jayway jsonpath throwing an error when reading a json path that does not exist despite being configured to

Question

I have some json that is like this:

{
  "root": {
    "metadata": {
      "name": "Farmer John",
      "hasTractor": false
    },
    "plants": {
      "corn": 137.137,
      "soy": 0.45
    },
    "animals": {
      "cow": 4,
      "sheep": 12,
      "pig": 1
    },
    "family": {
      "isMarried": true
    }
  }
}

That I am parsing like this using JsonPath:

val document = Configuration.defaultConfiguration()
        .addOptions(Option.DEFAULT_PATH_LEAF_TO_NULL)
        .jsonProvider()
        .parse(jsonString): Object
val value = JsonPath.read(document, "$.root.family.hasChild"): Any

But I am getting the error:

No results for path: $['root']['family']['hasChild']
com.jayway.jsonpath.PathNotFoundException: No results for path: $['root']['family']['hasChild']
    at com.jayway.jsonpath.internal.path.EvaluationContextImpl.getValue(EvaluationContextImpl.java:133)
    at com.jayway.jsonpath.JsonPath.read(JsonPath.java:187)
    at com.jayway.jsonpath.internal.JsonContext.read(JsonContext.java:102)

I should be getting null because I have the config option Option.DEFAULT_PATH_LEAF_TO_NULL set in the document creation code right? But instead I am getting that error

Edit:
I was able to get it working by simply catching the error and returning null like this:

val value = try {
  JsonPath.read(document, "$.root.family.hasChild"): Any
} catch {
  case _: PathNotFoundException => null
}

However, I am still looking for how to do it the "right" way

As mentioned in the title, jayway's `JsonPath` – Jared DuPont Dec 09 '20 at 19:09 — Jared DuPont, Dec 09 '20 at 19:09

wp78de · Accepted Answer · 2020-12-10T15:37:14.980

1

Try it like this using the JsonPath.parse() method:

Configuration configuration = Configuration.builder().options(Option.DEFAULT_PATH_LEAF_TO_NULL).build();
val value = JsonPath.parse(document, configuration).read("$.root.family.hasChild"));

Whether this is more or less efficient than catching an exception might depend on the implementation. Looking at the Jayway code, if the option DEFAULT_PATH_LEAF_TO_NULL and a non-existing leaf is encountered then simply null is returned, otherwise, an exception is thrown. The difference is probably not noticeable when dealing with a low number of cases, but things could add up if this happens a lot.

edited Dec 10 '20 at 15:37

answered Dec 10 '20 at 03:21

wp78de

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I did see that, but I was wondering if that is an efficient method? I am getting many values from the JSON and I couldn't tell if that method re-parsed the data every time a value was read – Jared DuPont Dec 10 '20 at 14:56
@JaredDuPont I have expanded the answer but I am not sure if we are still on topic if this turns into a performance question. – wp78de Dec 11 '20 at 04:44

jayway jsonpath throwing an error when reading a json path that does not exist despite being configured to

1 Answers1