What causes "Not supported to set bytes" in flowable/flowable-engine?

Do not call setBytes on the batch-delete configuration entity; it is unsupported by design.

flowable/flowable-engine · error · UnsupportedOperationException

Not supported to set bytes

Error message

Not supported to set bytes

What it means

BatchDeleteProcessConfig contains an inner entity class whose setBytes(byte[]) is deliberately implemented to throw UnsupportedOperationException. This configuration object never carries binary variable data, so mutating bytes on it is unsupported by design. Calling any bytes mutation on this entity always throws.

Solutions

Do not call setBytes on the batch-delete configuration entity; it is unsupported by design.
Check the entity type before calling setBytes (only real variable entities support byte persistence).
If binary data must be carried, use a persistent variable entity (e.g. VariableInstanceEntity) instead of this config object.

Example fix

// before
entity.setBytes(newBytes);
// after
if (entity instanceof VariableInstanceEntity) {
    ((VariableInstanceEntity) entity).setBytes(newBytes);
}

Defensive patterns

Strategy: validation

Validate before calling

if (entity instanceof VariableInstanceEntity) {
    entity.setBytes(bytes);
} else {
    throw new IllegalStateException("setBytes not supported on " + entity.getClass());
}

Type guard

boolean supportsBytes = (entity instanceof VariableInstanceEntity);

Prevention

Treat BatchDeleteProcessConfig's inner entity as a read-only configuration holder.
Only mutate bytes on persistent variable entities obtained from variable services.

When it happens

Trigger: Calling setBytes(...) on the inner variable/entity instance created inside BatchDeleteProcessConfig (BatchDeleteProcessConfig.java:555), e.g. via generic entity serialization or variable persistence code that iterates all Entity properties.

Common situations: Generic persistence/bulk-update frameworks reflectively calling setBytes on all variable entities; code written against a different entity type being reused with the batch-delete configuration; copy/merge utilities that blanket-copy field values.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/d182645ca4a0125e. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-engine/src/main/java/org/flowable/engine/impl/delete/BatchDeleteProcessConfig.java:555

            if (doubleNode.isNumber()) {
                return doubleNode.doubleValue();
            }
            return null;
        }

        @Override
        public void setDoubleValue(Double doubleValue) {
            throw new UnsupportedOperationException("Not supported to set double value");
        }

        @Override
        public byte[] getBytes() {
            throw new UnsupportedOperationException("Not supported to get bytes");
        }

        @Override
        public void setBytes(byte[] bytes) {
            throw new UnsupportedOperationException("Not supported to set bytes");
        }

        @Override
        public Object getCachedValue() {
            throw new UnsupportedOperationException("Not supported to set get cached value");
        }

        @Override
        public void setCachedValue(Object cachedValue) {
            throw new UnsupportedOperationException("Not supported to set cached value");
        }
    }
}

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