UnrecognizedPropertyException Java Origin: Application & API Last updated 15 Oct 2026

com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "x", not marked as ignorable

The JSON contains a field your Java class doesn’t have, and Jackson is configured to fail on unknown properties.

Exact message you may see Unrecognized fieldnot marked as ignorable
Explore the map of this error Full error map →
Seen on: Java

Meaning

Default ObjectMapper fails on unknown fields (Spring Boot’s does not). APIs adding new fields break strict clients.

Common causes

  • API added fields
  • Field name differs (snake_case vs camelCase)
  • Typo in @JsonProperty

⚡ Quick fix

  1. Ignore unknown fields: @JsonIgnoreProperties(ignoreUnknown = true) or FAIL_ON_UNKNOWN_PROPERTIES=false
  2. Map names with @JsonProperty / PropertyNamingStrategies.SNAKE_CASE

Detailed fix by platform

Java

  1. mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

How to diagnose

  1. Field — Which name?
  2. Naming — snake_case vs camelCase?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Application & API. Errors that are often confused with or caused by this one (click to open):

circular JSON — TypeError: Converting circular structure to JSON (JavaScript)circular JSONEJSONPARSE — npm ERR! code EJSONPARSE — Failed to parse json / Unexpected token in JSON at position (npm)EJSONPARSEentity.parse.failed — API Error: Malformed JSON in request body (entity.parse.failed / JSON parse error) (API)entity.parse.failedHttpMessageNotReadableException — HttpMessageNotReadableException: JSON parse error / Required request body is missing (Java)HttpMessageNotReadabl…InvalidDefinitionException — com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class X and no properties discovered (Java)InvalidDefinitionExce…is an invalid start of a value — System.Text.Json: '<' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0 (.NET)is an invalid start o…json_decode null — json_decode() returns null / JSON_ERROR_SYNTAX: Syntax error (PHP)json_decode nullJSONDecodeError — json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0) (Python)JSONDecodeErrorUnrecogni…

Explore the map of this error Full error map →

🧠 Still stuck? Analyze your error

Paste the full message, response headers or stack trace — we'll detect the platform and point to the most likely cause.

💬 What worked for others

No tips yet — did something else fix this for you?

Share what worked for you

Tips are checked by an editor before they appear. Links are removed.