FasterXML/jackson-databind · error · IllegalArgumentException

Cannot use FormatSchema of type

Error message

Cannot use FormatSchema of type {} for format {}

What it means

Thrown by ObjectReader._verifySchemaType() when a FormatSchema is set on the reader but the underlying parser factory cannot use it. Each format (JSON, CSV, YAML, XML, etc.) has its own schema type (e.g., CsvSchema); passing a schema from a different format is a type mismatch. The check uses the factory's canUseSchema() method.

Solutions

1. Ensure the schema type matches the reader's format: use the format-specific mapper (e.g., CsvMapper for CsvSchema, YAMLMapper for YAML schema).
2. Check factory.canUseSchema(schema) before calling with(schema) if the format is dynamic.
3. Verify you are using the correct mapper subclass: new CsvMapper().readerFor(type).with(csvSchema).

Example fix

// before
ObjectReader r = jsonMapper.readerFor(MyType.class).with(csvSchema); // throws: JSON factory can't use CSV schema
// after
ObjectReader r = csvMapper.readerFor(MyType.class).with(csvSchema);

// Check schema compatibility before setting
if (schema != null && !reader._parserFactory.canUseSchema(schema)) {
    throw new IllegalArgumentException("Schema " + schema.getClass() + " incompatible with format "
        + reader._parserFactory.getFormatName());
}

boolean schemaMatchesFactory(JsonFactory factory, FormatSchema schema) {
    return schema == null || factory.canUseSchema(schema);
}

When it happens

Trigger: Calling reader.with(schema) where schema is, e.g., a CsvSchema but the reader is backed by a JsonFactory. Also happens when a module registers a format factory but the wrong schema type is supplied, or when mixing format-specific readers without checking.

Common situations: Using a base ObjectMapper (JSON) and attempting to apply a YAML or CSV schema. Copy-pasting schema configuration from one format's code to another. Module ordering issues where a format-specific mapper is overridden by the default JSON factory.

Related errors

• Cannot use FormatSchema of type
• AnnotationIntrospector.
• AnnotationIntrospector returned `Class<
• AnnotationIntrospector returned Class
• AnnotationIntrospector returned key deserializer definition…

AI-assisted analysis of FasterXML/jackson-databind@87876ca5c0 (2026-08-11). Data as JSON: /api/errors/4bcbbf227cf24087. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/tools/jackson/databind/ObjectReader.java:2093

                if (_valueToUpdate != null) {
                    bt = _valueToUpdate.getClass();
                }
            }
            ctxt.reportTrailingTokens(bt, p, t);
        }
    }

    /*
    /**********************************************************************
    /* Internal methods, other
    /**********************************************************************
     */

    protected void _verifySchemaType(FormatSchema schema)
    {
        if (schema != null) {
            if (!_parserFactory.canUseSchema(schema)) {
                    throw new IllegalArgumentException("Cannot use FormatSchema of type "+schema.getClass().getName()
                            +" for format "+_parserFactory.getFormatName());
            }
        }
    }

    /**
     * Internal helper method called to create an instance of {@link DeserializationContext}
     * for deserializing a single root value.
     * Can be overridden if a custom context is needed.
     */
    protected DeserializationContextExt _deserializationContext() {
        return _contexts.createContext(_config, _schema, _injectableValues);
    }

    protected DeserializationContextExt _deserializationContext(JsonParser p) {
        return _contexts.createContext(_config, _schema, _injectableValues)
                .assignParser(p);
    }

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