JSONExtractor

This parameter is the JSON query whose value will be stored in the target attribute.

Each cell in the JSON Query column contains a button that opens a dialog containing the structure of the JSON dataset in a tree form. If the JSONExtractor is set to read from a file or URL, then selecting a value from the tree will populate the parameter with the appropriate query string to turn the selected values into features.

A JSON query is primarily used to refer to values in some JSON text. They can also be used to extract some metadata about the JSON text, such as the type (object, array, string, etc.) of JSON value or the number of elements in an array. The outermost JSON value, which must be an object or an array, is always referred to by the term "json".  Contained values can be referred to using JavaScript-like square bracket index operators.  

A value in an array can be referred to using its zero-based position in the array (for example, json[2] for the third element).

A value in an object can be referred to using its object key name

json["key"]

All of the values in an array or object can be collectively referred to using a wildcard index

json[*]

The query used by this transformer can have multiple expressions, which are separated by a '+' operator, as well as string literal values. This allows more complex attribute values to be easily created from the JSON text. For example:

json["name"]["first"] + " " + json["name"]["last"]

The JSONFragmenter transformer contains more information on JSON queries.

If the JSON query cannot be fully evaluated, a message will be logged, and the feature will be output without setting the target attribute.