CODEWITHSUNDEEP
javaarraysjson
Alfred Francis
Alfred Francis

Reputation: 451

How to parse Json using Java?

I want to parse a json object in java.The json file is {"l1":"1","l2":"0","f1":"0","connected":"0","all":"0"} i am trying to write a java program to print above json as

l1=1
l2=0
f1=0
connected=0
all=0

The number of entries in the json file can be increased, so i have to loop through the json and print all data. This is what i've done so far.

public class main {
    public static void main(String[] args){
        try{
            URL url = new URL("http://localhost/switch.json");
            JSONTokener tokener = new JSONTokener(url.openStream());
            JSONObject root = new JSONObject(tokener);
            JSONArray jsonArray = root.names();
            if (jsonArray != null) { 
               int len = jsonArray.length();
               for (int i=0;i<len;i++){ 
                  System.out.println(jsonArray.get(i).toString());
               } 
            }   
        }catch (Exception e) {
            e.printStackTrace();
            System.out.println("Error Occured");
        }
    }
}

the above program can only print the first item of each array. But i am trying get the result i mentioned in the beginning. Can anybody help ??

Upvotes: 3

Views: 290

Answers (2)

udalmik
udalmik

Reputation: 7988

It is simple JSON object, not an array. You need to iterate through keys and print data:

    JSONObject root = new JSONObject(tokener);
    Iterator<?> keys = root.keys();

    while(keys.hasNext()){
        String key = (String)keys.next();
        System.out.println(key + "=" + root.getString(key));
    }

Please note that above solution prints keys in a random order, due to usage of HashMap internally. Please refer to this SO question describing this behavior.

Upvotes: 4

DNA
DNA

Reputation: 42597

Your JSON file does not contain an array - it contains an object.

JSON arrays are enclosed in [] brackets; JSON objects are enclosed in {} brackets.

[1, 2, 3]                     // array
{ one:1, two:2, three:3 }     // object

Your code currently extracts the names from this object, then prints those out:

JSONObject root = new JSONObject(tokener);
JSONArray jsonArray = root.names();

Instead of looping over just the names, you need to use the names (keys) to extract each value from the object: 

JSONObject root = new JSONObject(tokener);
for (Iterator<?> keys= root.keys(); keys.hasNext();){
  System.out.println(key + "=" + root.get(keys.next()));
}

Note that the entries will not print out in any particular order, because JSON objects are not ordered:

An object is an unordered set of name/value pairs -- http://json.org/

See also the documentation for the JSONObject class.

Upvotes: 4

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