How to Update JSON Values Using Jackson in Java

Описание: Struggling to update values in a JSON file using Jackson in Java? This guide provides an easy solution, breaking down the process step-by-step to ensure you can modify your JSON objects without issues.
---
This video is based on the question https://stackoverflow.com/q/74031035/ asked by the user 'tester' ( https://stackoverflow.com/u/20114105/ ) and on the answer https://stackoverflow.com/a/74031404/ provided by the user 'Raymond Choi' ( https://stackoverflow.com/u/9402689/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Not able to update the values in jscon file -jackson

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Update JSON Values Using Jackson in Java: A Step-by-Step Guide

Working with JSON data in Java can sometimes lead to frustrating challenges, especially when it comes to updating values. One common issue developers face is the ClassCastException when trying to modify fields in a JSON node. In this guide, we'll delve into a specific scenario where a developer encountered this problem while attempting to change values in a JSON file using Jackson.

The Problem at Hand

The developer wanted to update two values in their JSON file:

project-name

email-subject

The JSON structure looked as follows:

[[See Video to Reveal this Text or Code Snippet]]

However, upon executing the update commands, the developer faced this exception:

[[See Video to Reveal this Text or Code Snippet]]

This error indicates that the program was trying to treat a JSON text node as an object node, which isn't allowed. So, how can we successfully make the necessary updates?

Solution Breakdown

Understanding the JSON Structure

Before diving into the solution, it's crucial to understand the hierarchy of the JSON structure:

notification is an object that contains one field: email-subject.

project-name is a field at the root level.

Given this structure, let’s look at how to correctly access and update these fields:

Step 1: Reading the JSON File

We start by creating an ObjectMapper instance and reading the JSON file:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Accessing the Nested Fields

Next, to access the notification object and the specific fields we want to update, we can do the following:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Updating the Fields

Here's where the magic happens! We can now update the fields correctly by ensuring that we're casting to the correct type:

[[See Video to Reveal this Text or Code Snippet]]

Step 4: Writing Back to the File

Once we have made our changes, the next step is to write the updated JSON back to the file:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following these structured steps, you can avoid the ClassCastException by ensuring you are correctly identifying the ObjectNode and making your updates to the appropriate nodes. Remember that an understanding of your JSON hierarchy is key to effectively using Jackson for JSON manipulation in Java.

If you find yourself in similar situations, use this guide to troubleshoot your code and refine your approach to JSON updates. Happy coding!