Java 解析JSON时如何找到父Json节点
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How to find parent Json node while parsing a JSON
提问by Optional
I am parsing a JSON Stream using Hymanson.
我正在使用 Hymanson 解析 JSON 流。
API that I am using is ObjectMapper.readTree(..)
我正在使用的 API 是 ObjectMapper.readTree(..)
Consider following stream:
考虑以下流：
{
"type": "array",
"items": {
"id": "http://example.com/item-schema",
"type": "object",
"additionalProperties": {"$ref": "#"}
}
}
Now when I read additionalProperties, I figure out there is a "$ref" defined here. Now to resolve the reference, I need to go to its parent and figure out the id (to resolve the base schema).
现在，当我阅读 additionalProperties 时，我发现这里定义了一个“$ref”。现在要解析引用，我需要转到其父级并找出 id（以解析基本架构）。
I can't find any API to go to parent of JsonNode holding additionalProperties. Is there a way I can achieve this?
我找不到任何 API 可以转到持有附加属性的 JsonNode 的父级。有没有办法实现这一目标？
Info:
信息：
Why I need this is I need to find the base schema against which $ref has to be resolved. And to figure out base schema, I need to know the id of its parents..
为什么我需要这个是我需要找到必须解决 $ref 的基本模式。为了找出基本模式，我需要知道它的父母的 id..
回答by StaxMan
Hymanson JSON Trees are singly-linked, there is no parent linkage. This has the benefit of reduced memory usage (since many leaf-level nodes can be shared) and slightly more efficient building, but downside of not being able to traverse up and down the hierarchy.
Hymanson JSON 树是单链接的，没有父链接。这样做的好处是减少了内存使用（因为可以共享许多叶级节点）和稍微更高效的构建，但缺点是无法上下遍历层次结构。
So you will need to keep track of that yourself, or use your own tree model.
所以你需要自己跟踪它，或者使用你自己的树模型。
回答by Addo Solutions
Got it!
知道了！
@Override
public void serialize(ObjectId value, JsonGenerator jgen, SerializerProvider provider) throws IOException {
JsonStreamContext parent = jgen.getOutputContext().getParent();
// Win!
}
回答by Mubashar
I am not able to understand the exact context of your problem. But I was doing some similar thing where I had to find a property value and then change it if the value meets some sort of criteria.
我无法理解您问题的确切背景。但是我正在做一些类似的事情，我必须找到一个属性值，然后在该值满足某种标准时更改它。
To search the value node I used atfunction with JsonPointerand to go to Parent I used JsonPointer.headfunction and used atagain on root json node.
要搜索我使用at函数的值节点JsonPointer并转到父级，我使用了JsonPointer.head函数并at在根 json 节点上再次使用。
example as below
示例如下
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);
//above is what you asked for as per my understanding
//following you can use to update the value node just for
//the sake of completeness why someone really look for parent
//node
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');
}
}
