..  include:: /Includes.rst.txt
..  _tce-introduction:
..  _datahandler-introduction:

============
Introduction
============

..  index::
    pair: DataHandler; Database
    pair: DataHandler; TCA
..  _tce-database:
..  _datahandler-database:

Database
========

The DataHandler is the class that handles **all** :ref:`data <datahandler-data>`
writing to database tables configured in TCA. In addition the class handles
:ref:`commands <datahandler-commands>` such as copy, move, delete. It will handle
undo/history and versioning of records and everything will be logged
to the :sql:`sys_log` table. It will make sure that write permissions are
evaluated correctly for the user trying to write to the database. Generally,
any processing specific option in the :php:`$GLOBALS['TCA']` array is handled
by DataHandler.

Using DataHandler for manipulation of the database content in the TCA-configured
tables guarantees that the data integrity of TYPO3 is
respected. This cannot be safely guaranteed, if you write to TCA-configured
database tables directly. It will also manage the relations
to files and other records.

DataHandler requires a backend login to work. This is due to the fact that
permissions are observed (of course) and thus DataHandler needs a backend user
to evaluate against. This means you cannot use DataHandler from the
frontend scope. Thus writing to tables (such as a guestbook) will have
to be done from the frontend *without* DataHandler.

..  seealso::
    The features of TCA are described in the :ref:`TCA Reference <t3tca:start>`.

..  index:: pair: DataHandler; Files
..  _tce-files:
..  _datahandler-files:

Files
=====

DataHandler can also handle files. The file operations are normally
performed in the :guilabel:`File > Filelist` module where you can manage a
directory on the server by copying, moving, deleting and editing files
and directories. The file operations are managed by two Core classes,
:php:`\TYPO3\CMS\Core\Utility\File\BasicFileUtility` and
:php:`\TYPO3\CMS\Core\Utility\File\ExtendedFileUtility`.