Question 110366 in Json Question posted in
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Evaluate JSON object with expression with variable name, Josson

We need to evaluate JSON object expressions in java.

We have the following source JSON object

{
  "a": 100,
  "b": 200,
  "c": 300,
  "d": "calc(a+c)",
  "f": {
    "g": 100,
    "h": 200,
    "i": "calc(g+h)"
  }
}

we need output this format

{
  "a": 100,
  "b": 200,
  "c": 300,
  "d": 400,
   "f": {
    "g": 100,
    "h": 200,
    "i": 300
  }
}

We tried

we tried https://github.com/octomix/josson but that is more of a filtering JSON.

Tags:

2

Answers


  1. 0

    Hope this helps. All the necessary information is mentioned inside the code itself.

    import java.util.Iterator;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.json.JSONObject;

public class Main {

    public static void main(String[] args) {

        String inputString = "{'a': 100, 'b': 200, 'c': 300, 'd': 'calc(a+c)', 'f': {'g': 100, 'h': 200, 'i': 'calc(g+h)'} }";

        JSONObject newJSON = parseJSONValue(inputString, new JSONObject());

        System.out.println(newJSON.toString());
        // {"a":100,"b":200,"c":300,"d":400,"f":{"g":100,"h":200,"i":300}}

    }

    public static JSONObject parseJSONValue(String inputString, JSONObject resultJSON) {

        // Parse your string as JSONObject
        JSONObject jsonObject = new JSONObject(inputString);
        Iterator<String> keys = jsonObject.keys();

        // Iterate through your keys
        while (keys.hasNext()) {

            String key = keys.next();
            Object value = jsonObject.get(key);

            if (value instanceof Integer) {

                // Your normal values

            } else if (value instanceof String) {

                // Your 'calc(x+y)' strings

                // Extract everything between "(" and ")" from calc(a+c)
                Pattern pattern = Pattern.compile("\((.*?)\)");
                Matcher m = pattern.matcher(value.toString());

                while (m.find()) {

                    // a+c
                    String evalString = m.group(1);

                    // Split by '+'
                    String[] splitEvalString = evalString.split("\+");

                    // Check if exactly 2 values are found
                    if (splitEvalString.length == 2) {
                        value = (Integer) jsonObject.get(splitEvalString[0])
                                + (Integer) jsonObject.get(splitEvalString[1]);
                    }

                }

            } else if (value instanceof JSONObject) {
                // Your nested JSONObjects
                // Recursively call this method
                value = parseJSONValue(value.toString(), new JSONObject());
            }

            // Add to your new JSON Object
            resultJSON.put(key, value);

        }

        return resultJSON;

    }

}
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  2. 0 
    Josson josson = Josson.fromJsonString(jsonString);
JsonNode node = josson.getNode("field(d:eval(d), f.field(i:eval(i)))");
System.out.println(node.toPrettyString());

    Output

    {
  "a" : 100,
  "b" : 200,
  "c" : 300,
  "d" : 400.0,
  "f" : {
    "g" : 100,
    "h" : 200,
    "i" : 300.0
  }
}

    For unknown structure

    This solution assumes

    • the evaluation statement contains ()
    • there is only one evaluation statement in each level
    • you need to know the next level child name (f in this example)

    Transformation

    JsonNode node = josson.getNode(
    "let($p: '.+\(.*\).*')" +
    ".field(entries().[value =~ $p].key :: eval(*[value =~ $p])," +
    "       f.field(entries().[value =~ $p].key :: eval(*[value =~ $p]))" +
    ")");

    Suggest to group all the expressions in a pre-defined array

    Josson josson = Josson.fromJsonString(
    "{" +
    "  "a": 100," +
    "  "b": 200," +
    "  "c": 300," +
    "  "f": {" +
    "    "g": 100," +
    "    "h": 200" +
    "  }," +
    "  "exp": ["$.calc(a+c)"," +
    "            "$.calc(g+h, g:f.g, h:f.h)"," +
    "            "$.concat(a, '+', c, '=', calc(a+c))"," +
    "            "$.concat(f.g, '+', f.h, '=', calc(g+h, g:f.g, h:f.h))"" +
    "           ]" +
    "}");
JsonNode node = josson.getNode("field([email protected]())");
System.out.println(node.toPrettyString());

    Output

    {
  "a" : 100,
  "b" : 200,
  "c" : 300,
  "f" : {
    "g" : 100,
    "h" : 200
  },
  "exp" : [ 400.0, 300.0, "100+300=400.0", "100+200=300.0" ]
}
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