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Header

The xtrasonnet header is a regular jsonnet comment of the following form:

/** xtrasonnet
input payload application/json
output application/xml

// this is a comment
preserveOrder=false
*/

Input directives

The input directives signal to xtrasonnet what the expected media types are at design time for given inputs. For more information about media types see the section on data formats.

The payload name is reserved for the "main" transformation input. All other inputs would have custom names.

If a given input to xtrasonnet is of an explicit media type at runtime, the header directive will be ignored.

Each input may be declared once; repeating a name is an error. To share media type parameters across declarations, see sharing parameters below.

Output directive

The output directive signals to xtrasonnet the desired media type, at design time, to output. For more information about media types see the section on data formats.

If programmatically, an explicit output media type is specified, the header directive will be ignored.

Like inputs, the output may be declared once.

Sharing media type parameters

Media type parameters can be declared once and shared, rather than repeated on every line. Directives layer general to specific, the more specific winning per parameter:

  1. dataformat <mediatype> — its parameters apply to every input and the output of that media type
  2. input * <mediatype> — its parameters apply to every input of that media type
  3. input <name> <mediatype> / output <mediatype> — the declaration itself
/** xtrasonnet
dataformat application/csv;quotechar='
input * application/csv;separator=|
input payload application/csv;header=absent
input other application/csv
output application/csv
*/

Here payload is read as CSV with quote char ', separator |, and no header line; other is read the same but with a header line; and the output is written with quote char ' and default settings otherwise.

Comments

Comments within the xtrasonnet header must start with two slashes //, otherwise they will be treated as unrecognized directives or options.

Preserve order

Developers may disregard the order of elements in Objects which may speed up execution.

Default value is true.