我有一些json:
{"continue":{"continue":"||","rvcontinue":"20021126020855|1194424"},"query":{"pages":{"468997":{"ns":0,"revisions":[{"revid":445765,"comment":"","user":"Nate Silva","parentid":0,"timestamp":"2002-11-26T02:01:24Z"}],"pageid":468997,"title":"Vodafone"}}}}
我想以递归方式解析json的时间戳:
private static LocalDate getTimeStamp(JSONObject json) throws IOException {
Iterator<?> keys = json.keys();
LocalDate ld = null;
// iterate recursively over all keys from the JSON until current key is
// timestamp
while (keys.hasNext()) {
String key = (String) keys.next();
if (key.equals("timestamp")) {
// timezone does not matter, as we just want to extract the date
DateTimeFormatter formatter = DateTimeFormatter.ofPattern(
"yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.ENGLISH);
ld = LocalDate.parse(json.get(key).toString(), formatter);
System.out.println(ld);
break;
}
// if the current value is another JSON object, call setTimeStamp
// with value as param
else if (json.get(key) instanceof JSONObject) {
getTimeStamp((JSONObject) json.get(key));
}
// handle current value being JSON array
else if (json.get(key) instanceof JSONArray) {
JSONArray jarray = (JSONArray) json.get(key);
for (int i = 0; i < jarray.length(); i++) {
if (jarray.get(i) instanceof JSONObject) {
getTimeStamp((JSONObject) jarray.get(i));
}
}
}
}
System.out.println(ld);
return ld;
}
我尝试过调试它,但是在调用break
之后我不知道调用该方法的原因。它返回null而不是时间戳,尽管它到达代码的那一部分。
答案 0 :(得分:3)
"timestamp"
键嵌套在您的JSON中,因此需要对您的方法进行一些递归调用才能获得它。
进行递归调用时,应使用这些调用返回的值。
变化
getTimeStamp((JSONObject) json.get(key));
到
ld = getTimeStamp((JSONObject) json.get(key));
if (ld != null) return ld;
并更改
getTimeStamp((JSONObject) jarray.get(i));
到
ld = getTimeStamp((JSONObject) jarray.get(i));
if (ld != null) return ld;
答案 1 :(得分:3)
您的代码返回null
,因为您忽略了递归调用的结果。您应该将它们存储在变量中,如果不是null
,则返回它:
while (keys.hasNext() && ld == null) {
...
else if (json.get(key) instanceof JSONObject) {
ld = getTimeStamp((JSONObject) json.get(key));
}
// handle current value being JSON array
else if (json.get(key) instanceof JSONArray) {
JSONArray jarray = (JSONArray) json.get(key);
for (int i = 0; i < jarray.length(); i++) {
if (jarray.get(i) instanceof JSONObject) {
ld = getTimeStamp((JSONObject) jarray.get(i));
if (ld != null)
break;
}
}
}
}
请注意,由于您要查找第一个时间戳,while
循环应在ld
变为非null
时停止。