JMeter: How to count JSON objects in an Array using jsonpath

Question

In JMeter I want to check the number of objects in a JSON array, which I receive from the server.

For example, on a certain request I expect an array with 5 objects.

[{...},{...},{...},{...},{...}]

After reading this: count members with jsonpath?, I tried using the following JSON Path Assertion:

• JSON Path: $
• Expected value: hasSize(5)
• Validate against expected value = checked

However, this doesn't seem to work properly. When I actually do receive 5 objects in the array, the response assertion says it doesn't match.

What am I doing wrong? Or how else can I do this?

Answer 1

Although JSONPath Extractor doesn't provide hasSize function it still can be done.

Given the example JSON from the answer by PMD UBIK-INGENIERIE, you can get matches number on book array in at least 2 ways:

1. Easiest (but fragile) way - using Regular Expression Extractor.

As you can see, there are 4 entries for category like:

{ "category": "reference",
{ \"category\": \"fiction\"
...

If you add a Regular Expression Extractor configured as follows:

It'll capture all the category entries and return matches number as below:

So you will be able to use this ${matches_matchNr} variable wherever required.

This approach is straightforward and easy to implement but it's very vulnerable to any changes in the response format. If you expect that JSON data may change in the foreseeable future continue with the next option.

2. Harder (but more stable) way - calling JsonPath methods from Beanshell PostProcessor

JMeter has a Beanshell scripting extension mechanism which has access to all variables/properties in scope as well as to the underlying JMeter and 3rd-party dependencies APIs. In this case you can call JsonPath library (which is under the hood of JsonPath Extractor) directly from Beanshell PostProcessor.

import com.jayway.jsonpath.Criteria;
import com.jayway.jsonpath.Filter;
import com.jayway.jsonpath.JsonPath;

Object json = new String(data);
List categories = new ArrayList();
categories.add("fiction");
categories.add("reference");
Filter filter = Filter.filter(Criteria.where("category").in(categories));
List books = JsonPath.read(json, "$.store.book[?]", new Filter[] {filter});

vars.put("JSON_ARRAY_SIZE", String.valueOf(books.size()));

The code above evaluates JSONPath expression of $.store.book[?] against parent sampler response, counts matches number and stores it into ${JSON_ARRAY_SIZE} JMeter Variable

which can later be reused in an if clause or an assertion.

References:

• JMeter – Working with JSON – Extract JSON response
• JMeter's User Manual Regular Expressions entry
• JSON Path Documentation and Examples
• How to use BeanShell: JMeter's favorite built-in component