I have a string which gets serialized to JSON in Javascript, and then deserialized to Java.
It looks like if the string contains a degree symbol, then I get a problem.
I could use some help in figuring out who to blame:
is it the Spidermonkey 1.8 implementation? (this has a JSON implementation built-in)
is it Google gson?
is it me for not doing something properly?
Here's what happens in JSDB:
js>s='15\u00f8C'
15°C
js>JSON.stringify(s)
"15°C"
I would have expected "15\u00f8C' which leads me to believe that Spidermonkey's JSON implementation isn't doing the right thing... except that the JSON homepage's syntax description (is that the spec?) says that a char can be
any-Unicode-character-
except-"-or-\-or-
control-character"
so maybe it passes the string along as-is without encoding it as \u00f8... in which case I would think the problem is with the gson library.
Can anyone help?
I suppose my workaround is to use either a different JSON library, or manually escape strings myself after calling JSON.stringify() -- but if this is a bug then I'd like to file a bug report.
This is not a bug in either implementation. There is no requirement to escape U+00B0. To quote the RFC:
2.5. Strings
The representation of strings is
similar to conventions used in the C
family of programming languages. A
string begins and ends with quotation
marks. All Unicode characters may be
placed within the quotation marks
except for the characters that must be
escaped: quotation mark, reverse
solidus, and the control characters
(U+0000 through U+001F).
Any character may be escaped.
Escaping everything inflates the size of the data (all code points can be represented in four or fewer bytes in all Unicode transformation formats; whereas encoding them all makes them six or twelve bytes).
It is more likely that you have a text transcoding bug somewhere in your code and escaping everything in the ASCII subset masks the problem. It is a requirement of the JSON spec that all data use a Unicode encoding.
hmm, well here's a workaround anyway:
function JSON_stringify(s, emit_unicode)
{
var json = JSON.stringify(s);
return emit_unicode ? json : json.replace(/[\u007f-\uffff]/g,
function(c) {
return '\\u'+('0000'+c.charCodeAt(0).toString(16)).slice(-4);
}
);
}
test case:
js>s='15\u00f8C 3\u0111';
15°C 3◄
js>JSON_stringify(s, true)
"15°C 3◄"
js>JSON_stringify(s, false)
"15\u00f8C 3\u0111"
This is SUPER late and probably not relevant anymore, but if anyone stumbles upon this answer, I believe I know the cause.
So the JSON encoded string is perfectly valid with the degree symbol in it, as the other answer mentions. The problem is most likely in the character encoding that you are reading/writing with. Depending on how you are using Gson, you are probably passing it a java.io.Reader instance. Any time you are creating a Reader from an InputStream, you need to specify the character encoding, or java.nio.charset.Charset instance (it's usually best to use java.nio.charset.StandardCharsets.UTF_8). If you don't specify a Charset, Java will use your platform default encoding, which on Windows is usually CP-1252.
Related
I am currently trying to format a JSON object using LabVIEW and have ran into the issue where it adds additional quotation marks invalidating my JSON formatting. I have not found a way around this so I thought just formatting the string manually would be enough.
Here is the JSON object that I have:
{
"contentType":"application/json",
"content":{
"msgType":2,
"objects":"["cat","dog","bird"]",
"count":3
}
}
Here is the JSON object I want with the quotation marks removed.
{
"contentType":"application/json",
"content":{
"msgType":2,
"objects":["cat","dog","bird"],
"count":3
}
}
I am still not an expert with regex and using a regex tester I was only able to grab the "objects" and "count" fields but I would still feel I would have to utilize substrings to remove the quotation marks.
Example I am using (would use a "count" to find the start of the next field and work backwards from there)
"([objects]*)"
Additionally, all the other Regex I have been looking at removes all instances of quotation marks whereas I only need a specific area trimmed. Thus, I feel that a specific regex replace would be a much more elegant solution.
If there is a better way to go about this I am happy to hear any suggestions!
Your question suggests that the built-in LabVIEW JSON tools are insufficient for your use case.
The built-in library converts LabVIEW clusters to JSON in a one-shot approach. Bundle all your data into a cluster and then convert it to JSON.
When it comes to parsing JSON, you use the path input terminal and the default type terminals to control what data is parsed from a JSON string.
If you need to handle JSON in a manner similar to say JavaScript, I would recommend something like the JSONText Toolkit which is free to use (and distribute) under the BSD licence. This allows more complex and iterative building of JSON strings from LabVIEW types and has text-path style element access along with many more features.
The Output controls from both my examples are identical - although JSONText provides a handy Pretty Print vi.
After using a regex from one of the comments, I ended up with this regex which allowed me to match the array itself.
(\[(?:"[^"]*"|[^"])+\])
I was able to split the the JSON string into before match, match and after match and removed the quotation marks from the end of 'before match' and start of 'after match' and concatenated the strings again to form a new output.
Postamble for future readers
Elm allows literal C:\Users\myuser in strings
This is consistent with the JSON spec
My problem was unrelated to this, but several layers of escaping convoluted the problem. Future lesson: fully producing a minimal working example would have found the error!
Original question
I have a Clojure backend that talks to an Elm frontend. I hit a bump when decoding JSON values in Elm.
\U below means the literal characters backslash and U, as if read from a text file. "\\U" is the same string as input in Clojure and Elm source (\ must be escaped). Note enclosing "".
Problem: encoding \U
The literal string \U, escaped "\\U" is not accepted by the Elm string decoder.
A blog post suggests that to obtain the literal string \U, this should be encoded in source code as "\\\\U", "escaping the unicode escape".
The literal string I want to send to the client is C:\Users\myuser. I prefer to send valid JSON from the server to the client.
Clojure standard library behavior
clojure.data.json does not do anything special for strings containing the literal \U. The example below shows that \U and \m are threated equally, the backslash is escaped, and the following character ignored.
project.core> (clojure.data.json/write-str "C:\\Users\\myuser")
"\"C:\\\\Users\\\\myuser\""
Manual workaround
Temporary workaround is manually escaping the strings I need:
(defn escape-backslash-u [s]
(clojure.string/replace s "\\U" "\\\\U"))
Concrete questions
Is clojure.data.json/write-str behaving correctly? As I understand the documentation, output should be valid unicode.
Are other JSON libraries behaving similarly?
Is Elm's Json.Decode behaving correctly by rejecting the literal string \U?
Solution progress
A friendly Clojurians Slack user pointed to the JSON standard specification, specifically sections 7. Strings and 8.2. Unicode characters.
I think you may be on the wrong track here.
The string you gave as an example, "C:\\Users\\myuser" is completely unproblematic, it does not contain any Unicode escape sequences. It is a string containing the ASCII characters ‘C’, ‘:’, ‘\’, ‘U’, and so on. The backslash is the escape character in Clojure strings so it needs to be escaped itself to represent a literal backslash.
In any case the string "C:\\Users\\myuser" can be serialized with (clojure.data.json/write-str "C:\\Users\\myuser"), and, as you know, this gives "\"C:\\\\Users\\\\myuser\"". All of this seems perfectly straightforward and sound.
Printing "\"C:\\\\Users\\\\myuser\"" results in the original string "C:\\Users\\myuser" being printed. That string is accepted as valid by JSONLint, again as expected.
I understood it as Elm beeing unable to decode \"C:\\\\User... to "C:\\User... because it interprets \u as start for an escape sequence.
I tried elm here with the following code:
import Html exposing (text)
main =
text "\"c:\\\\user\\\\foo\"" // from clojure.data.json/write-str
which in turn compiles/runs to
"c:\\user\\foo"
which looks fine to me.
Are you sure there is nothing else going on (middleware, transport) ?
I use jackson to parse json data. Now I have a problem with handling a \uXXXX issue.
The data I got here is like
{"UID":"here_\ud83d\udc3b"}
After I use ObjectMapper.readValue(jsonContent, UserId.class); to convert json to an instance of UserId, the UID property is not literally "here_\ud83d\udc3b". Jackson convert \ud83d\udc3b to 2 chars as the unicode value.
My question is, is it possible to let jackson skip this "Unicode transformation" and key the literal value "\ud83d\udc3b" as it is?
No. JSON parsers are required to handle Unicode escapes to produce underlying Unicode characters.
When writing, on the other hand, some characters may also be encoded using similar Unicode escapes.
So if you need to use escaping, you need to re-encode such values yourself.
I have a index.html with a which sends a text to a PHP code. This PHP sends it again by POST (curl) to a Node.js server, inserted in a JSON message (utf8-encoded)
//Node.js server file (app.js) -- gets the json and shows it in a <script> to save it in client JS
render(index, {json:{string:"mystring"}})
//Template to render (index.ejs)
var data = <%=JSON.stringify(json)%>;
So that I can pass those variables in the JSON to data. JSON is way bigger than here, I wrote only the part which creates a bug : the string contained here makes an "INvalid character" JS bug. What should I do ? Which encoding/decoding/escaping should I use ?
I have utf-8 everywhere, as all my other strings work, even with german or arabic characters. In this particular case, this is the "mystring" below which breaks the app :
If I remove the characters in the red circles It works.
Here is the string as it is in the JSON i receive :
"Otto\nTheater-, Konzert- und Gpb\n\u2028\u2028Rhoasse\u00dfe 20\u2028\n51065 K\u00f6ln\n\nTelefon: 0000-000000-0\u2028\nTelefax: 0000-000000\n\nE-Mail: address#mail.com\u2028"
Because it is a user-entered text, I must handle this kind of characters. I don't have access to the PHP part of the code, only to the nodeJS and client JS. How can I find and remove/convert those chars in JS ?
<%- JSON.stringify(data).replace(/[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g, "\\n") %>;
I ended up replacing invalid unicode characters (which are valid for JSON but not in JS code) with line breaks. This solves the problem
JSON is commonly thought to be a subset of JavaScript, but it isn't quite. Due to an unfortunate oversight, the raw characters U+2028 and U+2029 are permitted in JSON string literals, but not in JavaScript string literals. In JavaScript, they are interpreted as newlines and so having one in a string literal is a syntax error.
Consequently this:
var data = <%=JSON.stringify(json)%>;
isn't safe. You can make it so by manually replacing them with string-literal-escaped versions:
JSON.stringify(json).replace('\u2028', '\\u2028').replace('\u2029', '\\u2029')
Typically it's best to avoid this kind of problem, and keep code and data strictly separated, by dropping the JSON data into an HTML data- attribute. It can then be read out of the DOM from the client-side script and passed through JSON.parse. Then the only kind of escaping you have to worry about is normal HTML-escaping, which hopefully your templating language does by default.
The other characters in your answer are actually okay for JS string literals, except for the control characters, which JSON also escapes.
It may well make sense to remove some of these characters anyway, as an input filtering step. It's unusual and almost always undesirable to have cruft like U+2028 in your data. You could consider filtering out the characters unsuitable for use in markup which include U+2028/9 and other bad things like bidi overrides that can mess up your page rendering.
Seems like my data is getting corrupted when using HTTPapp.HTMLEncode( string ): String;
HTMLEncode( 'Jo&hn D<oe' ); // returns 'Jo&am'
This is not correct, and is corrupting my data. Does anyone have suggestions for VCL components that work better? Other than spending my time encoding all the cases
http://en.wikipedia.org/wiki/List_of_XML_and_HTML_character_entity_references
Update
After understanding more about HTML, I have found there is no need to encode the other characters referenced in my link. You would only need to know about the four HTML reserved characters being
&,<,>,"
The issue with the VCL HTTPApp.HTMLEncode( ) function is because of the buffer size and the new Delphi 2009/2010 specifications for default Unicode string types, this can be fixed the way that #mason says below, or it can be fixed with a call to WideFormatBuf( ) instead of the FormatBuf( ) that is currently in use.
Replacing the <, >, &, and " characters in a string is trivial. You could thus easily write your own routine for this. (And if your HTML page is UTF-8, there is absolutely no reason to encode any other characters, such as U+222B (the integral sign).)
But if you wish to stick to the Delphi RTL, then you can have a look at HTTPUtil.HTMLEscape with the exactly same signature as HTTPApp.HTMLEncode.
Or, have a look at this SO question.
You're probably using Delphi 2009 or 2010. It looks to me like they forgot to update HTMLEncode for Unicode. It's passing the wrong buffer lengths to FormatBuf.
The HTMLEncode routine is basically right, aside from that, and it's pretty short. You could probably just make your own copy. Everywhere it calls FormatBuf, it gives 5 parameters. The second and fourth are integer values. Double both of them in each call, (there are only four of them), and then it will work.
Also, you ought to open a QC report on this so it will get fixed.
Small hint: do not convert single quote (') to ' - some browsers do not understand this code because ' is not valid HTML
For details, see: "The Curse of '" and "XHTML and '"
(Both Delphi units mentioned do not convert single quotes).