Problem filtering jsonpath-plus result set

Question

Using the jsonpath-plus module (typescript), I'm attempting to navigate to a specific object in a json document. The target object is several levels down, and includes passing through 2 levels of arrays. The following jsonpath statement:

$..['gmd:DQ_AbsoluteExternalPositionalAccuracy']

returns the following result in the online jsonpath test website jsonpath.com:

[
  {
    "gmd:nameOfMeasure": {
      "gco:CharacterString": "Difference to ICESat LE90"
    },
    "gmd:result": {
      "gmd:DQ_QuantitativeResult": {
        "gmd:valueUnit": {
          "@xlink:href": "http://www.opengis.net/def/uom/OGC/1.0/metre"
        },
        "gmd:value": {
          "gco:Record": {
            "gco:Real": "0.655608"
          }
        }
      }
    }
  },
  {
    "gmd:nameOfMeasure": {
      "gco:CharacterString": "Difference to ICESat Vertical Mean"
    },
    "gmd:result": {
      "gmd:DQ_QuantitativeResult": {
        "gmd:valueUnit": {
          "@xlink:href": "http://www.opengis.net/def/uom/OGC/1.0/metre"
        },
        "gmd:value": {
          "gco:Record": {
            "gco:Real": "-0.005536"
          }
        }
      }
    }
  },
  {
    "gmd:nameOfMeasure": {
      "gco:CharacterString": "Difference to ICESat Vertical RMSE"
    },
    "gmd:result": {
      "gmd:DQ_QuantitativeResult": {
        "gmd:valueUnit": {
          "@xlink:href": "http://www.opengis.net/def/uom/OGC/1.0/metre"
        },
        "gmd:value": {
          "gco:Record": {
            "gco:Real": "0.398874"
          }
        }
      }
    }
  },
  {
    "gmd:nameOfMeasure": {
      "gco:CharacterString": "Difference to GCP LE90"
    },
    "gmd:result": {
      "gmd:DQ_QuantitativeResult": {
        "gmd:valueUnit": {
          "@xlink:href": "http://www.opengis.net/def/uom/OGC/1.0/metre"
        },
        "gmd:value": {
          "gco:Record": {
            "gco:Real": "2.897789"
          }
        }
      }
    }
  },
  {
    "gmd:nameOfMeasure": {
      "gco:CharacterString": "Difference to GCP Vertical Mean"
    },
    "gmd:result": {
      "gmd:DQ_QuantitativeResult": {
        "gmd:valueUnit": {
          "@xlink:href": "http://www.opengis.net/def/uom/OGC/1.0/metre"
        },
        "gmd:value": {
          "gco:Record": {
            "gco:Real": "-0.383740"
          }
        }
      }
    }
  },
  {
    "gmd:nameOfMeasure": {
      "gco:CharacterString": "Difference to GCP Vertical RMSE"
    },
    "gmd:result": {
      "gmd:DQ_QuantitativeResult": {
        "gmd:valueUnit": {
          "@xlink:href": "http://www.opengis.net/def/uom/OGC/1.0/metre"
        },
        "gmd:value": {
          "gco:Record": {
            "gco:Real": "1.760134"
          }
        }
      }
    }
  },
  {
    "gmd:nameOfMeasure": {
      "gco:CharacterString": "Absolute horizontal accuracy CE90"
    },
    "gmd:result": {
      "gmd:DQ_QuantitativeResult": {
        "gmd:valueUnit": {
          "@xlink:href": "http://www.opengis.net/def/uom/OGC/1.0/metre"
        },
        "gmd:value": {
          "gco:Record": {
            "gco:Real": "10"
          }
        }
      }
    }
  },
  {
    "gmd:nameOfMeasure": {
      "gco:CharacterString": "Absolute vertical accuracy LE90"
    },
    "gmd:result": {
      "gmd:DQ_QuantitativeResult": {
        "gmd:valueUnit": {
          "@xlink:href": "http://www.opengis.net/def/uom/OGC/1.0/metre"
        },
        "gmd:value": {
          "gco:Record": {
            "gco:Real": "10"
          }
        }
      }
    }
  }
]

The object I need to retrieve in this example is the last object (containing the string "Absolute vertical accuracy LE90"), but I can't count on it always being in the same position. I've tried to filter this result set by appending

[?(@['gmd:nameOfMeasure']['gco:CharacterString']=="Absolute vertical accuracy LE90")]

to the original jsonpath expression (resulting in the new expression

$..['gmd:DQ_AbsoluteExternalPositionalAccuracy'][?(@['gmd:nameOfMeasure']['gco:CharacterString']=="Absolute vertical accuracy LE90")]

but the filter statement has no effect on the result. Just for kicks, I tried the same expression in the Jayway jsonpath implementation for java at https://jsonpath.herokuapp.com/ and successfully filtered the result down to the one desired object.

Can anyone tell me how to filter this result set properly using jsonpath-plus?

Answer 1

Query your sample JSON using

$[?(@['gmd:nameOfMeasure']['gco:CharacterString']==="Absolute vertical accuracy LE90")]

works for me; maybe you could simply query in two steps.

Since only the inner JSON was provided I can only guestimate what's wrong when querying the full JSON. One thing to look out for: JsonPath-Plus expects that the JSON is wrapped in square brackets:

[
  {"gmd:DQ_AbsoluteExternalPositionalAccuracy": [
    ...inner json      
  }
]