How to change element value in ArrayNode

Question

I have this file (example.json):

{
    "messages" : [ "msg 1", "msg 2", "msg 3" ],
}

Then I create a JsonNode like this:

BufferedReader fileReader = new BufferedReader(new FileReader("example.json"));
JsonNode rootNode = mapper.readTree(fileReader);

How do I change the array element value from "msg 1" to "msg 1A" without removing the element and adding a new one with value "msg 1A"?

Ernest Sadykov · Accepted Answer · 2015-07-23 14:50:26Z

7

If you want to change first element of the messages array, use following code:

((ArrayNode) rootNode.withArray("messages")).set(0, new TextNode("msg 1A"));

UPD

Another version, which removes and then inserts element (that is what you try to avoid):

((ArrayNode) rootNode.withArray("messages")).remove(0);
((ArrayNode) rootNode.withArray("messages")).insert(0, new TextNode("msg 1A"));

edited Jul 23, 2015 at 14:50

answered Jul 23, 2015 at 14:26

Ernest Sadykov

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5 Comments

lg.lindstrom Over a year ago

Yes,, can do that. But that is actually what I not did want to do,, remove the element,, and add a new.

Ernest Sadykov Over a year ago

@lg.lindstrom actually, that is exactly what you want: my code changes the element. You can check that using source code of ArrayNode (which is backed up by ArrayList).

lg.lindstrom Over a year ago

uhhh,, I see the difference. I try it out.

Ernest Sadykov Over a year ago

@lg.lindstrom I understood what you meant. You cannot change the message itself in-place, because every array element is a TextNode, which is immutable.

lg.lindstrom Over a year ago

okey. I understand. This is not what I hoped for,, but a answer smile

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