I am trying to parse a json payload sent via a POST request to a NGINX/Openresty location. To do so, I combined Openresty's content_by_lua_block with its cjson module like this:
# other locations above
location /test {
content_by_lua_block {
ngx.req.read_body()
local data_string = ngx.req.get_body_data()
local cjson = require "cjson.safe"
local json = cjson.decode(data_string)
local endpoint_name = json['endpoint']['name']
local payload = json['payload']
local source_address = json['source_address']
local submit_date = json['submit_date']
ngx.say('Parsed')
}
}
Parsing sample data containing all required fields works as expected. A correct JSON object could look like this:
{
"payload": "the payload here",
"submit_date": "2018-08-17 16:31:51",
},
"endpoint": {
"name": "name of the endpoint here"
},
"source_address": "source address here",
}
However, a user might POST a differently formatted JSON object to the location. Assume a simple JSON document like
{
"username": "JohnDoe",
"password": "password123"
}
not containing the desired fields/keys.
According to the cjson module docs, using cjson (without its safe mode) will raise an error if invalid data is encountered. To prevent any errors being raised, I decided to use its safe mode by importing cjson.safe. This should return nil for invalid data and provide the error message instead of raising the error:
The cjson module will throw an error during JSON conversion if any invalid data is encountered. [...]
The cjson.safe module behaves identically to the cjson module, except when errors are encountered during JSON conversion. On error, the cjson_safe.encode and cjson_safe.decode functions will return nil followed by the error message.
However, I do not encounter any different error handling behavior in my case and the following traceback is shown in Openresty's error.log file:
2021/04/30 20:33:16 [error] 6176#6176: *176 lua entry thread aborted: runtime error: content_by_lua(samplesite:50):16: attempt to index field 'endpoint' (a nil value)
Which in turn results in an Internal Server Error:
<html>
<head><title>500 Internal Server Error</title></head>
<body>
<center><h1>500 Internal Server Error</h1></center>
<hr><center>openresty</center>
</body>
</html>
I think a workaround might be writing a dedicated function for parsing the JSON data and calling it with pcall() to catch any errors. However, this would make the safe mode kind of useless. What am I missing here?
Your “simple JSON document” is a valid JSON document. The error you are facing is not related to cjson, it's a standard Lua error:
resty -e 'local t = {foo = 1}; print(t["foo"]); print(t["foo"]["bar"])'
1
ERROR: (command line -e):1: attempt to index field 'foo' (a number value)
stack traceback:
...
“Safeness” of cjson.safe is about parsing of malformed documents:
cjson module raises an error:
resty -e 'print(require("cjson").decode("[1, 2, 3"))'
ERROR: (command line -e):1: Expected comma or array end but found T_END at character 9
stack traceback:
...
cjson.safe returns nil and an error message:
resty -e 'print(require("cjson.safe").decode("[1, 2, 3"))'
nilExpected comma or array end but found T_END at character 9
I'm using Latex since years but I'm new to embedded luacode (with Lualatex). Below you can see a simplified example:
\begin{filecontents*}{data.json}
[
{"firstName":"Max", "lastName":"Möller"},
{"firstName":"Anna", "lastName":"Smith"}
];
\end{filecontents*}
\documentclass[11pt]{article}
\usepackage{fontspec}
%\setmainfont{Carlito}
\usepackage{tikz}
\usepackage{luacode}
\begin{document}
\begin{luacode}
require("lualibs.lua")
local file = io.open('data.json','rb')
local jsonstring = file:read('*a')
file.close()
local jsondata = utilities.json.tolua(jsonstring)
tex.print('\\begin{tabular}{cc}')
for key, value in pairs(jsondata) do
tex.print(value["firstName"] .. ' & ' .. value["lastName"] .. '\\\\')
end
tex.print('\\hline\\end{tabular}')
\end{luacode}
\end{document}
When executing Lualatex following error occurs:
LuaTeX error [\directlua]:6: attempt to index field 'json' (a nil value) [\directlua]:6: in main chunk. \end{luacode}
When commenting the line \usepackage{fontspec} the output will be produced. Alternatively, the error can be avoided by commenting utilities.json.tolua(jsonstring) and all following lua-code lines.
So the question is: How can I use both "fontspec" package and json-data without generating an error message? Apart from this I have another question: How to enable german umlauts in output of luacode (see first "lastName" in example: Möller)?
Ah, I'm using TeX Live 2015/Debian on Ubuntu 16.04.
Thank you,
Jerome
I've been trying to pattern for the case where a user types in an invalid directory:
# let dir = Unix.opendir "adfalf";;
Exception: Unix.Unix_error (Unix.ENOENT, "opendir", "adfalf").
My function is as follows:
let files_of_dir d =
try
let dir = Unix.opendir d in
...
with
Unix_error (uerr, ucommand, dir) -> raise Not_found
Except I keep getting the compilation error:
Error: This variant pattern is expected to have type exn
The constructor Unix_error does not belong to type exn
I don't understand what I'm doing wrong w/ the pattern matching. If anyone could help me on this it would be greatly appreciated!
Some Other Notes:
I've been compiling my code using the following command on terminal:
ocamlbuild filename.byte
You need to say Unix.Unix_error, not just Unix_error. Note that this is what appears in your sample session.
I am calling a R script from Scala by using scala.sys.process. This script takes a command line argument in JSON format and processes it. I am using rjson's fromJSON function to store the JSON in a list.
This works very fine when I execute the R script from the command line:
$ ./dfChargerFlink.R '{"Id":"1","value":"ABC"}'
But when I call it from scala, I get the following error:
Error in fromJSON(commandArgs(1)) : unexpected character '''
Execution halted
This is the code I am using:
val shellCommand = "./dfChargerFlink.R '"+arg+"'"
return shellCommand !!
where arg is the JSON string.
You can notice that I have appended " ' " to both the sides of the JSON string as if I don't, I get this error:
Error in fromJSON(commandArgs(1)) : unclosed string
Execution halted
How can this be solved? Is it some bug?
I can't seem to catch an exception when using json.loads even though I specifically call it out. I largely see this when trying to stress my server with lots of client connection sending data very quickly. See my error below:
(I've replaced my IP address with X's in the error code)
EX: Unterminated string starting at: line 1 column 49 (char 48) Data:
'{"ap-hdop":0.55,"rtcmin":"38","ap-latdec":3.134,"a' error: uncaptured
python exception, closing channel
(:Unterminated string
starting at: line 1 column 49 (char 48)
[//faraday_server_handler.py|collect_incoming_data|34]
[/usr/lib/python2.7/json/init.py|loads|338]
[/usr/lib/python2.7/json/decoder.py|decode|366]
[/usr/lib/python2.7/json/decoder.py|raw_decode|382])
I understand this that the code fails because I simply miss a double quotes on the line:
'{"ap-hdop":0.55,"rtcmin":"38","ap-latdec":3.134,"a'
This line is usually a LOT longer so that "a.... was supposed to keep going and complete it's quotes.
Here's my relevant code:
def collect_incoming_data(self, data):
"""Read an incoming message from the client, place JSON message data into buffer"""
#self.logger.debug('collect_fing_data() -> (%d bytes)\n"""%s"""', len(data), data)
try:
loaded_data = json.loads(data)
except ValueError, ex:
self.handle_error()
type,value,traceback = sys.exc_info()
print type
#print "Collect Incoming Data: " . time.strftime("%Y-%m-%d %H:%M:%S",time.gmtime())
print "EX: ", ex
print "Data: ",repr(data)
Any ideas? I scoured the internet to see if I can find this issue, but I appear to be setting up to capture the exception which everyone else having this issue with loads seems to suggest to do.
EDIT 3/1/2016 - Evening
Commenting out my exception handle_error() let me see more of the error:
except ValueError, ex:
self.handle_error()
type,value,traceback = sys.exc_info()
print type
#print "Collect Incoming Data: " . time.strftime("%Y-%m-%d %H:%M:%S",time.gmtime())
print "EX: ", ex
print "Data: ",repr(data)
Below is my new error, I've commented out personal data. It's apparent that the issue I really have now is in-fact the unterminated string
EX: Unterminated string starting at:
line 1 column 49 (char 48) Data:
'{"ap-hdop":0.55,"rtcmin":"31","ap-latdec":XX.XXX,"a' EX: No JSON object could be decoded Data:
'p-latdeg":34,"adc6":2006,"adc7":2007,"adc4":2004,"adc5":2005,"adc2":2002,"adc3":2003,"adc0":2000,"adc1":2001,"gpio-0":30,"gpio-1":50,"gpio-2":70,"speed":5.0,"adc8":2008,"rtcday":"01","longdeg":118,"longdec":XX.XXX,"altitude":31.0,"ap-speed":0.0,"ap-pdop":0.77,"lat-dir":"N","long-dir":"W","hdop":0.01,"ap-rf":0,"alt-units":"M","rtcdow":"2","callsign":"XXXXX","ap-callsign":"XXXXX","id":1,"ap-id":1,"rtcyear":"2016","rtcmon":"03","ap-vdop":0.66,"ap-lat-dir":"N","vdop":0.02,"rtchour":"22","latdec":XX.XXX,"latdeg":34,"ap-longdeg":118,"ap-longdec":XX.XXX,"rtcsec":"15","ap-altitude":86.0,"ap-long-dir":"W","pdop":0.01,"ap-alt-units":"M","faraday-port":0}'
OK my original question was answered which was "Why am I not catching the ValueError exception even though I am providing code to do just that?"
#tadhg McDonald-jensen was correct with his comment to remove my call to handle_error().
I still have some other issues but they are a different question. Thanks!