apache/beam · error · UnsupportedOperationException

BoundedWindow unsupported in

Error message

BoundedWindow unsupported in %s

What it means

window() throws UnsupportedOperationException because the invoker implementation has no BoundedWindow provider bound. It is normally available in windowed contexts (ProcessElement/OnWindowExpiration with window parameter). The error context in the message identifies the invoker lacking support.

Solutions

1. Request the window via the method signature (BoundedWindow parameter) so the runner supplies it
2. Bind a window factory when constructing the invoker
3. Use a runner/DoFnTester version that populates window context
4. Guard c.window() behind instanceof checks when invoking in custom code

Example fix

// before
BoundedWindow w = context.window(); // may throw
// after
@ProcessElement
public void process(ProcessContext c, BoundedWindow window) { /* use window */ }

boolean windowed = context instanceof DoFn.WindowedContext;

if (!(context instanceof DoFn.WindowedContext)) return null; BoundedWindow w = context.window();

try { BoundedWindow w = invoker.window(doFn); } catch (UnsupportedOperationException e) { w = null; }

When it happens

Trigger: Calling invoker.window(doFn) (or a context resolving the window) on a DelegatingDoFnInvoker / generated invoker without a windowFactory; DoFn code calling c.window() when the runner didn't supply window info.

Common situations: Streaming/windowed DoFn code executed in a non-windowed test harness; custom invoker wiring that omits window suppliers; runners that do not expose BoundedWindow in the context.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Distinct does not support merging windowing strategies…
• PaneInfo unsupported in
• Attempted to get side input window for GlobalWindow from…
• Attempted to get side input window for GlobalWindow from…
• Calling .triggering() to specify a trigger or calling…

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/1e31ebdab5b9001e. Report an issue: GitHub.

Appendix: source

Thrown at sdks/java/core/src/main/java/org/apache/beam/sdk/transforms/reflect/DoFnInvoker.java:420

      throw new UnsupportedOperationException(
          String.format("MultiOutputReceiver unsupported in %s", getErrorContext()));
    }

    @Override
    public Object restriction() {
      throw new UnsupportedOperationException(
          String.format("Restriction unsupported in %s", getErrorContext()));
    }

    @Override
    public BoundedWindow window() {
      throw new UnsupportedOperationException(
          String.format("BoundedWindow unsupported in %s", getErrorContext()));
    }

    @Override
    public PaneInfo paneInfo(DoFn<InputT, OutputT> doFn) {
      throw new UnsupportedOperationException(
          String.format("PaneInfo unsupported in %s", getErrorContext()));
    }

    @Override
    public PipelineOptions pipelineOptions() {
      throw new UnsupportedOperationException(
          String.format("PipelineOptions unsupported in %s", getErrorContext()));
    }

    @Override
    public DoFn<InputT, OutputT>.StartBundleContext startBundleContext(DoFn<InputT, OutputT> doFn) {
      throw new UnsupportedOperationException(
          String.format("StartBundleContext unsupported in %s", getErrorContext()));
    }

    @Override
    public DoFn<InputT, OutputT>.FinishBundleContext finishBundleContext(
        DoFn<InputT, OutputT> doFn) {

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