Deprecated save and load methods in Abstract Model

You should use Module Service Contract.

For example for product you should use ProductRepositoryInterface

<?php
/**
 *
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */

namespace Magento\Catalog\Api;

/**
 * @api
 * @since 100.0.2
 */
interface ProductRepositoryInterface
{
    /**
     * Create product
     *
     * @param \Magento\Catalog\Api\Data\ProductInterface $product
     * @param bool $saveOptions
     * @return \Magento\Catalog\Api\Data\ProductInterface
     * @throws \Magento\Framework\Exception\InputException
     * @throws \Magento\Framework\Exception\StateException
     * @throws \Magento\Framework\Exception\CouldNotSaveException
     */
    public function save(\Magento\Catalog\Api\Data\ProductInterface $product, $saveOptions = false);

    /**
     * Get info about product by product SKU
     *
     * @param string $sku
     * @param bool $editMode
     * @param int|null $storeId
     * @param bool $forceReload
     * @return \Magento\Catalog\Api\Data\ProductInterface
     * @throws \Magento\Framework\Exception\NoSuchEntityException
     */
    public function get($sku, $editMode = false, $storeId = null, $forceReload = false);

    /**
     * Get info about product by product id
     *
     * @param int $productId
     * @param bool $editMode
     * @param int|null $storeId
     * @param bool $forceReload
     * @return \Magento\Catalog\Api\Data\ProductInterface
     * @throws \Magento\Framework\Exception\NoSuchEntityException
     */
    public function getById($productId, $editMode = false, $storeId = null, $forceReload = false);

    /**
     * Delete product
     *
     * @param \Magento\Catalog\Api\Data\ProductInterface $product
     * @return bool Will returned True if deleted
     * @throws \Magento\Framework\Exception\StateException
     */
    public function delete(\Magento\Catalog\Api\Data\ProductInterface $product);

    /**
     * @param string $sku
     * @return bool Will returned True if deleted
     * @throws \Magento\Framework\Exception\NoSuchEntityException
     * @throws \Magento\Framework\Exception\StateException
     */
    public function deleteById($sku);

    /**
     * Get product list
     *
     * @param \Magento\Framework\Api\SearchCriteriaInterface $searchCriteria
     * @return \Magento\Catalog\Api\Data\ProductSearchResultsInterface
     */
    public function getList(\Magento\Framework\Api\SearchCriteriaInterface $searchCriteria);
}

If Module Service Contract is not available you can use ResourceModel to save entities.

From what I understood, what is going to happen is Magento is going to switch to hydrators with extract() and hydrate() methods.

This link used to work but it seems like Magento team rolled it back: https://github.com/magento/magento2/blob/develop/lib/internal/Magento/Framework/Model/Entity/EntityHydrator.php

You can find the history of the commit here though: https://github.com/magento/magento2/tree/09132da06e18dde0f90aabfc962db2bc19b64f3c/lib/internal/Magento/Framework/Model/Entity

The important files are:

• EntityHydrator.php
• EntityMetadata.php
• HydratorInterface.php
• MetadataPool.php

I also suggest you check out the files under the Action folder as well as the Sequence files.

From what I understood (I may be totally wrong here):

• the files under the Action folder are CRUD actions
• the Sequence files are iterators ?

That was a conversation that happened a while ago (was it Alan Storm who mentionned it ? can't remember) so I'm not sure if Magento team is still going that way.

Update

From my research, the internal Magento ticket regarding this change is MAGETWO-50676, here are the related commits I managed to find:

• https://github.com/magento/magento2/commit/d57c81ced2419cde9d8af2f55062a783ec6a7789
• https://github.com/magento/magento2/commit/35d2da47a20e978c1cb970db79ee4ea60de56353
• https://github.com/magento/magento2/commit/074b3abc6803454542ff0527110e575309c42466

There's probably more TBH but I don't feel like browsing the entire repo for commit messages ^^

If you're not familiar with hydrators, I suggest you check that link out: http://www.webconsults.eu/blog/entry/108-What_is_a_Hydrator_in_Zend_Framework_2

Update from 2.1

Magento is now using the EntityManager class to replace the inheritance you can find more information here: Magento 2.1: using the entity manager

See description in the class code https://github.com/magento/magento2/blob/2.1/lib/internal/Magento/Framework/Model/AbstractModel.php#L626