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

Thrown by updateTask when the PUT /runtime/tasks/{taskId} request has no (or a null) JSON body. The handler requires a TaskRequest body even if all fields are optional; a missing body cannot be deserialized to a non-null TaskRequest.

Solutions

1. Send a JSON body, e.g. {"name":"new name"} with Content-Type: application/json
2. Send {} if you only want to trigger an update without changing fields
3. Verify no intermediary (proxy/gateway) strips the request body

Example fix

// before
restTemplate.put(TASK_URL + "/123", null);
// after
restTemplate.exchange(TASK_URL + "/123", HttpMethod.PUT, new HttpEntity<>(mapOf("name", "New name"), jsonHeaders()), Void.class);

if (!body || typeof body !== 'object' || Object.keys(body).length === 0) body = {}; // always send at least {}

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

catch (e) { if (e.status === 400 && /request body was expected/.test(e.body && e.body.message)) { /* resend with a JSON body */ } else throw e; }

When it happens

Trigger: PUT /runtime/tasks/{taskId} with no body, empty body, or Content-Type not set to application/json so Spring cannot bind a TaskRequest.

Common situations: Client sends PUT without a JSON payload to 'touch' a task; missing Content-Type header; proxy stripping the body.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

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 bulk updating tasks.
• baseUrl can not be null
• Failed to serialize to a RestVariable instance

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/fcffbc3d78171610. Report an issue: GitHub.

Appendix: source

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

            @ApiResponse(code = 404, message = "Indicates the requested task was not found.")
    })
    @GetMapping(value = "/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 = "/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 not use the in-memory task
        taskService.saveTask(task);
        task = taskService.createTaskQuery().taskId(task.getId()).singleResult();

        return restResponseFactory.createTaskResponse(task);

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