Pick the Nth item from a filter expression in JSONPath

问题

I've been trying to filter a specific element in my JSON using JSONPath and then to choose only the 1st item in the returned array of results.

My baisc JSONPath looks something like this:

$.store.book[?(@.category==fiction)].price

I want to add this [0] filter like this:

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

but it doesn't return results or if I put the [0] after the last "price" I get this error:

Filter: [0]['price'] can only be applied to arrays

I've been searching and couldn't find the right syntax to pull the 1st element in the array after applying a filter, just like in xpath.

This is the base JSON I'm working on:

{ "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
    }
  }
}

回答1:

Currently the only solution is:

List<Double> prices = JsonPath
   .parse(json)
   .read("$.store.book[?(@.category == 'fiction')].price");

Double firstPrice = prices.isEmpty() ? null : prices.get(0);

回答2:

how about when you want to use jsonpath with spring mvc, I ended up having

.andExpect(jsonPath("$[?(@.name.value == 'Item')].depth", is(Collections.singletonList(2))))

instead of

.andExpect(jsonPath("$[?(@.name.value == 'Item')][0].depth", is(2)))

which by the way used to work in older versions (0.9.1) for me

来源：https://stackoverflow.com/questions/30322086/pick-the-nth-item-from-a-filter-expression-in-jsonpath

标签

json

jsonpath