Solving MismatchedInputException in JSON Parsing with Java and Spring Boot

Learn how to resolve `MismatchedInputException` when parsing JSON in Java and Spring Boot by understanding JSON structure and modifying your classes accordingly.
---

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: Error parsing JSON (MismatchedInputException)

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding MismatchedInputException in JSON Parsing

When working with JSON in Java applications, specifically those built using Spring Boot, you might come across errors like MismatchedInputException, especially during the deserialization process. This error typically indicates that there is a mismatch between the JSON structure you are trying to parse and the data types defined in your Java classes. If you’ve encountered this issue, don’t worry; you’re not alone. Let’s delve into the problem and explore actionable solutions.

The Problem: Parsing Errors

Consider the following JSON examples causing errors:

Working JSON Example:

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

Non-Working JSON Example:

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

What Went Wrong?

The key issue here is the structure of the info field in both JSON examples. In the first example, info is an array of objects, while in the second example, it’s a single object containing an array (person). This discrepancy leads to the parsing error as the Java model cannot map the object structure properly.

Solution: Restructuring Classes

To fix the problem, you have two primary paths:

Modify the JSON Input: This means ensuring the JSON data aligns with your existing Java data structures.

Adjust the Java Classes: Modify your classes to accommodate the JSON format that you prefer.

Recommended Approach

Since changing JSON might not be an option, let's focus on adjusting your Java classes.

Current Setup:

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

Required Class Structure: (For Non-Working JSON)

You need to change the info variable in PersonResponse to accommodate the structure of the non-working JSON:

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

With this structure, you redefine the info variable in PersonResponse so it matches the object you are trying to parse—making it possible to process your non-working JSON correctly.

Summary

In summary, the MismatchedInputException error arises from a structural mismatch between your JSON data and Java class definitions. To resolve it:

Identify the structure of the JSON you are attempting to parse.

Modify your Java classes to match the expected JSON format.

By making the appropriate structural adjustments, you’ll be able to eliminate the parsing error and successfully deserialize your JSON data using Jackson in Spring Boot.

If you face any further challenges or have questions, feel free to ask in the comments below!