flowable/flowable-engine · error · FlowableIllegalArgumentException

variableName is null

Error message

variableName is null

What it means

GetTaskVariableInstanceCmd.execute() requires a variable name after validating taskId. If variableName is null it throws FlowableIllegalArgumentException('variableName is null'), since fetching a single variable instance is meaningless without knowing which variable to look up.

Solutions

1. Pass a non-empty variableName string to getVariableInstance/getVariableInstanceLocal.
2. Validate/trim the variable name parameter before invoking the task service.
3. If iterating variables dynamically, use getVariableInstances(taskId) instead of per-name lookup.

Example fix

// before
VariableInstance vi = cmmnTaskService.getVariableInstance(taskId, config.get("varName"));
// after
String varName = config.get("varName");
if (varName == null || varName.isEmpty()) {
    throw new IllegalArgumentException("varName must be configured");
}
VariableInstance vi = cmmnTaskService.getVariableInstance(taskId, varName);

if (variableName == null || variableName.trim().isEmpty()) { throw new IllegalArgumentException("variableName is required"); }

boolean hasVariableName(String name) { return name != null && !name.trim().isEmpty(); }

try { return taskService.getVariableInstance(taskId, variableName); } catch (FlowableIllegalArgumentException e) { log.warn("Invalid variable lookup: {}", e.getMessage()); return null; }

When it happens

Trigger: Calling cmmnTaskService.getVariableInstance(taskId, null) or getVariableInstanceLocal(taskId, null); a variable name sourced from config/UI that was never set.

Common situations: Variable name read from a properties file or request body with a missing key; typo where the name constant is null by initialization order; generic wrapper code that forwards a nullable name parameter.

Related errors

• taskId is null
• taskId is null
• taskId is null
• activatedBefore is null
• after time is null

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/5565db8986547085. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/cmd/GetTaskVariableInstanceCmd.java:48

    private static final long serialVersionUID = 1L;
    
    protected String taskId;
    protected String variableName;
    protected boolean isLocal;

    public GetTaskVariableInstanceCmd(String taskId, String variableName, boolean isLocal) {
        this.taskId = taskId;
        this.variableName = variableName;
        this.isLocal = isLocal;
    }

    @Override
    public VariableInstance execute(CommandContext commandContext) {
        if (taskId == null) {
            throw new FlowableIllegalArgumentException("taskId is null");
        }
        if (variableName == null) {
            throw new FlowableIllegalArgumentException("variableName is null");
        }

        CmmnEngineConfiguration cmmnEngineConfiguration = CommandContextUtil.getCmmnEngineConfiguration(commandContext);
        TaskEntity task = cmmnEngineConfiguration.getTaskServiceConfiguration().getTaskService().getTask(taskId);

        if (task == null) {
            throw new FlowableObjectNotFoundException("task " + taskId + " doesn't exist", Task.class);
        }

        VariableInstance variableEntity;

        if (isLocal) {
            variableEntity = task.getVariableInstanceLocal(variableName, false);
        } else {
            variableEntity = task.getVariableInstance(variableName, false);
        }

        return variableEntity;

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