# Kafka Connect TopicRegexRouter SMT Usage Reference for Confluent Cloud The following provides usage information for the Confluent SMT `io.confluent.connect.cloud.transforms.TopicRegexRouter`. #### IMPORTANT TopicRegexRouter is available only for managed [Source connectors](https://docs.confluent.io/cloud/current/connectors/index.html) and JDBC Sink connectors. For the equivalent SMT usage reference for self-managed connectors, see [RegexRouter](https://docs.confluent.io/platform/current/connect/transforms/regexrouter.html). ## Description Update the record’s topic using the configured Re2j regular expression and replacement string. Under the hood, the regex is compiled to a `com.google.re2j.Pattern`. If the pattern matches the input topic, `com.google.re2j.Matcher#replaceFirst()` is used with the replacement string to obtain the new topic. ## Installation This transformation is developed by Confluent and does not ship by default with Apache Kafka® or Confluent Cloud. You can install this transformation using the [confluent connect plugin install](https://docs.confluent.io/confluent-cli/current/command-reference/connect/plugin/confluent_connect_plugin_install.html) command: ```bash confluent connect plugin install confluentinc/connect-transforms:latest ``` ## Examples The following examples show how to configure and use `TopicRegexRouter`. ### Remove a topic prefix This configuration snippet shows how to remove the prefix `soe-` from the beginning of a topic. ```json "transforms": "dropPrefix", "transforms.dropPrefix.type": "io.confluent.connect.cloud.transforms.TopicRegexRouter", "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. ```json "transforms": "AddPrefix", "transforms.AddPrefix.type": "io.confluent.connect.cloud.transforms.TopicRegexRouter", "transforms.AddPrefix.regex": ".*", "transforms.AddPrefix.replacement": "acme_$0" ``` Before: `Order` After: `acme_Order` ### Remove part of a topic name This configuration snippet shows how to remove a string in a topic name. ```json "transforms": "RemoveString", "transforms.RemoveString.type": "io.confluent.connect.cloud.transforms.TopicRegexRouter", "transforms.RemoveString.regex": "(.)Stream_(.)", "transforms.RemoveString.replacement": "$1$2" ``` Before: `Order_Stream_Data` After: `Order_Data` ## Properties | Name | Description | Type | Default | Valid Values | Importance | |---------------|-----------------------------------------|--------|-----------|------------------|--------------| | `regex` | Regular expression to use for matching. | string | | valid Re2j regex | high | | `replacement` | Replacement string. | string | | | high | ## Predicates Transformations can be configured with *predicates* so that the transformation is applied only to records which satisfy a condition. You can use predicates in a transformation chain and, when combined with the [Kafka Connect Filter (Kafka) SMT Usage Reference for Confluent Cloud](filter-ak.md#ak-filter), predicates can conditionally filter out specific records. For details and examples, see [Predicates](filter-ak.md#predicates).