flowable/flowable-engine · error · FlowableException

A request body was expected when updating the task.

Error message

A request body was expected when updating the task.

What it means

PUT /cmmn-runtime/tasks/{taskId} expects a TaskRequest body describing the fields to update. Flowable throws a plain FlowableException if the deserialized body is null, i.e. the request was sent without a body or with an empty body.

Solutions

1. Send a JSON body with the task fields to update, e.g. {"name":"Reviewed","description":"..."}
2. Set the Content-Type: application/json header on the PUT request
3. Verify the HTTP client actually transmits the body (some clients omit it when no fields are set)

Example fix

// before
restTemplate.put("/cmmn-runtime/tasks/123", null);
// after
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON);
restTemplate.exchange("/cmmn-runtime/tasks/123", HttpMethod.PUT,
    new HttpEntity<>(Collections.singletonMap("name", "Reviewed"), headers), TaskResponse.class);

function canUpdateTask(patch) {
  return patch != null && typeof patch === 'object' && Object.keys(patch).length > 0;
}

function hasBody(b) {
  return b != null && typeof b === 'object';
}

try {
  await put(`/cmmn-runtime/tasks/${taskId}`, patch);
} catch (e) {
  if (e.status === 500 && /request body was expected/.test(e.body.message)) {
    throw new Error('PUT task requires a JSON body');
  }
  throw e;
}

When it happens

Trigger: PUT to /cmmn-runtime/tasks/{taskId} with no request body, an empty body, or a Content-Type that prevents JSON deserialization into TaskRequest.

Common situations: Calling the endpoint with GET-style tooling that omits the body; forgetting to set Content-Type: application/json; proxies or clients stripping empty bodies; sending body as form data.

Related errors

• A request body was expected when bulk updating tasks.
• A request body was expected when executing a task action.
• A request body was expected when executing the form submit.
• Invalid body was supplied
• No action found in request body.

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/0365fa5e6d77d108. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-cmmn-rest/src/main/java/org/flowable/cmmn/rest/service/api/runtime/task/TaskResource.java:80

            @ApiResponse(code = 404, message = "Indicates the requested task was not found.")
    })
    @GetMapping(value = "/cmmn-runtime/tasks/{taskId}", produces = "application/json")
    public TaskResponse getTask(@ApiParam(name = "taskId") @PathVariable String taskId) {
        return restResponseFactory.createTaskResponse(getTaskFromRequest(taskId));
    }

    @ApiOperation(value = "Update a task", tags = {
            "Tasks" }, notes = "All request values are optional. For example, you can only include the assignee attribute in the request body JSON-object, only updating the assignee of the task, leaving all other fields unaffected. When an attribute is explicitly included and is set to null, the task-value will be updated to null. Example: {\"dueDate\" : null} will clear the duedate of the task).")
    @ApiResponses(value = {
            @ApiResponse(code = 200, message = "Indicates the task was updated."),
            @ApiResponse(code = 404, message = "Indicates the requested task was not found."),
            @ApiResponse(code = 409, message = "Indicates the requested task was updated simultaneously.")
    })
    @PutMapping(value = "/cmmn-runtime/tasks/{taskId}", produces = "application/json")
    public TaskResponse updateTask(@ApiParam(name = "taskId") @PathVariable String taskId, @RequestBody TaskRequest taskRequest) {

        if (taskRequest == null) {
            throw new FlowableException("A request body was expected when updating the task.");
        }

        Task task = getTaskFromRequestWithoutAccessCheck(taskId);

        // Populate the task properties based on the request
        populateTaskFromRequest(task, taskRequest);

        if (restApiInterceptor != null) {
            restApiInterceptor.updateTask(task, taskRequest);
        }

        // Save the task and fetch again, it's possible that an
        // assignment-listener has updated
        // fields after it was saved so we can't use the in-memory task
        taskService.saveTask(task);
        task = taskService.createTaskQuery().taskId(task.getId()).singleResult();

        return restResponseFactory.createTaskResponse(task);

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