quarkusio/quarkus · error · RuntimeException

Don't know how to get event data (dataContentType: '%s', jav

Error message

Don't know how to get event data (dataContentType: '%s', javaType: '%s').

What it means

HeaderCloudEventImpl.data() extracts the event payload from HTTP headers/buffer. It supports only a few data types (e.g. String and byte[]); when the requested Java type (dataType) does not match the dataContentType or is otherwise unsupported, it throws a RuntimeException describing the content type and target type.

Source

Thrown at extensions/funqy/funqy-knative-events/runtime/src/main/java/io/quarkus/funqy/runtime/bindings/knative/events/HeaderCloudEventImpl.java:178

        return dataContentType;
    }

    @Override
    public T data() {
        if (data != null) {
            return data;
        }
        if (dataContentType() != null && dataContentType().startsWith("application/json") && !byte[].class.equals(dataType)) {
            data = reader.readValue(buffer.getBytes());
            return data;
        } else if (byte[].class.equals(dataType)) {
            data = (T) buffer.getBytes();
            return data;
        } else {
            String msg = String.format("Don't know how to get event data (dataContentType: '%s', javaType: '%s').",
                    dataContentType(), dataType.getTypeName());
            throw new RuntimeException(msg);
        }
    }
}

View on GitHub (pinned to e1c734241f)

Solutions

Use String.class or byte[].class for the data access, then deserialize manually with Jackson/ObjectMapper.
Ensure the function signature's input type matches a supported mapping (POJOs work only via the JSON CloudEvent implementation).
Set Content-Type to application/json so the JSON CloudEvent implementation handles POJO deserialization.
Add explicit handling in the function for raw String input and map it to a POJO yourself.

Example fix

// before
MyPojo p = event.data(MyPojo.class);
// after
String raw = event.data(String.class);
MyPojo p = new ObjectMapper().readValue(raw, MyPojo.class);

Defensive patterns

Strategy: type-guard

Validate before calling

if (!(String.class.equals(dataType) || byte[].class.equals(dataType))) {
    throw new IllegalArgumentException("HeaderCloudEventImpl supports only String or byte[] data: " + dataType);
}

Type guard

boolean headerDataSupported(Class<?> t) { return t == String.class || t == byte[].class; }

Try / catch

try { T d = event.data(dataType); } catch (RuntimeException e) { if (e.getMessage().startsWith("Don't know how to get event data")) { String raw = event.data(String.class); return manuallyMap(raw); } throw e; }

Prevention

Only request String or byte[] from header-based events
Ensure Content-Type is application/json for POJO payloads
Inspect ce-datacontenttype before choosing the data type
Prefer the JSON CloudEvent binding for typed access

When it happens

Trigger: Invoking data(SomePojo.class) (or another unsupported type) on a HeaderCloudEventImpl whose buffered data is only convertible to String or byte[], with a dataContentType like application/json but a non-String/byte[] target.

Common situations: A Funqy Knative function declares a POJO input while the binding path populated a header-based CloudEvent that only buffers raw bytes/strings; mismatched datacontenttype (e.g. text/plain) vs declared Java type.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/29b261604bc5b1ee. Report an issue: GitHub.