JsonPath Functions for Array Operations: min, max, avg, stddev, length, sum

The article continues the JsonPath practice series by introducing the function API that operates on JSON arrays, complementing the previously covered basic JsonPath queries.

Sample JSON data used in the examples:

JSONObject json = JSON.parseObject("{" +
        "    \"store\": {" +
        "        \"book\": [" +
        "            {" +
        "                \"category\": \"reference\"," +
        "                \"author\": \"Nigel Rees\"," +
        "                \"title\": \"Sayings of the Century\"," +
        "                \"page\": \"D\"," +
        "                \"pages\": [\"S\",\"X\",\"G\"]," +
        "                \"price\": 8.95" +
        "            }," +
        "            {" +
        "                \"category\": \"fiction\"," +
        "                \"author\": \"Evelyn Waugh\"," +
        "                \"title\": \"Sword of Honour\"," +
        "                \"page\": \"A\"," +
        "                \"pages\": [\"A\",\"B\"]," +
        "                \"price\": 12.99" +
        "            }," +
        "            {" +
        "                \"category\": \"fiction\"," +
        "                \"author\": \"Herman Melville\"," +
        "                \"title\": \"Moby Dick\"," +
        "                \"isbn\": \"0-553-21311-3\"," +
        "                \"page\": \"B\"," +
        "                \"pages\": [\"E\",\"F\"]," +
        "                \"price\": 8.99" +
        "            }," +
        "            {" +
        "                \"category\": \"fiction\"," +
        "                \"author\": \"J. R. R. Tolkien\"," +
        "                \"title\": \"The Lord of the Rings\"," +
        "                \"isbn\": \"0-395-19395-8\"," +
        "                \"page\": \"C\"," +
        "                \"pages\": [\"C\",\"D\"]," +
        "                \"price\": 22.99" +
        "            }" +
        "        ]," +
        "        \"bicycle\": {" +
        "            \"color\": \"red\"," +
        "            \"price\": 19.95" +
        "        }" +
        "    }," +
        "    \"expensive\": 10," +
        "    \"ss\": [32,32,4,23]" +
        "}");

Getting the Minimum Value of an Array

JsonPath expression: $.ss.min()

Object read = JsonPath.read(json, "$.ss.min()");
output(read);

Console output shows 4.0 (a double value).

Getting the Maximum Value of an Array

JsonPath expression: $.ss.max()

Object read = JsonPath.read(json, "$.ss.max()");
output(read);

Console output shows 32.0 (also a double ).

Getting the Average Value of an Array

JsonPath expression: $.ss.avg()

Object read = JsonPath.read(json, "$.ss.avg()");
output(read);

Console output shows 22.75 (a double ).

Getting the Standard Deviation of an Array

JsonPath expression: $.ss.stddev()

Object read = JsonPath.read(json, "$.ss.stddev()");
output(read);

Console output shows 11.431863365173676 (a double ).

Getting the Length of an Array

JsonPath expressions: $.ss.length() and $.store.book.length()

Object read = JsonPath.read(json, "$.ss.length()");
output(read);

Object read2 = JsonPath.read(json, "$.store.book.length()");
output(read2);

Console output shows 4 for the ss array.

Getting the Sum of an Array

JsonPath expression: $.ss.sum()

Object read = JsonPath.read(json, "$.ss.sum()");
output(read);

Console output shows 91.0 (a double ).

The series of JsonPath API tutorials is now complete; the author mentions upcoming content on a JsonPath utility using Groovy operator overloading.