我们在写代码时，都想自己的代码尽可能的不影响现有的代码。

或者说，最大化不改动任何代码的情况下，如何嵌入我们的新功能？这是我们常说的「非侵入式」的开发方式。

使用「非侵入式」的开发模式，主要在提供第三方插件和功能中最为常见。今天借助「Rollbar」第三方工具来说说如何做到「非侵入式」开发。

本文主要能学到:

1. Laravel Event / Listener 原理；
2. Rollbar for Laravel 的使用
3. 创建一个 Log to Dingding 群的功能

Laravel Event / Listener 原理

在 Laravel，主要利用 EventServiceProvider 来加载 Events / Listeners:

<?phpnamespace Illuminate\Events;use Illuminate\Support\ServiceProvider;
use Illuminate\Contracts\Queue\Factory as QueueFactoryContract;class EventServiceProvider extends ServiceProvider
{/*** Register the service provider.** @return void*/public function register(){$this->app->singleton('events', function ($app) {return (new Dispatcher($app))->setQueueResolver(function () use ($app) {return $app->make(QueueFactoryContract::class);});});}
}
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EventServiceProvider 返回的是 Dispatcher 对象。我们看看 Dispatcher 类：

<?phpnamespace Illuminate\Events;use Exception;
use ReflectionClass;
use Illuminate\Support\Arr;
use Illuminate\Support\Str;
use Illuminate\Container\Container;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Contracts\Broadcasting\ShouldBroadcast;
use Illuminate\Contracts\Events\Dispatcher as DispatcherContract;
use Illuminate\Contracts\Broadcasting\Factory as BroadcastFactory;
use Illuminate\Contracts\Container\Container as ContainerContract;class Dispatcher implements DispatcherContract
{/*** The IoC container instance.** @var \Illuminate\Contracts\Container\Container*/protected $container;/*** The registered event listeners.** @var array*/protected $listeners = [];/*** The wildcard listeners.** @var array*/protected $wildcards = [];/*** The queue resolver instance.** @var callable*/protected $queueResolver;/*** Create a new event dispatcher instance.** @param  \Illuminate\Contracts\Container\Container|null  $container* @return void*/public function __construct(ContainerContract $container = null){$this->container = $container ?: new Container;}/*** Register an event listener with the dispatcher.** @param  string|array  $events* @param  mixed  $listener* @return void*/public function listen($events, $listener){foreach ((array) $events as $event) {if (Str::contains($event, '*')) {$this->setupWildcardListen($event, $listener);} else {$this->listeners[$event][] = $this->makeListener($listener);}}}...}
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主要作用是绑定 Events 和 Listeners，当 Events触发时，直接执行 Listeners。

我们希望 log 除了在本地文件存储输出外，也想把 log 信息实时发到其他平台和渠道上，这时候我们就需要借助 LogServiceProvider 的 events / listeners绑定实现了。现在来看看 LogServiceProvider:

<?phpnamespace Illuminate\Log;use Monolog\Logger as Monolog;
use Illuminate\Support\ServiceProvider;class LogServiceProvider extends ServiceProvider
{/*** Register the service provider.** @return void*/public function register(){$this->app->singleton('log', function () {return $this->createLogger();});}/*** Create the logger.** @return \Illuminate\Log\Writer*/public function createLogger(){$log = new Writer(new Monolog($this->channel()), $this->app['events']);if ($this->app->hasMonologConfigurator()) {call_user_func($this->app->getMonologConfigurator(), $log->getMonolog());} else {$this->configureHandler($log);}return $log;}...
}
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这里将 $this->app['events'] 也就是 Dispatcher 传入，用户事件的注册：

    /*** 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);}
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有了 ServiceProvider 和 listen 就可以做到「非入侵」开发了。

Rollbar

Rollbar error monitoring integration for Laravel projects. This library adds a listener to Laravel's logging component. Laravel's session information will be sent in to Rollbar, as well as some other helpful information such as 'environment', 'server', and 'session'.

参考：docs.rollbar.com/docs/larave…

简单使用

使用该工具，只要在其官网注册账号，并产生一个 access token 即可

安装该工具，也只需要简单的两步：

composer require rollbar/rollbar-laravel// .env
ROLLBAR_TOKEN=[your Rollbar project access token]// 如果 < Laravel 5.5，则需要在 app.php 中添加
Rollbar\Laravel\RollbarServiceProvider::class,
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测试，只要有 Log 输出，rollbar 后台都可以收到信息，方便查看，而再也不需要去看 log 文件了。

剖析实现原理

我们来看看 rollbar 是不是我们所设想的那样实现的？

我们先看看 RollbarServiceProvider

<?php namespace Rollbar\Laravel;use Illuminate\Support\ServiceProvider;
use InvalidArgumentException;
use Rollbar\Rollbar;
use Rollbar\Laravel\RollbarLogHandler;class RollbarServiceProvider extends ServiceProvider
{/*** Indicates if loading of the provider is deferred.** @var bool*/protected $defer = false;/*** Bootstrap the application events.*/public function boot(){// Don't boot rollbar if it is not configured.if ($this->stop() === true) {return;}$app = $this->app;// Listen to log messages.$app['log']->listen(function () use ($app) {$args = func_get_args();// Laravel 5.4 returns a MessageLogged instance onlyif (count($args) == 1) {$level = $args[0]->level;$message = $args[0]->message;$context = $args[0]->context;} else {$level = $args[0];$message = $args[1];$context = $args[2];}$app['Rollbar\Laravel\RollbarLogHandler']->log($level, $message, $context);});}/*** Register the service provider.*/public function register(){// Don't register rollbar if it is not configured.if ($this->stop() === true) {return;}$app = $this->app;$this->app->singleton('Rollbar\RollbarLogger', function ($app) {$defaults = ['environment'       => $app->environment(),'root'              => base_path(),'handle_exception'  => true,'handle_error'      => true,'handle_fatal'      => true,];$config = array_merge($defaults, $app['config']->get('services.rollbar', []));$config['access_token'] = getenv('ROLLBAR_TOKEN') ?: $app['config']->get('services.rollbar.access_token');if (empty($config['access_token'])) {throw new InvalidArgumentException('Rollbar access token not configured');}$handleException = (bool) array_pull($config, 'handle_exception');$handleError = (bool) array_pull($config, 'handle_error');$handleFatal = (bool) array_pull($config, 'handle_fatal');Rollbar::init($config, $handleException, $handleError, $handleFatal);return Rollbar::logger();});$this->app->singleton('Rollbar\Laravel\RollbarLogHandler', function ($app) {$level = getenv('ROLLBAR_LEVEL') ?: $app['config']->get('services.rollbar.level', 'debug');return new RollbarLogHandler($app['Rollbar\RollbarLogger'], $app, $level);});}/*** Check if we should prevent the service from registering** @return boolean*/public function stop(){$level = getenv('ROLLBAR_LEVEL') ?: $this->app->config->get('services.rollbar.level', null);$token = getenv('ROLLBAR_TOKEN') ?: $this->app->config->get('services.rollbar.access_token', null);$hasToken = empty($token) === false;return $hasToken === false || $level === 'none';}
}
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这个比较好理解，先利用 register 注册两个 singleton，然后在 boot 方法中，注册 listener

    $app['log']->listen(function () use ($app){});
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其中 $app['log']，就是我们的上文说的 LogServiceProvider，将 listener 注册到 EventServiceProvider 中。

$this->dispatcher->listen(MessageLogged::class, $callback);
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最后我们看看 Rollbar facades 返回的是：RollbarLogHandler 对象

<?php namespace Rollbar\Laravel\Facades;use Illuminate\Support\Facades\Facade;class Rollbar extends Facade
{/*** Get a schema builder instance for the default connection.** @return \Rollbar\Laravel\RollbarLogHandler*/protected static function getFacadeAccessor(){return 'Rollbar\Laravel\RollbarLogHandler';}
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看看 RollbarLogHandler 实现，也主要是将 log 信息反馈到Rollbar 中，此处不做分析了。

模拟实现

通过对 Rollbar 简单的分析，就会发现原来通过简单 Listener，不用改现在的任何功能和代码，就能实现将 log 实时发到你想接收的地方。

所以我们可以尝试也写一个这样的功能，将 log 信息发到钉钉上。

好了，我们开始写 Log2Dingding 插件。

根据之前的文章我们可以很方便的组织好插件结构:

composer.json 设置:

{"name": "fanly/log2dingding","description": "Laravel Log to DingDing","license": "MIT","authors": [{"name": "fanly","email": "yemeishu@126.com"}],"require": {},"extra": {"laravel": {"providers": ["Fanly\\Log2dingding\\FanlyLog2dingdingServiceProvider"]}},"autoload": {"psr-4": {"Fanly\\Log2dingding\\": "src/"}}
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我们定义 ServiceProvider:

<?php
/*** User: yemeishu* Date: 2018/5/13* Time: 下午2:56*/
namespace Fanly\Log2dingding;use Fanly\Log2dingding\Dingtalk\Messager;
use Illuminate\Support\ServiceProvider;
use Fanly\Log2dingding\Support\Client;class FanlyLog2dingdingServiceProvider extends ServiceProvider {protected function registerFacade(){// Don't register rollbar if it is not configured.if ($this->stop() === true) {return;}$this->app->singleton('fanlylog2dd', function ($app) {$config['access_token'] = getenv('FANLYLOG_TOKEN') ?: $app['config']->get('services.fanly.log2dd.access_token');if (empty($config['access_token'])) {throw new InvalidArgumentException('log2dd access token not configured');}return (new Messager(new Client()))->accessToken($config['access_token']);});}/*** Bootstrap the application services.*/public function boot(){// Don't boot rollbar if it is not configured.if ($this->stop() === true) {return;}$app = $this->app;// Listen to log messages.$app['log']->listen(function () use ($app) {$args = func_get_args();// Laravel 5.4 returns a MessageLogged instance onlyif (count($args) == 1) {$level = $args[0]->level;$message = $args[0]->message;$context = $args[0]->context;} else {$level = $args[0];$message = $args[1];$context = $args[2];}$app['fanlylog2dd']->message("[ $level ] $message\n".implode($context))->send();});}/*** Register the application services.*/public function register(){$this->registerFacade();}private function stop(){$level = getenv('FANLYLOG_LEVEL') ?: $this->app->config->get('services.rollbar.level', null);$token = getenv('FANLYLOG_TOKEN') ?: $this->app->config->get('services.rollbar.access_token', null);$hasToken = empty($token) === false;return $hasToken === false || $level === 'none';}
}
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我们主要是创建一个发钉钉消息的单例，然后再注册 listener，只要获取 log 信息，就发送信息到钉钉上。

测试一下：

总结

最后做成插件，和 Rollbar 一样，引入：

composer require "fanly/log2dingding"// .env
FANLYLOG_TOKEN=56331868f7056a3e645e7dba034c5550e7af***
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同样的，其他信息都不需要设置，跑一个测试：

Laravel 框架的一大好处在于，可以以友好的方式实现我们「非入侵」开发，只要借助「ServiceProvider」和「Events/Listner」，就可以扩展我们的功能。

参考

• 「12步」制作 Laravel 插件 (一)mp.weixin.qq.com/s/AD05BiKjP…
• 「3步」发布 Laravel 插件 (二)mp.weixin.qq.com/s/RSYeHU7aR…
• fanly/log2dingding packagist.org/packages/fa…