flowable/flowable-engine · error · UnsupportedOperationException

Function has more than one local name

Error message

Function has more than one local name

What it means

FlowableMultiFunctionDelegate.localName() is a default interface method that deliberately throws UnsupportedOperationException("Function has more than one local name") because a multi-function delegate supports several local names instead of exactly one. Implementations must override localNames() and functionMethod(String,String) instead.

Solutions

1. Use localNames() (the Collection) instead of localName() when working with multi-function delegates
2. Add an instanceof FlowableMultiFunctionDelegate check and branch to localNames() / functionMethod(prefix, localName)
3. If this delegate should have a single name, implement FlowableFunctionDelegate directly with localName() and functionMethod()

Example fix

// before
String name = delegate.localName();
// after
String name = delegate instanceof FlowableMultiFunctionDelegate
        ? ((FlowableMultiFunctionDelegate) delegate).localNames().iterator().next()
        : delegate.localName();

// avoid calling localName() on multi-function delegates
if (delegate instanceof FlowableMultiFunctionDelegate) {
    List<String> names = new ArrayList<>(((FlowableMultiFunctionDelegate) delegate).localNames());
} else {
    String name = delegate.localName();
}

static boolean isMultiFunction(FlowableFunctionDelegate d) {
    return d instanceof FlowableMultiFunctionDelegate;
}

try {
    String name = delegate.localName();
} catch (UnsupportedOperationException e) {
    Collection<String> names = ((FlowableMultiFunctionDelegate) delegate).localNames();
}

When it happens

Trigger: Calling localName() directly on a FlowableMultiFunctionDelegate, or engine/function-lookup code that assumes single-name FlowableFunctionDelegate semantics and queries localName() on a multi-name function.

Common situations: Custom JUEL/flowable function registrars iterating all function delegates and calling localName() uniformly without an instanceof FlowableMultiFunctionDelegate check.

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

• Function Delegate has more than one function method
• Empty object, no variables can be set
• endOr() can only be called after calling or()
• endOr() can only be called after calling or()
• latest can only be used together with a deployment key

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/590ad3eebb4d2fc5. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-engine-common-api/src/main/java/org/flowable/common/engine/api/delegate/FlowableMultiFunctionDelegate.java:25

 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.flowable.common.engine.api.delegate;

import java.lang.reflect.Method;
import java.util.Collection;

/**
 * @author Filip Hrisafov
 */
public interface FlowableMultiFunctionDelegate extends FlowableFunctionDelegate {

    @Override
    default String localName() {
        throw new UnsupportedOperationException("Function has more than one local name");
    }

    @Override
    Collection<String> localNames();

    @Override
    default Method functionMethod() {
        throw new UnsupportedOperationException("Function Delegate has more than one function method");
    }

    @Override
    Method functionMethod(String prefix, String localName) throws  NoSuchMethodException;
}

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