How to validate a string is JSON or not in Java?

Question

I've already said, my question is different...question is already asked here, but i want a predefined method in java which checksgiven string is json format or not.

if there is no predefined method then at least tell a code which checks JSON Format or not, without using try catch block..

Thanks in advance...

It can easily be done using `try-catch` as shown [here](http://stackoverflow.com/a/10174938/2815219). — Raman Sahasi, Jan 25 '17 at 11:23
Possible duplicate of [How to check whether a given string is valid JSON in Java](http://stackoverflow.com/questions/10174898/how-to-check-whether-a-given-string-is-valid-json-in-java) — Autar, Jan 25 '17 at 11:24

score 3 · Answer 1 · edited Feb 23 '18 at 05:41

3

Use JSONObject's constructor from a String

    try {
        JSONObject o = new JSONObject(yourString);
    } catch (JSONException e) {
        LOGGER.error("No valid json");
    }

edited Feb 23 '18 at 05:41

Gowthaman M

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answered Jan 25 '17 at 11:11

SCouto

7,808
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is there any method ? which doesnt use try catch block? – sai Jan 25 '17 at 11:12
AFAIK this is the better way, you can build a method containing that block to avoid writing several catch's. Would that be acceptable according to your requirements? – SCouto Jan 25 '17 at 11:14
thanks for the reply. i just dont wanna use try catch blocks at all. like in javascript we hava a predefined function which validates string is json or not.. so i thought is there anything in java which automatically checks valid json or not.. i want boolean jsIsValid=method(string); – sai Jan 25 '17 at 11:20
1

@edsheeran First of all, Java is not JavaScript. Deal with it. And even [in JavaScript you are supposed to use `try-catch`](http://stackoverflow.com/a/9804835/1426227). – cassiomolin Jan 25 '17 at 11:22

Sanjay Kushwah · Answer 2 · 2020-02-15T17:02:37.023

0

public boolean isValidJson(String jsonStr) {
    Object json = new JSONTokener(jsonStr)).nextValue();
    if (json instanceof JSONObject || json instanceof JSONArray) {
      return true;
    } else {
      return false;
    }
}

Just pass any string in this function.

edited Feb 15 '20 at 17:02

answered May 29 '19 at 09:56

Sanjay Kushwah

190
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var jsonStr doesn't appear in function body – simon_xia Feb 14 '20 at 15:25
Just fixed the variable naming. Thanks for mentioning – Sanjay Kushwah Feb 15 '20 at 17:03
I think this one need some improvement. below example return true e.g. { "name" : mkj123 mk } – Jangid May 19 '21 at 15:14

score 0 · Answer 3 · answered Jul 03 '19 at 17:59

import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;    
/**
         * 
         * @param inputJosn
         * @return
         * @throws IOException 
         * @throws JsonParseException 
         * @throws JsonProcessingException
         */
        private static boolean isJsonValid(String inputJosn) throws JsonParseException, IOException  {
            ObjectMapper mapper = new ObjectMapper();
            mapper.enable(DeserializationFeature.FAIL_ON_READING_DUP_TREE_KEY);
            JsonFactory factory = mapper.getFactory();
            JsonParser parser = factory.createParser(inputJosn);
            JsonNode jsonObj = mapper.readTree(parser);
            System.out.println(jsonObj.toString());


            return true;
        }

How to validate a string is JSON or not in Java?

3 Answers3

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