A third party NuGet package throws an exception and in its exception message there is a an error and a JSON object:
Request failed, Message: {"Message":"Some error message"}
How can I extract the JSON from string and get the Message property?
I know that I could use Regex to format the string before passing it to deserializer or even trim the text until the first {
Is there a cleaner way to do it using Json.NET?
No.
Json.Net is built to parse JSON. If you have extra text in the string that is not JSON, the parser will not be able to make sense of it. Your best bet is to strip off the text before the first brace (and after the last brace), like you suggested in your question. You can make a helper method to do this easily:
public static string ExtractJson(string text)
{
int i = text.IndexOf('{');
int j = text.LastIndexOf('}');
return i > -1 && j > i ? text.Substring(i, j - i + 1) : null;
}
Once you've extracted the JSON, you can use Json.Net like you normally would.
Fiddle: https://dotnetfiddle.net/WoflVv
Related
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.
I would like to parse json string using JObject.Parse() of NewtonSoft.Json. Assume that the json string is like this:
{"json":"{\"count\":\"123\"}"}
The result of jObject.First.ToString() is "json": "{\"count\":\"123\"}".
The result of jObject["json"].ToString() is {"count":"123"}. Enumerating gets the same result as this.
The testing code I used is like this.
[TestMethod()]
public void JsonParseTest()
{
var json = "{\"json\":\"{\\\"count\\\":\\\"123\\\"}\"}";
var jObject = JObject.Parse(json);
Console.WriteLine($"json : {json}");
Console.WriteLine($"jObject.First.ToString() : {jObject.First}");
Console.WriteLine($"jObject[\"json\"].ToString() : {jObject["json"]}");
}
We can see that enumerating of jObject will lose the character '\'. What is the problem? I would be appreciated for any suggestion :)
EDIT 1
The version of NewtonSoft is 12.0.3 released in 2019.11.09.
The parser isn't loosing anything. There is no literal \ in your example. The backslashes are purely part of the JSON syntax to escape the " inside the string vlue. The value of the key json is {"count":"123"}.
If you want to have backslashes in that value (however I don't see why you would want that), then you need add them, just like you added them in your C# string (C# and JSON happen to have the same escaping mechanism):
{"json":"{\\\"count\\\":\\\"123\\\"}"}
with leads to the C# code:
var json = "{\"json\":\"{\\\\\\\"count\\\\\\\":\\\\\\\"123\\\\\\\"}\"}";
I'm using Flink to process the data coming from some data source (such as Kafka, Pravega etc).
In my case, the data source is Pravega, which provided me a flink connector.
My data source is sending me some JSON data as below:
{"key": "value"}
{"key": "value2"}
{"key": "value3"}
...
...
Here is my piece of code:
PravegaDeserializationSchema<ObjectNode> adapter = new PravegaDeserializationSchema<>(ObjectNode.class, new JavaSerializer<>());
FlinkPravegaReader<ObjectNode> source = FlinkPravegaReader.<ObjectNode>builder()
.withPravegaConfig(pravegaConfig)
.forStream(stream)
.withDeserializationSchema(adapter)
.build();
final StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
DataStream<ObjectNode> dataStream = env.addSource(source).name("Pravega Stream");
dataStream.map(new MapFunction<ObjectNode, String>() {
#Override
public String map(ObjectNode node) throws Exception {
return node.toString();
}
})
.keyBy("word") // ERROR
.timeWindow(Time.seconds(10))
.sum("count");
As you see, I used the FlinkPravegaReader and a proper deserializer to get the JSON stream coming from Pravega.
Then I try to transform the JSON data into a String, KeyBy them and count them.
However, I get an error:
The program finished with the following exception:
Field expression must be equal to '*' or '_' for non-composite types.
org.apache.flink.api.common.operators.Keys$ExpressionKeys.<init>(Keys.java:342)
org.apache.flink.streaming.api.datastream.DataStream.keyBy(DataStream.java:340)
myflink.StreamingJob.main(StreamingJob.java:114)
It seems that KeyBy threw this exception.
Well, I'm not a Flink expert so I don't know why. I've read the source code of the official example WordCount. In that example, there is a custtom splitter, which is used to split the String data into words.
So I'm thinking if I need to use some kind of splitter in this case too? If so, what kind of splitter should I use? Can you show me an example? If not, why did I get such an error and how to solve it?
I guess you have read the document about how to specify keys
Specify keys
The example codes use keyby("word") because word is a field of POJO type WC.
// some ordinary POJO (Plain old Java Object)
public class WC {
public String word;
public int count;
}
DataStream<WC> words = // [...]
DataStream<WC> wordCounts = words.keyBy("word").window(/*window specification*/);
In your case, you put a map operator before keyBy, and the output of this map operator is a string. So there is obviously no word field in your case. If you actually want to group this string stream, you need to write it like this .keyBy(String::toString)
Or you can even implement a customized keySelector to generate your own key.
Customized Key Selector
My application is using camel rest (2.15.2) to catch a POST json String and then uses jettison to convert to a JSON Object. It is working fine with normal request.
POST request: {"request"={"lname"="aaa", "fname"="bb"}}
1. String body = exchange.getIn().getBody(String.class);
2. JSONObject obj = new JSONObject(body);
When i debug, variable body = {request={lname=aaa, fname=bb}}.
And line 2 returns a JSONObject. so far so good
if we try to another the request:
{"request"={"lname"=" ", "fname"="aa"}}
then body = {request={lname= , fname=aa}}
line2 returns Exception.
Could you please help me to fix this issue: convert json string which contains element has empty value string to json object.
The above request is acceptable in my scenarios.
Error:
org.codehaus.jettison.json.JSONException: Missing value. at character
15 of {request={lname= , fname=aa}} at
org.codehaus.jettison.json.JSONTokener.syntaxError(JSONTokener.java:463)
at
org.codehaus.jettison.json.JSONTokener.nextValue(JSONTokener.java:356)
at org.codehaus.jettison.json.JSONObject.(JSONObject.java:230)
at
org.codehaus.jettison.json.JSONTokener.newJSONObject(JSONTokener.java:412)
at
org.codehaus.jettison.json.JSONTokener.nextValue(JSONTokener.java:327)
at org.codehaus.jettison.json.JSONObject.(JSONObject.java:230)
at org.codehaus.jettison.json.JSONObject.(JSONObject.java:311)
I am trying to parse some JSON objects which is made just of (string,string) pairs, in order to emulate Resjson behaviour. The file I am parsing contains this.
{
"greeting":"Hello world",
"_greeting.comment":"Hello comment.",
"_greeting.source":"Original Hello",
}
Please note the last comma is incorrect, and I also used http://jsonlint.com/ to test JSON syntax. It tells me it is incorrect, as I expected. My - slightly modified - code is :
string path = #"d:\resjson\example.resjson";
string jsonText = File.ReadAllText(path);
IDictionary<string, string> dict;
try
{
dict = JsonConvert.DeserializeObject<IDictionary<string, string>>(jsonText);
}
catch(Exception ex)
{
// code never reaches here
}
My above code returns the IDictionary with the 3 keys as if the formatting was correct. If I serialize back, the string obtained is without the last comma.
My questions are :
Is Newtonsoft.Json so permissive that it allows users slight errors ?
If so, can I set the permissiveness so that it is more strict ?
Is there a way to check if a string is valid JSON format, using
Newtonsoft.Json with and/or without the permissiveness?