REST Assured Jackson "JsonParseException" on the response body in CI
REST Assured used Jackson to deserialize the response body as JSON, but the body was not valid JSON. In CI this is usually an HTML error page, an empty body, or a proxy interstitial returned instead of the expected JSON.
What this error means
A test fails with "com.fasterxml.jackson.core.JsonParseException: Unexpected character ('<' (code 60))" when calling .as(), jsonPath(), or a JSON body matcher.
REST Assured
com.fasterxml.jackson.core.JsonParseException: Unexpected character ('<' (code 60)):
expected a valid value (JSON String, Number, Array, Object or token 'null', 'true' or 'false')
at [Source: (String)"<!DOCTYPE html>..."; line: 1, column: 2]Common causes
The response was HTML, not JSON
A 500 error page, a login redirect, or a gateway page returns HTML, so parsing the body as JSON fails on the first "<".
An empty or truncated body
A 204 No Content or a dropped connection returns nothing to parse, and Jackson raises a parse error.
How to fix it
Assert content type and log the body first
- Assert the response Content-Type is application/json before parsing.
- Log the body on failure to see what was actually returned.
- Fix the upstream cause (auth, error page) so real JSON comes back.
Java
given().accept("application/json")
.when().get("/users/1")
.then().contentType("application/json").log().ifValidationFails();Handle the error response explicitly
If an endpoint can return HTML on error, assert the status first so you fail on the status, not on a confusing parse error.
How to prevent it
- Assert Content-Type before deserializing the body.
- Check status before parsing so error pages fail clearly.
- Ensure auth is configured so you do not receive login HTML.
Frequently asked questions
What causes ""JsonParseException: Unexpected character""?
A 500 error page, a login redirect, or a gateway page returns HTML, so parsing the body as JSON fails on the first "<".
How do I fix "JsonParseException: Unexpected character"?
Assert content type and log the body first
Related guides
REST Assured "Expected status code <200> but was <500>" in CIFix REST Assured "Expected status code <200> but was <500>" in CI - the statusCode() expectation failed becau…
REST Assured "java.net.ConnectException: Connection refused" in CIFix REST Assured "java.net.ConnectException: Connection refused" in CI - the test fired a request before the…
Schemathesis "Undocumented HTTP status code" in CIFix Schemathesis "Undocumented HTTP status code" in CI - the API returned a status the OpenAPI schema does no…