I'm attempting to read the following JSON file ("my_file.json") into R, which contains the following:
[{"id":"484","comment":"They call me "Bruce""}]
using the jsonlite package (0.9.12), the following fails:
library(jsonlite)
fromJSON(readLines('~/my_file.json'))
receiving an error:
"Error in parseJSON(txt) : lexical error: invalid char in json text.
84","comment":"They call me "Bruce""}]
(right here) ------^"
Here is the output from R escaping of the file:
readLines('~/my_file.json')
"[{\"id\":\"484\",\"comment\":\"They call me \"Bruce\"\"}]"
Removing the quotes around "Bruce" solves the problem, as in:
my_file.json
[{"id":"484","comment":"They call me Bruce"}]
But what is the issue with the escapement?
In R strings literals can be defined using single or double quotes.
e.g.
s1 <- 'hello'
s2 <- "world"
Of course, if you want to include double quotes inside a string literal defined using double quotes you need to escape (using backslash) the inner quotes, otherwise the R code parser won't be able to detect the end of the string correctly (the same holds for single quote).
e.g.
s1 <- "Hello, my name is \"John\""
If you print (using cat¹) this string on the console, or you write this string on a file you will get the actual "face" of the string, not the R literal representation, that is :
> cat("Hello, my name is \"John\"")
Hello, my name is "John"
The json parser, reads the actual "face" of the string, so, in your case json reads :
[{"id":"484","comment":"They call me "Bruce""}]
not (the R literal representation) :
"[{\"id\":\"484\",\"comment\":\"They call me \"Bruce\"\"}]"
That being said, also the json parser needs double-quotes escaping when you have quotes inside strings.
Hence, your string should be modified in this way :
[{"id":"484","comment":"They call me \"Bruce\""}]
If you simply modify your file by adding the backslashes you will be perfectly able to read the json.
Note that the corresponding R literal representation of that string would be :
"[{\"id\":\"484\",\"comment\":\"They call me \\\"Bruce\\\"\"}]"
in fact, this works :
> fromJSON("[{\"id\":\"484\",\"comment\":\"They call me \\\"Bruce\\\"\"}]")
id comment
1 484 They call me "Bruce"
¹
the default R print function (invoked also when you simply press ENTER on a value) returns the corresponding R string literal. If you want to print the actual string, you need to use print(quote=F,stringToPrint), or cat function.
EDIT (on #EngrStudent comment on the possibility to automatize quotes escaping) :
Json parser cannot do quotes escaping automatically.
I mean, try to put yourself in the computer's shoes and image you should parse this (unescaped) string as json: { "foo1" : " : "foo2" : "foo3" }
I see at least three possible escaping giving a valid json:
{ "foo1" : " : \"foo2\" : \"foo3" }
{ "foo1\" : " : "foo2\" : \"foo3" }
{ "foo1\" : \" : \"foo2" : "foo3" }
As you can see from this small example, escaping is really necessary to avoid ambiguities.
Maybe, if the string you want to escape has a really particular structure where you can recognize (without uncertainty) the double-quotes needing to be escaped, you can create your own automatic escaping procedure, but you need to start from scratch, because there's nothing built-in.
Related
I receive JSON strings from a WebService with slashes in it.
When I parse them, Delphi adds backslashes.
V := TJSONObject.ParseJSONValue( '{"Kode":"ABC/123" }') ;
V.ToString returns : {"Kode":"ABC\\/123"}
What is best practice to parse JSON strings in Delphi?
And why does the function V.Value always returns an empty string?
In the unit System.JSON, I see the following code:
function TJSONAncestor.Value: string;
begin
Result := '';
end;
Do I need to add code myself to System units that ship with Delphi?
\ is required to be escaped as \\, so your claim that "Just removing the backslash in the result does not work, because the value could also be "ABC\123"" is wrong, as it would have to be "ABC\\123" instead.
The only other character required to be escaped is " as \". / is certainly not required to be escaped, but it MAY be escaped at the discretion of the implementation. It is not invalid to do so. As to WHY ToString() does that, you would have to ask Embarcadero.
If you needed to, you could easily do a search-and-replace of \/ into / without affecting other escape sequences, like \\ and \". Or, try using ToJSON() instead of ToString().
Regarding TJSONAncestor.Value(), TJSONAncestor is a base class, and its Value() is a virtual method that returns a blank string by default. Descendant classes (JSONString, TJSONNumber, etc) can override Value() to return more meaningful strings. But in your example, your input string represents a JSON object, so V will be pointing at a TJSONObject instance, and TJSONObject does not override Value() because it does not make sense for an object to be represented by a string. This is even documented behavior:
http://docwiki.embarcadero.com/Libraries/en/System.JSON.TJSONAncestor.Value
Returns the string representation of a simple JSON element like a string, number or boolean.
For structured JSON elements like an object and array returns empty string.
I have a csv file as followed:
Id,searchCriterion
18817,"{"basicSearchCriteria":{"name":{"text":"Kas"}}}"
I want to Post search criterion as a json in request body and prepared the following code as gatling scenario, but it does not work - I received 400 status code because of incorrect json in body:
val feeder = csv("search.csv")
object SearchWithCriteria
{
var request =
feed(feeder)
.exec(
http("POST with criteria page 1")
.post("api/resources?pageNumber=1&pageSize=10&id=${Id}")
.body(StringBody("""${searchCriterion}"""))
.check(status.is(200))
)
}
val basicSearch = scenario("Basic search (no search criteria)").exec(SearchWithCriteria.request)
setUp(
basicSearch.inject(rampUsers(1) during (1 seconds))
).protocols(httpProtocol)
When I past the json from csv file into body statement (as above) it works:
.body(StringBody("""{"basicSearchCriteria":{"name":{"text":"Kas"}}}"""))
Your file is not correct CSV because double quotes are reserved characters that have to be escaped.
From rfc4180:
If fields are not enclosed with double quotes, then double quotes may not appear inside the fields.
If double-quotes are used to enclose fields, then a double-quote appearing inside a field must be escaped by preceding it with another double quote.
You should have:
Id,searchCriterion
18817,"{""basicSearchCriteria"":{""name"":{""text"":""Kas""}}}"
We use Freemarker to transform one JSON to another. The input JSON is something like this:
{"k1": "a", "k2":"line1. \n line2"}
Post using the Freemarker template, the JSON is converted to:
{ \n\n "p1": "a", \n\n "p2": "line1. \n line2"}
Here is the logic we use to do the transformation
final Map<String, Object> input = JsonConverter.convertFromJson(input, Map.class);
final Template template = freeMarkerConfiguration.getTemplate("Template1.ftl");
final Writer out = new StringWriter();
template.process(input, out);
out.flush();
final String newlineFilteredResult = new JSONObject(out.toString).toString();
The conversion to JSON object fails due to a newline character inside a string for key k2 and gives the following exception:
Caused by: org.json.JSONException: Unterminated string at ...
I tried using the following but nothing works:
1. JSONObject.quote
2. JSONValue.escape
3. out.toString().replaceAll("[\n\r]+", "\\n");
I get the following exception due to the newline characters at the beginning as well:
Caused by: org.json.JSONException: Missing value at 1 [character 2 line 1]
Could someone please point me in the correct direction.
Edit
After further clarification from OP he had "${key}": "${value}" in his freemarker template and ${value} could contain line brakes. The solution in this case is to use ${value?json_string}.
Starting from FreeMarker 2.3.32 you can write "${key}": ${value?c} instead of "${key}": "${value}", because if the left-side of ?c is a string, now instead of failing, it quotes and escapes the string. Thus you don't even have to know if the left-side is a number/boolean, which must not be quoted (and ?c won't quote them), or a string, which must be quoted, as it's automatic.
Also, if the left-value is known to be missing/null sometimes, them ?cn will handle that case by printing a null literal.
Also, check out the c_format setting for best results, but by default string formatting is JSON compatible, so using ?c will be an improvement even without setting that.
I am trying to invoke my Lambda function by passing parameters as below. it contains apostrophe(').
https://invoke_url?param=[["kurlo jack's book","Adventure Books",8.8,1]]
Stringifyed to be 'https://invoke_url?param=%5B%5B%229780786706211%22s....`
I used the mapping below to pass parameter to lambda
"query": {
#foreach($queryParam in $input.params().querystring.keySet())
"$queryParam": "$util.escapeJavaScript($input.params().querystring.get($queryParam))" #if($foreach.hasNext),#end
#end
}
I got following error
{"message": "Could not parse request body into json: Unrecognized character escape \'\'\' (code 39)\n at [Source: [B#5b70c341; line: 29, column: 65]"}
i have also tried after removing double quotes from mapping template. But did't work.
Be sure to add .replaceAll("\\'","'") to your request body passthrough template after .escapeJavaScript(data)
I found this bit from AWS's documentation to be very helpful for this issue:
$util.escapeJavaScript()
Escapes the characters in a string using JavaScript string rules.
Note This function will turn any regular single quotes (') into
escaped ones (\'). However, the escaped single quotes are not valid in
JSON. Thus, when the output from this function is used in a JSON
property, you must turn any escaped single quotes (\') back to regular
single quotes ('). This is shown in the following example:
$util.escapeJavaScript(data).replaceAll("\\'","'")
I don't have a solution but I have narrowed the root cause. Lambda does not seem to like single quotes to be escaped with a single slash.
If you hardcode your mapping template to look like this:
{
"query-fixed": {
"param": "[[\"kurlo jack\\'s book\",\"Adventure Books\",8.8,1]]"
}
}
my test Lambda invocation succeeds. However, if you hardcode the template to this:
{
"query-fixed": {
"param": "[[\"kurlo jack\'s book\",\"Adventure Books\",8.8,1]]"
}
}
I get the same error message that you got above. Unfortunately, the second variation is what API Gateway produces for the Lambda invocation.
A workaround might involve using the template to replace single quotes escaped with slash to two slashes. See Replace a Substring of a String in Velocity Template Language
I'll follow up with Lambda internally and update if I hear anything or have a functional workaround.
Try changing your encoding of ' to %27 as per what is is defined in this W3Schools page (ironically their example does not encodes the single quote either, I guess its because it belongs to the "supported" ASSCII set of characters)
The "query string" (the part in the hyperlink after ?) must be a string. Whatever you have constructing that must be appended to it like: https://invoke_url?a=x&b=y
In your Lambda code put:
if( event.hasOwnProperty( 'params' ) )
if( event.params.hasOwnProperty( 'querystring' ) )
params = event.params.querystring;
(obviously some extraneous checks, probably unnecessary but ehh)
In your API Gateway go to:
APIs -> api_name -> Resources -> invoke_url -> GET -> Method Execution
Under URL Query String Parameters "Add query string" a and b (or whatever)
When you hit www.com/invoke_url?a=x&b=y you can now access them with:
...
params = event.params.querystring;
console.log( params.a, params.b );
...
Im using nodejs to parse some JSON files and insert them into mongodb,the JSON in these files have invalid JSON characters like \n,\" etc ..
The thing that i dont understand is that if i tried to parse like :
console.log(JSON.parse('{"foo":"bar\n"}'))
i get
undefined:1
{"foo":"bar
but if i tried to parse the input from the file (The file has the same string {"foo":"bar\n"})like:
new lazy(fs.createReadStream("info.json"))
.lines
.forEach(function(line){
var line = line.toString();
console.log(JSON.parse(line));
}
);
every thing works fine , i want to know if this fine and its ok to parse the files i have, or i should replace all invalid JSON characters before i parse the files ,
and why is there a difference between the two.
Thanks
If you can read "\n" if your text file, then it's not an end of line but the \ character followed by a n.
\n in a JavaScript string literal adds an end of line and they're forbidden in JSON strings.
See json.org :
To put an end of line in a JSON string, you must escape it, which means you must escape the \ in a JavaScript string so that there's "\n" in the string received by JSON.parse :
console.log(JSON.parse('{"foo":"bar\\n"}'))
This would produce an object whose foo property value would contain an end of line :