CODEWITHSUNDEEP
javajsonsimplejson
Rocking chief
Rocking chief

Reputation: 1069

Can't get value from JSONObject

So I am using the simple json library to perform some json operations. Right now I can construct a JSONObject from a json string but I am not able to get the value from the object I created. For example if I do something like:

String value = (String) jsonRecord.get("Key");

I will get an error saying:

java.lang.ClassCastException: org.json.simple.JSONObject cannot be cast to java.lang.String

I removed the type cast to string and it works in IntelliJ. However, when I do this at command line it gives me an error saying:

error: incompatible types: Object cannot be converted to String

The schema is as follows:

    {   
       "myArray": {
          "array": ["Decaf mocha", "Vanilla mocha", "Chai Latte"]
       },
        "Item": {
          "string": "Decaf macha"
        }
    }

Update: the toString() fixed the problem. But when I tried to get the array I am getting:

java.lang.ClassCastException: org.json.simple.JSONObject cannot be cast to org.json.simple.JSONArray

Can someone please suggest how to fix the problem? Thanks!

Upvotes: 0

Views: 6849

Answers (4)

Akoffice
Akoffice

Reputation: 381

Just need to add the current "org.json" dependency would resolve your issue as latest version holds get() method (JSONObject class) which returns Object.

Below is my maven dependency:-

<dependency>
    <groupId>org.json</groupId>
    <artifactId>json</artifactId>
    <version>20190722</version>
</dependency>

Below is my code which performs get key operation.

public void iterateJsonObject(JSONObject jsonObj) {
        jsonObj.keySet().forEach(keyStr ->
        {
            Object keyvalue = jsonObj.get(keyStr);
            System.out.println("key: "+ keyStr + " value: " + keyvalue);
        });
    }

Upvotes: 1

Leo Aso
Leo Aso

Reputation: 12473

Your value is a JSONObject, not a string. Your error message makes that quite clear. If you really want it as a string, use

String value = jsonRecord.get("Key").toString();

You can pass any object to System.out.println, not just strings, but to actually turn it to a string, you need to call toString() yourself.

However, if you're expecting an actual String as the Key, and not a JSONObject, then you should take a second look at your JSON, because you're doing something wrong.

UPDATE:

Okay, looking at your schema, I see the problem. Instead of mapping the keys to values directly, your JSON maps keys to objects which then contain values. So to get the array in the JSON you posted, instead of

value = jsonRecord.get("myArray")

you would use

JSONArray value = jsonRecord.getJSONObject("myArray").getJSONArray("array");

and for the string, you would use

String value = jsonRecord.getJSONObject("Item").getString("string");

Upvotes: 2

Nikhil Jain
Nikhil Jain

Reputation: 619

You are not converting the json record value that you are fetching into a string. 

String value = String.valueOf(jsonRecord.get("Key"));

his should fix your problem. You can also use toString() method but I personally prefer String.valueOf() over it because at times toString() tends to give garbage value.

Upvotes: 0

Mahachi
Mahachi

Reputation: 11

You can prevent the ClassCastException by using Generics, because Generics provide compile time checks and can be used to develop type-safe applications.

Upvotes: 0

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