How to add new node to Json using JsonPath?

Question

I'm working with JSON and facing some problems.

I want to insert/update a path in a JSON object. In the case that the path doesn't exist, it will be created then I insert a new value. In case that it exits, it will be updated by a new value

For example, I want to add new path like this:

val doc = JsonPath.parse(jsonString)
doc.add("$.user.name", "John")

but I always get this error, because the path doesn't exist:

class com.jayway.jsonpath.PathNotFoundException : Missing property in path $['user']

Therefore I want to create a new path if it does not exist.

This is my code, but jsonString doesn't change:

var jsonString = "{}" val conf = Configuration.defaultConfiguration().addOptions(Option.DEFAULT_PATH_LEAF_TO_NULL).addOptions(Option.SUPPRESS_EXCEPTIONS)
JsonPath.using(conf).parse(jsonString).set(JsonPath.compile("$.user.name"), "John") 
Log.d("TAG", "new json = $jsonString")

Please give me your advice. Thank you very much!!

This just skips lacking path or node but my json gets no changes — Uni
– Uni, Commented Aug 23, 2018 at 7:12

Yauhen · Accepted Answer · 2018-11-30 01:17:09Z

14

I tried three different JSON libraries with support of JsonPath/JsonPointer (Jackson, JsonPath and JSON-P) and none of them is able to reconstruct JSON object hierarchy in case of missing parent nodes. So I came up with my own solution for adding new values to JSON object using Jackson/JsonPointer as it allows to navigate through JsonPointer parts.

private static final ObjectMapper mapper = new ObjectMapper();

public void setJsonPointerValue(ObjectNode node, JsonPointer pointer, JsonNode value) {
    JsonPointer parentPointer = pointer.head();
    JsonNode parentNode = node.at(parentPointer);
    String fieldName = pointer.last().toString().substring(1);

    if (parentNode.isMissingNode() || parentNode.isNull()) {
        parentNode = StringUtils.isNumeric(fieldName) ? mapper.createArrayNode() : mapper.createObjectNode();
        setJsonPointerValue(parentPointer, parentNode); // recursively reconstruct hierarchy
    }

    if (parentNode.isArray()) {
        ArrayNode arrayNode = (ArrayNode) parentNode;
        int index = Integer.valueOf(fieldName);
        // expand array in case index is greater than array size (like JavaScript does)
        for (int i = arrayNode.size(); i <= index; i++) {
            arrayNode.addNull();
        }
        arrayNode.set(index, value);
    } else if (parentNode.isObject()) {
        ((ObjectNode) parentNode).set(fieldName, value);
    } else {
        throw new IllegalArgumentException("`" + fieldName + "` can't be set for parent node `"
                + parentPointer + "` because parent is not a container but " + parentNode.getNodeType().name());
    }
}

Usage:

ObjectNode rootNode = mapper.createObjectNode();

setJsonPointerValue(rootNode, JsonPointer.compile("/root/array/0/name"), new TextNode("John"));
setJsonPointerValue(rootNode, JsonPointer.compile("/root/array/0/age"), new IntNode(17));
setJsonPointerValue(rootNode, JsonPointer.compile("/root/array/4"), new IntNode(12));
setJsonPointerValue(rootNode, JsonPointer.compile("/root/object/num"), new IntNode(81));
setJsonPointerValue(rootNode, JsonPointer.compile("/root/object/str"), new TextNode("text"));
setJsonPointerValue(rootNode, JsonPointer.compile("/descr"), new TextNode("description"));

System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(rootNode));

This generates and prints the following JSON object:

{
  "root" : {
    "array" : [ {
      "name" : "John",
      "age" : 17
    }, null, null, null, 12 ],
    "object" : {
      "num" : 81,
      "str" : "text"
    }
  },
  "descr" : "description"
}

For sure, this doesn't cover all corner cases but works in most of the cases. Hope this helps someone else.

edited Nov 30, 2018 at 1:17

answered Nov 28, 2018 at 23:39

Yauhen

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3 Comments

Yu Jiaao Over a year ago

setJsonPointerValue(node, parentPointer, parentNode); // recursively reconstruct hierarchy

Volker Bach Dec 5, 2024 at 15:31

Dude, you saved my sprint

Yauhen Dec 6, 2024 at 22:32

Haha nice, glad it is still helpful for someone 6 years later 🙂

user598656 · Accepted Answer · 2020-03-20 10:27:43Z

2

To create a new node try put(path, key, object) on the WriteContext interface implemented by the result of JsonPath.parse(jsonString).

answered Mar 20, 2020 at 10:27

user598656

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Comments

NumeroUno · Accepted Answer · 2018-08-22 16:58:56Z

1

You can do it as follows:

JsonPath.parse(jsonString).set(JsonPath.compile("$.user.name"), "John");

answered Aug 22, 2018 at 16:58

NumeroUno

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6 Comments

Uni Over a year ago

I'm supposing that the beginning json is empty like this {} I still get this error class com.jayway.jsonpath.PathNotFoundException : Missing property in path $['user']

NumeroUno Over a year ago

Can you try with following: private static Configuration conf = Configuration.defaultConfiguration().addOptions(Option.DEFAULT_PATH_LEAF_TO_NULL).addOptions(Option.SUPPRESS_EXCEPTIONS); JsonPath.using(conf).parse(...

Uni Over a year ago

var jsonString = "{}" val conf = Configuration.defaultConfiguration().addOptions(Option.DEFAULT_PATH_LEAF_TO_NULL).addOptions(Option.SUPPRESS_EXCEPTIONS) JsonPath.using(conf).parse(jsonString).set(JsonPath.compile("$.user.name"), "John") Log.d("TAG", "new json = $jsonString") I tried your solution but jsonString doesn't change. Could you please help? I'm using Kotlin language. Thank you

Uni Over a year ago

It seems that it didn't work. Could you plz help? Thank you

aksh1618 Over a year ago

@NumeroUno Even with configuration, this works for a single key, but not for nested path; i.e. <"{}", "$.key", "value"> works, but <"{}", "$.nested.key", "value"> doesn't.

|

Neetu T · Accepted Answer · 2024-01-05 15:36:49Z

0

Put will help you to add or update the key:

JsonPath.parse(jsonString).put("user", "name", "John");

answered Jan 5, 2024 at 15:36

Neetu T

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