flowable/flowable-engine · error · FlowableIllegalArgumentException

Could not process multipart content

Error message

Could not process multipart content

What it means

FlowableIllegalArgumentException wrapping an IOException from processing the multipart request body in setBinaryVariable. Reading the uploaded file stream (file.getInputStream()) or other multipart I/O failed, so the variable could not be stored; the original IOException is preserved as cause.

Source

Thrown at modules/flowable-rest/src/main/java/org/flowable/rest/service/api/runtime/process/BaseExecutionVariableResource.java:185

                stream.close();
                
            } else {
                throw new FlowableContentNotSupportedException("Serialized objects are not allowed");
            }

            RestVariable variable = null;
            
            if (!async) {
                variable = getVariableFromRequestWithoutAccessCheck(execution, variableName, scope, false);
                
                // We are setting the scope because the fetched variable does not have it
                variable.setVariableScope(scope);
            }
            
            return variable;

        } catch (IOException ioe) {
            throw new FlowableIllegalArgumentException("Could not process multipart content", ioe);
        } catch (ClassNotFoundException ioe) {
            throw new FlowableContentNotSupportedException("The provided body contains a serialized object for which the class was not found: " + ioe.getMessage());
        }

    }

    protected RestVariable setSimpleVariable(RestVariable restVariable, Execution execution, boolean isNew, boolean async) {
        if (restVariable.getName() == null) {
            throw new FlowableIllegalArgumentException("Variable name is required");
        }

        // Figure out scope, revert to local if omitted
        RestVariableScope scope = restVariable.getVariableScope();
        if (scope == null) {
            scope = RestVariableScope.LOCAL;
        }

        Object actualVariableValue = restResponseFactory.getVariableValue(restVariable);

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Check the wrapped IOException cause — usually container temp-dir or stream failure
2. Verify the servlet container's multipart temp directory exists and is writable
3. Increase max multipart/file size limits (server max-file-size, spring multipart settings)
4. Retry the upload with a complete, untruncated request body

Example fix

// before
// server: default temp dir, no size config
// after
# application.properties
spring.servlet.multipart.max-file-size=20MB
spring.servlet.multipart.max-request-size=25MB

if (!file.exists() || file.length() == 0) throw new IllegalArgumentException("empty upload rejected before send");
// and confirm server limits accept the size before uploading

try {
    client.uploadBinaryVariable(executionId, name, file);
} catch (HttpClientErrorException.BadRequest e) {
    log.error("multipart processing failed", e);
    // check server temp dir / size limits, then retry
}

When it happens

Trigger: Binary variable upload where obtaining/reading the MultipartFile stream throws IOException — interrupted upload, temp-dir failure, container-level multipart parsing errors.

Common situations: Servlet container temp directory full or read-only; request aborted by client mid-upload; multipart size limits causing premature stream termination; misconfigured multipart resolver.

Understand the failure class

Background: "failed to read file", EACCES, ENOENT and "could not read <path>" errors: when a program can't read a file from disk — this error's family across 49 libraries.

Related errors

• Could not process multipart content
• Error getting binary variable
• Multipart request is required
• Multipart request with file content is required
• No file content was found in request body.

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/6f408f2aa3417c03. Report an issue: GitHub.