Resolving the Unrecognized Token 'message' Error in Spring Boot WebClient POST Requests

A practical guide to troubleshooting the `Unrecognized token 'message'` error when sending POST requests in Spring Boot using WebClient. Learn how to adjust your response mapping and ensure proper JSON handling.
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Resolving the Unrecognized Token 'message' Error in Spring Boot WebClient POST Requests

If you're working with Spring Boot and using WebClient for making POST requests, you may encounter the error: Unrecognized token 'message': was expecting (JSON String, Number, Array, Object or token 'null', 'true' or 'false'). This error typically arises when the server's response or the structure of your request does not match expectations. In this guide, we'll dive into understanding this error and how to fix it effectively.

The Problem Explained

When you send a POST request, the system is trying to parse the JSON you provided, but it encounters a token ('message') that it didn't expect, resulting in a parsing error. Let's break down what might cause this issue:

Mismatched Expectations: The server could be expecting a specific format or doesn't recognize the fields defined in your request body.

Response Mismatch: If the server's response format doesn't match your expected type, it can also lead to parsing errors.

In essence, the expected JSON format and the actual data being sent or received have to align closely.

The Solution

To resolve the issue, follow these steps:

Step 1: Verify Your DTO Class

Ensure that your Data Transfer Object (DTO) class is correctly annotated and structured. Here's the DTO class you provided:

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

This appears to be correct, as long as the server expects these fields as part of the request body.

Step 2: Adjust the Service Layer to Match Expected Response

The service layer method sendSms currently expects a response of type BulkSmsRequestResourceTest, but based on the server's response code, it appears to return just a simple string message. Let's modify your service method to ensure it correctly handles the response type:

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

Step 3: Debugging Tips

Log the Request: Before sending your request, log the contents of the JSON body to make sure it matches what the server expects.

Check Server-Side Code: Review the server-side handling of the POST request to confirm that it's coded to parse the incoming request as expected.

Use Tools for Testing: Tools like Postman or Insomnia can help you manually test and analyze your requests and responses before and after setting up your Java methods.

Conclusion

The Unrecognized token 'message' error often indicates a mismatch between what your application is sending and what the server expects. By ensuring both the request and response formats align and making adjustments in your service layer, you can effectively resolve this issue.

For success in coding, always pay close attention to the data structures and formats you're working with to avoid parsing errors like these. Happy coding!