# Avoiding Field Reference Grammer in JSON Parsing

**URL:** https://discuss.elastic.co/t/avoiding-field-reference-grammer-in-json-parsing/177899
**Category:** Logstash
**Created:** [April 22, 2019, 8:33pm UTC](https://discuss.elastic.co/t/avoiding-field-reference-grammer-in-json-parsing/177899 "2019-04-22T20:33:52Z")
**Posts on this page:** 1
**Showing post:** 4

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### Author: ![hal74](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@hal74](https://discuss.elastic.co/u/hal74)
#### Post date: [May 7, 2019, 12:57pm UTC](https://discuss.elastic.co/t/avoiding-field-reference-grammer-in-json-parsing/177899/4 "2019-05-07T12:57:13Z")

</div>

Not much movement on this ☹

Since it seems to be an issue for others, I thought I would post a temporary fix using a ruby filter (ala option 1 and 2 above). This is a temporary strategy, that may or may not work depending on your use case. At least it will stop pipeline crashes in logstash `7.0.0` with forced strict FR Grammar.

This filter will JSON parse a JSON encoded string in the `[data]` field and strip `[` or `]` from any `Hash` keys and set the parsed object back to the `[data]` field:

```
filter {      
  ruby {
    code => "
      def sanitize_field_reference(item)
        case item
        when Hash
          item.keys.each{ |k| item[k.gsub(/[\[\]]/, '')] = sanitize_field_reference(item.delete(k)) }
          return item
        when Array
          return item.map { |e| sanitize_field_reference(e) }
        else
          return item
        end
      end

      event.set('[data]', sanitize_field_reference(JSON.parse(event.get('[data]'))))"
  }
}

```

Would still welcome a more maintainable or production worthy answer regarding decoding valid JSON objects that contain Field Reference Grammar tokens.

Cheers,

Hal

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