Laravel-Log

思考并回答以下问题：

源码

Illuminate\Log\Logger.php

<?php

namespace Illuminate\Log;

use Closuore;
use Illuminate\Contracts\Events\Dispatcher;
use Illuminate\Contracts\Support\Arrayable;
use Illuminate\Contracts\Support\Jsonable;
use Illuminate\Log\Events\MessageLogged;
use Psr\Log\LoggerInterface;
use RuntimeException;

class Logger implements LoggerInterface
{
    /**
     * The underlying logger implementation.
     *
     * @var \Psr\Log\LoggerInterface
     */
    protected $logger;

    /**
     * The event dispatcher instance.
     *
     * @var \Illuminate\Contracts\Events\Dispatcher|null
     */
    protected $dispatcher;

    /**
     * Create a new log writer instance.
     *
     * @param  \Psr\Log\LoggerInterface  $logger
     * @param  \Illuminate\Contracts\Events\Dispatcher|null  $dispatcher
     * @return void
     */
    public function __construct(LoggerInterface $logger, Dispatcher $dispatcher = null)
    {
        $this->logger = $logger;
        $this->dispatcher = $dispatcher;
    }

    /**
     * Log an emergency message to the logs.
     *
     * @param  string  $message
     * @param  array  $context
     * @return void
     */
    public function emergency($message, array $context = [])
    {
        $this->writeLog(__FUNCTION__, $message, $context);
    }

    /**
     * Log a message to the logs.
     *
     * @param  string  $level
     * @param  string  $message
     * @param  array  $context
     * @return void
     */
    public function log($level, $message, array $context = [])
    {
        $this->writeLog($level, $message, $context);
    }

    /**
     * Dynamically pass log calls into the writer.
     *
     * @param  string  $level
     * @param  string  $message
     * @param  array  $context
     * @return void
     */
    public function write($level, $message, array $context = [])
    {
        $this->writeLog($level, $message, $context);
    }

    /**
     * Write a message to the log.
     *
     * @param  string  $level
     * @param  string  $message
     * @param  array  $context
     * @return void
     */
    protected function writeLog($level, $message, $context)
    {
        $this->logger->{$level}($message = $this->formatMessage($message), $context);

        $this->fireLogEvent($level, $message, $context);
    }

    /**
     * Register a new callback handler for when a log event is triggered.
     *
     * @param  \Closure  $callback
     * @return void
     *
     * @throws \RuntimeException
     */
    public function listen(Closure $callback)
    {
        if (! isset($this->dispatcher)) 
        {
            throw new RuntimeException('Events dispatcher has not been set.');
        }

        $this->dispatcher->listen(MessageLogged::class, $callback);
    }

    /**
     * Fires a log event.
     *
     * @param  string  $level
     * @param  string  $message
     * @param  array  $context
     * @return void
     */
    protected function fireLogEvent($level, $message, array $context = [])
    {
        // 如果设置了事件分配器，则将参数传递给日志侦听器。 
        // 这些对于构建概要分析器或其他工具（在给定的“请求”周期内汇总所有日志消息）很有用。
        if (isset($this->dispatcher)) {
            $this->dispatcher->dispatch(new MessageLogged($level, $message, $context));
        }
    }

    /**
     * Format the parameters for the logger.
     *
     * @param  mixed  $message
     * @return mixed
     */
    protected function formatMessage($message)
    {
        if (is_array($message)) 
        {
            return var_export($message, true);
        } 
        elseif ($message instanceof Jsonable) 
        {
            return $message->toJson();
        } 
        elseif ($message instanceof Arrayable) 
        {
            return var_export($message->toArray(), true);
        }

        return $message;
    }

    /**
     * Get the underlying logger implementation.
     *
     * @return \Psr\Log\LoggerInterface
     */
    public function getLogger()
    {
        return $this->logger;
    }

    /**
     * Get the event dispatcher instance.
     *
     * @return \Illuminate\Contracts\Events\Dispatcher
     */
    public function getEventDispatcher()
    {
        return $this->dispatcher;
    }

    /**
     * Set the event dispatcher instance.
     *
     * @param  \Illuminate\Contracts\Events\Dispatcher  $dispatcher
     * @return void
     */
    public function setEventDispatcher(Dispatcher $dispatcher)
    {
        $this->dispatcher = $dispatcher;
    }

    /**
     * Dynamically proxy method calls to the underlying logger.
     *
     * @param  string  $method
     * @param  array  $parameters
     * @return mixed
     */
    public function __call($method, $parameters)
    {
        return $this->logger->{$method}(...$parameters);
    }
}

Illuminate\Mail\Events\MessageSending.php

<?php

namespace Illuminate\Mail\Events;

class MessageSending
{
    /**
     * The Swift message instance.
     *
     * @var \Swift_Message
     */
    public $message;

    /**
     * The message data.
     *
     * @var array
     */
    public $data;

    /**
     * Create a new event instance.
     *
     * @param  \Swift_Message  $message
     * @param  array  $data
     * @return void
     */
    public function __construct($message, $data = [])
    {
        $this->data = $data;
        $this->message = $message;
    }
}

Illuminate\Log\ParsesLogConfiguration.php

namespace Illuminate\Log;

use InvalidArgumentException;
use Monolog\Logger as Monolog;

trait ParsesLogConfiguration
{
    /**
     * The Log levels.
     *
     * @var array
     */
    protected $levels = [
        'debug'     => Monolog::DEBUG,
        'info'      => Monolog::INFO,
        'notice'    => Monolog::NOTICE,
        'warning'   => Monolog::WARNING,
        'error'     => Monolog::ERROR,
        'critical'  => Monolog::CRITICAL,
        'alert'     => Monolog::ALERT,
        'emergency' => Monolog::EMERGENCY,
    ];

    /**
     * Get fallback log channel name.
     *
     * @return string
     */
    abstract protected function getFallbackChannelName();

    /**
     * Parse the string level into a Monolog constant.
     *
     * @param  array  $config
     * @return int
     *
     * @throws \InvalidArgumentException
     */
    protected function level(array $config)
    {
        $level = $config['level'] ?? 'debug';

        if (isset($this->levels[$level])) {
            return $this->levels[$level];
        }

        throw new InvalidArgumentException('Invalid log level.');
    }

    /**
     * Extract the log channel from the given configuration.
     *
     * @param  array  $config
     * @return string
     */
    protected function parseChannel(array $config)
    {
        return $config['name'] ?? $this->getFallbackChannelName();
    }
}

Illuminate\Log\LogServiceProvider

<?php

namespace Illuminate\Log;

use Illuminate\Support\ServiceProvider;

class LogServiceProvider extends ServiceProvider
{
    /**
     * Register the service provider.
     *
     * @return void
     */
    public function register()
    {
        $this->app->singleton('log', function ($app) {
            return new LogManager($app);
        });
    }
}

Illuminate\Log\LogManager.php

<?php

namespace Illuminate\Log;

use Closure;
use Illuminate\Support\Str;
use InvalidArgumentException;
use Monolog\Formatter\LineFormatter;
use Monolog\Handler\ErrorLogHandler;
use Monolog\Handler\FormattableHandlerInterface;
use Monolog\Handler\HandlerInterface;
use Monolog\Handler\RotatingFileHandler;
use Monolog\Handler\SlackWebhookHandler;
use Monolog\Handler\StreamHandler;
use Monolog\Handler\SyslogHandler;
use Monolog\Handler\WhatFailureGroupHandler;
use Monolog\Logger as Monolog;
use Psr\Log\LoggerInterface;
use Throwable;

class LogManager implements LoggerInterface
{
    use ParsesLogConfiguration;

    /**
     * The application instance.
     *
     * @var \Illuminate\Contracts\Foundation\Application
     */
    protected $app;

    /**
     * The array of resolved channels.
     *
     * @var array
     */
    protected $channels = [];

    /**
     * The registered custom driver creators.
     *
     * @var array
     */
    protected $customCreators = [];

    /**
     * The standard date format to use when writing logs.
     *
     * @var string
     */
    protected $dateFormat = 'Y-m-d H:i:s';

    /**
     * Create a new Log manager instance.
     *
     * @param  \Illuminate\Contracts\Foundation\Application  $app
     * @return void
     */
    public function __construct($app)
    {
        $this->app = $app;
    }

    /**
     * Register a custom driver creator Closure.
     *
     * @param  string  $driver
     * @param  \Closure  $callback
     * @return $this
     */
    public function extend($driver, Closure $callback)
    {
        $this->customCreators[$driver] = $callback->bindTo($this, $this);

        return $this;
    }
}