Sitemap/JSON error

Here’s one for a JSON/Sitemap guru plase:

I have a JSON item whose value is like …

{
    'Motor current below expectation' : 20 ,
    'Motor voltage' : 4,
etc...
}

I have a sitemap label:

Text label="Diag [JSONPATH($.['Motor current below expectation']):%s]" item=i_TRV_Lounge_Get_Diagnostics

But OH is thowing a Java exception , too long to post here:

I have used the online JSON expression validator here: https://jsonpath.herokuapp.com/
which correctly parses the value using the expression $.[‘Motor current below expectation’]

What am I doing wrong?

I would use the JSONPATH on an item, having said that, I would also spare a separate item for each data packet you want to display.
My guess is that the sitemap can’t do the transformation.

This seems an odd way to go about it, but it should be able to work.
More clues please -

What kind of Item?
May we see say an events.log entry of a change, showing what the actual contents are?

That’s just making it hard.
The first few lines probably have a hint, at least.

the item does, and it contains - post transformation - a json block, as per OP, so i want to now declare seperate labels in the sitemap that parses the JSON (item) as in OP, to display on the sitemap.

so, any idea why the transform isn’t working?

thanks, i will post all as requested, i just wondered why its not working, the syntax is good?

why is it hard, it’s logical i felt, see my previous post before this one in reply to opus.

Ups, sorry for this false statement. However, I would suggest to spare an item for each value.

It is hard to diagnose problems when you keep both the nature of the patient and the symptoms a secret, that’s all.

no no no
i was saying"why is it hard" or an,“odd way” in reply to a previous post, claiming in taking the hard way, which i am not.

i simply asked, what is wrong with the JSON transformation syntax, that’s all, please, i waa not asking about design decisions, just and simply, what is wrong with my JSON syntax on the label. To me it appears reasonable and sitemap labels can have this attribute, I’m sure…looking at doc?

:+1::flushed:

It’s the hard way to go about it because openHAB Items are intended to hold a single piece of information - temperature, on/off, message.
You’ve chosen to embed multiple bits of information in a single Item, and now want to fish just one bit out.
It’s unconventional.

I don’t know. Your error message is still secret. Your Item type is still secret. Your Item state is secret.

If you want a guess, try escaping the single quotemarks.

1 Like

I’m on a mobile, in the field, working … its nigh impossible to get the info, until I’m on my laptop later at home on my LAN.

and my item does contains one piece of data, a JSON block from an MQTT query. no.prob.

the syntax works on JSON check tool online, that’s the point (and focus) of the OP, the JSON syntax on a label.

never mind,work it out myself when I’m home.

OH
and thankyou for the escape option, l shall try that too.

found this,

so i think its the use of two square brackets/parentheses pairs, in the transform inside the string on the label…commencing at "Diag ["

I shall investigate…

I caution you that the openHAB “JSONPATH Transformation Service” is not JSONPATH. For a start, it’d be no use returning lists for an Item label transform…
Such a test is not entirely conclusive.

ok, apologies for the delay, I was home late yesterday and did not switch on the laptop.

Ok, so here is the item:(I did away with the transform on a site label , as you all recommended):from the .items file

	/* Diagnostics */
	String i_TRV_Lounge_Diag1 { channel="mqtt:topic:b_MQTT_Broker:t_TRV_Lounge:c_Diagnostics" [profile="transform:JSONPATH", function="<jsonPath>", sourceFormat="$.[\'Motor current below expectation\']"] }

…the item contents and the transformation error (both from openhab.log,file:

2020-01-13 10:44:19.319 [INFO ] [el.core.internal.ModelRepositoryImpl] - Loading model 'TRV.items'
2020-01-13 10:44:19.523 [WARN ] [ofiles.JSonPathTransformationProfile] - Could not transform state '{
        "Motor current below expectation":      false,
        "Motor current always high":    false,
        "Motor taking too long":        false,
        "discrepancy between air and pipe sensors":     false,
        "air sensor out of expected range":     false,
        "pipe sensor out of expected range":    false,
        "low power mode is enabled":    false,
        "no target temperature has been set by host":   false,
        "valve may be sticking":        false,
        "valve exercise was successful":        false,
        "valve exercise was unsuccessful":      false,
        "driver micro has suffered a watchdog reset and needs data refresh":    false,
        "driver micro has suffered a noise reset and needs data refresh":       false,
        "battery voltage has fallen below 2p2V and valve has been opened":      false,
        "request for heat messaging is enabled":        false,
        "request for heat":     false
}' with function '<jsonPath>' and format '['Motor current below expectation']'

I have not linked the item to a sitemap label as yet because I’m just trying to get the item definition working.

Other item definitions of the transform JSON source strain I tried were:

** No period/dot after the $
	String i_TRV_Lounge_Diag1 { channel="mqtt:topic:b_MQTT_Broker:t_TRV_Lounge:c_Diagnostics" [profile="transform:JSONPATH", function="<jsonPath>", sourceFormat="$[\'Motor current below expectation\']"] }

and 

** Use double quotes instead of single
	String i_TRV_Lounge_Diag1 { channel="mqtt:topic:b_MQTT_Broker:t_TRV_Lounge:c_Diagnostics" [profile="transform:JSONPATH", function="<jsonPath>", sourceFormat="$.[\"Motor current below expectation\"]"] }

and

** Remove period/dot and use double quotes
	String i_TRV_Lounge_Diag1 { channel="mqtt:topic:b_MQTT_Broker:t_TRV_Lounge:c_Diagnostics" [profile="transform:JSONPATH", function="<jsonPath>", sourceFormat="$[\"Motor current below expectation\']"] }

and

** Remove period/dot and use single quotes
	String i_TRV_Lounge_Diag1 { channel="mqtt:topic:b_MQTT_Broker:t_TRV_Lounge:c_Diagnostics" [profile="transform:JSONPATH", function="<jsonPath>", sourceFormat="$[\"Motor current below expectation\']"] }

Rather bizzrely, the last definition above “works” as in throws no error, but yields a strange string…

M. { "Motor current below expectation": false, "Motor current always high"

mmm???

I would say there are newline characters in your source JSON

Yes, that’s a good observation, I thought the same after reading the link in the OP which had newlines in so. I tried things like \n and 0x20 and %20 all to no avail. Perhaps OH JSON doesnt have newline escapes?

Do you think I could get away with REGEX instead, I’m ok with REGEX strings ??

I dunno. “whitespace” between JSON tokens is allowed, and that includes newlines. People get in the cart with newlines embedded in the data as a rule, not what is happening here.
Having said that, JSON’s idea of “whitespace” is fairly limited and there are a bunch of invisible characters that can ruin the show.

I’d be inclined to pull the raw JSON into a rule for analysis, but if you just want to mend it, press on.
In this case you know the “data” is limited to true/flase which should simplify any matching.

Tried with regex , which does not throw an error in the online checker (when using \s instead of the OH escape \s, but does throw an error in OH.:

rule


rule "Parse Diagnostics"
when
    Item i_TRV_Lounge_Get_Diagnostics received update
then
    i_TRV_Lounge_Diag1 = transform("REGEX", "(?:\"Motor current below expectation\":\\s+)(true|false)", i_TRV_Lounge_Get_Diagnostics.state.toString)
      logInfo("TRV_Refresh.rules", "!! Diag updated.")
end

i_TRV_Diag1 is now just an String item with no other attributes:

String i_TRV_Diag1

The regex ues two groups , one that is non-capture and one that is … which should contain either true or false

 {
       "Motor current below expectation":      false,
        "Motor current always high":    false,
        "Motor taking too long":        false,
        "discrepancy between air and pipe sensors":     false,
        "air sensor out of expected range":     false,
        "pipe sensor out of expected range":    false,
        "low power mode is enabled":    false,
        "no target temperature has been set by host":   false,
        "valve may be sticking":        false,
        "valve exercise was successful":        false,
        "valve exercise was unsuccessful":      false,
        "driver micro has suffered a watchdog reset and needs data refresh":    false,
        "driver micro has suffered a noise reset and needs data refresh":       false,
        "battery voltage has fallen below 2p2V and valve has been opened":      false,
        "request for heat messaging is enabled":        false,
        "request for heat":     false
}

The item i_TRV_Lounge_Get_Diagnostics correctly contains the above structure.

2020-01-13 14:27:59.821 [ERROR] [ntime.internal.engine.RuleEngineImpl] - Rule 'Parse Diagnostics': An error occurred during the script execution: Cannot assign a value in null context.

I’m really stuck here, cant use a JSONPATH nor can I use a regex.

If that is an Item, you don’t send states to Items in that way.

Why not take baby steps for now

var mywork = transform( ...

I couldn’t comment on your REGEX, but will note that like JSONPATH, REGEX transformation service is not REGEX. Rich @rlkoshak is fond of saying
"In openHAB, your REGEX expression must match the full message and the part that get’s returned is in the first capture group (first set of parens)"
which seems important but means little to me.

yeah, should have mentioned, I tried using a var but that didnt work either, so I tried the sendCommand which didnt work either.
I debugged and it is the string in the transform pattern that is the problem, but I do not know why because it works perfectly in https://regex101.com/ - provided I remove the escape on the \s+

Making it more complicated is unlikely to help. For now, concentrate on just getting your extraction into a string variable.

At the moment, you don’t know if your source data is iffy or your technique is wrong.
Try to get this working first, extract fred value -

val fakedata = "{ \"fred\" : false }"

Then build on it, e.g. "fred with spaces", then add a "mary":true. When you know the tools work, apply to your real data.