NiFi | How to replace text based on length of field in JSON records

Question

I have data coming into NiFi in JSON format. Below is the sample

{
  "company_name": "mycompany",
  "companytyp": "producer",
  "Welcomemes": "welcome_message1",
  "logo": "//somepath/to/logo URL "
}

I have been trying to apply a JOLT transformation for the following condition:

• If the length of logo field is more than 10 characters then replace it with blank value
• If the length of logo field is less than or equal to 10 characters then keep the provided value

I have not been able to achieve this. Would really appreciate some help & guidance. I am open to using any other processor too but the preference will be JOLT transformation

Input 1:

{
  "company_name": "mycompany",
  "companytyp": "producer",
  "Welcomemes": "welcome_message1",
  "logo": "This logo value is more than 10 characters "
}

Expected Output 1

{
  "company_name": "mycompany",
  "companytyp": "producer",
  "Welcomemes": "welcome_message1",
  "logo": ""
}

Input 2:

  "company_name": "mycompany",
  "companytyp": "producer",
  "Welcomemes": "welcome_message1",
  "logo": "short logo"
}

Expected Output 2

{
  "company_name": "mycompany",
  "companytyp": "producer",
  "Welcomemes": "welcome_message1",
  "logo": "short logo"
}

Answer 1

I couldn't figure out how to put in an empty string but this spec will replace those logo fields with a single space:

[
  {
    "operation": "modify-overwrite-beta",
    "spec": {
      "logo": "=substring(@(1,logo),0,11)",
      "logo_size": "=size(@(1,logo))"
    }
  },
  {
    "operation": "shift",
    "spec": {
      "logo_size": {
        "11": {
          "# ": "logo"
        },
        "*": {
          "@(2,logo)": "logo"
        }
      },
      "logo": null,
      "*": "&"
    }
  }
]