// /src/Acme/Bundle/CustomMassActionBundle/MassEditAction/Operation/CapitalizeValues.php
<?php

namespace Acme\Bundle\CustomMassActionBundle\MassEditAction\Operation;

use Pim\Bundle\EnrichBundle\MassEditAction\Operation\AbstractMassEditOperation;

class CapitalizeValues extends AbstractMassEditOperation
{
    /**
     * {@inheritdoc}
     */
    public function getOperationAlias()
    {
        return 'capitalize-values';
    }

    /**
     * {@inheritdoc}
     */
    public function getFormType()
    {
        return 'acme_custom_mass_action_operation_capitalize_values';
    }

    /**
     * {@inheritdoc}
     */
    public function getFormOptions()
    {
        return [];
    }

    /**
     * {@inheritdoc}
     */
    public function getActions()
    {
        return [
            'field'   => 'name',
            'options' => ['locale' => null, 'scope' => null]
        ];
    }
}

// /src/Acme/Bundle/CustomMassActionBundle/Connector/Processor/MassEdit/Product/CapitalizeValuesProcessor.php
<?php

namespace Acme\Bundle\CustomMassActionBundle\Connector\Processor\MassEdit\Product;

use Akeneo\Tool\Component\StorageUtils\Updater\PropertySetterInterface;
use Akeneo\Pim\Enrichment\Component\Product\Connector\Processor\MassEdit\AbstractProcessor;
use Akeneo\Pim\Enrichment\Component\Product\Exception\InvalidArgumentException;
use Akeneo\Pim\Enrichment\Component\Product\Model\ProductInterface;
use Symfony\Component\Validator\Validator\ValidatorInterface;

class CapitalizeValuesProcessor extends AbstractProcessor
{
    /** @var PropertySetterInterface */
    protected $propertySetter;

    /** @var ValidatorInterface */
    protected $validator;

    /**
     * @param PropertySetterInterface $propertySetter
     * @param ValidatorInterface      $validator
     */
    public function __construct(PropertySetterInterface $propertySetter, ValidatorInterface $validator)
    {
        $this->propertySetter = $propertySetter;
        $this->validator      = $validator;
    }

    /**
     * {@inheritdoc}
     */
    public function process($product)
    {
        /** @var ProductInterface $product */

        // This is where you put your custom logic. Here we work on a
        // $product the Reader gave us.

        // This is the configuration we receive from our Operation
        $actions = $this->getConfiguredActions();

        // Retrieve custom config from the action
        $field = $actions['field'];
        $options = $actions['options'];

        // Capitalize the attribute value of the product
        $originalValue    = $product->getValue($field)->getData();
        $capitalizedValue = strtoupper($originalValue);

        // Use the property setter to update the product
        $newData = ['field' => $field, 'value' => $capitalizedValue, 'options' => $options];
        $this->setData($product, [$newData]);

        // Validate the product
        if (null === $product || (null !== $product && !$this->isProductValid($product))) {
            $this->stepExecution->incrementSummaryInfo('skipped_products');

            return null; // By returning null, the product won't be saved by the Writer
        }

        // Used on the Reporting Screen to have a summary on the Mass Edit execution
        $this->stepExecution->incrementSummaryInfo('mass_edited');

        return $product; // Send the product to the Writer to be saved
    }

    /**
     * Validate the product and raise a warning if not
     *
     * @param ProductInterface $product
     *
     * @return bool
     */
    protected function isProductValid(ProductInterface $product)
    {
        $violations = $this->validator->validate($product);
        $this->addWarningMessage($violations, $product);

        return 0 === $violations->count();
    }

    /**
     * Set data from $actions to the given $product
     *
     * @param ProductInterface $product
     * @param array            $actions
     *
     * @return CapitalizeValuesProcessor
     */
    protected function setData(ProductInterface $product, array $actions)
    {
        foreach ($actions as $action) {
            $this->propertySetter->setData($product, $action['field'], $action['value'], $action['options']);
        }

        return $this;
    }
}