Get Count of json key using Java Stream
问题
https://stackoverflow.com/questions/67016736/get-count-of-json-key-using-java-stream
I have a json object that looks like this
[{
"startAt": 1617605301292,
"endAt": 1617605317095,
"duration": 15803,
"selection": {
"selected.Speed": "0",
"selected.Low": "65535",
"selected.Fast": "7173",
"selected.medium": "5"
},
"details": {
"phase": [{
"value": "2",
"timestamp": 1617605301316
}]
}
},
{
"startAt": 1617603849697,
"endAt": 1617603966378,
"duration": 116681,
"selection": {
"selected.Speed": "0",
"selected.Low": "65535",
"selected.Fast": "123",
"selected.medium": "5"
},
"details": {
"phase": [{
"value": "2",
"timestamp": 1617603849749
}]
}
}
]
I need to count how many times selected.Fast has occurred. I am trying with stream and this is what I have written so far
List<Map<String, Object>> jsonObj = mapper.readValue(jArr, new TypeReference<List<Map<String, Object>>>(){});
Map<String, Long> counted = jsonObj.stream()
.map(x -> x.get("selection").toString() )
.collect(Collectors.toList())
.stream()
.collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
System.out.println(counted.toString());
But I am getting count of all the key inside selection object, and I want count for specific Json key which isselected.FastFor Exampleselected.Fast:"7173" -> occurred - 5times selected.Fast:"123" -> occurred - 2times
Any help would be appreciated.
解答
将不确定层级的json记录，输出所有层级的字段名。用Java 实现代码较长。
用Java 下的开源包 SPL 很容易写，只要 1 句：
A |
|
1 |
=json(file("data.json").read()).groups(#4.#3;count(~)).("selected.Fast:\""/#1/"\"-> occurred -"/#2/"times") |
SPL 提供了 JDBC 供 Java 调用，把上面的脚本存为 count.splx，在 Java 中以存储过程的方式调用脚本文件：
…
Class.forName("com.esproc.jdbc.InternalDriver");
con= DriverManager.getConnection("jdbc:esproc:local://");
st = con.prepareCall("call count()");
st.execute();
…
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