如何在 Java 中修改 JsonNode？
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How to modify JsonNode in Java?
提问by mstfdz
I need to change a JSON attribute's value in Java, I can get the value properly but I couldn't modify the JSON.
我需要在 Java 中更改 JSON 属性的值，我可以正确获取该值，但无法修改 JSON。
here is the code below
这是下面的代码
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?
做这个的最好方式是什么？
采纳答案by Sharon Ben Asher
JsonNodeis immutable and is intended for parse operation. However, it can be cast into ObjectNode(and ArrayNode) that allow mutations:
JsonNode是不可变的，用于解析操作。但是，它可以被转换为允许突变的ObjectNode(and ArrayNode)：
((ObjectNode)jsonNode).put("value", "NO");
For an array, you can use:
对于数组，您可以使用：
((ObjectNode)jsonNode).putArray("arrayName").add(object.ge??tValue());
回答by Eugen Halca
回答by Xdsasdf
I think you can just cast to ObjectNode and use putmethod. Like this
我认为你可以转换为 ObjectNode 并使用put方法。像这样
ObjectNode o = (ObjectNode) jsonNode;
o.put("value", "NO");
ObjectNode o = (ObjectNode) jsonNode;
o.put("value", "NO");
回答by Mubashar
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
只是为了理解其他人可能无法清楚地了解整个画面，以下代码对我有用，可以找到一个字段然后更新它
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");
}
}
回答by Alejandro
The @Sharon-Ben-Asher answer is ok.
@Sharon-Ben-Asher 的回答没问题。
But in my case, for an array i have to use:
但就我而言，对于数组，我必须使用：
((ArrayNode) jsonNode).add("value");
回答by matrixanomaly
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):
添加一个答案，因为其他一些人在已接受的答案的评论中表示赞同，他们在尝试转换为 ObjectNode（包括我自己）时遇到此异常：
Exception in thread "main" java.lang.ClassCastException:
com.fasterxml.Hymanson.databind.node.TextNode cannot be cast to com.fasterxml.Hymanson.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.
解决方案是获取“父”节点，并执行put，有效地替换整个节点，无论原始节点类型如何。
If you need to "modify" the node using the existing value of the node:
如果您需要使用节点的现有值“修改”节点：
getthe value/array of theJsonNode- Perform your modification on that value/array
- Proceed to call
puton the parent.
get的值/数组JsonNode- 对该值/数组执行修改
- 继续打电话
put给父母。
Code, where the goal is to modify subfield, which is the child node of NodeAand Node1:
代码，其中的目标是修改和subfield的子节点：NodeANode1
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:
学分：
I got this inspiration from here, thanks to wassgreen@
感谢wassgreen@，我从这里得到了这个灵感
