Sorry, I never saw that you finally gave the raw json in your original question. Otherwise, I would have responded.
The problem you face is that I don't think that there is a function in matlab that knows how to parse the escape codes in your json properly as UTF-8. jsondecode probably assumes a native character set, not UTF-8. I'll write an enhancement request to mathworks to suggest adding a character set option to jsondecode.
So, instead you have detect these escape codes and replace them by their native equivalent. Thankfully, a regexprep with a dynamic replacement expression can do that in one go:
%read message as text
rawtext = fileread('message.json');
%detect \u escape codes and convert them to native using dynamic replacement regular expressions
nativetext = regexprep(rawtext, '(\\u[A-Za-z0-9]{4})*', '${native2unicode(sscanf($0, ''\\\\u%4x'')'', ''UTF-8'')}');
%decode json
conversation = jsondecode(nativetext);
You can see that the text is now decoded properly (R2018b on Windows, this may not be the case with all versions of matlab or all OSes):
>> cellfun(@(s) s.content, conversation.messages, 'UniformOutput', false)
ans =
4×1 cell array
{'You sent a sticker.' }
{'thanks' }
{'ok。i just wanted to find jian。now i find him。 good luck bro?'}
{'Exams are coming up ?' }
Explanation of the regexp:
- \\u: match '\u' (literal '\' has to be escaped in regular expressions), followed by
- [A-Za-z0-9]{4}: match 4 consecutive characters among 'ABCDEFabcdef0123456789'
- (...)*: match continuous runs of the above as many times as necessary
This is then converted by
native2unicode(sscanf($0, '\u%4x')', 'UTF-8')
in the replacement expression, where $0 is the matched text (a continuous run of \uxxxx, eg. '\u00f0\u009f\u0091\u008d'). sscanf converts each \uxxxx into its decimal equivalent and native2unicode converts the utf8 to whatever matlab expects (utf16?)
