How can I collect JSON node names using Groovy JSONpath?

[Pavel Furs]

Hello,

I need to parse a JSON which looks like:
{
    "root": {
        "names": {
            "randomName1": {},
            "randomName2": {},
            "randomName3": {},
        }
    }
}
The goal is to collect element names into List<String>
According to http://groovy.codehaus.org/Reading+XML+using+Groovy%27s+XmlSlurper, the path expression should look like:

root.names.'*'.name()
or
root.names.'*'.collect{it.name()}

However I'm getting "java.lang.IllegalArgumentException: No signature of method: Script1.name() is applicable for argument types: () values: []" error while trying to use these expressions.

Could you please assist?
Thanks.

[Johan Haleby]

Hi,

Depth-first searching doesn't work (afaik) in Groovy with JSON documents unfortunately.

Here's what you can do:

List<String> list = from(json).getList("root.names*.getKey()", String.class);

Which will return [randomName3, randomName2, randomName1]. I don't know why the order is reversed but you can easily fix this (if order is important):

List<String> list = from(json).getList("root.names*.getKey().reverse()", String.class);

"*." means that for each element in the "root.names" list invoke method "getKey()". 

Regards,

/Johan

[Pavel Furs]

Thanks! It works fine.

Is there anywhere complete list of methods available for JSON?

[Johan Haleby]

Not that I know of. You can search for groovy collection tutorial or something like that. If you find a good reference please let us know.

/Johan