Parsing JSON string

Parse JSON string using com.google.gson library in Java

com.google.gson library needs to be added to use this code.

Here is the example string:

String companyDetails = {"companyName":"abcd","address":"abcdefg"}

JSON strings can be parsed using below syntax in Java:

JsonParser parser =  new JsonParser();
JsonElement jsonElement = parser.parse(companyDetails);
JsonObject jsonObj = jsonElement.getAsJsonObject();
String comapnyName = jsonObj.get("companyName").getAsString();

Parse JSON string in JavaScript

In JavaScript, the JSON object is used to parse a JSON string. This method is only available in modern browsers (IE8+, Firefox 3.5+, etc).

When a valid JSON string is parsed, the result is a JavaScript object, array or other value.

JSON.parse('"bar of foo"')
// "bar of foo" (type string)
JSON.parse("true")
// true (type boolean)
JSON.parse("1")
// 1 (type number)
JSON.parse("[1,2,3]")
// [1, 2, 3] (type array)
JSON.parse('{"foo":"bar"}')
// {foo: "bar"} (type object)
JSON.parse("null")
// null (type object)

Invalid strings will throw a JavaScript error

JSON.parse('{foo:"bar"}')
// Uncaught SyntaxError: Unexpected token f in JSON at position 1
JSON.parse("[1,2,3,]")
// Uncaught SyntaxError: Unexpected token ] in JSON at position 7
JSON.parse("undefined")
// Uncaught SyntaxError: Unexpected token u in JSON at position 0

The JSON.parse method includes an optional reviver function which can limit or modify the parse result

JSON.parse("[1,2,3,4,5,6]", function(key, value) {
  return value > 3 ? '' : value;
})
// [1, 2, 3, "", "", ""]

var x = {};
JSON.parse('{"a":1,"b":2,"c":3,"d":4,"e":5,"f":6}', function(key, value) {
  if (value > 3) { x[key] = value; }
})
// x = {d: 4, e: 5, f: 6}

In the last example, the JSON.parse returns an undefined value. To prevent that, return the value inside the reviver function.

Parse JSON file with Groovy

Suppose we have the following JSON data:

{
    "TESTS": 
    [
         {
              "YEAR": "2017",
              "MONTH": "June",
              "DATE": "28"                  
         }
    ]
}

import groovy.json.JsonSlurper

class JSONUtils {

private def data;
private def fileName = System.getProperty("jsonFileName")

public static void main(String[] args)
{
    JSONUtils jutils = new JSONUtils()
    def month = jutils.get("MONTH");
}

Below is the parser:

private parseJSON(String fileName = "data.json")
{ 
    def jsonSlurper = new JsonSlurper()
    def reader

    if(this.fileName?.trim())
    {
        fileName = this.fileName
    }

    reader = new BufferedReader(new InputStreamReader(new FileInputStream(fileName),"UTF-8"));
    data = jsonSlurper.parse(reader);
    return data
}

def get(String item)
{
    def result = new ArrayList<String>();
    data = parseJSON()        
    data.TESTS.each{result.add(it."${item}")}
    return  result
}

}