How To Add BotDetect CAPTCHA Protection to Spring 5 Forms

Protecting your Spring MVC 5 forms with BotDetect Java Captcha requires a few steps, outlined on this page.

You can also see how BotDetect Captcha protection has been added to various kinds of Spring MVC forms and projects by running the BotDetect Captcha Spring integration code examples coming with the BotDetect installation. You can also reuse the code example source code that fits your requirements.

CAPTCHA Integration Steps

To add BotDetect Captcha protection to a Spring MVC application:

Add BotDetect library in the classpath
Register CaptchaServlet
Display Captcha protection on the Spring MVC form
Validate Captcha user input during Spring MVC form submission

Add BotDetect Java CAPTCHA Library Dependency

Here is how to add BotDetect Java CAPTCHA Library dependency in various dependency management scenarios:

Manual
Maven
Gradle
Ant+Ivy
Ant

Install BotDetect Java CAPTCHA dependencies

Download and unpack the BotDetect Java CAPTCHA library archive.

The folder where you unpacked the BotDetect archive will be referred as the <BDC-DIR> in this guide. It contains the BotDetect jars.

Copy the .jar files listed below to /your-app-backend-folder/WEB-INF/lib folder:

<BDC-DIR>/botdetect-4.0.beta3.7.jar
<BDC-DIR>/botdetect-servlet-4.0.beta3.7.jar
<BDC-DIR>/botdetect-jsp20-4.0.beta3.7.jar

Install BotDetect Java CAPTCHA dependencies

The free version Maven artifacts are available from our public repository; while the enterprise version jars are available in the root folder of the enterprise version's archive.

To reference the BotDetect dependency from our public repository, the repository itself has to be declared first -- add the highlighted lines to your app's pom.xml file:

<repository>
  <id>captcha</id>
  <name>BotDetect Captcha Repository</name>
  <url>https://git.captcha.com/botdetect-java-captcha.git/blob_plain/HEAD:/</url>
</repository>

Then, in the same file, declare the BotDetect dependency, too:

<dependency>
  <groupId>com.captcha</groupId>
  <artifactId>botdetect-jsp20</artifactId>
  <version>4.0.beta3.7</version>
</dependency>

Install BotDetect Java CAPTCHA dependencies

The free version Maven artifacts are available from our public repository; while the enterprise version jars are available in the root folder of the enterprise version's archive.

To reference the BotDetect dependency from our public repository, the repository itself has to be declared first -- add the highlighted line to your app's build.gradle file:

repositories {
  maven {
    url "https://git.captcha.com/botdetect-java-captcha.git/blob_plain/HEAD:/"
  }
  ...    
}

Then, in the same file, declare the BotDetect dependency, too:

dependencies {
  ...
  compile 'com.captcha:botdetect-jsp20:4.0.beta3.7'
  ...
}

Install BotDetect Java CAPTCHA dependencies

The free version Maven artifacts are available from our public repository; while the enterprise version jars are available in the root folder of the enterprise version's archive.

To reference the BotDetect dependency from our public repository, the repository itself has to be declared first -- add the highlighted line to your app's ivy-settings.xml file:

<ivysettings>
  <properties file="build.properties" />
  <settings defaultResolver="default-chain"/>
  <resolvers>
    <chain name="default-chain">
      <ibiblio name="botdetect" 
               root="https://git.captcha.com/botdetect-java-captcha.git/blob_plain/HEAD:" 
               m2compatible="true"/>
      ...
    </chain>
  </resolvers>
</ivysettings>

Then, declare the BotDetect dependency in your app's ivy.xml file:

<ivy-module version="2.0">
  <info organisation="org.apache" module="WebProject" />

  <!-- Classpath management, thanks Maven -->
  <configurations>
    <conf name="compile" description="compile dependencies"/>
    <conf name="runtime" description="runtime dependencies" extends="compile"/>
    <conf name="test"    description="test dependencies" extends="runtime"/>
  </configurations>

  <dependencies>
    <dependency org="com.captcha" 
	        name="botdetect-jsp20" 
	        rev="4.0.beta3.7" 
	        conf="compile->default"/>
    ...
  </dependencies>
</ivy-module>

And then, ensure that your app's build.xml file has a build target with the ivy:retrieve task:

<target name="resolve" description="retrieve dependencies with ivy">
  <echo message="Getting dependencies..." />
  <ivy:retrieve />
  <ivy:cachepath pathid="compile.path" conf="compile" />
  <ivy:cachepath pathid="runtime.path" conf="runtime" />
  <ivy:cachepath pathid="test.path" conf="test" />
</target>

Install BotDetect Java CAPTCHA dependencies

The free version BotDetect jars are available from our public repository; while the enterprise version jars are available in the root folder of the enterprise version's archive.

To declare the BotDetect dependencies from our public repository, an additional target has to be added to your app's build.xml file.

The target name will be the botdetect-dependencies-target, and it should consist of the following lines:

<target name="botdetect-dependencies" description="BotDetect Java CAPTCHA library">
    <echo message="Getting BotDetect..." />
    <mkdir dir="lib" />
    <get src="https://git.captcha.com/botdetect-java-captcha.git/blob_plain/HEAD:/com/captcha/botdetect/4.0.beta3.7/botdetect-4.0.beta3.7.jar" dest="lib/botdetect-4.0.beta3.7.jar" usetimestamp="true" />
    <get src="https://git.captcha.com/botdetect-java-captcha.git/blob_plain/HEAD:/com/captcha/botdetect-servlet/4.0.beta3.7/botdetect-servlet-4.0.beta3.7.jar" dest="lib/botdetect-servlet-4.0.beta3.7.jar" usetimestamp="true" />
    <get src="https://git.captcha.com/botdetect-java-captcha.git/blob_plain/HEAD:/com/captcha/botdetect-jsp20/4.0.beta3.7/botdetect-jsp20-4.0.beta3.7.jar" dest="lib/botdetect-jsp20-4.0.beta3.7.jar" usetimestamp="true" />
</target>

To retrieve BotDetect dependencies during the build, reference the botdetect-dependencies-target inside the depends attribute of your compile target, by adding the lines listed below into the same file:

<target name="compile" depends="botdetect-dependencies">
  <copydir src="${web.dir}" dest="${build.dir}" />
  <mkdir dir="${web.classes.dir}" />
  <javac destdir="${web.classes.dir}" source="${jdk.version}" target="${jdk.version}"
    debug="true" includeantruntime="false" classpathref="compile.path">
    <src path="${src.dir}" />
  </javac>
</target>

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Register `CaptchaServlet`

Application `web.xml` configuration file setting

<servlet>
  <servlet-name>BotDetect Captcha</servlet-name>
  <servlet-class>com.captcha.botdetect.web.servlet.CaptchaServlet</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>BotDetect Captcha</servlet-name>
  <url-pattern>/botdetectcaptcha</url-pattern>
</servlet-mapping>

Spring Boot servlet registration

In case you are using Spring Boot servlet is registered in a following way:

@SpringBootApplication
public class SpringBootWebApplication {

    [...]

    @Bean
    ServletRegistrationBean captchaServletRegistration () {
      ServletRegistrationBean srb = new ServletRegistrationBean();
      srb.setServlet(new CaptchaServlet());
      srb.addUrlMappings("/botdetectcaptcha");
      return srb;
    }
}

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Display Captcha Protection on the Spring MVC Form

We'll assume you already have a form which can be posted (<form method="post" ...), with other fields in place.

BotDetect custom captcha tag is designed to add CAPTCHA protection to Spring MVC form as simple as possible.

At the top of the file put BotDetect taglib declaration:

<%@taglib prefix="botDetect" uri="https://captcha.com/java/jsp"%>

To display the Captcha test on your form, you will need the following Html elements:

A textbox for the Captcha code user input, with a label displaying Captcha instructions
The Captcha markup including the image, sound and reload icons etc., which will be generated by the Captcha tag.

For example:

<botDetect:captcha id="exampleCaptcha" userInputID="captchaCode"/>

<div class="validationDiv">
    <input id="captchaCode" type="text" name="captchaCode"
            value="${basicExample.captchaCode}"/>
    <input type="submit" name="submit" value="Submit" />
    <span class="correct">${basicExample.captchaCorrect}</span>
    <span class="incorrect">${basicExample.captchaIncorrect}</span>
</div>

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When you open your form in a browser, the above declarations should render as:

If you are adding Captcha protection to multiple Spring MVC forms in the same website, you should initialize each Captcha object with unique name (e.g. "registrationCaptcha", "commentCaptcha", ...).

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Validate Captcha User Input During Spring MVC Form Submission

Since we want to ensure only real human users can perform a certain action (e.g. account registration or comment submission), we also have to add Captcha validation code which will process form submissions, and only allow certain actions if Captcha validation succeeds.

Add CAPTCHA Validation Logic to Spring MVC Controller

When the form is submitted, the Captcha validation result must be checked and the protected action (user registration, comment posting, email sending, ...) only performed if the Captcha test was passed. You just have to create Captcha object instance with the same name as the one used on the form first. For example, this code should be part of or invoked from controller's onSubmit method:

[...]
import com.captcha.botdetect.web.servlet.Captcha;

@Controller
public class ExampleController {
  
  [...]
  
  @RequestMapping(value = "/validate", method = RequestMethod.POST)
  public ModelAndView onSubmit(HttpServletRequest request, 
            @Valid @ModelAttribute("example")BasicExample basicExample) 
  {
    // validate the Captcha to check we're not dealing with a bot
    Captcha captcha = Captcha.load(request, "exampleCaptcha");
    boolean isHuman = captcha.validate(basicExample.getCaptchaCode());
    
    if (isHuman) {
      // TODO: Captcha validation passed, perform protected action
    } else {
      // TODO: Captcha validation failed, show error message
    }

    return new ModelAndView("example", "basicExample", basicExample);
  }
    
}

This approach is shown in the BotDetect Spring MVC 5 Basic CAPTCHA integration code example included in the BotDetect download package.

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Please Note

BotDetect Java Captcha Library v4.0.Beta3.7 is an in-progress port of BotDetect 4 Captcha, and we need you to guide our efforts towards a polished product. Please let us know if you encounter any bugs, implementation issues, or a usage scenario you would like to discuss.