How to Transform JSON with Jolt to Include Attributes in Array Elements

Learn how to easily use `Jolt` to modify your JSON data by adding attributes into each element of an array, with a straightforward example and a clear step-by-step guide.
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Transforming JSON with Jolt: Moving an Attribute in Array Elements

Introduction

In the world of data processing, JSON (JavaScript Object Notation) has become a standard format for data exchange. However, sometimes the JSON data structure does not meet our needs, especially when it comes to reorganizing and modifying its attributes. A common task developers encounter is the need to add certain fields into each object within an array. In this guide, we will address a specific question regarding the Jolt transformation library in JSON processing and provide a solution that will help you manipulate your data effectively.

The Problem

Suppose you have a JSON input that consists of various attributes, including an array of objects. The objective is to include a specific attribute (in this case, ref) into each of the objects within that array. Here’s a look at the original data and the desired outcome:

Original JSON:

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Desired JSON Output:

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The Attempted Jolt Specification

You’ve likely tried various Jolt specifications; however, they may not have produced the results you aimed for. Here’s an example of what you might have attempted:

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Unfortunately, this wasn't working out as expected. Let’s break down how to achieve the desired transformation effectively.

The Solution

To successfully transform the JSON according to the desired output, you can utilize the shift operation in your Jolt specification. Below is the specification that will achieve the goal of adding the ref field to each element in the array:

Jolt Specification

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Explanation of the Specification

Let’s delve into the components of this Jolt specification to understand how it operates:

operation: "shift"` - This instruction tells Jolt that we want to rearrange and transfer data according to the defined specifications.

Key Elements in the spec:

"id": "id": This maintains the id key from the original JSON.

"table": This references the array of objects, where we want to apply changes.

"*": {: The wildcard allows us to target all elements in the table array.

"*": "&2.[&1].&": This takes each original object from the array and retains all their existing keys and values.

"@ (2,ref)": "&2.[&1].ref": This line assigns the ref attribute to each object in the table, pulling it from the outer context at position @ (2) and placing it correctly within the nested structures.

Additional Notes

Using Ampersands (&): In Jolt specifications, ampersands used at the end of a key will assist in mapping substitutions without the need to repeat keys.

Changing Array Names: If needed, you can rename the current array (e.g., from table to tab) for better clarity or organizational structure.

Representing Keys: The constructs .[&1] are essential in indicating which elements are being combined within the newly structured JSON objects.

Handling All Keys: Using "*" recursively covers all keys within your specified array without the need to name them individually.

Conclusion

By following the aforementioned steps and utilizing the provided Jolt specification, you can effectively transform your JSON data to include any desired attributes in each element of an array. Mastering these transformations does not just enhance the efficiency of your data manipulation but also empowers your applications to manage data more effectively.

Feel free to experiment with different specifications and configurations to meet your specific data manipulation needs. If you have any questions or would like to share yo