CKSource

CKFinder functionality can be extended with server-side plugins. Although the full source code of the CKFinder server connector is available and can be modified in any way desired, a much better way of enhancing the CKFinder connector is to create a plugin.

The main advantages of plugins are:

Upgrades are much easier.
The plugin code is stored in a single place.
Plugins can be easily disabled when they are not needed anymore.

Common use cases:

Adding a new server-side command (i.e. fileditor and imageresize plugin).
Working with uploaded files (i.e. watermark plugin).
Extending information returned by the Init command (i.e. imageresize plugin).

Creating a plugin

Step1: Create plugin folder

Create a directory for your plugin inside of the "plugins" directory (by default CKFinder comes with three plugins: dummy, fileeditor, imagreresize). Let's use "myplugin" as the plugin name and use the same name for our new folder.

Step2: Create JavaScript plugin

Inside of your plugin's folder ("myplugin") create an empty file named plugin.js.
(If your plugin is a pure server side plugin, you may skip that step)

Step3: Create .dll file with your plugin

// Let's skip that step for now

Step4: Enable plugin

Copy .dll file with a plugin to the "bin" folder of your application
In config.ascx add your plugin to the Plugins list:

Plugins = new string[] {
	// class name, assembly name
	"CKFinder.Plugins.FileSize, CKFinder_FileSize"
};

ASP.NET plugin system

Hooks

CKFinder provides several hooks that can be used to extend the functionality of the CKFinder application. Assigning a function (also known as an event handler) to a hook will cause that function to be called at the appropriate point in the main CKFinder code, to perform whatever additional task(s) the developer thinks would be useful at that point. Each hook can have multiple handlers assigned to it, in which case it will call the functions in the order that they are assigned.

Registering an event handler to a hook is very simple:

// MyBeforeExecuteCommandEventHandler is our custom event handler (method)
CKFinderEvent.BeforeExecuteCommand += 
       new CKFinder.Connector.CKFinderEvent.Hook( this.MyBeforeExecuteCommandEventHandler );

Available hooks (events)

Hook	Since	Description
AfterFileUpload	2.0	Executed after successful file upload.
BeforeExecuteCommand	2.0	Executed before a server side command is executed.
InitCommand	2.0	Executed straight before sending the result of the Init command.

Enabling JavaScript plugin

Sometimes a server side plugin might come with a client side (JavaScript) plugin, that should be automatically enabled when the server side plugin is enabled.
The JavascriptPlugins property is a special variable that does that.

To enable a plugin, simply define it's name (to add multiple plugins, separate their names with a comma).

public string JavascriptPlugins
{
	get { return "myplugin"; }
}

This code is virtually equal to specyfying in config.js:

config.extraPlugins = 'myplugin';

but the advantage of defining it in a plugin is that it will be enabled only when the server side plugin is also enabled.

Sample plugin: FileSize (adding new server side command - complete example)

Introduction

Probably the best way to learn new things is to write a code, so let's write a plugin that adds a new server side command to the connector. We'll create a command that returns a size of a given file.

If you're unfamiliar with CKFinder architecture, please take a look at Server Side Integration documentation. Alternatively, just bear in mind that CKFinder is an AJAX application and that the connection between the user interface running in a browser and the server connector is simply made of AJAX calls to the connector. Check AJAX calls in Firebug to better understand CKFinder.

The FileSize plugin should provide a new command named "FileSize", in other words, calling:

/ckfinder/core/connector/aspx/connector.aspx?command=FileSize&type=Files&currentFolder=%2F&fileName=foobar.jpg

(assuming that foobar.jpg exists) should return a valid XML response:

<Connector resourceType="Files">
<Error number="0"/>
<CurrentFolder path="/" url="/ckfinder/userfiles/files/" acl="255"/>
<FileSize size="5647"/>
</Connector>

Creating project

Let's create a .dll file now.

Create a new C# project (Class Library).
Add reference to CKFinder.dll (right-click "References" in the "Solution Explorer", use "Browse" to select CKFinder.dll from the directory you have saved it).
In Project Properties change Assembly name to CKFinder_FileSize and Default namespace to CKFinder.Plugins
Rename the default file created by VS (Class1.cs) into FileSize.cs.

The whole plugins will be in a single file (FileSize.cs). For the sake of simplicity, let's take a look at Filesize.cs that just does exactly what we need:

namespace CKFinder.Connector.CommandHandlers
{
  // Since we want to send a XML response, we'll extend the XmlCommandHandlerBase class
  public class FileSizeCommandHandler : XmlCommandHandlerBase
  {
    public FileSizeCommandHandler() : base() {}

    // (5) The buildXml method is used to construct an XML response
    protected override void BuildXml()
    {
      string fileName = Request["FileName"];
      string filePath = System.IO.Path.Combine( this.CurrentFolder.ServerPath, fileName );

      long fileSize = new System.IO.FileInfo( filePath ).Length;

      // (6) Adding a <FileSize> element to the XML response.
      XmlNode oFileSize = XmlUtil.AppendElement( this.ConnectorNode, "FileSize" );
      XmlUtil.SetAttribute( oFileSize, "size", fileSize.ToString() );
    }
  }
}

namespace CKFinder.Plugins
{
  public class FileSize : CKFinder.CKFinderPlugin
  {
    public string JavascriptPlugins
    {
      get { return "myplugin"; }
    }

    public void Init( CKFinder.Connector.CKFinderEvent CKFinderEvent )
    {
      // (1) Register our custom BeforeExecuteCommand event handler (MyBeforeExecuteCommandEventHandler function).
      CKFinderEvent.BeforeExecuteCommand += 
            new CKFinder.Connector.CKFinderEvent.Hook( this.MyBeforeExecuteCommandEventHandler );
    }

    // (2) Our event handler
    protected void MyBeforeExecuteCommandEventHandler( object sender, CKFinder.Connector.CKFinderEventArgs args )
    {
      String command = (String)args.data[0];

      // (3) Register the "FileSize" command
      if ( command == "FileSize" )
      {
        HttpResponse Response = (HttpResponse)args.data[1];

        // (4) Our custom class (FileSizeCommandHandler) will do the rest
        CKFinder.Connector.CommandHandlers.CommandHandlerBase commandHandler =
          new CKFinder.Connector.CommandHandlers.FileSizeCommandHandler();

        // The sendResponse method is defined in XmlCommandHandlerBase, it creates 
        // a basic XML response and calls the buildXml()method 
        commandHandler.SendResponse( Response );
      }
    }
  }
}

Step1: Register an event handler

$config['Hooks']['BeforeExecuteCommand'][] = array($CommandHandler_FileSize, "onBeforeExecuteCommand");

Step2: Create a class

If your plugin returns an XML response, you'll usually just extend the XmlCommandHandlerBase class to reduce the amount of code to write, however it is not a requirement.

// (2) Include base XML command handler
require_once CKFINDER_CONNECTOR_LIB_DIR . "/CommandHandler/XmlCommandHandlerBase.php";

// Since we will send a XML response, we'll extend the XmlCommandHandlerBase
class CKFinder_Connector_CommandHandler_FileSize extends CKFinder_Connector_CommandHandler_XmlCommandHandlerBase

Step3: Create an event handler

Our event handler defined in (1) is called "onBeforeExecuteCommand", so let's define such function.

function onBeforeExecuteCommand( &$command )
// ...

Step4: Create the buildXml method

In the onBeforeExecuteCommand method we have called sendResponse. The sendResponse method is defined in XmlCommandHandlerBase class, it creates a basic XML response and calls the buildXml method, which we need to define.

function buildXml()
// ...

Step5: Construct the XML response

The main task of the buildXml method is to construct an XML response, so we're doing it below:

$oNode = new Ckfinder_Connector_Utils_XmlNode("FileSize");
$oNode->addAttribute("size", $size);
$this->_connectorNode->addChild($oNode);

Full source code

plugin.php

The full source code of a plugin with all necessary security checks: (save the code as plugin.php in "plugins/myplugin" folder)

<?php

// A simple protection against calling this file directly.
if (!defined('IN_CKFINDER')) exit;

// Include base XML command handler
require_once CKFINDER_CONNECTOR_LIB_DIR . "/CommandHandler/XmlCommandHandlerBase.php";

// Since we will send a XML response, we'll reuse the XmlCommandHandler
class CKFinder_Connector_CommandHandler_FileSize extends CKFinder_Connector_CommandHandler_XmlCommandHandlerBase
{
    // The buildXml method is used to construct an XML response
    function buildXml()
    {
        // A "must have", checking whether the connector is enabled and the basic parameters (like current folder) are safe.
        $this->checkConnector();
        $this->checkRequest();

        // Checking ACL permissions, we're just getting an information about a file, so FILE_VIEW permission seems to be ok.
        if (!$this->_currentFolder->checkAcl(CKFINDER_CONNECTOR_ACL_FILE_VIEW)) {
            $this->_errorHandler->throwError(CKFINDER_CONNECTOR_ERROR_UNAUTHORIZED);
        }

        // Make sure we actually received a file name
        if (!isset($_GET["fileName"])) {
            $this->_errorHandler->throwError(CKFINDER_CONNECTOR_ERROR_INVALID_NAME);
        }

        $fileName = CKFinder_Connector_Utils_FileSystem::convertToFilesystemEncoding($_GET["fileName"]);
        $resourceTypeInfo = $this->_currentFolder->getResourceTypeConfig();

        // Use the resource type configuration object to check whether the extension of a file to check is really allowed.
        if (!$resourceTypeInfo->checkExtension($fileName)) {
            $this->_errorHandler->throwError(CKFINDER_CONNECTOR_ERROR_INVALID_EXTENSION);
        }

        // Make sure that the file name is really ok and has not been sent by a hacker
        if (!CKFinder_Connector_Utils_FileSystem::checkFileName($fileName) || $resourceTypeInfo->checkIsHiddenFile($fileName)) {
            $this->_errorHandler->throwError(CKFINDER_CONNECTOR_ERROR_INVALID_REQUEST);
        }

        $filePath = CKFinder_Connector_Utils_FileSystem::combinePaths($this->_currentFolder->getServerPath(), $fileName);

        if (!file_exists($filePath) || !is_file($filePath)) {
            $this->_errorHandler->throwError(CKFINDER_CONNECTOR_ERROR_FILE_NOT_FOUND);
        }

        $size = filesize($filePath);

        // *** The main part of this plugin ****
        // Adding a <FileSize> element to the XML response.
        $oNode = new Ckfinder_Connector_Utils_XmlNode("FileSize");
        $oNode->addAttribute("size", $size);
        $this->_connectorNode->addChild($oNode);
    }

    // Register the "FileSize" command
    function onBeforeExecuteCommand( &$command )
    {
        if ( $command == 'FileSize' )
        {
            // The sendResponse method is defined in XmlCommandHandlerBase, it creates 
            // a basic XML response and calls the buildXml()method 
            $this->sendResponse();
            // false = stop further execution.
            return false;
        }

        return true ;
    }
}

$CommandHandler_FileSize = new CKFinder_Connector_CommandHandler_FileSize();
// Register the onBeforeExecuteCommand method to be called by the BeforeExecuteCommand hook.
$config['Hooks']['BeforeExecuteCommand'][] = array($CommandHandler_FileSize, "onBeforeExecuteCommand");
// (Optional) Register a javascript plugin named "myplugin"
$config['Plugins'][] = 'myplugin';

plugin.js

.. and the client side (JavaScript) plugin that will call the FileSize command: (save the code as plugin.js in "plugins/myplugin" folder)

CKFinder.addPlugin( 'myplugin', function( api ) {
	api.addFileContextMenuOption( { label : 'File Size', command : "FileSize" } , function( api, file )
	{
		api.connector.sendCommand( 'FileSize', { fileName : api.getSelectedFile().name }, function( xml )
		{
			if ( xml.checkError() )
				return;

			var size = xml.selectSingleNode( 'Connector/FileSize/@size' );
			api.openMsgDialog( "", "The exact size of a file is: " + size.value + " bytes");
		} );
	});
});