flowable/flowable-engine · error · ELException

error.property.method.invocation

Error message

error.property.method.invocation

What it means

ELException (error.property.method.invocation) thrown when Method.invoke raises IllegalArgumentException — the actual argument values supplied to the expression do not match the method's declared parameter types. It carries the original exception as cause.

Source

Thrown at modules/flowable-engine-common/src/main/java/org/flowable/common/engine/impl/de/odysseus/el/tree/impl/ast/AstProperty.java:217

	@Override
	public Object invoke(Bindings bindings, ELContext context, Class<?> returnType, Class<?>[] paramTypes, Object[] paramValues) {
		Object base = prefix.eval(bindings, context);
		if (base == null) {
			throw new PropertyNotFoundException(LocalMessages.get("error.property.base.null", prefix));
		}
		Object property = getProperty(bindings, context);
		if (property == null && strict) {
			throw new PropertyNotFoundException(LocalMessages.get("error.property.method.notfound", "null", base));
		}
		String name = bindings.convert(property, String.class);
		Method method = findMethod(name, base.getClass(), returnType, paramTypes);
		try {
			return method.invoke(base, paramValues);
		} catch (IllegalAccessException e) {
			throw new ELException(LocalMessages.get("error.property.method.access", name, base.getClass()), e);
		} catch (IllegalArgumentException e) {
			throw new ELException(LocalMessages.get("error.property.method.invocation", name, base.getClass()), e);
		} catch (InvocationTargetException e) {
			throw new ELException(LocalMessages.get("error.property.method.invocation", name, base.getClass()), e.getCause());
		}
	}

	@Override
	public AstNode getChild(int i) {
		return i == 0 ? prefix : null;
	}
}

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Match argument types to the method signature, adding explicit conversions in the expression if needed.
2. Change the method to accept the types actually passed (e.g. Object, Number, or a wrapper).
3. Convert values before evaluation (set variables of the correct type in the ELContext).
4. Ensure the argument count matches the declared parameters, including varargs handling.

Example fix

// before
${calc.add("1", 2)} // add(int, int) — String literal fails
// after
${calc.add(1, 2)}

java.lang.reflect.Method m = base.getClass().getMethod("add", int.class, int.class);
for (Object arg : args) {
    if (arg instanceof String && m.getParameterTypes()[0] == int.class) {
        throw new IllegalArgumentException("pass numeric literals in EL, not strings");
    }
}

boolean argsMatch(java.lang.reflect.Method m, Object... args) {
    Class<?>[] pts = m.getParameterTypes();
    if (args.length != pts.length) return false;
    for (int i = 0; i < pts.length; i++) {
        if (args[i] != null && !pts[i].isInstance(args[i])
            && !isCoercible(args[i], pts[i])) return false;
    }
    return true;
}

try {
    result = expr.invoke(ctx);
} catch (jakarta.el.ELException e) {
    if (e.getCause() instanceof IllegalArgumentException) {
        log.warn("EL argument type mismatch: {}", e.getMessage());
        throw new IllegalStateException("fix argument types in expression", e);
    }
    throw e;
}

When it happens

Trigger: invoke() on ${obj.method(a, b)} where an argument's runtime type is incompatible with the method signature (e.g. passing a String where an int/Long is expected, or wrong number of arguments).

Common situations: EL coercion not converting types as expected (string literals vs numbers); changed method signatures after expression deployment; passing null to primitive parameters; type erasure surprises with collections.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• error.property.method.notfound
• error.property.method.returntype
• error.property.method.access
• <exception message from evaluation failure>
• TypeConverter ${clazz} could not be instantiated

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/2ab9d5b04eeafad9. Report an issue: GitHub.