# Can I use conditionals inside json {} filter?

**URL:** <https://discuss.elastic.co/t/can-i-use-conditionals-inside-json-filter/311547>\
**Category:** Logstash\
**Created:** [August 5, 2022, 2:05pm UTC](https://discuss.elastic.co/t/can-i-use-conditionals-inside-json-filter/311547 "2022-08-05T14:05:55Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![mfloris](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/mfloris/32/100500_2.png) [@mfloris](https://discuss.elastic.co/u/mfloris)\
**Post date:** [August 5, 2022, 2:05pm UTC](https://discuss.elastic.co/t/can-i-use-conditionals-inside-json-filter/311547/1 "2022-08-05T14:05:55Z")

</div>

My input does not always contain some fields and I want to parse it accordingly, like this:

```auto
filter {
  json {
    source => "message"
    if "thisField" in [message] {
      add_field => { "MyField" => "%{[message][thisField]}" }
    } else {
      add_field => { "MyField" => "empty" }
    }
  }
}

```

I'm getting syntax errors and I can't find examples of what I'm doing online, therefore I suspect it's not allowed. Is it? If not, what other path could I follow?

---

<div class="post-metadata">

**Author:** ![Badger](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/badger/32/25190_2.png) [@Badger](https://discuss.elastic.co/u/Badger)\
**Post date:** [August 5, 2022, 2:40pm UTC](https://discuss.elastic.co/t/can-i-use-conditionals-inside-json-filter/311547/2 "2022-08-05T14:40:07Z")

</div>

You cannot use conditionals inside a plugin configuration. You can do

```
json { source => "message" }
if "thisField" in [message] {
    mutate { add_field => { "MyField" => "%{[message][thisField]}" } }
} else {
    mutate { add_field => { "MyField" => "empty" } }
}

```

Although I suspect the %{[message][thisField]} reference is wrong.

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [September 2, 2022, 2:40pm UTC](https://discuss.elastic.co/t/can-i-use-conditionals-inside-json-filter/311547/3 "2022-09-02T14:40:15Z")

</div>

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