Issue Posting Data to Tag via WebDev doPost – Receiving Byte Array Instead of String

Ignition
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1

I'm trying to post data to an Ignition tag using the WebDev module's doPost method. Below is my setup:

-->WebDev doPost Script (Module: Test)

import os
import xml.etree.ElementTree as ET
from xml.dom import minidom

reqdict = str(request)
xmlResponse = "<RESPOK/>"

dsCols = ["key", "val"]
dsRows = [  ]
ssRows = [  ]

data = request['data']
xmlMessage = str(request["headers"]["Content-Type"])

#Create tag path
tn = str(system.date.toMillis(system.date.now()))
baseTagPath = "[Sample_Tags]New_Tag/Outbox"
tagType = "UdtInstance"
typeId = "[Sample_Tags]_types_/Newtags"

tag = {
    "name": tn,
    "typeId": typeId,
    "tagType": tagType,
}
system.tag.configure(baseTagPath, [tag], "a")

#Read and decode data
if "text/xml" in str(request["headers"]["Content-Type"]):
    strData = str(request['data'])

string_output = strData.decode('utf-8')  # Possible issue here?
xmlMessage = strData

#Write to tags
for i in request:
    dsRows.append([i, str(request[i])])
for i in session:
    ssRows.append([i, str(session[i])])

btp = baseTagPath + "/" + tn
system.tag.writeBlocking(
    [btp + "/lastRequest", btp + "/lastReqTS", btp + "/lastReqData", btp + "/lastSessionData"],
    [xmlMessage, system.date.now(), system.dataset.toDataSet(dsCols, dsRows), system.dataset.toDataSet(dsCols, ssRows)]
)

system.tag.writeBlocking(
    ["[Sample_Tags]New_Tag/lastRequest", "[Sample_Tags]New_Tag/lastReqTS", "[Sample_Tags]New_Tag/lastReqData", "[Sample_Tags]New_Tag/lastSessionData"],
    [xmlMessage, system.date.now(), system.dataset.toDataSet(dsCols, dsRows), system.dataset.toDataSet(dsCols, ssRows)]
)

return {'response': unicode(xmlResponse), 'contentType': "application/xml"}

-->Payload Sent via Script Console:

ewmUrl = "https://localhost:8088/system/webdev/Test"
payload = [{"data": "this is a testcase"}]
res = system.net.httpPost(ewmUrl, postData=payload, username=username, password=password)
print res

--> Response Output:

image
image153×108 6.42 KB

-->problem:
When I check the tag value (lastRequest or inside Outbox/...), I get something like:
array['b',[32]]

image
image860×425 51.6 KB

It seems like the posted data is being interpreted as a byte array instead of a string, even though I'm sending a plain string.

What I Need Help With:

  • How can I correctly extract the string content from request['data']?
  • Is the decode('utf-8') failing silently or misused?
  • Should I post the payload differently to avoid byte format?

Need your guidance to solve this issue.
Thanks in advance.

1 Like
2

Please edit your post to have your code as preformatted text, see Wiki - how to post code on this forum. You can edit your post by clicking the pencil icon in the bottom right.

Also, if possible please provide actual screenshots, instead of camera pictures of your screen. Users on mobile will not be able to read your second screenshot(I can barely read any of it)

To start, try adding some logging statements throughout your script to determine what format the data is in at various points and what the value of the data actually is. You might need to decode a byte array into a usable format.

3 Likes