Batch Metadata Expressions

Introduced in version 23.1

Introduction

Using Metadata Expressions a new batch task is available and named BatchExpressionTemplatesTask. It takes as an argument a list of metadata sidecar-like arguments. An example of such metadata sidecar is

{
    "Descriptive": {
       "Title": "#{R('Descriptive.Title').toUpperCase()}",
       "Description": "#{R('Descriptive.Title') + ': ' + R('Dynamic.CustomDescription')}",
       "Keywords": {"Keyword": "#{R('Dynamic.CustomTag')}"}
    },
    "Dynamic": {
        "Orientation": "#{(R('Technical.Width') > R('Technical.Height')) ? 'Horizontal' : 'Vertical'}",
        "AdditionalInformation": "My custom field"
    }
}

Merging

When the templated sidecar is evaluated against a record it will result for example in the following metadata sidecar

{
    "Descriptive": {
       "Title": "MY TEST FILE",
       "Description": "My test file: this is a test file",
       "Keywords": {"Keyword": ["My custom tag"]}
    },
   "Dynamic": {
        "Orientation": "Horizontal",
        "AdditionalInformation": "My custom field"
    }
}

This metadata sidecar will then be merged against the record using the same rules as when MediaHaven Rest API - Updating a record.

Output after evaluating the expression

After evaluating all expressions in the input metadata sidecar, the result is a new metadata sidecar in JSON. The conversion follows the following rules

Output after evaluating the expression	Conversion into JSON

Output after evaluating the expression	Conversion into JSON
`String`	JSON string
`Boolean`	JSON boolean
`Long`	JSON number
`List<String>`	JSON array
`Map<String>`	JSON object
`Map<String,List<String>>`	JSON object containing JSON arrays

Notice how the string "#{R('Dynamic.CustomTag')}" is evaluated into an array ["My custom tag"]. The end result is a valid metadata sidecar for “Keywords” namely "Keywords": {"Keyword": ["My custom tag"]} whereas before evaluating the expression "Keywords": {"Keyword": "#{...}"} is not a strictly valid metadata sidecar because the value of "Keyword" must be an array and not a string.