模板模式
模板模式
模板模式准备一个抽象类，将部分逻辑以具体方法以及具体构造形式实现，然后声明一些抽象方法来迫使子类实现剩余的逻辑。不同的子类可以以不同的方式实现这些抽象方法，从而对剩余的逻辑有不同的实现。先制定一个顶级逻辑框架，而将逻辑的细节留给具体的子类去实现。
讲到模板模式，我不得不提的就是我们著名的PSR-3规范，
PSR-3为我们提供了模板的接口
namespace Psr\Log;
/**
* Describes a logger instance.
*
* The message MUST be a string or object implementing __toString().
*
* The message MAY contain placeholders in the form: {foo} where foo
* will be replaced by the context data in key "foo".
*
* The context array can contain arbitrary data, the only assumption that
* can be made by implementors is that if an Exception instance is given
* to produce a stack trace, it MUST be in a key named "exception".
*
* See https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-3-logger-interface.md
* for the full interface specification.
*/
interface LoggerInterface
{
/**
* System is unusable.
*
* @param string $message
* @param array $context
* @return void
*/
public function emergency($message, array $context = array());
/**
* Action must be taken immediately.
*
* Example: Entire website down, database unavailable, etc. This should
* trigger the SMS alerts and wake you up.
*
* @param string $message
* @param array $context
* @return void
*/
public function alert($message, array $context = array());
/**
* Critical conditions.
*
* Example: Application component unavailable, unexpected exception.
*
* @param string $message
* @param array $context
* @return void
*/
public function critical($message, array $context = array());
/**
* Runtime errors that do not require immediate action but should typically
* be logged and monitored.
*
* @param string $message
* @param array $context
* @return void
*/
public function error($message, array $context = array());
/**
* Exceptional occurrences that are not errors.
*
* Example: Use of deprecated APIs, poor use of an API, undesirable things
* that are not necessarily wrong.
*
* @param string $message
* @param array $context
* @return void
*/
public function warning($message, array $context = array());
/**
* Normal but significant events.
*
* @param string $message
* @param array $context
* @return void
*/
public function notice($message, array $context = array());
/**
* Interesting events.
*
* Example: User logs in, SQL logs.
*
* @param string $message
* @param array $context
* @return void
*/
public function info($message, array $context = array());
/**
* Detailed debug information.
*
* @param string $message
* @param array $context
* @return void
*/
public function debug($message, array $context = array());
/**
* Logs with an arbitrary level.
*
* @param mixed $level
* @param string $message
* @param array $context
* @return void
*/
public function log($level, $message, array $context = array());
}
以上代码提供了记录各个级别日志的接口，下面我们使用模板模式做一个日志的实现。
/**
* Describes log levels.
*/
class LogLevel
{
const EMERGENCY = 'emergency';
const ALERT = 'alert';
const CRITICAL = 'critical';
const ERROR = 'error';
const WARNING = 'warning';
const NOTICE = 'notice';
const INFO = 'info';
const DEBUG = 'debug';
}
/**
* Class ILogger
* @datetime 2020/7/17 7:16 PM
* @author roach
* @email [email protected]
*/
abstract class ILogger
{
/**
* @param string $message
* @param array $context
* @return string
* @datetime 2020/7/17 7:17 PM
* @author roach
* @email [email protected]
*/
public static function interpolate($message, array $context = array())
{
// build a replacement array with braces around the context keys
$replace = array();
foreach ($context as $key => $val) {
// check that the value can be cast to string
if (!is_array($val) && (!is_object($val) || method_exists($val, '__toString'))) {
$replace['{' . $key . '}'] = $val;
}
}
// interpolate replacement values into the message and return
return strtr($message, $replace);
}
/**
* System is unusable.
*
* @param string $message
* @param array $context
* @return void
*/
public function emergency($message, array $context = array())
{
$this->log(LogLevel::EMERGENCY, $message, $context);
}
/**
* Action must be taken immediately.
*
* Example: Entire website down, database unavailable, etc. This should
* trigger the SMS alerts and wake you up.
*
* @param string $message
* @param array $context
* @return void
*/
public function alert($message, array $context = array())
{
$this->log(LogLevel::ALERT, $message, $context);
}
/**
* Critical conditions.
*
* Example: Application component unavailable, unexpected exception.
*
* @param string $message
* @param array $context
* @return void
*/
public function critical($message, array $context = array())
{
$this->log(LogLevel::CRITICAL, $message, $context);
}
/**
* Runtime errors that do not require immediate action but should typically
* be logged and monitored.
*
* @param string $message
* @param array $context
* @return void
*/
public function error($message, array $context = array())
{
$this->log(LogLevel::ERROR, $message, $context);
}
/**
* Exceptional occurrences that are not errors.
*
* Example: Use of deprecated APIs, poor use of an API, undesirable things
* that are not necessarily wrong.
*
* @param string $message
* @param array $context
* @return void
*/
public function warning($message, array $context = array())
{
$this->log(LogLevel::WARNING, $message, $context);
}
/**
* Normal but significant events.
*
* @param string $message
* @param array $context
* @return void
*/
public function notice($message, array $context = array())
{
$this->log(LogLevel::NOTICE, $message, $context);
}
/**
* Interesting events.
*
* Example: User logs in, SQL logs.
*
* @param string $message
* @param array $context
* @return void
*/
public function info($message, array $context = array())
{
$this->log(LogLevel::INFO, $message, $context);
}
/**
* Detailed debug information.
*
* @param string $message
* @param array $context
* @return void
*/
public function debug($message, array $context = array())
{
$this->log(LogLevel::DEBUG, $message, $context);
}
/**
* Logs with an arbitrary level.
*
* @param mixed $level
* @param string $message
* @param array $context
* @return void
*/
abstract public function log($level, $message, array $context = array());
}
/**
* Class File
* @datetime 2020/7/17 7:23 PM
* @author roach
* @email [email protected]
*/
class File extends ILogger
{
/**
* @var string
* @datetime 2020/7/17 7:20 PM
* @author roach
* @email [email protected]
*/
protected $_fileName;
/**
* @param $fileName
* @datetime 2020/7/17 7:21 PM
* @author roach
* @email [email protected]
*/
public function setFileName($fileName)
{
$this->_fileName = $fileName;
}
/**
* @param string $level
* @param string $message
* @param array $context
* @datetime 2020/7/17 7:23 PM
* @author roach
* @email [email protected]
*/
public function log($level, $message, array $context = array())
{
$message = '{datetime} {level} {ip} {url} '.$message.PHP_EOL;
$context['datetime'] = date('Y-m-d H:i:s');
$context['level'] = $level;
$context['ip'] = $_SERVER['REMOTE_ADDR'];
$context['url'] = $_SERVER['REQUEST_URI'];
$message = self::interpolate($message, $context);
file_put_contents($this->_fileName, $message, FILE_APPEND | LOCK_EX);
}
}
class Db extends ILogger
{
/**
* @var \PDO
* @datetime 2020/7/17 7:24 PM
* @author roach
* @email [email protected]
*/
protected $_pdo;
/**
* @param PDO $pdo
* @datetime 2020/7/17 7:24 PM
* @author roach
* @email [email protected]
*/
public function setPdo(\PDO $pdo)
{
$this->_pdo = $pdo;
}
/**
* @param mixed $level
* @param string $message
* @param array $context
* @datetime 2020/7/17 7:28 PM
* @author roach
* @email [email protected]
*/
public function log($level, $message, array $context = array())
{
$message = self::interpolate($message, $context);
$stmt = $this->_pdo->prepare('INSERT INTO `roach_log`(`level`,`ip`,`url`,`msg`,`add_time`)VALUES(?,?,?,?,?)');
$stmt->execute([
$level,
$_SERVER['REMOTE_ADDR'],
$_SERVER['REQUEST_URI'],
self::interpolate($message, $context),
time()
]);
}
}
分析以上代码，
ILogger是抽象的模板类，实现了部分逻辑，但是log方法没有实现，交给子类实现，作者实现了File和Db子类，如果您感兴趣可以实现其他类，如Redis、Kafka等。
看过策略模式文章的同学也许有疑问了，这不是策略模式吗？把
log方法封装了起来，从本质上来讲算是解决了不同算法的问题，但是严格上来讲，缺少了一个Context对象，不过不重要，只要我们的代码符合开闭原则，我们以设计模式六大原则来编写代码就可以了，严格按照模式来编写代码是没有意义的。