Java JsonPath 数组的长度

Question

我有一个像这样的 Json:

{
    "hello": {
        "hello": [
            {
                "wwrjgn": "aerg",
                "aaa": "gggg",
                "rfshs": {
                    "segse": "segsegs",
                    "xx": "rgwgwgw",
                    "x-e ": "eergye"
                },
                "egg": "sgsese",
                "segess": "sgeses",
                "segess": "segess"
            },
            {
                "esges": "segesse",
                "segesg": "ws",
                "rddgdr": {
                    "rdrdrdg": “srgsesees"
                },
                "drr": 3600,
                "esese": "uytk",
                "wew": "699",
                "eses": “qe4ty"
            }
        ],
        "how": www"
    }
}

我执行以下操作:

Object document = 
Configuration.defaultConfiguration().addOptions().jsonProvider()
            .parse(ka.toJSONString());
int queries = JsonPath.read(document, "$..hello.length()");

    System.out.println("THE LENGTH OF THE NUMBER OF QUERIES " + queries);

我得到:

nested exception is java.lang.ClassCastException: net.minidev.json.JSONArray 
cannot be cast to java.base/java.lang.Integer] with root cause
java.lang.ClassCastException: net.minidev.json.JSONArray cannot be cast to 
java.base/java.lang.Integer

在这里尝试:http://jsonpath.herokuapp.com/?path= $..hello.length()我得到:

[
   2,
   2
]

这就是我需要的。

知道我做错了什么吗？提前致谢。

Answer 1

这个...

JsonPath.read(document, "$..hello.length()")

... 会将其响应转换为 net.minidev.json.JSONArray 的实例不能转换为 int 。这解释了ClassCastException

你看到的原因......

[
   2,
   2
]

...当尝试在线评估器时，这是toString()对于JSONArray实例返回该字符串。

要获取代码中的“查询数量的长度”，只需将 JsonPath 输出读取为 JSONArray然后获取该类型的大小属性。例如:

JSONArray read = JsonPath.read(document, "$..hello.length()");
// prints:
//    THE LENGTH OF THE NUMBER OF QUERIES 2
System.out.println("THE LENGTH OF THE NUMBER OF QUERIES " + read.size());

您还可以返回 List<Integer ，例如:

List<Integer> read = JsonPath.read(document, "$..hello.length()");
// prints:
//    THE LENGTH OF THE NUMBER OF QUERIES 2
System.out.println("THE LENGTH OF THE NUMBER OF QUERIES " + read.size());