json-path:数组过滤器结果中的第一个元素

Question

我刚接触json-path，但我经常使用xpath。我的问题是用json-path提取前一个过滤器产生的数组的nth元素。例如，使用以下json

{
    "store": {
        "book": [
            {
                "category": "reference",
                "author": "Nigel Rees",
                "title": "Sayings of the Century",
                "price": 8.95
            },
            {
                "category": "fiction",
                "author": "Evelyn Waugh",
                "title": "Sword of Honour",
                "price": 12.99
            },
            {
                "category": "fiction",
                "author": "Herman Melville",
                "title": "Moby Dick",
                "isbn": "0-553-21311-3",
                "price": 8.99
            },
            {
                "category": "fiction",
                "author": "J. R. R. Tolkien",
                "title": "The Lord of the Rings",
                "isbn": "0-395-19395-8",
                "price": 22.99
            }
        ],
        "bicycle": {
            "color": "red",
            "price": 19.95
        }
    },
    "expensive": 10
}

我想将第一本书与“小说”类别相匹配。

我试着用

$..book[?(@.category=='fiction')][0]

但似乎它与任何在线评估工具都不起作用。

错误在哪里？

提前谢谢。

Answer 1

您可以尝试将books数组映射到满足条件的列表中，并从中获取nth元素。像这样：

List<Map<String, Object>> bookList = JsonPath.parse(your_json).read("$..book[?(@.category=='fiction')]", List.class);
System.out.println("Printing the nth book = "+expensiveBooks.get(n));