Parsing and Serializing JSON

Working with JSON data in Iguana is easy. You can parse, create, and serialize JSON data efficiently using the built-in json module. Below is a quick guide on how to manage JSON data in the Translator.

Parsing JSON:

To parse incoming JSON data, use the json.parse{} function. This will convert a JSON string into a Lua table, which can then be manipulated easily.

Parse JSON strings into a Lua table

Try it out with this simple code snippet:

local jsonTemplate = [[   
{   
   "firstname":"John",   
   "lastname":"Doe",   
   "birthdate":"1997–04–11",   
   "phone":"(905)343–2352"   
}   
]]   
   
function main(Data)   
  -- parse JSON   
  local msg = json.parse{data=jsonTemplate}   
  local name = msg.firstname..’ ’..msg.lastname   
  trace(name)   
end   

Use the annotations to view the lua table generated from the JSON string.

Generating and Serializing JSON:

To generate JSON, use json.serialize{} to serialize Lua tables into a JSON Object or Array.

STEP 1: Generate a Lua Table

First, you can create a Lua table, either by following a static template or dynamically based on available inbound data from a source system.

For example, take this sample HL7 message and use it as sample data to map to a lua table. For practice, create a simple VMD called adt.vmd file and import the ADT^A04 for HL7v2.3.

MSH|^~\&|SENDING_APP|SENDING_FACILITY|RECEIVING_APP|RECEIVING_FACILITY|20110613083617||ADT^A04|934576120|P|2.3||||   
EVN|A04|20110613083617|||   
PID|1||135769||Mouse^Mickey||19281118|M|||123 Main St.^^Lake Buena Vista^FL^32830||(407)939–1289|||||1719|99999999|||   
PV1|1|O|||||7^Disney^Walt^^MD^^^^||   

Using a Predefined Template:

Typically, the JSON template values will start as empty strings or JSON NULLs, ready to be populated.

local jsonTemplate = [[   
{   
   "firstname":"",   
   "lastname":"",   
   "birthdate":"",   
   "phone":""   
}   
]]   
   
function main(Data)   
   -- parse JSON   
   local msg = json.parse{data=jsonTemplate}   
   
   -- map HL7 to Lua table   
   local msgIn = hl7.parse{vmd=’adt.vmd’, data=Data}   
   
   msg.firstname = msgIn.PID[5][2]:nodeValue()   
   msg.lastname  = msgIn.PID[5][1]:nodeValue()   
   msg.birthdate = msgIn.PID[7]:nodeValue()   
   msg.phone     = msgIn.PID[13][1]:nodeValue()   
end   

Dynamic Generation:

function main(Data)   
   -- create lua table   
   local msg = {}   
   -- map HL7 to Lua table   
   local msgIn = hl7.parse{vmd=’adt.vmd’, data=Data}   
   
   msg.firstname = msgIn.PID[5][2]:nodeValue()   
   msg.lastname  = msgIn.PID[5][1]:nodeValue()   
   msg.birthdate = msgIn.PID[7]:nodeValue()   
   msg.phone     = msgIn.PID[13][1]:nodeValue()   
end   

Both methods will result in the same Lua table:

STEP 2: Serialize the Lua table to a JSON string

Once you've built or modified your Lua table, you can serialize it back into JSON format using the json.serialize{} function.

This is useful when you need to send the data to an external service or log it in JSON format.

local jsonString = json.serialize{data=msg}

You can also use The string viewing window to view this json string in different view modes.