I am looking at extracting the root element of a JSON document. It looks like this is possible neither using JsonPointer nor JsonPath as my attempts to look up for such an expression has been unsuccessful. Any tips would be appreciated. TIA.
Sample document:
{
"MESSAGE1_ROOT_INPUT": {
"CTRL_SEG": "test"
}
}
The below using gson 2.9.0:
$.*~
produces:
{"CTRL_SEG": "test"}
while JSONPath Online produces this:
[
"MESSAGE1_ROOT_INPUT"
]
The attempt is to get text "MESSAGE1_ROOT_INPUT" using JsonPath/JsonPointer expression(s). Note that, extracting this the traditional (substring or regex on a stringified json text) way, would preferably be my last resort.
Background: We are building an API service that accepts JSON documents with different roots. Such as, MESSAGE2_ROOT_INPUT, MESSAGE3_ROOT_INPUT, etc. It is based on this, the routing of a message further will occur.
Supported/Employed Languages: Java/GSON Library/RegEx
Gson does not natively support JSONPath or JSON Pointer. However, you can quite efficiently obtain the name of the first property using JsonReader:
public static String getFirstPropertyName(Reader reader) throws IOException {
// Don't have to call JsonReader.close(); that would just close the provided reader
JsonReader jsonReader = new JsonReader(reader);
jsonReader.beginObject();
return jsonReader.nextName();
}
There are however two things to keep in mind:
This only reads the beginning of the JSON document; it neither verifies that the complete JSON document has valid syntax, nor checks if there might be more top-level properties
This consumes some data from the Reader; to further process the data you have to buffer the data to allow re-reading it again (you can also first store the JSON in a String and pass a StringReader to JsonReader)
I want to get a nested field in a json string using JSONPath.
Take for example the following json:
{
"ID": "2ac464eb-352f-4e36-8b9f-950a24bb9586",
"PAYLOAD": "{\"#type\":\"Event\",\"id\":\"baf223c4-4264-415a-8de5-61c9c709c0d2\"}"
}
If I want to extract the #type field, I expect to do it like this
$.PAYLOAD.#type
But that doesn't seem to work..
Also tried this:
$.PAYLOAD['#type']
Do I need to use escape chars or something?
Posting my comment as an answer
"{\"#type\":\"Event\",\"id\":\"baf223c4-4264-415a-8de5-61c9c709c0d2\"}"
Isn't JSON, it's a string containing encoded JSON.
Since JsonPath can't decode such string, you'll have to use a language of your desire to decode the string.
Eg: Decoding JSON String in Java
I'm calling an API from Go and trying to push json string data from another api call into it.
I can hand craft the calls using a payload like
payload := strings.NewReader('[{"value1":333, "value2":444}]'
and everything is happy.
I'm now trying to covert this to take the json string {"value1":333, "value2":444} as an input parameter of type string to a function, but when I try and use that as the payload, the api is responding with
expected type: JSONArray, found: JSONObject
I naively tried setting the input to the function as []string and appending the data to an array as the input, but then strings.NewReader complained that it was being fed an array.. which is was.
I'm at a loss to work out how to convert a string of json into a json array that the api will be happy with.
I tried just surrounding the string with [] but the compiler threw a fit about incorrect line termination.
Must have been doing something wrong with the string, surrounding the {} with [] let the function pass the data, but there must be a better way than this.
Any ideas, or am I making this harder than it should be?
You were on the right track with the brackets, but you actually need to append the characters to the string. For example:
str := `{"value1":333, "value2":444}`
str = "[" + str + "]"
// [{"value1":333, "value2":444}]
https://play.golang.org/p/rWHCLDCAngd
If you use brackets outside a string or rune literal, then it is parsed as Go language syntax.
So I have some json that looks like this, which I got after taking it out of some other json by doing response.body.to_json:
{\n \"access_token\": \"<some_access_token>\",\n \"token_type\": \"Bearer\",\n \"expires_in\": 3600,\n \"id_token\": \<some_token>\"\n}\n"
I want to pull out the access_token, so I do
to_return = {token: responseJson[:access_token]}
but this gives me a
TypeError: no implicit conversion of Symbol into Integer
Why? How do I get my access token out? Why are there random backslashes everywhere?
to_json doesn't parse JSON - it does the complete opposite: it turns a ruby object into a string containing the JSON representation of that object is.
It's not clear from your question what response.body is. It could be a string, or depending on your http library it might have already been parsed for you.
If the latter then
response.body["access_token"]
Will be your token, if the former then try
JSON.parse(response.body)["access_token"]
Use with double quotes when calling access_token. Like below:
to_return = {token: responseJson["access_token"]}
Or backslashes are escaped delimiters and make sure you first parse JSON.
I'm trying to build a restful API and I'm struggling on how to serialize JSON data to a HTTP query string.
There are a number of mandatory and optional arguments that need to be passed in the request, e.g (represented as a JSON object below):
{
"-columns" : [
"name",
"column"
],
"-where" : {
"-or" : {
"customer_id" : 1,
"services" : "schedule"
}
},
"-limit" : 5,
"return" : "table"
}
I need to support a various number of different clients so I'm looking for a standardized way to convert this json object to a query string. Is there one, and how does it look?
Another alternative is to allow users to just pass along the json object in a message body, but I read that I should avoid it (HTTP GET with request body).
Any thoughts?
Edit for clarification:
Listing how some different languages encodes the given json object above:
jQuery using $.param: -columns[]=name&-columns[]=column&-where[-or][customer_id]=1&-where[-or][services]=schedule&-limit=5&return=column
PHP using http_build_query: -columns[0]=name&-columns[1]=column&-where[-or][customer_id]=1&-where[-or][services]=schedule&-limit=5&return=column
Perl using URI::query_form: -columns=name&-columns=column&-where=HASH(0x59d6eb8)&-limit=5&return=column
Perl using complex_to_query: -columns:0=name&-columns:1=column&-limit=5&-where.-or.customer_id=1&-where.-or.services=schedule&return=column
jQuery and PHP is very similar. Perl using complex_to_query is also pretty similar to them. But none look exactly the same.
URL-encode (https://en.wikipedia.org/wiki/Percent-encoding) your JSON text and put it into a single query string parameter. for example, if you want to pass {"val": 1}:
mysite.com/path?json=%7B%22val%22%3A%201%7D
Note that if your JSON gets too long then you will run into a URL length limitation problem. In which case I would use POST with a body (yes, I know, sending a POST when you want to fetch something is not "pure" and does not fit well into the REST paradigm, but neither is your domain specific JSON-based query language).
There is no single standard for JSON to query string serialization, so I made a comparison of some JSON serializers and the results are as follows:
JSON: {"_id":"5973782bdb9a930533b05cb2","isActive":true,"balance":"$1,446.35","age":32,"name":"Logan Keller","email":"logankeller#artiq.com","phone":"+1 (952) 533-2258","friends":[{"id":0,"name":"Colon Salazar"},{"id":1,"name":"French Mcneil"},{"id":2,"name":"Carol Martin"}],"favoriteFruit":"banana"}
Rison: (_id:'5973782bdb9a930533b05cb2',age:32,balance:'$1,446.35',email:'logankeller#artiq.com',favoriteFruit:banana,friends:!((id:0,name:'Colon Salazar'),(id:1,name:'French Mcneil'),(id:2,name:'Carol Martin')),isActive:!t,name:'Logan Keller',phone:'+1 (952) 533-2258')
O-Rison: _id:'5973782bdb9a930533b05cb2',age:32,balance:'$1,446.35',email:'logankeller#artiq.com',favoriteFruit:banana,friends:!((id:0,name:'Colon Salazar'),(id:1,name:'French Mcneil'),(id:2,name:'Carol Martin')),isActive:!t,name:'Logan Keller',phone:'+1 (952) 533-2258'
JSURL: ~(_id~'5973782bdb9a930533b05cb2~isActive~true~balance~'!1*2c446.35~age~32~name~'Logan*20Keller~email~'logankeller*40artiq.com~phone~'*2b1*20*28952*29*20533-2258~friends~(~(id~0~name~'Colon*20Salazar)~(id~1~name~'French*20Mcneil)~(id~2~name~'Carol*20Martin))~favoriteFruit~'banana)
QS: _id=5973782bdb9a930533b05cb2&isActive=true&balance=$1,446.35&age=32&name=Logan Keller&email=logankeller#artiq.com&phone=+1 (952) 533-2258&friends[0][id]=0&friends[0][name]=Colon Salazar&friends[1][id]=1&friends[1][name]=French Mcneil&friends[2][id]=2&friends[2][name]=Carol Martin&favoriteFruit=banana
URLON: $_id=5973782bdb9a930533b05cb2&isActive:true&balance=$1,446.35&age:32&name=Logan%20Keller&email=logankeller#artiq.com&phone=+1%20(952)%20533-2258&friends#$id:0&name=Colon%20Salazar;&$id:1&name=French%20Mcneil;&$id:2&name=Carol%20Martin;;&favoriteFruit=banana
QS-JSON: isActive=true&balance=%241%2C446.35&age=32&name=Logan+Keller&email=logankeller%40artiq.com&phone=%2B1+(952)+533-2258&friends(0).id=0&friends(0).name=Colon+Salazar&friends(1).id=1&friends(1).name=French+Mcneil&friends(2).id=2&friends(2).name=Carol+Martin&favoriteFruit=banana
The shortest among them is URL Object Notation.
How about you try this sending them as follows:
http://example.com/api/wtf?
[-columns][]=name&
[-columns][]=column&
[-where][-or][customer_id]=1&
[-where][-or][services]=schedule&
[-limit]=5&
[return]=table&
I tried with a REST Client
And on the server side (Ruby with Sinatra) I checked the params, it gives me exactly what you want. :-)
Another option might be node-querystring. It also uses a similar scheme to the ones you've so far listed.
It's available in both npm and bower, which is why I have been using it.
Works well for nested objects.
Passing complex objects as query parameters of a url.
In the example below, obj is the JSON object to pass into query parameters.
Injecting JSON object as query parameters:
value = JSON.stringify(obj);
URLSearchParams to convert a string to an object representing search params. toString to retain string type for appending to url:
queryParams = new URLSearchParams(value).toString();
Pass the query parameters using template literals:
url = `https://some-url.com?key=${queryParams}`;
Now url will contain the JSON object as query parameters under key (user-defined name)
Extracing JSON from url:
This is assuming you have access to the url (either as string or URL object)
url_obj = new URL(url); (only if url is NOT a URL object, otherwise ignore this step)
Extract all query parameters in the url:
queryParams = new URLSearchParams(url_obj.search);
Use the key to extract the specific value:
obj = JSON.parse(queryParams.get('key').slice(0, -1));
slice() is used to extract a tailing = in the query params which is not required.
Here obj will be the same object passed in the query params.
I recommend to try these steps in the web console to understand better.
You can test with JSON examples here: https://json.org/example.html