject">
            </label>
            <div class="error subject"></div>


            <label>
                <span>Message:</span>
                <textarea id="message" name="message"></textarea>
            </label>
            <div class="error message"></div>


            <!-- captcha challenge: placeholder -->
            <div id="botdetect-captcha" data-captchastylename="jqueryFormCaptcha"></div>

            <label>
                <span>Retype the characters from the picture:</span>
                <!-- captcha code: user-input textbox -->
                <input 
                    type="text" 
                    id="userCaptchaInput" 
                >
            </label>

            <button type="submit" id="submitButton" class="btn btn-primary">Send</button>
        </form>
    </section>
    
    <script src="node_modules/jquery/jquery.min.js"></script>
    <script src="node_modules/jquery-captcha/dist/jquery-captcha.min.js"></script>
    <script src="js/contact.js"></script>
</body>
</html>

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Frontend: contact.js

The src/main/webapp/js/contact.js source file does the following:

  • Sets the captchaEndpoint property to point to the captcha endpoint path on backend
  • Loads the captcha challenges from backend
  • Sends the post request with the captcha id and the user entered captcha code to backend
  • Processes the captcha validation results:
    • when the captcha validation fails -- it reloads captcha and displays an error message
    • when the captcha validation succeeds -- it executes by the captcha protected action
$(function () {

    // create the frontend captcha instance in the DOM.ready event-handler;
    // and set the captchaEndpoint property to point to 
    // the captcha endpoint path on your app's backend
    var captcha = $('#botdetect-captcha').captcha({
        captchaEndpoint: 'simple-captcha-endpoint'
    });

    // the validation-error messages for the form's data-input fields
    var errorMessages = {
        name: 'Name must be at least 3 chars long!',
        email: 'Email is invalid!',
        subject: 'Subject must be at least 10 chars long!',
        message: 'Message must be at least 10 chars long!'
    };

    // the global variables that hold the validation-status flags of the form's data-input fields;
    // those validation-status flags will be checked on form submit
    var isNameValid = false,
        isEmailValid = false,
        isSubjectValid = false,
        isMessageValid = false;

    function validateName() {
        var name = $('#name').val();
        isNameValid = (name.length >= 3);
        if (isNameValid) {
            $('.name').text('');
        } else {
            $('.name').text(errorMessages.name);
        }
    }

    function validateEmail() {
        var email = $('#email').val();
        var emailRegEx = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
        isEmailValid = emailRegEx.test(email);
        if (isEmailValid) {
            $('.email').text('');
        } else {
            $('.email').text(errorMessages.email);
        }
    }

    function validateSubject() {
        var subject = $('#subject').val();
        isSubjectValid = (subject.length >= 10);
        if (isSubjectValid) {
            $('.subject').text('');
        } else {
            $('.subject').text(errorMessages.subject);
        }
    }

    function validateMessage() {
        var message = $('#message').val();
        isMessageValid = (message.length >= 10);
        if (isMessageValid) {
            $('.message').text('');
        } else {
            $('.message').text(errorMessages.message);
        }
    }

    // validate the form's data-input fields on blur event
    $('#name').blur(validateName);
    $('#email').blur(validateEmail);
    $('#subject').blur(validateSubject);
    $('#message').blur(validateMessage);

    // process the contact form on submit event
    $('#contactForm').submit(function (event) {

        if (isNameValid && isEmailValid && isSubjectValid && isMessageValid) {
            
            // get the user-entered captcha code value to be validated at the backend side
            var userEnteredCaptchaCode = captcha.getUserEnteredCaptchaCode();

            // get the id of a captcha instance that the user tried to solve
            var captchaId = captcha.getCaptchaId();

            var postData = {
                name: $('#name').val(),
                email: $('#email').val(),
                subject: $('#subject').val(),
                message: $('#message').val(),
                // add the user-entered captcha code value to the post data
                userEnteredCaptchaCode: userEnteredCaptchaCode,
                // add the id of a captcha instance to the post data
                captchaId: captchaId
            };

            // post both the form-data and captcha data to the backend
            $.ajax({
                method: 'POST',
                url: 'contact',
                dataType: 'json',
                contentType: 'application/json',
                data: JSON.stringify(postData),
                success: function (response) {
                    if (response.success == false) {
                        // captcha validation failed; show the error message
                        $('#form-messages')
                            .removeClass()
                            .addClass('alert alert-error')
                            .text(response.errors.userEnteredCaptchaCode);
                        // call the captcha.reloadImage()
                        // in order to generate a new captcha challenge
                        captcha.reloadImage();
                    } else {
                        // captcha validation succeeded; proceed with the workflow
                        window.location.replace('notify_page/contact_success_notify.html');
                    }
                },
                error: function (error) {
                    throw new Error(error);
                }
            });

        } else {
            $('#form-messages')
                .removeClass()
                .addClass('alert alert-error')
                .text('Please enter valid values.');
        }

        event.preventDefault();
    });
});

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Backend: web.xml

The src/main/webapp/WEB-INF/web.xml source file does the following:

  • Registers the simple-captcha-endpoint path
  • Maps it to the com.captcha.botdetect.web.servlet.SimpleCaptchaServlet
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee                 http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
    <session-config>
        <session-timeout>
            30
        </session-timeout>
    </session-config>
    <servlet>
        <servlet-name>BotDetect Captcha</servlet-name>
        <servlet-class>com.captcha.botdetect.web.servlet.SimpleCaptchaServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>BotDetect Captcha</servlet-name>
        <url-pattern>/simple-captcha-endpoint</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>Contact Captcha</servlet-name>
        <servlet-class>com.captcha.botdetect.examples.jquery.contact_form.ContactServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Contact Captcha</servlet-name>
        <url-pattern>/contact</url-pattern>
    </servlet-mapping>
    <welcome-file-list>
        <welcome-file>basic.html</welcome-file>
    </welcome-file-list>
</web-app>

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Backend: botdetect.xml

The src/main/webapp/WEB-INF/botdetect.xml source file contains the following:

  • Captcha style definitions consisting of:
    • The name of a captcha style
    • The ID of an <input> element in which user enters captcha codes
    • Other option settings -- the captcha code length in this particular case
<?xml version="1.0" encoding="UTF-8"?>
<botdetect xmlns="https://captcha.com/schema/java" 
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:schemaLocation="https://captcha.com/schema/java 
            https://captcha.com/schema/java/botdetect-4.0.beta3.7.xsd">

    <captchaStyles>        
        <captchaStyle>
            <name>jqueryFormCaptcha</name>
            <userInputID>userCaptchaInput</userInputID>
            <codeLength>4-6</codeLength>
        </captchaStyle>
    </captchaStyles>
</botdetect>

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Backend: ContactServlet.java

The src/main/java/com/captcha/botdetect/examples/jquery/contact_form/
ContactServlet.java source file does the following:

  • Extracts the userEnteredCaptchaCode and captchaId values posted from the frontend
  • Validates captchas by calling the validate(userEnteredCaptchaCode, captchaId) method
  • Returns the json-formatted captcha validation results to frontend
package com.captcha.botdetect.examples.jquery.contact_form;

import com.captcha.botdetect.web.servlet.SimpleCaptcha;
import com.google.gson.Gson;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.Map;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ContactServlet extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        
        PrintWriter out = response.getWriter();
        Gson gson = new Gson();
        
        response.setContentType("application/json; charset=utf-8");
        
        JsonParser parser = new JsonParser();
        JsonObject formDataObj = (JsonObject) parser.parse(request.getReader());
        
        String name = formDataObj.get("name").getAsString();
        String email = formDataObj.get("email").getAsString();
        String subject = formDataObj.get("subject").getAsString();
        String message = formDataObj.get("message").getAsString();
        String userEnteredCaptchaCode = formDataObj.get("userEnteredCaptchaCode").getAsString();
        String captchaId = formDataObj.get("captchaId").getAsString();

        // validate the form data
        Map<String, String> errors = new HashMap<String, String>();
        
        if (!isValidName(name)) {
            errors.put("name", "Name must be at least 3 chars long!");
        }
        
        if (!isValidEmail(email)) {
            errors.put("email", "Email is invalid!");
        }
        
        if (!isValidSubject(subject)) {
            errors.put("message", "Subject must be at least 10 chars long!");
        }
        
        if (!isValidMessage(message)) {
            errors.put("message", "Message must be at least 10 chars long!");
        }
        
        // validate the user entered captcha code        
        if (!isCaptchaCorrect(request, userEnteredCaptchaCode, captchaId)) {
            errors.put("userEnteredCaptchaCode", "CAPTCHA validation failed!");
            // TODO: consider logging the attempt
        }
        
        if (errors.isEmpty()) {
            // TODO: all validations succeeded; execute the protected action
            // (send email, write to database, etc...)
        }
        
        // create an object that stores the validation result
        ContactValidationResult validationResult = new ContactValidationResult();
        validationResult.setSuccess(errors.isEmpty());
        validationResult.setErrors(errors);
        
        try {
            // return the json string with the validation result to the frontend
            out.write(gson.toJson(validationResult));
        } finally {
            out.close();
        }
    }
    
    // the captcha validation function
    private boolean isCaptchaCorrect(HttpServletRequest request, String userEnteredCaptchaCode, String captchaId) {
        // create a captcha instance to be used for the captcha validation        
        SimpleCaptcha captcha = SimpleCaptcha.load(request);
        // execute the captcha validation        
        return captcha.validate(userEnteredCaptchaCode, captchaId);
    }
    
    private boolean isValidName(String name) {
        if (name == null) {
            return false;
        }
        return (name.length() >= 3);
    }
    
    private boolean isValidEmail(String email) {
        if (email == null) {
            return false;
        }
        return email.matches("^[\\w-_\\.+]*[\\w-_\\.]\\@([\\w]+\\.)+[\\w]+[\\w]$");
    }
    
    private boolean isValidSubject(String subject) {
        if (subject == null) {
            return false;
        }
        return (subject.length() > 9) && (subject.length() < 255);
    }
    
    private boolean isValidMessage(String message) {
        if (message == null) {
            return false;
        }
        return (message.length() > 9) && (message.length() < 255);
    }
}

class ContactValidationResult {

    private boolean success;
    private Map<String, String> errors;

    public ContactValidationResult() {
        errors = new HashMap<String, String>();
    }

    public boolean getSuccess() {
        return success;
    }

    public void setSuccess(boolean success) {
        this.success = success;
    }

    public Map<String, String> getErrors() {
        return errors;
    }

    public void setErrors(Map<String, String> errors) {
        this.errors = errors;
    }
}

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..............................................................

jQuery-based Frontend and the plain PHP on Backend

This is a partial walk-through of the example source code. It is not meant to replace a proper step-by-step guide. If you are new to BotDetect, skip it for now; and do start your first jQuery captcha integration by following our step-by-step jQuery CAPTCHA Integration Guide.

Introduction

This contact form jQuery captcha example shows the code required to display and validate captchas in a contact form of the application with a jQuery frontend and the plain PHP backend.

Download the BotDetect PHP CAPTCHA Library archive and run this example

Within this page, the root folder of the extracted archive is referred as the <BDC-DIR>.

This example is in the <BDC-DIR>/examples/s_api-captcha-jquery-plainphp/ folder; and contains the following files:

Frontend: contact.html

The contact.html source file does the following:

  • Loads the BotDetect CAPTCHA jQuery Plugin into the page
  • Displays the captcha and user-input markups on the page
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>BotDetect jQuery CAPTCHA Examples</title>
  <link href="styles/styles.css" type="text/css" rel="stylesheet">
</head>
<body>
    <header>
        <div class="header-content"><h1>BotDetect jQuery CAPTCHA Examples</h1></div>
    </header>

    <nav>
      <ul class="nav">
        <li><a href="basic.html">Basic Example</a></li>
        <li><a href="contact.html" class="active">Contact Example</a></li>
      </ul>
    </nav>

    <section id="main-content">
        <form id="contactForm" method="POST">
            <div id="form-messages"></div>

            <label>
                <span>Name:</span>
                <input type="text" id="name" name="name">
            </label>
            <div class="error name"></div>


            <label>
                <span>Email</span>
                <input type="email" id="email" name="email" >
            </label>
            <div class="error email"></div>


            <label>
                <span>Subject:</span>
                <input type="text" id="subject" name="subject">
            </label>
            <div class="error subject"></div>


            <label>
                <span>Message:</span>
                <textarea id="message" name="message"></textarea>
            </label>
            <div class="error message"></div>


            <!-- captcha challenge: placeholder -->
            <div id="botdetect-captcha" data-captchastylename="jqueryFormCaptcha"></div>

            <label>
                <span>Retype the characters from the picture:</span>
                <!-- captcha code: user-input textbox -->
                <input 
                    type="text" 
                    id="userCaptchaInput" 
                >
            </label>

            <button type="submit" id="submitButton" class="btn btn-primary">Send</button>
        </form>
    </section>
    
    <script src="node_modules/jquery/jquery.min.js"></script>
    <script src="node_modules/jquery-captcha/dist/jquery-captcha.min.js"></script>
    <script src="js/contact.js"></script>
</body>
</html>

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Frontend: contact.js

The js/contact.js source file does the following:

  • Sets the captchaEndpoint property to point to the captcha endpoint path on backend
  • Loads the captcha challenges from backend
  • Sends the post request with the captcha id and the user entered captcha code to backend
  • Processes the captcha validation results:
    • when the captcha validation fails -- it reloads captcha and displays an error message
    • when the captcha validation succeeds -- it executes by the captcha protected action
$(function () {

    // create the frontend captcha instance in the DOM.ready event-handler;
    // and set the captchaEndpoint property to point to 
    // the captcha endpoint path on your app's backend
    var captcha = $('#botdetect-captcha').captcha({
        captchaEndpoint: 'botdetect-captcha-lib/simple-botdetect.php'
    });

    // the validation-error messages for the form's data-input fields
    var errorMessages = {
        name: 'Name must be at least 3 chars long!',
        email: 'Email is invalid!',
        subject: 'Subject must be at least 10 chars long!',
        message: 'Message must be at least 10 chars long!'
    };

    // the global variables that hold the validation-status flags of the form's data-input fields;
    // those validation-status flags will be checked on form submit
    var isNameValid = false,
        isEmailValid = false,
        isSubjectValid = false,
        isMessageValid = false;

    function validateName() {
        var name = $('#name').val();
        isNameValid = (name.length >= 3);
        if (isNameValid) {
            $('.name').text('');
        } else {
            $('.name').text(errorMessages.name);
        }
    }

    function validateEmail() {
        var email = $('#email').val();
        var emailRegEx = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
        isEmailValid = emailRegEx.test(email);
        if (isEmailValid) {
            $('.email').text('');
        } else {
            $('.email').text(errorMessages.email);
        }
    }

    function validateSubject() {
        var subject = $('#subject').val();
        isSubjectValid = (subject.length >= 10);
        if (isSubjectValid) {
            $('.subject').text('');
        } else {
            $('.subject').text(errorMessages.subject);
        }
    }

    function validateMessage() {
        var message = $('#message').val();
        isMessageValid = (message.length >= 10);
        if (isMessageValid) {
            $('.message').text('');
        } else {
            $('.message').text(errorMessages.message);
        }
    }

    // validate the form's data-input fields on blur event
    $('#name').blur(validateName);
    $('#email').blur(validateEmail);
    $('#subject').blur(validateSubject);
    $('#message').blur(validateMessage);

    // process the contact form on submit event
    $('#contactForm').submit(function (event) {

        if (isNameValid && isEmailValid && isSubjectValid && isMessageValid) {
            
            // get the user-entered captcha code value to be validated at the backend side
            var userEnteredCaptchaCode = captcha.getUserEnteredCaptchaCode();

            // get the id of a captcha instance that the user tried to solve
            var captchaId = captcha.getCaptchaId();

            var postData = {
                name: $('#name').val(),
                email: $('#email').val(),
                subject: $('#subject').val(),
                message: $('#message').val(),
                // add the user-entered captcha code value to the post data
                userEnteredCaptchaCode: userEnteredCaptchaCode,
                // add the id of a captcha instance to the post data
                captchaId: captchaId
            };

            // post both the form-data and captcha data to the backend
            $.ajax({
                method: 'POST',
                url: 'form/contact.php',
                dataType: 'json',
                contentType: 'application/json',
                data: JSON.stringify(postData),
                success: function (response) {
                    if (response.success == false) {
                        // captcha validation failed; show the error message
                        $('#form-messages')
                            .removeClass()
                            .addClass('alert alert-error')
                            .text(response.errors.userEnteredCaptchaCode);
                        // call the captcha.reloadImage()
                        // in order to generate a new captcha challenge
                        captcha.reloadImage();
                    } else {
                        // captcha validation succeeded; proceed with the workflow
                        window.location.replace('notify_page/contact_success_notify.html');
                    }
                },
                error: function (error) {
                    throw new Error(error);
                }
            });

        } else {
            $('#form-messages')
                .removeClass()
                .addClass('alert alert-error')
                .text('Please enter valid values.');
        }

        event.preventDefault();
    });
});

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Backend: botdetect.xml

The botdetect-captcha-lib/config/botdetect.xml source file contains the following:

  • Captcha style definitions consisting of:
    • The name of a captcha style
    • The ID of an <input> element in which user enters captcha codes
    • Other option settings -- the captcha code length in this particular case
<?xml version="1.0" encoding="UTF-8"?>
<botdetect xmlns="https://captcha.com/schema/php"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="https://captcha.com/schema/php
            https://captcha.com/schema/php/botdetect-4.2.5.xsd">

  <captchaStyles>
    <captchaStyle>
      <name>angularBasicCaptcha</name>
      <userInputID>userCaptchaInput</userInputID>
      <codeLength>3-5</codeLength>
    </captchaStyle>
  </captchaStyles>
</botdetect>

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Backend: contact.php

The form/contact.php source file does the following:

  • Extracts the $userEnteredCaptchaCode and $captchaId values posted from the frontend
  • Validates captchas by calling the Validate($userEnteredCaptchaCode, $captchaId) method
  • Returns the json-formatted captcha validation results to frontend
<?php header('Content-Type: application/json');

if ($_SERVER['REQUEST_METHOD'] === 'POST') {

  require('../botdetect-captcha-lib/simple-botdetect.php');

  $postedData = (array) json_decode(file_get_contents('php://input'), true);

  $name = $postedData['name'];
  $email = $postedData['email'];
  $subject = $postedData['subject'];
  $message = $postedData['message'];
  $userEnteredCaptchaCode = $postedData['userEnteredCaptchaCode'];
  $captchaId = $postedData['captchaId'];

  // validate the form data
  $error = array();

  if (!isValidName($name)) {
    $error['name'] = "Name must be at least 3 chars long!";
  }

  if (!isValidEmail($email)) {
    $error['email'] = "Email is invalid!";
  }

  if (!isValidSubject($subject)) {
    $error['subject'] = "Subject must be at least 10 chars long!";
  }

  if (!isValidMessage($message)) {
    $error['message'] = "Message must be at least 10 chars long!";
  }

  // validate the user entered captcha code
  if (!isCaptchaCorrect($userEnteredCaptchaCode, $captchaId)) {
    $error['userEnteredCaptchaCode'] = "CAPTCHA validation failed!";
    // TODO: consider logging the attempt
  }

  if (empty($error)) {
    // TODO: all validations succeeded; execute the protected action
    // (send email, write to database, etc...)
  }

  // return the json string with the validation result to the frontend
  $result = array('success' => empty($error), 'errors' => $error);
  echo json_encode($result, true); exit;
}

// the captcha validation function
function isCaptchaCorrect($userEnteredCaptchaCode, $captchaId) {
  // create a captcha instance to be used for the captcha validation
  $captcha = new SimpleCaptcha();
  // execute the captcha validation
  return $captcha->Validate($userEnteredCaptchaCode, $captchaId);
}

function isValidName($name) {
  if($name == null) {
    return false;
  }
  return (strlen($name) >= 3);
}

function isValidEmail($email) {
  if($email == null) {
    return false;
  }

  return preg_match("/^[\\w-_\\.+]*[\\w-_\\.]\\@([\\w]+\\.)+[\\w]+[\\w]$/", $email, $matches);
}

function isValidSubject($subject) {
  if($subject == null) {
    return false;
  }

  return (strlen($subject) > 9) && (strlen($subject) < 255);
}

function isValidMessage($message) {
  if($message == null) {
    return false;
  }

  return (strlen($message) > 9) && (strlen($message) < 255);
}

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Please Note

The new experimental Simple API is still work-in-progress. This Integration Guide & Examples require you to have the jQuery Captcha Plugin v2.3.0 on frontend, and one of the following BotDetect CAPTCHA releases on backend: ASP.NET v4.4.2+, Java v4.0.Beta3.7+, PHP v4.2.5+.

Current BotDetect Versions

Popular Content

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