Format Dates with Full Month

Given the following JSON:

"Available online": "29 January 2020",

Received": "8 November 2019",
"Revised": [
"16 January 2020"
"Accepted": "23 January 2020",
"Publication date": "1 May 2020"

The Date can be captured with dd MMMM yyyy:


Add a sub-transformation with step “transformation executor”

You can bundle a couple of steps as a transformation and call those steps in another transformation.

My scenario: determine publication date

I often use the Crossref Rest API to get information about publications. Depending on the publisher there are different kind of dates associated with a DOI and the dates can have different resolutions. Sometimes just a year or a year and a month.

Get publications dates from different DOIs (using REST and JSON) – Simple_Rest_Query_Crossref.ktr

In order to get always a specific publication date with the resolution I use a couple of steps and logic to determine the “relevant” publication date out from those different date fields.

Adding a couple of steps to determine “publication_date”

To reuse those steps in different transformations without copying each time all these steps I can now save those steps as own transformation. Let’s add a “Get rows from result” and “Copy rows to result” at the beginning and and end this sub-transformation.

subtransformation – Publication_Date_Sub.ktr

Then we can add a “Transformation executor” step in the main transformation. In this step we add the expected “fields” of the sub-transformation in the tab “Results row”

Adding a “transformation executor”-Step in the main transformation – Publication_Date_Main.ktr

As output of a “transformation executor” step there are several options available:

Output-Options of “transformation executor”-Step

There seems to be no option to get the results and pass through the input steps data for the same rows. Probably since the output of the sub-transformation can have more more or less rows than the input. Yet we can create a work-around by going on the the input data and add the results of the sub-transformation with a common (presorted) identifier. At the end we have the original data and the result of the sub-transformation combined.


Pentaho Data Integration (PDI) offers the input step “JSON-Input” to read out data from a JSON file or stream. Often I use this step after a REST-API-Query, so I would have the JSON-Input as a field from a previous step.

In order to test the field-extraction, it’s helpful to save some local samples of the possible responses. In the tab “File” you first can do your tests with the local file and switch later to “Source is from a previous step”.

Since recently Pentaho offers an “internal helper” to select the fields. However it unfortunately does not to work for most of my use-cases. Instead I found very useful.

Get JSON Path to the data you want to extract via

Then add the fields with the corresponding path in PDI:

Extracting various fields from the JSON response of the Crossref REST API (e.g.