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jsonxpathjsonpath
magdmartin
magdmartin

Reputation: 1787

select a JSON element which have no node name

I have multiple JSON file who have all the same schema:

{"q0":{"query":"William","limit":3}}
{"q1":{"query":"Joe","limit":3}}

Using xpath or JSONPath I would like to extract each element into a table:

|id | query   |limit |
|q0 | William | 3    |
|q1 | Joe     | 3    |

I have no problem getting the query and limit field using ..query and ..limit but I can'a find the syntax to extract the id field (ie q0 and q1).

I've been trying @* and $* with no success. So is there a way to select a JSON element which have no node name?

As said in the comment, I am using talend tExtractJSONField component which use XPath to parse JSON.

Upvotes: 3

Views: 3924

Answers (4)

Hakan Bilgin
Hakan Bilgin

Reputation: 1122

Acutally, you can use XPath on your JSON structure using DefiantJS. This library extends the global object JSON with the method "search" - with which you can query JSON structure with XPath. The method returns the matches as an array.

var data = [
       {
          "q0": {
             "query": "William",
             "limit": 3
          }
       },
       {
          "q1": {
             "query": "Joe",
             "limit": 1
          }
       },
       {
          "q1": {
             "query": "Bill",
             "limit": 2
          }
       }
    ],
    found_1 = JSON.search(data, "//*[limit=3]"),
    found_2 = JSON.search(data, "//*[limit>1]");

document.getElementById('output_1').innerHTML = found_1[0].query;
document.getElementById('output_2').innerHTML = found_2[0].length;

To see this in action, check out this fiddle; http://jsfiddle.net/hbi99/zWU6x/

Also, check out the XPath Evaluator here to see and test XPath queries; http://defiantjs.com/#xpath_evaluator

Upvotes: 0

dirkk
dirkk

Reputation: 6218

Using . you can get the current element. There is no possibility using JsonPath to extract key names. Hence, you can do this in JavaScript by using for and grabbing the key name.

The following HTML shows a complete example:

<html>

  <head>
    <link rel="stylesheet" href="style.css">
    <script src="jsonpath.js"></script>    
  </head>

  <body>
    <h1 id="h1"></h1>
    <script type="text/javascript">
      var o = {"q0":{"query":"WilLIAM","limit":3}};
      var key;
      for(var i in jsonPath(o, ".")[0]) key = i;
      document.getElementById("h1").appendChild(document.createTextNode(
        key
        ));
    </script>
  </body>

</html>

Here is a Plunkr: http://plnkr.co/edit/CaZD1lVhr1E2S8VN5vnP

Upvotes: 2

Purushotham
Purushotham

Reputation: 3818

By using Google's Gson library you can read as below.

HashMap<String, JsonElement> myMap = new Gson().fromJson(jsonString, new TypeToken<HashMap<String, JsonElement>>(){}.getType());

String id = null, query = null;
int limit = 0;

for (Entry<String, JsonElement> entry : myMap.entrySet()) {
  id = entry.getKey();
  if(entry.getValue() != null) {
    JsonElement je = entry.getValue();
    if(je.isJsonObject()) {
      JsonObject jo = je.getAsJsonObject();
      query = jo.get("query").getAsString();
      limit = jo.get("limit").getAsInt();
    }
  }
}
print("id : " + id + " query : " + query + " limit : " + limit);

Upvotes: 0

Francois Beaussier
Francois Beaussier

Reputation: 568

The documentation at http://goessner.net/articles/JsonPath/ would point to $.q0.

Upvotes: 0

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