flowable/flowable-engine · error · UnsupportedOperationException

org.flowable.cdi.impl.ProcessVariableMap.isEmpty() is not su

Error message

org.flowable.cdi.impl.ProcessVariableMap.isEmpty() is not supported.

What it means

ProcessVariableMap.isEmpty() throws UnsupportedOperationException unconditionally. Since size() is unsupported too, emptiness cannot be determined through this map view; the library treats the map as a keyed accessor only.

Source

Thrown at modules/flowable-cdi/src/main/java/org/flowable/cdi/impl/ProcessVariableMap.java:67

        businessProcess.setVariable(key, value);
        return variableBefore;
    }

    @Override
    public void putAll(Map<? extends String, ? extends Object> m) {
        for (Map.Entry<? extends String, ? extends Object> newEntry : m.entrySet()) {
            businessProcess.setVariable(newEntry.getKey(), newEntry.getValue());
        }
    }

    @Override
    public int size() {
        throw new UnsupportedOperationException(ProcessVariableMap.class.getName() + ".size() is not supported.");
    }

    @Override
    public boolean isEmpty() {
        throw new UnsupportedOperationException(ProcessVariableMap.class.getName() + ".isEmpty() is not supported.");
    }

    @Override
    public boolean containsKey(Object key) {
        throw new UnsupportedOperationException(ProcessVariableMap.class.getName() + ".containsKey() is not supported.");
    }

    @Override
    public boolean containsValue(Object value) {
        throw new UnsupportedOperationException(ProcessVariableMap.class.getName() + ".containsValue() is not supported.");
    }

    @Override
    public Object remove(Object key) {
        throw new UnsupportedOperationException("ProcessVariableMap.remove is unsupported. Use ProcessVariableMap.put(key, null)");
    }

    @Override

View on GitHub (pinned to d6d39ce1c6)

Solutions

Check the specific variable instead: map.get("name") != null.
Use BusinessProcess.getVariable(name) for targeted existence checks via the engine.
Remove isEmpty()-based logic around the CDI variable map entirely.

Example fix

// before
if (processVariableMap.isEmpty()) { ... }

// after
if (processVariableMap.get("myVar") == null) { ... } // check the variable you actually care about

Defensive patterns

Strategy: try-catch

Try / catch

try { empty = processVariableMap.isEmpty(); } catch (UnsupportedOperationException e) { empty = (processVariableMap.get("knownVar") == null); }

Prevention

Check specific variables with get(name) instead of isEmpty()
Do not wrap the CDI map in generic Map utilities
Prefer engine VariableScope APIs for introspection

When it happens

Trigger: Calling isEmpty() directly, or indirect callers such as Apache Commons/Google Collections helpers, JSP/EL expressions checking empty vars, or Map-based validation that calls isEmpty() first.

Common situations: Template expressions like ${not processVariables.empty}; defensive checks in generic code that operates on any Map; migration of code that previously used a plain HashMap of variables.

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

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/1c58c7693e144d68. Report an issue: GitHub.