.. _regexrouter:

.. meta::
   :title: RegExRouter (org.apache.kafka.connect.transforms.RegexRouter)
   :description: This document provides Confluent usage information for the Apache Kafka single message transform (SMT) org.apache.kafka.connect.transforms.RegexRouter.

===========
RegexRouter
===========

The following provides usage information for the |ak-tm| SMT ``org.apache.kafka.connect.transforms.RegexRouter``.

Description
-----------
Update the record's topic using the configured regular expression and replacement string.

Under the hood, the regex is compiled to a ``java.util.regex.Pattern``. If the pattern matches the input topic, ``java.util.regex.Matcher#replaceFirst()`` is used with the replacement string to obtain the new topic.

Examples
--------

The following examples show how to configure and use ``RegexRouter``.

----------------------
Remove a Topic Prefix
----------------------

This configuration snippet shows how to remove the  prefix ``soe-`` from the
beginning of a topic.

.. sourcecode:: properties

   "transforms":"dropPrefix",
   "transforms.dropPrefix.type":"org.apache.kafka.connect.transforms.RegexRouter",
   "transforms.dropPrefix.regex":"soe-(.*)",
   "transforms.dropPrefix.replacement":"$1"
   
Before: ``soe-Order``

After: ``Order``

-------------------
Add a Topic Prefix
-------------------

This configuration snippet shows how to add the  prefix ``acme_`` to the
beginning of a topic.

.. sourcecode:: properties

   "transforms=AddPrefix"
   "transforms.AddPrefix.type"="org.apache.kafka.connect.transforms.RegexRouter"
   "transforms.AddPrefix.regex=.*"
   "transforms.AddPrefix.replacement=acme_$0"
   
Before: ``Order``

After: ``acme_Order``

Properties
----------

.. list-table::
   :header-rows: 1
   :widths: 15 30 10 10 10 10

   *  - Name
      - Description
      - Type
      - Default
      - Valid Values
      - Importance
   *  - ``regex``
      - Regular expression to use for matching.
      - string
      -
      - valid regex
      - high
   *  - ``replacement``
      - Replacement string.
      - string
      -
      -
      - high