Batch Metadata Expressions

Introduced in version 23.1

Introduction

From version 23.1 you can create a batch offering rich metadata expressions where the new metadata of the item can be determined by

The (previous) metadata of the item
Combinations of fields
Conditions
Textual operations

Batch with metadata expressions

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

When putting a string in metadata sidecar that has the pattern #{...} it will be evaluated using the Spring Expression Language. Inside an expression, you can reference the metadata using R(<Dotted key>) or record(<Dotted key>) for example R('Descriptive.Title') or record('Descriptive.Title').

The R takes an optional second argument, which is the default value when the metadata field is not present.

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.

The output of the metadata accessor

The output of the metadata accessor R or record is the following depending on which field type the dotted key refers to:

Level	Case	Effect	Example Expression	Example Output
Top	SimpleField	String	`R('Descriptive.Title')`	`My title`
Top	ListField	List of Strings	`R('Descriptive.Keywords')`	`["A", "B", "C"]`
Top	MapField	Map of Strings	`R('Structural.Versioning')`	`{"Status": "HEAD", "Version": "2"}`
Top	MultiItemField	Map of List of Strings	`R('Descriptive.Authors')`	`{"Authors": ["Cedric"], "Director": ["Alice", "Bob"]}`
Top	Others	Not allowed
Sub	Child of ListField	List of Strings	`R('Descriptive.Keywords.Keyword')`	`["A", "B", "C"]`
Sub	Child of MultiItemField	List of Strings	`R('Descriptive.Authors.Director')`	`["Alice", "Bob"]`
Sub	Child of MapField	String	`R('Structural.Versioning.Status')`	`HEAD`
Sub	Other	Not allowed

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
`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.

Restrictions

The available features of SPel are for security reasons restricted to the following patterns

Literal expressions
Boolean and relational operators
Inline lists, maps, etc
Ternary operator
The method named “R” or “record”