How to Resolve 400 Bad Request Errors When Sending JSON Requests with HTTPClient in Spring Boot

Discover how to troubleshoot and fix `400 Bad Request` errors when using Java's HTTPClient for REST API requests in a Spring Boot application.
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Understanding the 400 Bad Request Error in Java HTTPClient

Problem Overview

The issue occurs when sending JSON data to a specific URL using the HTTPClient, while receiving the desired response when making the same request via Postman or Spring’s RestTemplate. Here's a breakdown of the scenario:

Request Body:

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

Output with HTTPClient: 400 Bad Request error

Output with Postman: Successful response

In such cases, it's vital to ensure that your HTTPClient request is correctly configured to match what Postman is sending.

Troubleshooting the Issue

1. Compare the Requests

The first step in troubleshooting this issue is to compare the headers in the requests being sent by the HttpClient and Postman. Upon inspection, it was discovered that the following headers may be missing in the HTTPClient request:

Accept

Upgrade

Http2-Settings

2. Update Your Code

Here’s how to modify your existing Java code to include these headers. Adding the Accept header and ensuring you’re using HTTP/1.1 can help align your request more closely with what the server expects.

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

Conclusion

If you've experienced similar challenges or have further questions, share your thoughts in the comments below!