Pentaho HTTP Post using JSON

2
votes

I'm brand new to Pentaho and I'm trying to do the following workflow:

  • read a bunch of lines out of a DB
  • do some transformations
  • POST them to a REST web service in JSON

I've got the first two figured out using an input step and the Json Output step.

However I have two problems doing the final step:

1) I can't get the JSON formatted how I want. It insists on doing {""=[{...}]} when I just want {...}. This isn't a big deal - I can work around this since I have control over the web service and I could relax the input requirements a bit. (Note: this page http://wiki.pentaho.com/display/EAI/JSON+output gives an example for the output I want by setting no. rows in a block=1 and an empty JSON block name, but it doesn't work as advertised.)

2) This is the critical one. I can't get the data to POST as JSON. It posts as key=value, where the key is the name I specify in the HTTP Post field name (on the 'Fields' tab) and the value is the encoded JSON. I just want to post the JSON as the request body. I've tried googling on this but can't find anyone else doing it, leading me to believe that I'm just approaching this wrong. Any pointers in the right direction?

Edit: I'm comfortable scripting (in Javascript or another language) but when I tried to use XmlHttpRequest in a custom javascript snippet I got an error that XmlHttpRequest is not defined.

Thanks!

2
jsonhttppentaho

2 Answers

5
votes

This was trivial...just needed to use the REST Client (http://wiki.pentaho.com/display/EAI/Rest+Client) instead of the HTTP Post task. Somehow all my googling didn't discover that, so I'll leave this answer here in case someone else has the same problem as me.

3
votes

1.) you need to parse the JSON using a Modified Java Script step. e.g. if the Output Value from the JSON Output is called result and its' contents are {"data"=[{...}]}, you should call var plainJSON = JSON.stringify(JSON.parse(result).data[0]) to get the JSON.

2.) In the HTTP Post step, the Request entity field should be plainJSON. Also, don't forget to add a header for Content-Type as application/json (you might have to add that as a constant)