diff --git a/core/modules/aggregator/aggregator.services.yml b/core/modules/aggregator/aggregator.services.yml
index c2828c9..f622f27 100644
--- a/core/modules/aggregator/aggregator.services.yml
+++ b/core/modules/aggregator/aggregator.services.yml
@@ -1,13 +1,13 @@
 services:
   plugin.manager.aggregator.fetcher:
     class: Drupal\aggregator\Plugin\AggregatorPluginManager
-    arguments: [fetcher, '@container.namespaces']
+    arguments: [fetcher, '@container.namespaces', '@cache.cache', '@language_manager']
   plugin.manager.aggregator.parser:
     class: Drupal\aggregator\Plugin\AggregatorPluginManager
-    arguments: [parser, '@container.namespaces']
+    arguments: [parser, '@container.namespaces', '@cache.cache', '@language_manager']
   plugin.manager.aggregator.processor:
     class: Drupal\aggregator\Plugin\AggregatorPluginManager
-    arguments: [processor, '@container.namespaces']
+    arguments: [processor, '@container.namespaces', '@cache.cache', '@language_manager']
   access_check.aggregator.categories:
     class: Drupal\aggregator\Access\CategoriesAccessCheck
     arguments: ['@database']
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Form/SettingsForm.php b/core/modules/aggregator/lib/Drupal/aggregator/Form/SettingsForm.php
index 0bc2e80..eb40df6 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Form/SettingsForm.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Form/SettingsForm.php
@@ -7,10 +7,13 @@
 
 namespace Drupal\aggregator\Form;
 
+use Drupal\aggregator\Plugin\AggregatorPluginManager;
+use Drupal\Component\Utility\String;
 use Drupal\Core\Config\Context\ContextInterface;
-use Drupal\system\SystemConfigFormBase;
 use Drupal\Core\Config\ConfigFactory;
-use Drupal\aggregator\Plugin\AggregatorPluginManager;
+use Drupal\Core\Plugin\PluginFormInterface;
+use Drupal\Core\StringTranslation\TranslationInterface;
+use Drupal\system\SystemConfigFormBase;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
@@ -26,6 +29,13 @@ class SettingsForm extends SystemConfigFormBase {
   protected $managers = array();
 
   /**
+   * The instantiated plugin instances that have configuration forms.
+   *
+   * @var array
+   */
+  protected $configurableInstances = array();
+
+  /**
    * The aggregator plugin definitions.
    *
    * @var array
@@ -49,10 +59,12 @@ class SettingsForm extends SystemConfigFormBase {
    *   The aggregator parser plugin manager.
    * @param \Drupal\aggregator\Plugin\AggregatorPluginManager $processor_manager
    *   The aggregator processor plugin manager.
+   * @param \Drupal\Core\StringTranslation\TranslationInterface $translation_manager
+   *   The string translation manager.
    */
-  public function __construct(ConfigFactory $config_factory, ContextInterface $context, AggregatorPluginManager $fetcher_manager, AggregatorPluginManager $parser_manager, AggregatorPluginManager $processor_manager) {
+  public function __construct(ConfigFactory $config_factory, ContextInterface $context, AggregatorPluginManager $fetcher_manager, AggregatorPluginManager $parser_manager, AggregatorPluginManager $processor_manager, TranslationInterface $translation_manager) {
     parent::__construct($config_factory, $context);
-
+    $this->translationManager = $translation_manager;
     $this->managers = array(
       'fetcher' => $fetcher_manager,
       'parser' => $parser_manager,
@@ -61,7 +73,7 @@ public function __construct(ConfigFactory $config_factory, ContextInterface $con
     // Get all available fetcher, parser and processor definitions.
     foreach (array('fetcher', 'parser', 'processor') as $type) {
       foreach ($this->managers[$type]->getDefinitions() as $id => $definition) {
-        $this->definitions[$type][$id] = format_string('@title <span class="description">@description</span>', array('@title' => $definition['title'], '@description' => $definition['description']));
+        $this->definitions[$type][$id] = String::format('@title <span class="description">@description</span>', array('@title' => $definition['title'], '@description' => $definition['description']));
       }
     }
   }
@@ -75,19 +87,20 @@ public static function create(ContainerInterface $container) {
       $container->get('config.context.free'),
       $container->get('plugin.manager.aggregator.fetcher'),
       $container->get('plugin.manager.aggregator.parser'),
-      $container->get('plugin.manager.aggregator.processor')
+      $container->get('plugin.manager.aggregator.processor'),
+      $container->get('string_translation')
     );
   }
 
   /**
-   * Implements \Drupal\Core\Form\FormInterface::getFormID().
+   * {@inheritdoc}
    */
   public function getFormID() {
     return 'aggregator_admin_form';
   }
 
   /**
-   * Implements \Drupal\Core\Form\FormInterface::buildForm().
+   * {@inheritdoc}
    */
   public function buildForm(array $form, array &$form_state) {
     $config = $this->configFactory->get('aggregator.settings');
@@ -95,11 +108,11 @@ public function buildForm(array $form, array &$form_state) {
     // Global aggregator settings.
     $form['aggregator_allowed_html_tags'] = array(
       '#type' => 'textfield',
-      '#title' => t('Allowed HTML tags'),
+      '#title' => $this->t('Allowed HTML tags'),
       '#size' => 80,
       '#maxlength' => 255,
       '#default_value' => $config->get('items.allowed_html'),
-      '#description' => t('A space-separated list of HTML tags allowed in the content of feed items. Disallowed tags are stripped from the content.'),
+      '#description' => $this->t('A space-separated list of HTML tags allowed in the content of feed items. Disallowed tags are stripped from the content.'),
     );
 
     // Only show basic configuration if there are actually options.
@@ -107,8 +120,8 @@ public function buildForm(array $form, array &$form_state) {
     if (count($this->definitions['fetcher']) > 1) {
       $basic_conf['aggregator_fetcher'] = array(
         '#type' => 'radios',
-        '#title' => t('Fetcher'),
-        '#description' => t('Fetchers download data from an external source. Choose a fetcher suitable for the external source you would like to download from.'),
+        '#title' => $this->t('Fetcher'),
+        '#description' => $this->t('Fetchers download data from an external source. Choose a fetcher suitable for the external source you would like to download from.'),
         '#options' => $this->definitions['fetcher'],
         '#default_value' => $config->get('fetcher'),
       );
@@ -116,8 +129,8 @@ public function buildForm(array $form, array &$form_state) {
     if (count($this->definitions['parser']) > 1) {
       $basic_conf['aggregator_parser'] = array(
         '#type' => 'radios',
-        '#title' => t('Parser'),
-        '#description' => t('Parsers transform downloaded data into standard structures. Choose a parser suitable for the type of feeds you would like to aggregate.'),
+        '#title' => $this->t('Parser'),
+        '#description' => $this->t('Parsers transform downloaded data into standard structures. Choose a parser suitable for the type of feeds you would like to aggregate.'),
         '#options' => $this->definitions['parser'],
         '#default_value' => $config->get('parser'),
       );
@@ -125,8 +138,8 @@ public function buildForm(array $form, array &$form_state) {
     if (count($this->definitions['processor']) > 1) {
       $basic_conf['aggregator_processors'] = array(
         '#type' => 'checkboxes',
-        '#title' => t('Processors'),
-        '#description' => t('Processors act on parsed feed data, for example they store feed items. Choose the processors suitable for your task.'),
+        '#title' => $this->t('Processors'),
+        '#description' => $this->t('Processors act on parsed feed data, for example they store feed items. Choose the processors suitable for your task.'),
         '#options' => $this->definitions['processor'],
         '#default_value' => $config->get('processors'),
       );
@@ -134,35 +147,67 @@ public function buildForm(array $form, array &$form_state) {
     if (count($basic_conf)) {
       $form['basic_conf'] = array(
         '#type' => 'details',
-        '#title' => t('Basic configuration'),
-        '#description' => t('For most aggregation tasks, the default settings are fine.'),
+        '#title' => $this->t('Basic configuration'),
+        '#description' => $this->t('For most aggregation tasks, the default settings are fine.'),
         '#collapsed' => FALSE,
       );
       $form['basic_conf'] += $basic_conf;
     }
 
+    // Call buildConfigurationForm() on the active fetcher and parser.
+    foreach (array('fetcher', 'parser') as $type) {
+      $active = $config->get($type);
+      if (array_key_exists($active, $this->definitions[$type])) {
+        $instance = $this->managers[$type]->createInstance($active);
+        if ($instance instanceof PluginFormInterface) {
+          $form = $instance->buildConfigurationForm($form, $form_state);
+          // Store the instance for validate and submit handlers.
+          // Keying by ID would bring conflicts, because two instances of a
+          // different type could have the same ID.
+          $this->configurableInstances[] = $instance;
+        }
+      }
+    }
+
     // Implementing processor plugins will expect an array at $form['processors'].
     $form['processors'] = array();
-    // Call settingsForm() for each active processor.
+    // Call buildConfigurationForm() for each active processor.
     foreach ($this->definitions['processor'] as $id => $definition) {
       if (in_array($id, $config->get('processors'))) {
-        $form = $this->managers['processor']->createInstance($id)->settingsForm($form, $form_state);
+        $instance = $this->managers['processor']->createInstance($id);
+        if ($instance instanceof PluginFormInterface) {
+          $form = $instance->buildConfigurationForm($form, $form_state);
+          // Store the instance for validate and submit handlers.
+          // Keying by ID would bring conflicts, because two instances of a
+          // different type could have the same ID.
+          $this->configurableInstances[] = $instance;
+        }
       }
     }
+
     return parent::buildForm($form, $form_state);
   }
 
   /**
-   * Implements \Drupal\Core\Form\FormInterface::submitForm().
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, array &$form_state) {
+    parent::validateForm($form, $form_state);
+    // Let active plugins validate their settings.
+    foreach ($this->configurableInstances as $instance) {
+      $instance->validateConfigurationForm($form, $form_state);
+    }
+  }
+
+  /**
+   * {@inheritdoc}
    */
   public function submitForm(array &$form, array &$form_state) {
     parent::submitForm($form, $form_state);
     $config = $this->configFactory->get('aggregator.settings');
-    // Let active processors save their settings.
-    foreach ($this->definitions['processor'] as $id => $definition) {
-      if (in_array($id, $config->get('processors'))) {
-        $this->managers['processor']->createInstance($id)->settingsSubmit($form, $form_state);
-      }
+    // Let active plugins save their settings.
+    foreach ($this->configurableInstances as $instance) {
+      $instance->submitConfigurationForm($form, $form_state);
     }
 
     $config->set('items.allowed_html', $form_state['values']['aggregator_allowed_html_tags']);
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Plugin/AggregatorPluginManager.php b/core/modules/aggregator/lib/Drupal/aggregator/Plugin/AggregatorPluginManager.php
index 67d8c4d..6362b51 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Plugin/AggregatorPluginManager.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Plugin/AggregatorPluginManager.php
@@ -7,16 +7,14 @@
 
 namespace Drupal\aggregator\Plugin;
 
-use Drupal\Component\Plugin\PluginManagerBase;
-use Drupal\Component\Plugin\Factory\DefaultFactory;
-use Drupal\Core\Language\Language;
-use Drupal\Core\Plugin\Discovery\AnnotatedClassDiscovery;
-use Drupal\Core\Plugin\Discovery\CacheDecorator;
+use Drupal\Core\Cache\CacheBackendInterface;
+use Drupal\Core\Language\LanguageManager;
+use Drupal\Core\Plugin\DefaultPluginManager;
 
 /**
  * Manages aggregator plugins.
  */
-class AggregatorPluginManager extends PluginManagerBase {
+class AggregatorPluginManager extends DefaultPluginManager {
 
   /**
    * Constructs a AggregatorPluginManager object.
@@ -25,9 +23,13 @@ class AggregatorPluginManager extends PluginManagerBase {
    *   The plugin type, for example fetcher.
    * @param \Traversable $namespaces
    *   An object that implements \Traversable which contains the root paths
-   *   keyed by the corresponding namespace to look for plugin implementations,
+   *   keyed by the corresponding namespace to look for plugin implementations.
+   * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
+   *   Cache backend instance to use.
+   * @param \Drupal\Core\Language\LanguageManager $language_manager
+   *   The language manager.
    */
-  public function __construct($type, \Traversable $namespaces) {
+  public function __construct($type, \Traversable $namespaces, CacheBackendInterface $cache_backend, LanguageManager $language_manager) {
     $type_annotations = array(
       'fetcher' => 'Drupal\aggregator\Annotation\AggregatorFetcher',
       'parser' => 'Drupal\aggregator\Annotation\AggregatorParser',
@@ -38,8 +40,8 @@ public function __construct($type, \Traversable $namespaces) {
       'Drupal\aggregator\Annotation' => DRUPAL_ROOT . '/core/modules/aggregator/lib',
     );
 
-    $this->discovery = new AnnotatedClassDiscovery("Plugin/aggregator/$type", $namespaces, $annotation_namespaces, $type_annotations[$type]);
-    $this->discovery = new CacheDecorator($this->discovery, "aggregator_$type:" . language(Language::TYPE_INTERFACE)->id);
-    $this->factory = new DefaultFactory($this->discovery);
+    parent::__construct("Plugin/aggregator/$type", $namespaces, $annotation_namespaces, $type_annotations[$type]);
+    $this->setCacheBackend($cache_backend, $language_manager, "aggregator_$type");
   }
+
 }
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Plugin/AggregatorPluginSettingsBase.php b/core/modules/aggregator/lib/Drupal/aggregator/Plugin/AggregatorPluginSettingsBase.php
new file mode 100644
index 0000000..55013e1
--- /dev/null
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Plugin/AggregatorPluginSettingsBase.php
@@ -0,0 +1,25 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\aggregator\Plugin\AggregatorPluginSettingsBase.
+ */
+
+namespace Drupal\aggregator\Plugin;
+
+use Drupal\Component\Plugin\ConfigurablePluginInterface;
+use Drupal\Component\Plugin\PluginBase;
+use Drupal\Core\Plugin\PluginFormInterface;
+
+/**
+ * Base class for aggregator plugins that implement settings forms.
+ */
+abstract class AggregatorPluginSettingsBase extends PluginBase implements PluginFormInterface, ConfigurablePluginInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateConfigurationForm(array &$form, array &$form_state) {
+  }
+
+}
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Plugin/ProcessorInterface.php b/core/modules/aggregator/lib/Drupal/aggregator/Plugin/ProcessorInterface.php
index d635f86..a6fed6d 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Plugin/ProcessorInterface.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Plugin/ProcessorInterface.php
@@ -21,31 +21,6 @@
 interface ProcessorInterface {
 
   /**
-   * Returns a form to configure settings for the processor.
-   *
-   * @param array $form
-   *   The form definition array where the settings form is being included in.
-   * @param array $form_state
-   *   An associative array containing the current state of the form.
-   *
-   * @return array
-   *   The form elements for the processor settings.
-   */
-  public function settingsForm(array $form, array &$form_state);
-
-  /**
-   * Adds processor specific submission handling for the configuration form.
-   *
-   * @param array $form
-   *   The form definition array where the settings form is being included in.
-   * @param array $form_state
-   *   An associative array containing the current state of the form.
-   *
-   * @see \Drupal\aggregator\Plugin\ProcessorInterface::settingsForm()
-   */
-  public function settingsSubmit(array $form, array &$form_state);
-
-  /**
    * Processes feed data.
    *
    * @param \Drupal\aggregator\Entity\Feed $feed
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Plugin/aggregator/fetcher/DefaultFetcher.php b/core/modules/aggregator/lib/Drupal/aggregator/Plugin/aggregator/fetcher/DefaultFetcher.php
index 986d66e..38306d7 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Plugin/aggregator/fetcher/DefaultFetcher.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Plugin/aggregator/fetcher/DefaultFetcher.php
@@ -7,12 +7,15 @@
 
 namespace Drupal\aggregator\Plugin\aggregator\fetcher;
 
+use Drupal\aggregator\Annotation\AggregatorFetcher;
 use Drupal\aggregator\Plugin\FetcherInterface;
 use Drupal\aggregator\Entity\Feed;
-use Drupal\aggregator\Annotation\AggregatorFetcher;
 use Drupal\Core\Annotation\Translation;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Guzzle\Http\ClientInterface;
 use Guzzle\Http\Exception\BadResponseException;
 use Guzzle\Http\Exception\RequestException;
+use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
  * Defines a default fetcher implementation.
@@ -25,14 +28,39 @@
  *   description = @Translation("Downloads data from a URL using Drupal's HTTP request handler.")
  * )
  */
-class DefaultFetcher implements FetcherInterface {
+class DefaultFetcher implements FetcherInterface, ContainerFactoryPluginInterface {
+
+  /**
+   * The HTTP client to fetch the feed data with.
+   *
+   * @var \Guzzle\Http\ClientInterface
+   */
+  protected $httpClient;
+
+  /**
+   * Constructs a DefaultFetcher object.
+   *
+   * @param \Guzzle\Http\ClientInterface $http_client
+   *   A Guzzle client object.
+   */
+  public function __construct(ClientInterface $http_client) {
+    $this->httpClient = $http_client;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, array $plugin_definition) {
+    return new static(
+      $container->get('http_default_client')
+    );
+  }
 
   /**
-   * Implements \Drupal\aggregator\Plugin\FetcherInterface::fetch().
+   * {@inheritdoc}
    */
   public function fetch(Feed $feed) {
-    // @todo: Inject the http client.
-    $request = \Drupal::httpClient()->get($feed->url->value);
+    $request = $this->httpClient->get($feed->url->value);
     $feed->source_string = FALSE;
 
     // Generate conditional GET headers.
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Plugin/aggregator/processor/DefaultProcessor.php b/core/modules/aggregator/lib/Drupal/aggregator/Plugin/aggregator/processor/DefaultProcessor.php
index eefadcd..ec7d193 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Plugin/aggregator/processor/DefaultProcessor.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Plugin/aggregator/processor/DefaultProcessor.php
@@ -7,12 +7,15 @@
 
 namespace Drupal\aggregator\Plugin\aggregator\processor;
 
-use Drupal\Component\Plugin\PluginBase;
+use Drupal\aggregator\Annotation\AggregatorProcessor;
+use Drupal\aggregator\Plugin\AggregatorPluginSettingsBase;
 use Drupal\aggregator\Plugin\ProcessorInterface;
 use Drupal\aggregator\Entity\Feed;
-use Drupal\aggregator\Annotation\AggregatorProcessor;
 use Drupal\Core\Annotation\Translation;
 use Drupal\Core\Database\Database;
+use Drupal\Core\Config\ConfigFactory;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
  * Defines a default processor implementation.
@@ -25,14 +28,51 @@
  *   description = @Translation("Creates lightweight records from feed items.")
  * )
  */
-class DefaultProcessor extends PluginBase implements ProcessorInterface {
+class DefaultProcessor extends AggregatorPluginSettingsBase implements ProcessorInterface, ContainerFactoryPluginInterface {
+
+  /**
+   * Contains the configuration object factory.
+   *
+   * @var \Drupal\Core\Config\ConfigFactory
+   */
+  protected $configFactory;
+
+  /**
+   * Constructs a DefaultProcessor object.
+   *
+   * @param array $configuration
+   *   A configuration array containing information about the plugin instance.
+   * @param string $plugin_id
+   *   The plugin_id for the plugin instance.
+   * @param array $plugin_definition
+   *   The plugin implementation definition.
+   * @param \Drupal\Core\Config\ConfigFactory $config
+   *   The configuration factory object.
+   */
+  public function __construct(array $configuration, $plugin_id, array $plugin_definition, ConfigFactory $config) {
+    $this->configFactory = $config;
+    // @todo Refactor aggregator plugins to ConfigEntity so merging
+    //   the configuration here is not needed.
+    parent::__construct($configuration + $this->getConfiguration(), $plugin_id, $plugin_definition);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, array $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('config.factory')
+    );
+  }
 
   /**
-   * Implements \Drupal\aggregator\Plugin\ProcessorInterface::settingsForm().
+   * {@inheritdoc}
    */
-  public function settingsForm(array $form, array &$form_state) {
-    $config = \Drupal::config('aggregator.settings');
-    $processors = $config->get('processors');
+  public function buildConfigurationForm(array $form, array &$form_state) {
+    $processors = $this->configuration['processors'];
     $info = $this->getPluginDefinition();
     $items = drupal_map_assoc(array(3, 5, 10, 15, 20, 25), array($this, 'formatItems'));
     $period = drupal_map_assoc(array(3600, 10800, 21600, 32400, 43200, 86400, 172800, 259200, 604800, 1209600, 2419200, 4838400, 9676800), 'format_interval');
@@ -52,7 +92,7 @@ public function settingsForm(array $form, array &$form_state) {
     $form['processors'][$info['id']]['aggregator_summary_items'] = array(
       '#type' => 'select',
       '#title' => t('Number of items shown in listing pages'),
-      '#default_value' => $config->get('source.list_max'),
+      '#default_value' => $this->configuration['source']['list_max'],
       '#empty_value' => 0,
       '#options' => $items,
     );
@@ -60,7 +100,7 @@ public function settingsForm(array $form, array &$form_state) {
     $form['processors'][$info['id']]['aggregator_clear'] = array(
       '#type' => 'select',
       '#title' => t('Discard items older than'),
-      '#default_value' => $config->get('items.expire'),
+      '#default_value' => $this->configuration['items']['expire'],
       '#options' => $period,
       '#description' => t('Requires a correctly configured <a href="@cron">cron maintenance task</a>.', array('@cron' => url('admin/reports/status'))),
     );
@@ -68,7 +108,7 @@ public function settingsForm(array $form, array &$form_state) {
     $form['processors'][$info['id']]['aggregator_category_selector'] = array(
       '#type' => 'radios',
       '#title' => t('Select categories using'),
-      '#default_value' => $config->get('source.category_selector'),
+      '#default_value' => $this->configuration['source']['category_selector'],
       '#options' => array('checkboxes' => t('checkboxes'),
       'select' => t('multiple selector')),
       '#description' => t('For a small number of categories, checkboxes are easier to use, while a multiple selector works well with large numbers of categories.'),
@@ -76,27 +116,27 @@ public function settingsForm(array $form, array &$form_state) {
     $form['processors'][$info['id']]['aggregator_teaser_length'] = array(
       '#type' => 'select',
       '#title' => t('Length of trimmed description'),
-      '#default_value' => $config->get('items.teaser_length'),
+      '#default_value' => $this->configuration['items']['teaser_length'],
       '#options' => drupal_map_assoc(array(0, 200, 400, 600, 800, 1000, 1200, 1400, 1600, 1800, 2000), array($this, 'formatCharacters')),
-      '#description' => t("The maximum number of characters used in the trimmed version of content.")
+      '#description' => t('The maximum number of characters used in the trimmed version of content.'),
     );
     return $form;
   }
 
   /**
-   * Implements \Drupal\aggregator\Plugin\ProcessorInterface::settingsSubmit().
+   * {@inheritdoc}
    */
-  public function settingsSubmit(array $form, array &$form_state) {
-    $config = \Drupal::config('aggregator.settings');
-    $config->set('items.expire', $form_state['values']['aggregator_clear'])
-      ->set('items.teaser_length', $form_state['values']['aggregator_teaser_length'])
-      ->set('source.list_max', $form_state['values']['aggregator_summary_items'])
-      ->set('source.category_selector', $form_state['values']['aggregator_category_selector'])
-      ->save();
+  public function submitConfigurationForm(array &$form, array &$form_state) {
+    $this->configuration['items']['expire'] = $form_state['values']['aggregator_clear'];
+    $this->configuration['items']['teaser_length'] = $form_state['values']['aggregator_teaser_length'];
+    $this->configuration['source']['list_max'] = $form_state['values']['aggregator_summary_items'];
+    $this->configuration['source']['category_selector'] = $form_state['values']['aggregator_category_selector'];
+    // @todo Refactor aggregator plugins to ConfigEntity so this is not needed.
+    $this->setConfiguration($this->configuration);
   }
 
   /**
-   * Implements \Drupal\aggregator\Plugin\ProcessorInterface::process().
+   * {@inheritdoc}
    */
   public function process(Feed $feed) {
     if (!is_array($feed->items)) {
@@ -147,7 +187,7 @@ public function process(Feed $feed) {
   }
 
   /**
-   * Implements \Drupal\aggregator\Plugin\ProcessorInterface::remove().
+   * {@inheritdoc}
    */
   public function remove(Feed $feed) {
     $iids = Database::getConnection()->query('SELECT iid FROM {aggregator_item} WHERE fid = :fid', array(':fid' => $feed->id()))->fetchCol();
@@ -164,7 +204,7 @@ public function remove(Feed $feed) {
    * Expires items from a feed depending on expiration settings.
    */
   public function postProcess(Feed $feed) {
-    $aggregator_clear = \Drupal::config('aggregator.settings')->get('items.expire');
+    $aggregator_clear = $this->configuration['items']['expire'];
 
     if ($aggregator_clear != AGGREGATOR_CLEAR_NEVER) {
       // Remove all items that are older than flush item timer.
@@ -181,6 +221,24 @@ public function postProcess(Feed $feed) {
   }
 
   /**
+   * {@inheritdoc}
+   */
+  public function getConfiguration() {
+    return $this->configFactory->get('aggregator.settings')->get();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setConfiguration(array $configuration) {
+    $config = $this->configFactory->get('aggregator.settings');
+    foreach ($configuration as $key => $value) {
+      $config->set($key, $value);
+    }
+    $config->save();
+  }
+
+  /**
    * Helper function for drupal_map_assoc.
    *
    * @param int $count
@@ -207,4 +265,5 @@ protected function formatItems($count) {
   protected function formatCharacters($length) {
     return ($length == 0) ? t('Unlimited') : format_plural($length, '1 character', '@count characters');
   }
+
 }
diff --git a/core/modules/aggregator/tests/Drupal/aggregator/Tests/Plugin/AggregatorPluginSettingsBaseTest.php b/core/modules/aggregator/tests/Drupal/aggregator/Tests/Plugin/AggregatorPluginSettingsBaseTest.php
new file mode 100644
index 0000000..9c120c3
--- /dev/null
+++ b/core/modules/aggregator/tests/Drupal/aggregator/Tests/Plugin/AggregatorPluginSettingsBaseTest.php
@@ -0,0 +1,123 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\aggregator\Tests\Plugin\AggregatorPluginSettingsBaseTest
+ */
+
+namespace Drupal\aggregator\Tests\Plugin {
+
+use Drupal\aggregator\Form\SettingsForm;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Tests plugins settings on aggregator plugins.
+ *
+ * @group Drupal
+ * @group Aggregator
+ */
+class AggregatorPluginSettingsBaseTest extends UnitTestCase {
+
+  /**
+   * The aggregator settings form object under test.
+   *
+   * @var \Drupal\aggregator\Form\SettingsForm
+   */
+  protected $settingsForm;
+
+  /**
+   * The stubbed config factory object.
+   *
+   * @var \PHPUnit_Framework_MockObject_MockBuilder
+   */
+  protected $configFactory;
+
+  /**
+   * The stubbed aggregator plugin managers array.
+   *
+   * @var array
+   */
+  protected $managers;
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Aggregator plugin settings tests',
+      'description' => 'Test settings configuration of individual aggregator plugins.',
+      'group' => 'Aggregator',
+    );
+  }
+
+  public function setUp() {
+    $this->configFactory = $this->getConfigFactoryStub(
+      array(
+        'aggregator.settings' => array(
+          'processors' => array('aggregator_test'),
+        ),
+        'aggregator_test.settings' => array(),
+      )
+    );
+    foreach (array('fetcher', 'parser', 'processor') as $type) {
+      $this->managers[$type] = $this->getMockBuilder('Drupal\aggregator\Plugin\AggregatorPluginManager')
+        ->disableOriginalConstructor()
+        ->getMock();
+      $this->managers[$type]->expects($this->once())
+        ->method('getDefinitions')
+        ->will($this->returnValue(array('aggregator_test' => array('title' => '', 'description' => ''))));
+    }
+
+    $this->settingsForm = new SettingsForm(
+      $this->configFactory,
+      $this->getMock('Drupal\Core\Config\Context\ContextInterface'),
+      $this->managers['fetcher'],
+      $this->managers['parser'],
+      $this->managers['processor'],
+      $this->getStringTranslationStub()
+    );
+  }
+
+  /**
+   * Test for AggregatorPluginSettingsBase.
+   *
+   * Ensure that the settings form calls build, validate and submit methods on
+   * plugins that extend AggregatorPluginSettingsBase.
+   */
+  public function testSettingsForm() {
+    // Emulate a form state of a sumbitted form.
+    $form_state = array('values' => array('dummy_length' => '', 'aggregator_allowed_html_tags' => ''));
+
+    $test_processor = $this->getMock(
+      'Drupal\aggregator_test\Plugin\aggregator\processor\TestProcessor',
+      array('buildConfigurationForm', 'validateConfigurationForm', 'submitConfigurationForm'),
+      array(array(), 'aggregator_test', array('description' => ''), $this->configFactory)
+    );
+    $test_processor->expects($this->at(0))
+      ->method('buildConfigurationForm')
+      ->with($this->anything(), $form_state)
+      ->will($this->returnArgument(0));
+    $test_processor->expects($this->at(1))
+      ->method('validateConfigurationForm')
+      ->with($this->anything(), $form_state);
+    $test_processor->expects($this->at(2))
+      ->method('submitConfigurationForm')
+      ->with($this->anything(), $form_state);
+
+    $this->managers['processor']->expects($this->once())
+      ->method('createInstance')
+      ->with($this->equalTo('aggregator_test'))
+      ->will($this->returnValue($test_processor));
+
+    $form = $this->settingsForm->buildForm(array(), $form_state);
+    $this->settingsForm->validateForm($form, $form_state);
+    $this->settingsForm->submitForm($form, $form_state);
+  }
+
+}
+
+}
+
+namespace {
+  // @todo Remove after https://drupal.org/node/1858196 is in.
+  if (!function_exists('drupal_set_message')) {
+    function drupal_set_message() {}
+  }
+}
diff --git a/core/modules/aggregator/tests/modules/aggregator_test/lib/Drupal/aggregator_test/Plugin/aggregator/processor/TestProcessor.php b/core/modules/aggregator/tests/modules/aggregator_test/lib/Drupal/aggregator_test/Plugin/aggregator/processor/TestProcessor.php
index f6f605d..04a5c5a 100644
--- a/core/modules/aggregator/tests/modules/aggregator_test/lib/Drupal/aggregator_test/Plugin/aggregator/processor/TestProcessor.php
+++ b/core/modules/aggregator/tests/modules/aggregator_test/lib/Drupal/aggregator_test/Plugin/aggregator/processor/TestProcessor.php
@@ -7,11 +7,14 @@
 
 namespace Drupal\aggregator_test\Plugin\aggregator\processor;
 
-use Drupal\Component\Plugin\PluginBase;
+use Drupal\aggregator\Plugin\AggregatorPluginSettingsBase;
 use Drupal\aggregator\Plugin\ProcessorInterface;
 use Drupal\aggregator\Entity\Feed;
 use Drupal\aggregator\Annotation\AggregatorProcessor;
 use Drupal\Core\Annotation\Translation;
+use Drupal\Core\Config\ConfigFactory;
+use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
  * Defines a default processor implementation.
@@ -24,14 +27,49 @@
  *   description = @Translation("Test generic processor functionality.")
  * )
  */
-class TestProcessor extends PluginBase implements ProcessorInterface {
+class TestProcessor extends AggregatorPluginSettingsBase implements ProcessorInterface, ContainerFactoryPluginInterface {
 
   /**
-   * Implements \Drupal\aggregator\Plugin\ProcessorInterface::settingsForm().
+   * Contains the configuration object factory.
+   *
+   * @var \Drupal\Core\Config\ConfigFactory
    */
-  public function settingsForm(array $form, array &$form_state) {
-    $config = \Drupal::config('aggregator.settings');
-    $processors = $config->get('processors');
+  protected $configFactory;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function create(ContainerInterface $container, array $configuration, $plugin_id, array $plugin_definition) {
+    return new static(
+      $configuration,
+      $plugin_id,
+      $plugin_definition,
+      $container->get('config.factory')
+    );
+  }
+
+  /**
+   * Constructs a TestProcessor object.
+   *
+   * @param array $configuration
+   *   A configuration array containing information about the plugin instance.
+   * @param string $plugin_id
+   *   The plugin_id for the plugin instance.
+   * @param array $plugin_definition
+   *   The plugin implementation definition.
+   * @param \Drupal\Core\Config\ConfigFactory $config
+   *   The configuration factory object.
+   */
+  public function __construct(array $configuration, $plugin_id, array $plugin_definition, ConfigFactory $config) {
+    $this->configFactory = $config;
+    parent::__construct($configuration + $this->getConfiguration(), $plugin_id, $plugin_definition);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildConfigurationForm(array $form, array &$form_state) {
+    $processors = $this->configFactory->get('aggregator.settings')->get('processors');
     $info = $this->getPluginDefinition();
 
     $form['processors'][$info['id']] = array(
@@ -46,22 +84,21 @@ public function settingsForm(array $form, array &$form_state) {
       '#type' => 'number',
       '#min' => 1,
       '#max' => 1000,
-      '#default_value' => \Drupal::config('aggregator_test.settings')->get('items.dummy_length'),
+      '#default_value' => $this->configuration['items']['dummy_length'],
     );
     return $form;
   }
 
   /**
-   * Implements \Drupal\aggregator\Plugin\ProcessorInterface::settingsSubmit().
+   * {@inheritdoc}
    */
-  public function settingsSubmit(array $form, array &$form_state) {
-    \Drupal::config('aggregator_test.settings')
-      ->set('items.dummy_length', $form_state['values']['dummy_length'])
-      ->save();
+  public function submitConfigurationForm(array &$form, array &$form_state) {
+    $this->configuration['items']['dummy_length'] = $form_state['values']['dummy_length'];
+    $this->setConfiguration($this->configuration);
   }
 
   /**
-   * Implements \Drupal\aggregator\Plugin\ProcessorInterface::process().
+   * {@inheritdoc}
    */
   public function process(Feed $feed) {
     foreach ($feed->items as &$item) {
@@ -71,7 +108,7 @@ public function process(Feed $feed) {
   }
 
   /**
-   * Implements \Drupal\aggregator\Plugin\ProcessorInterface::remove().
+   * {@inheritdoc}
    */
   public function remove(Feed $feed) {
     // Append a random number, just to change the feed description.
@@ -79,11 +116,30 @@ public function remove(Feed $feed) {
   }
 
   /**
-   * Implements \Drupal\aggregator\Plugin\ProcessorInterface::postProcess().
+   * {@inheritdoc}
    */
   public function postProcess(Feed $feed) {
     // Double the refresh rate.
     $feed->refresh->value *= 2;
     $feed->save();
   }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getConfiguration() {
+    return $this->configFactory->get('aggregator_test.settings')->get();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setConfiguration(array $configuration) {
+    $config = $this->configFactory->get('aggregator_test.settings');
+    foreach ($configuration as $key => $value) {
+      $config->set($key, $value);
+    }
+    $config->save();
+  }
+
 }
diff --git a/core/tests/Drupal/Tests/UnitTestCase.php b/core/tests/Drupal/Tests/UnitTestCase.php
index c8f32a6..576c015 100644
--- a/core/tests/Drupal/Tests/UnitTestCase.php
+++ b/core/tests/Drupal/Tests/UnitTestCase.php
@@ -147,4 +147,20 @@ protected function getBlockMockWithMachineName($machine_name) {
     return $block;
   }
 
+  /**
+   * Returns a stub translation manager that just returns the passed string.
+   *
+   * @return \PHPUnit_Framework_MockObject_MockBuilder
+   *   A MockBuilder of \Drupal\Core\StringTranslation\TranslationInterface
+   */
+  public function getStringTranslationStub() {
+    $translation = $this->getMockBuilder('Drupal\Core\StringTranslation\TranslationManager')
+      ->disableOriginalConstructor()
+      ->getMock();
+    $translation->expects($this->any())
+      ->method('translate')
+      ->will($this->returnArgument(0));
+    return $translation;
+  }
+
 }