7.2. JSON Attributes

GeoMesa supports native JSON integration with GeoTools data stores. Simple feature String-type attributes can be marked as JSON and then queried using CQL. JSON attributes must be specified when creating a simple feature type:

import org.locationtech.geomesa.utils.interop.SimpleFeatureTypes;

// append the json hint after the attribute type, separated by a colon
String spec = "json:String:json=true,dtg:Date,*geom:Point:srid=4326"
SimpleFeatureType sft = SimpleFeatureTypes.createType("mySft", spec);
dataStore.createSchema(sft);

JSON attributes are still strings, and are set as any other strings. The value must be a valid JSON object or array:

String json = "{ \"foo\" : \"bar\" }";
SimpleFeature sf = ...
sf.setAttribute("json", json);

JSON attributes can be queried using JSONPath expressions. The first part of the path refers to the simple feature attribute name, and the rest of the path is applied to the JSON attribute. Note that in ECQL, path expressions must be enclosed in double quotes.

Filter filter = ECQL.toFilter("\"$.json.foo\" = 'bar'")
SimpleFeature sf = ...
sf.setAttribute("json", "{ \"foo\" : \"bar\" }");
filter.evaluate(sf); // returns true
sf.getAttribute("\"$.json.foo\""); // returns "bar"
sf.setAttribute("json", "{ \"foo\" : \"baz\" }");
filter.evaluate(sf); // returns false
sf.getAttribute("\"$.json.foo\""); // returns "baz"
sf.getAttribute("\"$.json.bar\""); // returns null

Note

GeoMesa does not support the JSONPath functions stddev(), keys(), concat() and append().

7.2.1. JSONPath CQL Filter Function

JSON attributes can contain periods and spaces. In order to query these attributes through an ECQL filter use the jsonPath CQL filter function. This passes the path to an internal interpreter function that understands how to handle these attribute names.

Filter filter = ECQL.toFilter("jsonPath('$.json.foo') = 'bar'")
SimpleFeature sf = ...
sf.setAttribute("json", "{ \"foo\" : \"bar\" }");
filter.evaluate(sf); // returns true

To handle periods and spaces in attribute names, enclose the attribute in the standard bracket notation. However, since the path is being passed to the jsonPath function as a string literal parameter, the single quotes need to be escaped with an additional single quote.

Filter filter = ECQL.toFilter("jsonPath('$.json.[''foo.bar'']') = 'bar'")
SimpleFeature sf = ...
sf.setAttribute("json", "{ \"foo.bar\" : \"bar\" }");
filter.evaluate(sf); // returns true

Similarly for spaces:

Filter filter = ECQL.toFilter("jsonPath('$.json.[''foo bar'']') = 'bar'")
SimpleFeature sf = ...
sf.setAttribute("json", "{ \"foo bar\" : \"bar\" }");
filter.evaluate(sf); // returns true

7.2.2. JSONPath With GeoServer Styles

When using JSON path in GeoServer styles (SLD or CSS), the attribute and path must be separated out in order for the GeoTools renderer to work correctly. In this case, pass in two arguments, the first being a property expression in double quotes of the JSON-type attribute name, and the second being the path:

* {
  mark: symbol(arrow);
  mark-size: 12px;
  mark-rotation: [ jsonPath("json", 'foo') ];
  :mark {
    fill: #009900;
  }
}