杰克逊：无法从 JsonNode 获取字符串值

Question

I have a root-JsonNode

JsonNode payloadNode;

with the following textValue (log.warn("PAYLOAD_NODE" + payloadNode.textValue());):

 {"id":0,"uid":""}

But when I,m trying to get String-value from this node:

 JsonNode idNode = payloadNode.get("id");

I receive null

Answer 1

Have a look at this .

Method to use for accessing String values. Does NOT do any conversions for non-String value nodes; for non-String values (ones for which isTextual() returns false) null will be returned. For String values, null is never returned (but empty Strings may be)

As it is a text value it is just a string that has no field "id".

So if you have something like this:

String s = "{\"id\":0,\"uid\":\"\"}";
payloadNode = om.valueToTree(s);

you would get such a log output if your JsonNode was just a string as in my example. You need to read your possible string as a json tree so like:

payloadNode = om.readTree(s);

Doing this will give you "0" for id and null for textValue() .