How can I replace a Java Jackson TextNode by another one (update)?

Question

My goal is to update some textual fields in a JsonNode.

    List<JsonNode> list = json.findValues("fieldName");
    for(JsonNode n : list){
        // n is a TextNode. I'd like to change its value.
    }

I don't see how this could be done. Do you have any suggestion?

Did you see http://stackoverflow.com/questions/17967531/jackson-api-partially-update-a-string — Semih Eker, Feb 19 '15 at 13:18
I don't have POJO that represents my Json. Do I really need to do all that in order to update a simple textNode??!! — yo_haha, Feb 19 '15 at 14:22
See also: http://wiki.fasterxml.com/JacksonHowToCustomDeserializers and http://www.baeldung.com/jackson-deserialization — Dave Jarvis, Sep 23 '16 at 01:46

score 31 · Accepted Answer · answered Feb 21 '15 at 18:22

31

The short answer is: you can't. TextNode does not expose any operations that allows you to alter the contents.

With that being said, you can easily traverse the nodes in a loop or via recursion to get the desired behaviour. Imagine the following:

public class JsonTest {
    public static void change(JsonNode parent, String fieldName, String newValue) {
        if (parent.has(fieldName)) {
            ((ObjectNode) parent).put(fieldName, newValue);
        }

        // Now, recursively invoke this method on all properties
        for (JsonNode child : parent) {
            change(child, fieldName, newValue);
        }
    }

    @Test
    public static void main(String[] args) throws IOException {
        String json = "{ \"fieldName\": \"Some value\", \"nested\" : { \"fieldName\" : \"Some other value\" } }";
        ObjectMapper mapper = new ObjectMapper();
        final JsonNode tree = mapper.readTree(json);
        change(tree, "fieldName", "new value");
        System.out.println(tree);
    }
}

The output is:

{"fieldName":"new value","nested":{"fieldName":"new value"}}

answered Feb 21 '15 at 18:22

wassgren

18,651
6
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Thanks for the code. What I finally did was looping over the jsonNode and constructing a StringBuilder with values I wanted. – yo_haha Feb 23 '15 at 08:31
@yo_haha, great! Make sure to escape the strings properly if you do not use JsonNode! – wassgren Feb 23 '15 at 08:37
This doesn't really help though if you want to change the text of the key instead of the value. In your example, what if I want to change "fieldName" to some other text but leave everything else the same? – Dasmowenator Feb 11 '19 at 20:32
The OP wanted to change to value. – wassgren Feb 12 '19 at 17:13
"put" is now deprecated, can use "set" instead. – a3765910 Apr 08 '22 at 04:22

Harshad Vyawahare · Answer 2 · 2016-07-13T08:34:06.503

5

Because you cannot modify a TextNode, you can instead get all the parentNodes of that field, and call the put operation on it with the same field name and a new value. It will replace the existing field and change the value.

List<JsonNode> parentNodes = jsonNode.findParents("fieldName");
if(parentNodes != null) {
  for(JsonNode parentNode : parentNodes){
    ((ObjectNode)parentNode).put("fieldName", "newValue");
  }
}

edited Jul 13 '16 at 08:34

answered Jul 12 '16 at 09:55

Harshad Vyawahare

568
7
14

2

It's always better to add an explanation to the code you're posting as an answer, so that it will helps visitors understand why this is a good answer. – abarisone Jul 12 '16 at 11:46
1

@abarisone - Because the code was self explanatory, I did not put an explanation. I have put it now, please check if it looks good. – Harshad Vyawahare Jul 13 '16 at 08:36

How can I replace a Java Jackson TextNode by another one (update)?

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