theonedev/onedev · error · IllegalArgumentException

Error parsing media type '{0}'

Error message

Error parsing media type '{0}'

What it means

Jersey's MediaTypeProvider implements the ParamConverter-style fromString for javax.ws.rs.core.MediaType. It parses a header string with HttpHeaderReader and rethrows any ParseException as IllegalArgumentException with message "Error parsing media type '{0}'". This happens when the raw string is not a syntactically valid media type (type/subtype with optional parameters).

Source

Thrown at server-core/src/main/java/org/glassfish/jersey/message/internal/MediaTypeProvider.java:77

    }

    @Override
    public MediaType fromString(String header) {

        throwIllegalArgumentExceptionIfNull(header, MEDIA_TYPE_IS_NULL);

		var commaIndex = header.indexOf(',');
		if (commaIndex != -1) {
			var colonIndex = header.indexOf(';', commaIndex);
			if (colonIndex != -1)
				header = header.substring(0, commaIndex) + header.substring(colonIndex);
			else 
				header = header.substring(0, commaIndex);
		}
        try {
            return valueOf(HttpHeaderReader.newInstance(header));
        } catch (ParseException ex) {
            throw new IllegalArgumentException(
                    "Error parsing media type '" + header + "'", ex);
        }
    }

    /**
     * Create a new {@link javax.ws.rs.core.MediaType} instance from a header reader.
     *
     * @param reader header reader.
     * @return new {@code MediaType} instance.
     *
     * @throws ParseException in case of a header parsing error.
     */
    public static MediaType valueOf(HttpHeaderReader reader) throws ParseException {
        // Skip any white space
        reader.hasNext();

        // Get the type
        final String type = reader.nextToken().toString();

View on GitHub (pinned to d44925c47c)

Solutions

1. Inspect the raw request header and fix the client so it sends a valid type/substring media type
2. Test the string with MediaType.valueOf locally to reproduce and correct it
3. Add a request filter to validate/reject malformed headers with a clear 400 before resource matching

Example fix

// before
curl -X POST -H 'Content-Type: applicationjson' ...
// after
curl -X POST -H 'Content-Type: application/json' ...

try { javax.ws.rs.core.MediaType.valueOf(headerValue); } catch (IllegalArgumentException e) { return Response.status(400).build(); }

boolean isValidMediaType(String s) { try { javax.ws.rs.core.MediaType.valueOf(s); return true; } catch (IllegalArgumentException e) { return false; } }

try { MediaType mt = MediaType.valueOf(raw); } catch (IllegalArgumentException e) { throw new BadRequestException("Malformed media type: " + raw); }

When it happens

Trigger: Jersey encounters an HTTP header value such as Content-Type or Accept that cannot be parsed as a media type, e.g. "text/plain; charset=UTF-8;" malformed, missing subtype, or stray characters; also via MediaType.valueOf(...) on a bad string.

Common situations: Clients sending malformed Content-Type or Accept headers; proxies/gateways rewriting headers incorrectly; test code passing hand-built media type strings to MediaType.valueOf.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

• Http request failed (url: %s, status code: %d, error message
• Http request failed (status: %s)
• Exception obtaining parameters
• Unauthenticated
• Project not specified

AI-assisted analysis of theonedev/onedev@d44925c47c (2026-09-06). Data as JSON: /api/errors/ec2103d31c944d4a. Report an issue: GitHub.