1 前言

一个问题，一篇文章，一出故事。
老板访问NextCloud已删除文件的分享链接,链接范例如下，
https://nextcloud.cmdschool.org/index.php/s/grqtC3nzaNSZ17Qz4Dq8
页面有如下错误提示，

笔者使用如下命令修改NextCloud的配置，

vim /var/www/nextcloud/config/config.php

使用如下配置重新定义程序的日志级别为调试模式，

'loglevel' => 0

然后查看后台发现如下错误提示，

Exception: Call to a member function isReadable() on string in file '/var/www/nextcloud/apps/files_sharing/lib/Controller/ShareController.php' line 318
/var/www/nextcloud/lib/private/AppFramework/App.php - line 164:

OC\AppFramework\Http\Dispatcher->dispatch(OCA\Files_Sh ... {}, "showShare")

/var/www/nextcloud/lib/private/Route/Router.php - line 304:

OC\AppFramework\App::main("OCA\\Files_ ... r", "showShare", OC\AppFramew ... {}, { token: "b7 ... "})

/var/www/nextcloud/lib/base.php - line 1017:

OC\Route\Router->match("/s/grqtC3nzaNSZ17Qz4Dq8")

/var/www/nextcloud/index.php - line 36:

OC::handleRequest()

造成的原因是 Error: Call to a member function isReadable() on string
/var/www/nextcloud/apps/files_sharing/lib/Controller/ShareController.php - line 343:

OCA\Files_Sharing\Controller\ShareController->validateShare(OC\Share20\Share {})

/var/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php - line 217:

OCA\Files_Sharing\Controller\ShareController->showShare("")

/var/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php - line 126:

OC\AppFramework\Http\Dispatcher->executeController(OCA\Files_Sh ... {}, "showShare")

/var/www/nextcloud/lib/private/AppFramework/App.php - line 164:

OC\AppFramework\Http\Dispatcher->dispatch(OCA\Files_Sh ... {}, "showShare")

/var/www/nextcloud/lib/private/Route/Router.php - line 304:

OC\AppFramework\App::main("OCA\\Files_ ... r", "showShare", OC\AppFramew ... {}, { token: "b7 ... "})

/var/www/nextcloud/lib/base.php - line 1017:

OC\Route\Router->match("/s/grqtC3nzaNSZ17Qz4Dq8")

/var/www/nextcloud/index.php - line 36:

OC::handleRequest()

2 最佳实践

2.1 定位错误代码

vim /var/www/nextcloud/apps/files_sharing/lib/Controller/ShareController.php

根据日志的提示定位到318行的代码，

return $share->getNode()->isReadable() && $share->getNode()->isShareable();

注：改行可以找到错误日志中提到的“isReadable()”函数

2.2 调试错误代码

vim /var/www/nextcloud/apps/files_sharing/lib/Controller/ShareController.php

错误行加入如下代码，

var_dump($share->getNode());
die;
return $share->getNode()->isReadable() && $share->getNode()->isShareable();

再次访问错误链接，
https://nextcloud.cmdschool.org/index.php/s/grqtC3nzaNSZ17Qz4Dq8
可见如下提示，

string(0) ""

注：由于文件已经删除，返回的对象为空，所以报错

2.3 修复错误代码

vim /var/www/nextcloud/apps/files_sharing/lib/Controller/ShareController.php

加入如下代码，

if (empty($share->getNode())) {
        return false;
}
return $share->getNode()->isReadable() && $share->getNode()->isShareable();

注：判断如果获取到的文件或目录对象为空，则返回“false”

2.4 测试错误代码

https://nextcloud.cmdschool.org/index.php/s/grqtC3nzaNSZ17Qz4Dq8

参阅文档
=====================
https://docs.nextcloud.com/server/stable/admin_manual/configuration_server/logging_configuration.html