flowable/flowable-engine · error · UnsupportedOperationException

org.flowable.cdi.impl.ProcessVariableMap.size() is not suppo

Error message

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

What it means

ProcessVariableMap deliberately implements only name-based get/put. size() cannot be answered without enumerating all process variables, so the method throws UnsupportedOperationException unconditionally with the fully qualified method name in the message.

Source

Thrown at modules/flowable-cdi/src/main/java/org/flowable/cdi/impl/ProcessVariableMap.java:62

    public Object put(String key, Object value) {
        if (key == null) {
            throw new IllegalArgumentException("This map does not support 'null' keys.");
        }
        Object variableBefore = businessProcess.getVariable(key);
        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

View on GitHub (pinned to d6d39ce1c6)

Solutions

Do not use ProcessVariableMap for introspection; use BusinessProcess or the Task/Execution variable query API instead.
Track variable count in your own code if you need it.
Refactor tests to assert on get(name) results rather than size().

Example fix

// before
int count = processVariableMap.size();

// after
boolean hasVar = processVariableMap.get("myVar") != null; // only name-based access is supported

Defensive patterns

Strategy: try-catch

Try / catch

try { count = processVariableMap.size(); } catch (UnsupportedOperationException e) { /* use engine query API instead */ }

Prevention

Treat ProcessVariableMap as a keyed accessor only: get/put by name
Use BusinessProcess or engine variable queries for counts
Document at injection points that bulk operations throw

When it happens

Trigger: Any call to size() on the injected map, including indirect calls from code that inspects Map objects (debug logging, Map.toString via entrySet is separate, Spring/CDI tooling, assert statements like assertEquals(0, map.size())).

Common situations: Unit tests asserting on variable counts via the map; generic Map utility code that calls size() before use; debugging frameworks that dump map contents.

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/737c3cc0526e7c23. Report an issue: GitHub.