# Kafka Connect ReplaceField (Confluent) SMT Usage Reference for Confluent Cloud The following provides usage information for the Confluent SMT `io.confluent.connect.transforms.ReplaceField`. ## Description Filter or rename fields within a Struct or Map. Use the concrete transformation type designed for the record key (`io.confluent.connect.transforms.ReplaceField$Key`) or value (`io.confluent.connect.transforms.ReplaceField$Value`). ## Examples These examples show how to configure and use `ReplaceField` to drop or rename a field. ### `Including all fields` The configuration snippet shows how to use `ReplaceField` transformation to exclude the `dont` field, and rename specific nested fields within the `foo` structure to `xyz`, `bar`, `luck`, and `happy` respectively. ```json "transforms": "ReplaceField", "transforms.ReplaceField.type": "io.confluent.connect.transforms.ReplaceField$Value", "transforms.ReplaceField.exclude": "dont", "transforms.ReplaceField.renames": "foo.a2:xyz,foo:bar,foo.a3.b1:luck,foo.a3.b2.c1:happy" ``` This transforms the original message as seen below: Before: `{abc=42, etc=etc, foo={a1=k1, a2={b2={c1=f4}, b1={c1=f4}}, a3={b2={c1=f4}, b1={c1=f4}}}, dont=whatever}` After: `{etc=etc, bar={a1=k1, a3={b2={happy=f4}, luck={c1=f4}}, xyz={b2={c1=f4}, b1={c1=f4}}}, abc=42}` ### `Including one-level field` The configuration snippet shows how to use `ReplaceField` transformation to exclude the `dont` field, include only the `foo.a3` field, and rename specific fields within the `foo` to `xyz`, `bar`, `luck`, and `happy`. ```json "transforms": "ReplaceField", "transforms.ReplaceField.type": "io.confluent.connect.transforms.ReplaceField$Value", "transforms.ReplaceField.exclude": "dont", "transforms.ReplaceField.renames": "foo.a2:xyz,foo:bar,foo.a3.b1:luck,foo.a3.b2.c1:happy", "transforms.ReplaceField.include": "foo.a3" ``` This transforms the original message as seen below: Before: `{abc=42, etc=etc, foo={a1=k1, a2={b2={c1=f4}, b1={c1=f4}}, a3={b2={c1=f4}, b1={c1=f4}}}, dont=whatever}` After: `{foo={a3={b2={happy=f4}, luck={c1=f4}}}}` ### `Including multi-level fields` The configuration snippet shows how to use `ReplaceField` transformation to exclude the `dont` field, include only the `foo.a3.b2.c1` and `foo.a2` fields, and rename specific fields within the `foo` to `xyz`, `bar`, `luck`, and `happy`. ```json "transforms": "ReplaceField", "transforms.ReplaceField.type": "io.confluent.connect.transforms.ReplaceField$Value", "transforms.ReplaceField.exclude": "dont", "transforms.ReplaceField.renames": "foo.a2:xyz,foo:bar,foo.a3.b1:luck,foo.a3.b2.c1:happy", "transforms.ReplaceField.include": "foo.a3.b2.c1,foo.a2" ``` This transforms the original message as seen below: Before: `{abc=42, etc=etc, foo={a1=k1, a2={b2={c1=f4}, b1={c1=f4}}, a3={b2={c1=f4}, b1={c1=f4}}}, dont=whatever}` After: `{foo={a3={b2={happy=f4}}, xyz={b2={c1=f4}, b1={c1=f4}}}}` ### `Excluding multi-level fields` The configuration snippet shows how to use `ReplaceField` transformation to exclude the `dont`, `foo.a1`, `foo.a2.b2`, `foo.a3.b1.c1` fields, and rename specific fields within the `foo` to `xyz`, `bar`, `luck`, and `happy`. ```json "transforms": "ReplaceField", "transforms.ReplaceField.type": "io.confluent.connect.transforms.ReplaceField$Value", "transforms.ReplaceField.exclude": "dont,foo.a1,foo.a2.b2,foo.a3.b1.c1", "transforms.ReplaceField.renames": "foo.a2:xyz,foo:bar,foo.a3.b1:luck,foo.a3.b2.c1:happy", "transforms.ReplaceField.include": "" ``` This transforms the original message as seen below: Before: `{abc=42, etc=etc, foo={a1=k1, a2={b2={c1=f4}, b1={c1=f4}}, a3={b2={c1=f4}, b1={c1=f4}}}, dont=whatever}` After: `{etc=etc, bar={a3={b2={happy=f4}, luck={}}, xyz={b1={c1=f4}}}, abc=42}` ### `Excluding none` The configuration snippet shows how to use `ReplaceField` transformation to only rename specific fields within the `foo` to `xyz`, `bar`, `luck`, and `happy` without excluding or including any fields. ```json "transforms": "ReplaceField", "transforms.ReplaceField.type": "io.confluent.connect.transforms.ReplaceField$Value", "transforms.ReplaceField.exclude": "", "transforms.ReplaceField.renames": "foo.a2:xyz,foo:bar,foo.a3.b1:luck,foo.a3.b2.c1:happy", "transforms.ReplaceField.include": "" ``` This transforms the original message as seen below: Before: `{abc=42, etc=etc, foo={a1=k1, a2={b2={c1=f4}, b1={c1=f4}}, a3={b2={c1=f4}, b1={c1=f4}}}, dont=whatever}` After: `{bar={a1=k1, a3={b2={happy=f4}, luck={c1=f4}}, xyz={b2={c1=f4}, b1={c1=f4}}}, abc=42, etc=etc, dont=whatever}` ### `Fields in both including and excluding lists` The configuration snippet shows how to use `ReplaceField` transformation to rename certain fields, while also specifying which fields to include or exclude. In the following example, only included fields should be subject to renaming and transformed in the final output. ```json "transforms": "ReplaceField", "transforms.ReplaceField.type": "io.confluent.connect.transforms.ReplaceField$Value", "transforms.ReplaceField.exclude": "foo.a1,foo.a2", "transforms.ReplaceField.renames": "foo.a2:xyz,foo:bar,foo.a3.b1:luck,foo.a3.b2.c1:happy", "transforms.ReplaceField.include": "foo.a2,foo.a3.b2.c1" ``` This transforms the original message as seen below: Before: `{abc=42, etc=etc, foo={a1=k1, a2={b2={c1=f4}, b1={c1=f4}}, a3={b2={c1=f4}, b1={c1=f4}}}, dont=whatever}` After: `{foo={a3={b2={happy=f4}}}}` ## Properties | Name | Description | Type | Default | Valid Values | Importance | |-----------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------|-----------|------------------------------------------------------------------------------------|--------------| | `exclude` | Fields to exclude from the resulting Struct or Map. This takes
precedence over the include list. | list | “” | Comma-separated list of fields to exclude. | medium | | `renames` | Field rename mappings. For example, a nested field renaming list is `foo.a3.c1:bar,abc.c2.d2:def`. Here, `foo.a3.c1` represents the field `c1` to be renamed to `bar` value. Similarly, `abc.c2.d2` represents the field `d2` to be renamed to `def` value. | list | “” | Comma-separated list of colon-delimited renaming pairs, e.g.
`foo:bar,abc:xyz` | medium | | `include` | Fields to include. If specified, only the named fields will be included
in the resulting Struct or Map. | list | “” | Comma-separated list of fields to include. | medium | | `replace.null.with.default` | Fields to replace null with the default value. If set to `true`, it replaces null with the default value.
Otherwise, leave them as null. | boolean | “” | true or false | medium | | `delimiter` | Special characters act as a delimiter.
For example, a period (.) in `foo.a3.c1`. | string | “.” | Special characters. For example, `$, -` and cannot be a colon (:). | medium | ## 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).