Logo Questions Linux Laravel Mysql Ubuntu Git Menu
 

How to modify JsonNode in Java?

Tags:

java

json

jackson

People also ask

What is ObjectNode in Java?

A ObjectNode provides a node for a linked list with Object data in each node.

How do you find the value of JsonNode?

We can access a field, array or nested object using the get() method of JsonNode class. We can return a valid string representation using the asText() method and convert the value of the node to a Java int using the asInt() method of JsonNode class.


JsonNode is immutable and is intended for parse operation. However, it can be cast into ObjectNode (and ArrayNode) that allow mutations:

((ObjectNode)jsonNode).put("value", "NO");

For an array, you can use:

((ObjectNode)jsonNode).putArray("arrayName").add(object.ge‌​tValue());

Adding an answer as some others have upvoted in the comments of the accepted answer they are getting this exception when attempting to cast to ObjectNode (myself included):

Exception in thread "main" java.lang.ClassCastException: 
com.fasterxml.jackson.databind.node.TextNode cannot be cast to com.fasterxml.jackson.databind.node.ObjectNode

The solution is to get the 'parent' node, and perform a put, effectively replacing the entire node, regardless of original node type.

If you need to "modify" the node using the existing value of the node:

  1. get the value/array of the JsonNode
  2. Perform your modification on that value/array
  3. Proceed to call put on the parent.

Code, where the goal is to modify subfield, which is the child node of NodeA and Node1:

JsonNode nodeParent = someNode.get("NodeA")
                .get("Node1");

// Manually modify value of 'subfield', can only be done using the parent.
((ObjectNode) nodeParent).put('subfield', "my-new-value-here");

Credits:

I got this inspiration from here, thanks to wassgreen@


I think you can just cast to ObjectNode and use put method. Like this

ObjectNode o = (ObjectNode) jsonNode; o.put("value", "NO");


The @Sharon-Ben-Asher answer is ok.

But in my case, for an array i have to use:

((ArrayNode) jsonNode).add("value");

You need to get ObjectNode type object in order to set values. Take a look at this


Just for the sake of understanding of others who may not get the whole picture clear following code works for me to find a field and then update it

ObjectMapper mapper = new ObjectMapper();
JsonNode rootNode = mapper.readTree(JsonString);    
JsonPointer valueNodePointer = JsonPointer.compile("/GrandObj/Obj/field");
JsonPointer containerPointer = valueNodePointer.head();
JsonNode parentJsonNode = rootNode.at(containerPointer);

if (!parentJsonNode.isMissingNode() && parentJsonNode.isObject()) {
    ObjectNode parentObjectNode = (ObjectNode) parentJsonNode;
    //following will give you just the field name. 
    //e.g. if pointer is /grandObject/Object/field
    //JsonPoint.last() will give you /field 
    //remember to take out the / character 
    String fieldName = valueNodePointer.last().toString();
    fieldName = fieldName.replace(Character.toString(JsonPointer.SEPARATOR), StringUtils.EMPTY);
    JsonNode fieldValueNode = parentObjectNode.get(fieldName);

    if(fieldValueNode != null) {
        parentObjectNode.put(fieldName, "NewValue");
    }
}