jsonpath-count

Posted on: 2019-10-08 2019-10-08
Tags: JSON

Count with JsonPath

JSON

1. Overview

In this quick tutorial, we’ll explore how to use JsonPath to count
objects and arrays in a JSON document.

JsonPath provides a standard mechanism to traverse through specific
parts of a JSON document. We can say JsonPath is to JSON what XPath is
to XML.

2. Required Dependencies

We’re using the following
JsonPath Maven dependency, which
is, of course, available on
Maven
Central:

<dependency>
    <groupId>com.jayway.jsonpath</groupId>
    <artifactId>json-path</artifactId>
    <version>2.4.0</version>
</dependency>

3. Sample JSON

The following JSON will be used to illustrate the examples:

{
    "items":{
        "book":[
            {
                "author":"Arthur Conan Doyle",
                "title":"Sherlock Holmes",
                "price":8.99
            },
            {
                "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
        }
    },
    "url":"mystore.com",
    "owner":"baeldung"
}

4. Count JSON Objects

The root element is denoted by the Dollar symbol “$”. In the following
JUnit test, we call JsonPath.read() with the JSON String and the
JSON path “$” that we want to count:

public void shouldMatchCountOfObjects() {
    Map<String, String> objectMap = JsonPath.read(json, "$");
    assertEquals(3, objectMap.keySet().size());
}

By counting the size of the resulting Map, we know how many elements
are at the given path within the JSON structure.

5. Count JSON Array Size

In the following JUnit test, we query the JSON to find the array
containing all books under the items element:

public void shouldMatchCountOfArrays() {
    JSONArray jsonArray = JsonPath.read(json, "$.items.book[*]");
    assertEquals(2, jsonArray.size());
}

6. Conclusion

In this article, we’ve covered some basic examples on how to count items
within a JSON structure.

You can explore more path examples in the
official JsonPath
docs.

As always, the code examples can be
found in the GitHub
repository.

getdocs

3043