Although TDI 7.1 FP5 ships with a JSON parser, it would appear that the parser doesn’t actually work (even at FP6).  The example AL that is shipped doesn’t work either – they both generate the same error – it looks like the JSON parser doesn’t quite register properly within the AL;

15:30:32,468 ERROR - [WriteJSON] CTGDIS810E handleException - cannot handle exception , initialize 
java.lang.Exception: CTGDIS159E This Connector has no configured Parser. 

This may be resolved in 7.1.1, but in this environment that version isn’t available.

Of course there is a workaround in the form of JSON Simple.  Drop the JSON Simple json-simple-1.1.1.jar into the “<IDI install dir>\jars” folder & restart TDI to make it available.

JSON Encoding

This is a simple approach which encodes an object as a JSON string.  The encoding will accept quite complex structures too.  I have it quite happily accepting a java.util.LinkedList where each element is itself a HashMap.  The only trick is that the JS object need to have been initialised properly;

// Init the object
var theObject = org.json.simple.JSONValue.parse("{}");

// Populate the object = "Mr Object"; = "999 ObjectHelp";

// Get the JSON string
var jsonString = org.json.simple.JSONValue.toJSONString(theObject);

JSON decoding

To decode JSON – again use a FileSystem connector & the following code;

var jsonString = work.getString("jsonString");
if ((jsonString != "") && (jsonString != null)) {
    var jsonWrapper = org.json.simple.JSONValue.parse(jsonString);
    g_QueryResult = jsonWrapper[0];

Generating JSON obviously has many uses, but in this case I was generating data to be consumed by a couple of jquery plugins – DataTables and jqplot.  More on how to generate the correct structure for those plugins later.