在 Groovy 中递归提取 JSON 字段值 [英] Recursively extracting JSON field values in Groovy
问题描述
我需要实现一个方法来扫描特定 targetField
的 JSON 字符串,并返回该字段的值(如果存在)或 null
(如果没有):
I need to implement a method that will scan a string of JSON for a particular targetField
and either return the value of that field (if it exists), or null
(if it doesn't):
// Ex: extractFieldValue(/{ "fizz" : "buzz" }/, 'fizz') => 'buzz'
// Ex: extractFieldValue(/{ "fizz" : "buzz" }/, 'foo') => null
String extractFieldValue(String json, String targetField) {
// ...
}
此解决方案必须是递归的,并且可以在(分层)JSON 字符串中的任何嵌套级别工作.它还需要适用于 JSON 数组.
This solution has to be recursive and work at any nesting-level in the (hierarchical) JSON string. Also it needs to work for JSON arrays as well.
迄今为止我最好的尝试:
My best attempt so far:
String extractFieldValue(String json, String targetField) {
def slurper = new JsonSlurper()
def jsonMap = slurper.parseText(json)
jsonMap."${targetField}"
}
这仅适用于顶级(非嵌套)JSON 字段.我问谷歌大神如何递归使用 JsonSlurper
,但找不到任何有用的东西.这里有什么想法吗?
This only works on top-level (non-nested) JSON fields. I asked the Google Gods how to use JsonSlurper
recursively, but couldn't find anything useful. Any ideas here?
推荐答案
在名为 json
的变量中给定此输入字符串:
Given this input string in a variable called json
:
{
"a":"a",
"b":{"f":"f", "g":"g"},
"c":"c",
"d":"d",
"e":[{"h":"h"}, {"i":{"j":"j"}}],
}
这个脚本:
import groovy.json.JsonSlurper
def mapOrCollection (def it) {
it instanceof Map || it instanceof Collection
}
def findDeep(def tree, String key) {
switch (tree) {
case Map: return tree.findResult { k, v ->
mapOrCollection(v)
? findDeep(v, key)
: k == key
? v
: null
}
case Collection: return tree.findResult { e ->
mapOrCollection(e)
? findDeep(e, key)
: null
}
default: return null
}
}
('a'..'k').each { key ->
def found = findDeep(new JsonSlurper().parseText(json), key)
println "${key}: ${found}"
}
给出以下结果:
a: a
b: null
c: c
d: d
e: null
f: f
g: g
h: h
i: null
j: j
k: null
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