Parsing Json Numerical Values In Java

Question

My Java program takes a JSON string as an argument and parses it. I am using json-simple parser. Here is the link to it. I am trying to pass the following JSON string as an argument to the program.

{
  "obj":"timeout" , 
  "valInMs":15000
}

I am trying to get the value for "valInMs" . Following is the java code that is doing this

JSONParser parser = new JSONParser();
JSONObject jsonObj;
jsonObj = (JSONObject) parser.parse(jsonString);
Integer timeout = (Integer) paramJson.get("valInMs");

The above code raises java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.Integer .

I am trying to understand what should the program be expecting when it comes across a JSON numberic value. One cannot determine the "type" by looking at the JSON object.

How should a java program be handling this ?

Form json.org it seems like a Json "value" (out of many other things that it can be) can be "number" . A "number" can be one of the following:

number
 - int
 - int frac
 - int exp
 - int frac exp

It is quite unfortunate that JSON-Simple (apparently) lacks any sort of rigorous documentation. — Hot Licks
– Hot Licks, Commented Oct 2, 2014 at 18:30
I haven't tried it, but I think you can use int timeout = Integer.parseInt(paramJson.get("valInMs").toString()); — Indrajith
– Indrajith, Commented Oct 2, 2014 at 18:32

Hot Licks · Accepted Answer · 2014-10-02 18:25:28Z

1

Number timeoutNum = (Number) paramJson.get("valInMs");
Long timeoutLong = null;
Double timeoutDouble = null;
if (timeoutNum instanceof Long) {
    timeoutLong = (Long) timeoutNum;
}
else if (timeoutNum instanceof Double) {
    timeoutDouble = (Double) timeoutNum;
}
else { ... punt ... }

Or one can use intValue() et al on timeoutNum, if necessary coercing between integer and float.

answered Oct 2, 2014 at 18:25

Hot Licks

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Comments

Dream Green House · Accepted Answer · 2015-08-13 11:36:55Z

0

// This works for me

if (jobj.get("valInMs") != null)
{
    Number val = (Number) jobj.get("valInMs");
    int valInMs = val.intValue();
}
else
    valInMs = 0;

answered Aug 13, 2015 at 11:36

Dream Green House

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