Question 110746 in Json Question posted in
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How to conditionally extract a Json value using JayWay JsonPath?

I have the following JSON:

{
   "A":{
      "C":{
         "date":"2022-01-23"
      }
   },
   "B":{
      "D":{
         "date":"2022-01-24"
      }
   }
}

I would like to extract the value $.A.C.date if it is not null, else I would like to extract $.B.D.date.

Basically I would like to write an if else expression using JsonPath.
However, I don’t manage to make it work.

This is what I’ve tried:

String expression = "$.[?($.[?(@.A.C.date != null)].date || $.[?(@.B.D.date != null)].date)]";
JsonPath jsonPath = JsonPath.compile(expression);
String json = "...my JSON...";
Object extractedValue = jsonPath.read(json);
System.out.println(extractedValue);

… but the output I get is simply an empty array: [].

I have also tried this:

"$.[?($.[?(@.A.C.date != null)].A.C.date || $.[?(@.B.D.date != null)].B.D.date)]"

… but the output is a list with all the elements (because conditions match in both cases), yet I thought that writing .A.C.date was extracting just the date and not everything:

[
    {"A":{"C":{"date":"2022-01-23"}},
    "B":{"D":{"date":"2022-01-24"}}}
]

Anyone has an idea? I can’t find anything online which is similar to this.

This is the dependency I’m using:

<dependency>
    <groupId>com.jayway.jsonpath</groupId>
    <artifactId>json-path</artifactId>
    <version>2.4.0</version>
</dependency>
Tags:

2

Answers


  1. 0

    You may consider another library Josson to do the job.

    https://github.com/octomix/josson

    Josson josson = Josson.fromJsonString(
    "{" +
    "   "A":{" +
    "      "C":{" +
    "         "date":"2022-01-23"" +
    "      }" +
    "   }," +
    "   "B":{" +
    "      "D":{" +
    "         "date":"2022-01-24"" +
    "      }" +
    "   }," +
    "   "E":{" +
    "      "F":{" +
    "         "date":null" +
    "      }" +
    "   }" +
    "}");
String date = josson.getString("coalesce(A.C.date, B.D.date)");
System.out.println(date);
date = josson.getString("coalesce(E.F.date, B.D.date)");
System.out.println(date);
date = josson.getString("*.*.date[isNotNull()]");
System.out.println(date);
date = josson.getString("*().date[isNotNull()]");
System.out.println(date);
JsonNode node = josson.getNode("**.**.date[isNotNull()]*");
System.out.println(node.toString());

    Output

    2022-01-23
2022-01-24
2022-01-23
2022-01-23
["2022-01-23","2022-01-24"]
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  2. 0

    Here is a possible solution using com.jayway.jsonpath

    import com.jayway.jsonpath.JsonPath;

import java.util.List;

class Scratch {
    public static void main(String[] args) {
        JsonPath jsonPath = JsonPath.compile("$.*.*[?(@.date != "null")].date");
        List<String> read = jsonPath.read("{n" +
                "   "A":{n" +
                "      "C":{n" +
                "         "date":"2022-01-23"n" +
                "      }n" +
                "   },n" +
                "   "B":{n" +
                "      "D":{n" +
                "         "date":"2022-01-24"n" +
                "      }n" +
                "   }n" +
                "}");
        System.out.println(read.get(0));
    }
}

    It gets all the non-null dates then prints the first.

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