{"record":{"id":"295d4a514a9cf0b2","repo":"FasterXML/jackson-databind","slug":"cannot-use-formatschema-of-type-for-format-295d4a","errorCode":null,"errorMessage":"Cannot use FormatSchema of type {} for format {}","messagePattern":"Cannot use FormatSchema of type (.+?) for format (.+?)","errorType":"exception","errorClass":"IllegalArgumentException","httpStatus":null,"severity":"error","filePath":"src/main/java/tools/jackson/databind/ObjectWriter.java","lineNumber":1279,"sourceCode":"    /**\n     * Overridable helper method used for constructing\n     * {@link SerializationContext} to use for serialization.\n     */\n    protected final SerializationContextExt _serializationContext() {\n        return _serializationContexts.createContext(_config, _generatorSettings);\n    }\n\n    /*\n    /**********************************************************************\n    /* Internal methods\n    /**********************************************************************\n     */\n\n    protected void _verifySchemaType(FormatSchema schema)\n    {\n        if (schema != null) {\n            if (!_generatorFactory.canUseSchema(schema)) {\n                    throw new IllegalArgumentException(\"Cannot use FormatSchema of type \"+schema.getClass().getName()\n                            +\" for format \"+_generatorFactory.getFormatName());\n            }\n        }\n    }\n\n    /**\n     * Helper method that applies configured {@link GeneratorInitializer},\n     * if any, to the given generator and returns it.\n     *\n     * @since 3.2\n     */\n    protected JsonGenerator _initializeGenerator(JsonGenerator gen) {\n        GeneratorInitializer init = _config.getGeneratorInitializer();\n        if (init != null) {\n            init.initialize(_config, gen);\n        }\n        return gen;\n    }","sourceCodeStart":1261,"sourceCodeEnd":1297,"githubUrl":"https://github.com/FasterXML/jackson-databind/blob/a50c7d2a1d57234ac4adf70dbd88ac90db6436e4/src/main/java/tools/jackson/databind/ObjectWriter.java#L1261-L1297","documentation":"ObjectWriter._verifySchemaType() mirrors the reader-side guard: before serializing with a FormatSchema, it confirms the schema is usable by the writer's generator factory (e.g. a CsvSchema must go with a CsvFactory/CSV generator). If the schema doesn't match the configured dataformat, it throws IllegalArgumentException naming the schema class and the expected format name. This prevents writing malformed output to the wrong backend.","triggerScenarios":"Calling writer.withSchema(csvSchema) on a writer from a JsonMapper; passing an AvroSchema to a JSON generator; reusing a schema object cached from a different mapper after switching dataformats; generic 'write with schema' helper that accepts any FormatSchema and forwards it.","commonSituations":"Multiple format-specific writers in one app and a schema wired to the wrong one via DI; module upgrade where the schema class identity changed; copy-paste of a working CSV write but forgetting to also switch the mapper to CsvMapper; a shared ObjectMapper bean used for both JSON and CSV inadvertently.","solutions":["Obtain both the writer and the schema from the same format-specific mapper (CsvMapper, YAMLMapper, AvroMapper).","Use mapper.writer(schema) only on the mapper whose tokenStreamFactory().canUseSchema(schema) returns true.","Cache schema + writer together as a pair to avoid cross-wiring.","In DI, qualify the mapper beans (@Qualifier) so the schema-bearing component gets the right one."],"exampleFix":"// before\nJsonMapper m = JsonMapper.builder().build();\nCsvSchema csv = CsvSchema.emptySchema().withHeader();\nm.writer(csv).writeValue(out, rows); // throws\n// after\nCsvMapper m = CsvMapper.builder().build();\nCsvSchema csv = m.schemaFor(Row.class).withHeader();\nm.writer(csv).writeValue(out, rows);","handlingStrategy":"validation","validationCode":"if (schema != null && !mapper.tokenStreamFactory().canUseSchema(schema)) {\n    throw new IllegalArgumentException(\"schema mismatch\");\n}\nmapper.writer(schema).writeValue(out, value);","typeGuard":"boolean schemaMatchesWriter(JsonMapper m, FormatSchema s) {\n    return s != null && m.tokenStreamFactory().canUseSchema(s);\n}","tryCatchPattern":"try {\n    mapper.writer(schema).writeValue(out, value);\n} catch (IllegalArgumentException e) {\n    if (e.getMessage().startsWith(\"Cannot use FormatSchema\")) {\n        // switch to the format-specific mapper for this schema\n    }\n    throw e;\n}","preventionTips":["Pair the writer and schema from one format-specific mapper (CsvMapper, YAMLMapper, etc.).","Cache the mapper+schema together to avoid cross-wiring in DI.","Qualify mapper beans (@Qualifier) in multi-format apps."],"tags":["object-writer","schema","dataformat","configuration"],"analyzedSha":"a50c7d2a1d57234ac4adf70dbd88ac90db6436e4","analyzedAt":"2026-08-06T20:31:51.404Z","schemaVersion":2},"datasetVersion":"2026-08-07T02:17:10.218Z"}