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

Same family as error 793 but in JsonCloudEventImpl: after trying JSON deserialization paths, if the requested dataType cannot be produced from the event JSON (unsupported combination of dataContentType and Java type), it throws this RuntimeException.

Source

Thrown at extensions/funqy/funqy-knative-events/runtime/src/main/java/io/quarkus/funqy/runtime/bindings/knative/events/JsonCloudEventImpl.java:229

                    if (event.has("data")) {
                        data = (T) mapper.writeValueAsBytes(event.get("data"));
                        return data;
                    } else if (event.has("data_base64")) {
                        String txt = event.get("data_base64").asText();
                        data = (T) Base64.getDecoder().decode(txt);
                        return data;
                    } else {
                        return null;
                    }
                }

            } catch (JacksonException e) {
                throw new RuntimeException(e);
            }
        } 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

Declare the function input as String or byte[] and deserialize manually.
Set the event's Content-Type to application/json so Jackson can map it to the POJO.
Add a Jackson @JsonDeserialize mapping/default constructor to the target type.
Align the function's input type with the actual event payload type.

Example fix

// before
MyPojo p = event.data(MyPojo.class); // content-type: text/plain
// after
byte[] raw = event.data(byte[].class);
MyPojo p = MAPPER.readValue(raw, MyPojo.class);

Defensive patterns

Strategy: validation

Validate before calling

if (!"application/json".equals(event.dataContentType()) && !isSimpleType(dataType)) {
    throw new IllegalArgumentException("JSON event data requires application/json or String/byte[] target");
}

Type guard

boolean jsonDataTypeSupported(String contentType, Class<?> t) {
    return "application/json".equals(contentType) || t == String.class || t == byte[].class;
}

Try / catch

try { return event.data(dataType); } catch (RuntimeException e) { if (e.getMessage().startsWith("Don't know how to get event data")) { byte[] raw = event.data(byte[].class); return MAPPER.readValue(raw, dataType); } throw e; }

Prevention

Match the function input type to the event's ce-datacontenttype
Use application/json for structured POJO payloads
Give POJOs default constructors and Jackson annotations
Fall back to byte[] + manual deserialization for exotic content types

When it happens

Trigger: Calling data(SomeUnsupportedType.class) on a JsonCloudEventImpl where the content type is not JSON-mappable to the target type (e.g. text/plain content with a POJO target, or a complex type with no Jackson mapping).

Common situations: Function signature declares a POJO but the event's ce-datacontenttype is text/plain or absent; target type lacks a default constructor/Jackson mapping; binary content requested as a structured type.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/86663d0464f6315b. Report an issue: GitHub.