Feign DecodeException: JSON Parse Error - Expecting '[', Found '{' - Spring Boot

This error message indicates that your Spring Boot application encountered a problem while using Feign to decode a JSON response. Specifically, the Feign client expected a JSON array (starting with '['), but received an object (starting with '{' instead). This mismatch often arises from incorrect JSON data formatting or the inclusion of unsupported content within the response.

Here's a breakdown of the error:

• feign.codec.DecodeException: Error while extracting response...: This indicates that Feign couldn't properly extract the data from the response.
• nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error...: This further clarifies the issue as a JSON parsing error.
• exepct '[', but {, pos 1, line 1, column 2...: This is the key clue! It points to a discrepancy between the expected JSON array structure and the actual JSON object structure.

To resolve this error, you need to investigate the source of the incorrect JSON response. This could involve:

• Verifying the API documentation: Ensure that the API you're calling is indeed returning an array of SysHosDis objects as you expect.
• Inspecting the actual response: Use debugging tools to examine the raw JSON response from the API to confirm its structure.
• Reviewing the Feign client configuration: Check the Feign client's decoder configuration and ensure it aligns with the expected JSON format.
• Debugging the code that handles the JSON response: Identify the code section responsible for parsing the JSON response and carefully inspect it for potential errors in JSON handling.

Once you pinpoint the issue, you can then implement the appropriate solution, such as adjusting the code to correctly handle the JSON response format or contacting the API provider to address any discrepancies in their documentation or response structure.