Скачать или смотреть Resolving the HttpMessageNotReadableException in Spring Boot's JSON Parsing

Learn how to fix the `HttpMessageNotReadableException` error when serializing JSON in Spring Boot and Kotlin. Discover the importance of proper string formatting in your API responses.
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This video is based on the question https://stackoverflow.com/q/63581338/ asked by the user 'Maksym Rybalkin' ( https://stackoverflow.com/u/12898912/ ) and on the answer https://stackoverflow.com/a/63581443/ provided by the user 'Vüsal' ( https://stackoverflow.com/u/4213803/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the HttpMessageNotReadableException

If you’re developing a Spring Boot application and working with JSON data, you may occasionally encounter the HttpMessageNotReadableException. This typically signals that there was an error parsing the JSON data being handled by your application. It can be frustrating, especially if you're unsure of what went wrong.

In this guide, we will discuss a common scenario that raises this exception, particularly in Kotlin, and provide a clear solution.

The Problem

Consider the following Kotlin data class designed to hold response information for an application:

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You may be trying to serialize an instance of this class into JSON format, as shown in the partner() function:

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However, when executing this code block, you receive the following error:

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The error indicates that there is a problem with the JSON structure, specifically with how the catalogUrl is being formatted.

Diagnosing the Issue

The root cause of the error lies in how JSON strings are constructed in the withBody method. The catalogUrl is expected to be a proper JSON string but could be missing the necessary quotation marks if archiveUrl is unquoted.

This can cause Jackson (the JSON library used by Spring) to misinterpret the value of catalogUrl, leading to the parsing error.

Key Takeaway

JSON strings must be properly formatted with quotation marks surrounding their values.

The Solution

To fix the issue, you need to ensure that the value assigned to catalogUrl is appropriately wrapped in quotes. Here’s how you should modify your withBody definition:

Replace this line:

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With this corrected line:

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Revised Code Example

Here’s what the updated function would look like after implementing the above change:

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Conclusion

By ensuring that your JSON strings are properly formatted, you can avoid HttpMessageNotReadableException and other related parsing errors in your Spring Boot applications. Whenever you serialize data to JSON, pay close attention to the syntax—especially quotation marks—since they are critical for valid JSON.

If you encounter similar JSON parsing issues in the future, remember to check the format of the strings you are handling. Happy coding!