Apache JMeter Correlation Using the JSON Extractor


Example

JSON is a commonly used data format that is used in web based applications. The JMeter JSON Extractor provides a way to use JSON Path expressions for extracting values from JSON-based responses in JMeter. This post processor must be placed as a child of the HTTP Sampler or for any other sampler that has responses.

To use this component, open the JMeter menu and: Add -> Post Processors -> JSON Extractor.

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The JSON Extractor is very similar to the Regular Expression Extractor. Almost all the main fields are mentioned in that example. There is only one specific JSON Extractor parameter: ‘Compute concatenation var’. In case many results are found, this extractor will concatenate them by using the ‘,’ separator and storing it in a var named _ALL.

Let’s assume this server response with JSON:

{ 
    "store": {
        "book": [ 
          { "category": "reference",
            "author": "Nigel Rees",
            "title": "Sayings of the Century",
            "price": 8.95
          },
          { "category": "fiction",
            "author": "Evelyn Waugh",
            "title": "Sword of Honour",
            "price": 12.99
          },
          { "category": "fiction",
            "author": "Herman Melville",
            "title": "Moby Dick",
            "isbn": "0-553-21311-3",
            "price": 8.99
          },
          { "category": "fiction",
            "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
    }
  }
}

The table below provides a great example of different ways to extract data from a specified JSON:

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Through this link you can find a more detailed description of the JSON Path format, with related examples.