Fixes #13. Implement DB message source.

framework/yii/i18n/DbMessageSource.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\i18n;
+
+use Yii;
+use yii\base\InvalidConfigException;
+use yii\helpers\ArrayHelper;
+use yii\caching\Cache;
+use yii\db\Connection;
+use yii\db\Query;
+
+/**
+ * DbMessageSource extends [[MessageSource]] and represents a message source that stores translated
+ * messages in database.
+ *
+ * The database must contain the following two tables:
+ *
+ * ~~~
+ * CREATE TABLE tbl_source_message (
+ *     id INTEGER PRIMARY KEY,
+ *     category VARCHAR(32),
+ *     message TEXT
+ * );
+ *
+ * CREATE TABLE tbl_message (
+ *     id INTEGER,
+ *     language VARCHAR(16),
+ *     translation TEXT,
+ *     PRIMARY KEY (id, language),
+ *     CONSTRAINT fk_message_source_message FOREIGN KEY (id)
+ *         REFERENCES tbl_source_message (id) ON DELETE CASCADE ON UPDATE RESTRICT
+ * );
+ * ~~~
+ *
+ * The `tbl_source_message` table stores the messages to be translated, and the `tbl_message` table stores
+ * the translated messages. The name of these two tables can be customized by setting [[sourceMessageTable]]
+ * and [[messageTable]], respectively.
+ *
+ * When [[cachingDuration]] is set as a positive number, message translations will be cached.
+ *
+ * @author resurtm <resurtm@gmail.com>
+ * @since 2.0
+ */
+class DbMessageSource extends MessageSource
+{
+	/**
+	 * Prefix which would be used when generating cache key.
+	 */
+	const CACHE_KEY_PREFIX = 'DbMessageSource';
+
+	/**
+	 * @var Connection|string the DB connection object or the application component ID of the DB connection.
+	 * After the DbMessageSource object is created, if you want to change this property, you should only assign
+	 * it with a DB connection object.
+	 */
+	public $db = 'db';
+	/**
+	 * @var Cache|string the cache object or the application component ID of the cache object.
+	 * The messages data will be cached using this cache object. Note, this property has meaning only
+	 * in case [[cachingDuration]] set to non-zero value.
+	 * After the DbMessageSource object is created, if you want to change this property, you should only assign
+	 * it with a cache object.
+	 */
+	public $cache = 'cache';
+	/**
+	 * @var string the name of the source message table. Defaults to `{{%source_message}}`.
+	 */
+	public $sourceMessageTable = '{{%source_message}}';
+	/**
+	 * @var string the name of the translated message table. Defaults to `{{%message}}`.
+	 */
+	public $messageTable = '{{%message}}';
+	/**
+	 * @var integer the time in seconds that the messages can remain valid in cache.
+	 * Defaults to 0, meaning the caching is disabled.
+	 */
+	public $cachingDuration = 0;
+
+	/**
+	 * Initializes the DbMessageSource component.
+	 * This method will initialize the [[db]] property to make sure it refers to a valid DB connection.
+	 * Configured [[cache]] component would also be initialized.
+	 * @throws InvalidConfigException if [[db]] is invalid or [[cache]] is invalid.
+	 */
+	public function init()
+	{
+		parent::init();
+		if (is_string($this->db)) {
+			$this->db = Yii::$app->getComponent($this->db);
+		}
+		if (!$this->db instanceof Connection) {
+			throw new InvalidConfigException("DbMessageSource::db must be either a DB connection instance or the application component ID of a DB connection.");
+		}
+		if ($this->cachingDuration > 0) {
+			if (is_string($this->cache)) {
+				$this->cache = Yii::$app->getComponent($this->cache);
+			}
+			if (!$this->cache instanceof Cache) {
+				throw new InvalidConfigException("DbMessageSource::cache must be either a cache object or the application component ID of the cache object.");
+			}
+		}
+	}
+
+	/**
+	 * Loads the message translation for the specified language and category.
+	 * Child classes should override this method to return the message translations of
+	 * the specified language and category.
+	 * @param string $category the message category
+	 * @param string $language the target language
+	 * @return array the loaded messages. The keys are original messages, and the values
+	 * are translated messages.
+	 */
+	protected function loadMessages($category, $language)
+	{
+		if ($this->cachingDuration === 0) {
+			return $this->retrieveMessages($category, $language);
+		} else {
+			$key = static::CACHE_KEY_PREFIX . ".messages.{$category}.{$language}";
+			$messages = $this->cache->get($key);
+			if ($messages === false) {
+				$messages = $this->retrieveMessages($category, $language);
+				$this->cache->set($key, $messages, $this->cachingDuration);
+			}
+			return $messages;
+		}
+	}
+
+	/**
+	 * Loads the messages from database.
+	 * You may override this method to customize the message storage in the database.
+	 * @param string $category the message category.
+	 * @param string $language the target language.
+	 * @return array the messages loaded from database.
+	 */
+	protected function retrieveMessages($category, $language)
+	{
+		$query = new Query();
+		$messages = $query->select(array('t1.message message', 't2.translation translation'))
+			->from(array($this->sourceMessageTable . ' t1', $this->messageTable . ' t2'))
+			->where('t1.id = t2.id AND t1.category = :category AND t2.language = :language')
+			->params(array(':category' => $category, ':language' => $language))
+			->createCommand($this->db)
+			->queryAll();
+		return ArrayHelper::map($messages, 'message', 'translation');
+	}
+}