flowable/flowable-engine · error · ELException

error.function.params

error.function.params

Error message

error.function.params

What it means

Tree.bind() resolved the function Method but its arity does not match the parsed call: for varargs functions the method may take at most paramCount+1 parameters, otherwise it must take exactly paramCount. JUEL throws ELException error.function.params naming the function image.

Solutions

1. Update the expression to pass the number of arguments the registered Method expects.
2. Change the registered Method (or add an overload) to match the arity used in expressions; prefer a varargs signature for flexible arity.
3. Re-scan deployed process definitions for function calls after changing function signatures.
4. Catch ELException and validate function arity in a startup test suite.

Example fix

// before
// method: sum(int a, int b); expression: ${math:sum(1, 2, 3)} -> error.function.params
// after
public static int sum(int... values) { ... } // or fix the expression to ${math:sum(1, 2)}

Method m = fnMapper.resolveFunction(prefix, localName);
if (m != null && argCount != m.getParameterCount()
    && !(m.isVarArgs() && m.getParameterCount() <= argCount + 1)) {
    throw new IllegalStateException(fn + " expects " + m.getParameterCount() + " args, got " + argCount);
}

try {
    bindings = tree.bind(fnMapper, varMapper, converter);
} catch (ELException e) {
    throw new ConfigurationException("Function signature mismatch: " + e.getMessage(), e);
}

When it happens

Trigger: Expression calls ns:fn(a, b) but the resolved Method (a) has no varargs and a different number of parameters than the call, or (b) is varargs with more declared parameters than call args + 1.

Common situations: A registered function's signature was changed (parameters added/removed) while expressions in process definitions still use the old arity; overloading confusion where resolveFunction picked a wrong overload; copy-pasted expressions reused with a different function of the same name.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• Builder is missing constructor (can't pass features)
• Cannot change fixed value with
• Cannot coerce property to array index:
• Cannot coerce property to array index:
• Cannot find method with parameters in

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/41a7c4f887b0769e. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-engine-common/src/main/java/org/flowable/common/engine/impl/de/odysseus/el/tree/Tree.java:128

				throw new ELException(LocalMessages.get("error.function.nomapper"));
			}
			methods = new Method[functions.size()];
			for (int i = 0; i < functions.size(); i++) {
				FunctionNode node = functions.get(i);
				String image = node.getName();
				Method method = null;
				int colon = image.indexOf(':');
				if (colon < 0) {
					method = fnMapper.resolveFunction("", image);
				} else {
					method = fnMapper.resolveFunction(image.substring(0, colon), image.substring(colon + 1));
				}
				if (method == null) {
					throw new ELException(LocalMessages.get("error.function.notfound", image));
				}
				if (node.isVarArgs() && method.isVarArgs()) {
					if (method.getParameterTypes().length > node.getParamCount() + 1) {
						throw new ELException(LocalMessages.get("error.function.params", image));
					}
				} else {
					if (method.getParameterTypes().length != node.getParamCount()) {
						throw new ELException(LocalMessages.get("error.function.params", image));
					}
				}
				methods[node.getIndex()] = method;
			}
		}
		ValueExpression[] expressions = null;
		if (identifiers.size() > 0) {
			expressions = new ValueExpression[identifiers.size()];
			for (int i = 0; i < identifiers.size(); i++) {
				IdentifierNode node = identifiers.get(i);
				ValueExpression expression = null;
				if (varMapper != null) {
					expression = varMapper.resolveVariable(node.getName());
				}

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