How to use jQuery to send JSON data to a Grails app

This took me a while to figure out, so here it is for anyone else who’d like to know. This information is quite relevant and questions often arise, so you can find it in the dissertation discussion chapter on beginner programmers, so I decided to share my conclusions here. Firstly, I was quite surprised to learn that jQuery doesn’t have a built-in method for turning objects into JSON, so you’ll need the JSON parser/creator from Then you can write your javascript POST function using the jQuery ajax method. Here I’ve left the content type as text/plain, which is not strictly correct but works with the Groovy code.

function postTreeData(){
        type: "POST",
        url: "savedata",
        contentType : "text/plain",
        dataType: 'json',
        data: JSON ...
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