I need to change a JSON attribute's value in Java, I can get the value properly but I couldn't modify the JSON.
here is the code below
JsonNode blablas = mapper.readTree(parser).get("blablas");
for (JsonNode jsonNode : blablas) {
String elementId = jsonNode.get("element").asText();
String value = jsonNode.get("value").asText();
if (StringUtils.equalsIgnoreCase(elementId, "blabla")) {
if(value != null && value.equals("YES")){
// I need to change the node to NO then save it into the JSON
}
}
}
What is the best way to do this?
You need to get ObjectNode
type object in order to set values.
Take a look at this
The @Sharon-Ben-Asher answer is ok.
But in my case, for an array i have to use:
((ArrayNode) jsonNode).add("value");
I think you can just cast to ObjectNode and use put
method. Like this
ObjectNode o = (ObjectNode) jsonNode;
o.put("value", "NO");
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:
get
the value/array of the JsonNode
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@
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");
}
}
Source: Stackoverflow.com