How to Use JSON Extractor in JMeter

How to Use JSON Extractor in JMeter

What is a JSON Extractor?

A JSON Extractor is a powerful tool used in performance testing to parse and extract data from JSON (JavaScript Object Notation) responses. JSON is a lightweight data format commonly used for APIs and web services to exchange information. By using a JSON Extractor, you can retrieve specific values from a JSON response, which is particularly useful for validating responses, storing data for later use, or passing values between requests in a test plan. In JMeter, a popular performance testing software, JSON Extractor plays a crucial role in automating API testing and performance validation.

How to Extract a JSON File?

Extracting data from a JSON file is a common task in both API testing and performance testing. JSON files can be used to store configuration details, user data, or response information that needs to be validated. Here’s a step-by-step guide to extracting data from a JSON file using JMeter:

1. Create a Dummy Sampler Returning JSON Data in Response:

Start by creating a dummy sampler retuning JSON response that contains the data you want to extract. This can be done using a JMeter Plugin Manager.

JSON example:

{
"user": {
"id": 1,
"name": "John Doe",
"email": "john.doe@example.com"
  }
}

2. Add a JSON Extractor to Your Test Plan:

Add a JSON Extractor after making a request that returns a JSON response (like a REST API call). To do this, right-click on the HTTP request sampler and navigate to Add → Post Processors → JSON Extractor.

3. Configure the JSON Extractor:

In the JSON Extractor configuration, define the JSON Path expressions to extract specific data. For example, to extract the user’s name, use the JSON path expression: `$.user.name`.

Specify the variable name where the extracted data will be stored. This allows you to use the data in subsequent requests or assertions.

4. Run the Test Plan:

Execute the test plan, and JMeter will parse the JSON response, extract the specified data, and store it in the defined variable for further use.

How to Parse a JSON Object?

Parsing a JSON object means reading and extracting meaningful data from it. In JMeter, parsing a JSON object is made simple with the use of a JSON Extractor:

1. Understanding JSON Format:

JSON objects are structured in key-value pairs, where data is organized hierarchically. For example:

     {
       "user": {
         "id": 1,
         "name": "Jane Doe",
         "details": {
           "email": "jane.doe@example.com",
           "phone": "123-456-7890"
         }
       }
     }

2. Using JSON Extractor to Parse the Object:

To parse the JSON object above, use JSON Path expressions in the JSON Extractor. For instance, to extract the email, use `$.user.details.email`. This path navigates through the object structure to retrieve the desired data.

3. Handling Complex JSON Structures:

JSON Extractor allows handling complex JSON structures by providing various options such as `Match No.` for extracting multiple values and `Default Value` to handle cases where the JSON path expression does not match any data.

4. Visualizing JSON Data:

To better understand and visualize JSON data, use tools like a JSON formatter or JSON file opener. These tools format and display JSON in a more readable structure, making it easier to create accurate JSON Path expressions for parsing.

Example of Using a JSON Extractor

To illustrate the use of a JSON Extractor, let’s consider a scenario where you need to extract data from a JSON response returned by an API call. Suppose you have a test plan in JMeter that sends an HTTP request to a JSON server or JSON placeholder API endpoint:

1. Set Up the HTTP Request Sampler:

Configure an HTTP Request sampler to make a GET request to an API that returns a JSON response, such as `https://jsonplaceholder.typicode.com/users/1`.

2. Add a JSON Extractor to the Sampler:

After configuring the HTTP Request sampler, add a JSON Extractor to parse the JSON response.

3. Configure the JSON Extractor:

In the JSON Extractor’s configuration, set the variable name to store the extracted email, such as `userEmail` and set the JSON Path expression to extract the user’s email: `$.email`.

4. Use the Extracted Data:

Now we can use the `${userEmail}` variable in subsequent HTTP requests or assertions to validate the response.

Conclusion

The JSON Extractor in JMeter is a powerful tool that allows you to parse and extract data from JSON responses, a common format in modern APIs. This capability is particularly useful in performance testing, API automation, and validating web services. By integrating JSON Extractor into your JMeter test plans, you can efficiently retrieve key information from JSON files or API responses, store them in variables, and utilize them for further tests.

When combined with other tools, such as Loadium, the testing process becomes even more powerful. Loadium, a highly versatile load testing software, provides enhanced support for running complex JMeter performance tests. It helps you scale your tests, visualize results in real-time, and even automate the entire performance testing process. Through Loadium’s seamless integration with JMeter, users can run tests on multiple endpoints, automate the extraction of data through JSON Extractor, and gain comprehensive insights into the performance of APIs and web applications.

Be sure to check out Loadium Blog Page for more topics, latest news, and in-depth articles on software testing.