apache/pulsar · error · RuntimeException

Invalid Java object for schema type + type + : + val.getCl

Error message

Invalid Java object for schema type + type +  :  + val.getClass() +  for field : " + name + "

What it means

SchemaUtils.validateFieldSchema checks that the Java value supplied for a field matches the expected Java classes for the field's SchemaType. When no class list is registered for that schema type at all, it throws RuntimeException 'Invalid Java object for schema type ... for field ...', meaning the type cannot accept any Java object in this validation path.

Source

Thrown at pulsar-common/src/main/java/org/apache/pulsar/client/impl/schema/SchemaUtils.java:126

        SCHEMA_TYPE_CLASSES.put(
                SchemaType.BYTES,
                Arrays.asList(byte[].class, ByteBuffer.class, ByteBuf.class));
        // build the reverse mapping
        SCHEMA_TYPE_CLASSES
                .forEach((type, classes) -> classes.forEach(clz -> JAVA_CLASS_SCHEMA_TYPES.put(clz, type)));
    }

    public static void validateFieldSchema(String name,
                                           SchemaType type,
                                           Object val) {
        if (null == val) {
            return;
        }

        List<Class<?>> expectedClasses = SCHEMA_TYPE_CLASSES.get(type);

        if (null == expectedClasses) {
            throw new RuntimeException("Invalid Java object for schema type " + type
                    + " : " + val.getClass()
                    + " for field : \"" + name + "\"");
        }

        boolean foundMatch = false;
        for (Class<?> expectedCls : expectedClasses) {
            if (expectedCls.isInstance(val)) {
                foundMatch = true;
                break;
            }
        }

        if (!foundMatch) {
            throw new RuntimeException("Invalid Java object for schema type " + type
                    + " : " + val.getClass()
                    + " for field : \"" + name + "\"");
        }

View on GitHub (pinned to 820761864e)

Solutions

Use a concrete supported SchemaType (INT8..STRING, BOOLEAN, BYTES, DATE, TIME, TIMESTAMP, etc.) for the field.
Remove manual calls to validateFieldSchema for special types (AUTO/AUTO_CONSUME/AUTO_PUBLISH/KEY_VALUE) that are not meant to validate plain Java objects.
Wrap validation in try/catch for RuntimeException to surface which field/type combination is unsupported, then correct the schema definition.

Example fix

// before
SchemaUtils.validateFieldSchema("f", val, SchemaType.AUTO_CONSUME, false);
// after
SchemaUtils.validateFieldSchema("f", val, SchemaType.INT32, false); // concrete type with registered classes

Defensive patterns

Strategy: try-catch

Validate before calling

if (val != null && Set.of(SchemaType.AUTO, SchemaType.AUTO_CONSUME, SchemaType.AUTO_PUBLISH,
        SchemaType.KEY_VALUE, SchemaType.JSON, SchemaType.NONE).contains(type)) {
    throw new IllegalArgumentException("schema type " + type + " cannot validate plain Java objects");
}

Try / catch

try {
    SchemaUtils.validateFieldSchema(name, val, type, required);
} catch (RuntimeException e) {
    throw new SchemaException("field '" + name + "' uses unsupported schema type " + type, e);
}

Prevention

Use concrete SchemaTypes with registered Java class mappings for field validation.
Never run plain-object field validation for AUTO*/KEY_VALUE/JSON/NONE types.
Catch RuntimeException and surface the field name for faster diagnosis.

When it happens

Trigger: Calling schema validation (e.g. Avro-based record schema building with SchemaUtils.validateFieldSchema) with a SchemaType that has no entry in SCHEMA_TYPE_CLASSES (such as special/auto types or unsupported types) while passing a non-null value.

Common situations: Using AUTO_, KEY_VALUE, JSON, or similar schema types in a manual field-validation flow; building schemas programmatically from POJOs where field type annotation maps to an unsupported SchemaType enum.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

AI-assisted analysis of apache/pulsar@820761864e (2026-09-06). Data as JSON: /api/errors/80a754ca70ebe5a6. Report an issue: GitHub.