Need to update the value in a Json node

Question

I have some arbitrary Json and I want to replace some of the text fields with objects. The text fields have a certain pattern, for example, say they start with a dollar sign $. I have no idea in advance what the keys are.

The object I want to replace it with is a Pojo probably a Map or List, which can be easily serialized to Json

For example

{
   "key1" : "some value",
   "key2" : "$replaceMe",
   "key3" : {
       "key4" : "more complex",
       "key5" : "$andMe"
}

So after the replacement, the object would look something like this

{
   "key1" : "some value",
   "key2" : {},
   "key3" : {
       "key4" : "more complex",
       "key5" : {}
}

where {} represents the new object that replaced the string that was previously there

I figured out several ways to traverse the tree, but can't figure out a good way to keep track of the objects to be replaced and how to replace them.

How about [this](https://stackoverflow.com/questions/30997362/how-to-modify-jsonnode-in-java?noredirect=1&lq=1)? — yejianfengblue, Jul 19 '21 at 04:10

score 1 · Accepted Answer · answered Jul 19 '21 at 11:35

1

You can iterate over the JsonNode nodes of your json file checking the child nodes of every parent node : you can check if there are children nodes representing basic JSON String value with theJsonNode#isTextual method and if their text starts with the dollar sign like below:

ObjectMapper mapper = new ObjectMapper();
//with a generic parent jsnode and one child node of it
if (child.isTextual() && child.asText().startsWith("$")) {
    //delete the old text value and create an empty objectnode
    ((ObjectNode)parent).set(fieldName, mapper.createObjectNode());
}

For the creation of an empty ObjectNode child you can use the ObjectMapper#createObjectNode method like I have done above.

answered Jul 19 '21 at 11:35

dariosicily

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Thanks, my issues was not realizing I have to go through the parent. Can I iterate through the parents and change the structure as I go along? – Peter Kronenberg Jul 19 '21 at 12:56
1

@PeterKronenberg You are welcome. Yes , you can change it while iterating always storing the parent before and then change the children. – dariosicily Jul 19 '21 at 14:26
1

Moreover, all the nodes you are interested are leaves of the json tree. – dariosicily Jul 19 '21 at 18:42

Need to update the value in a Json node

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