quarkusio/quarkus · error · IllegalArgumentException

The parameter type [" + params[i].getClass() + "] can not be

Error message

The parameter type [" + params[i].getClass() + "] can not be assigned to the type for the target method [" + parameterTypes[i] + "]

What it means

validateParameters() throws IllegalArgumentException when a supplied argument's type is not assignable to the declared parameter type (compared via boxed types). It enforces type safety for reflectively invoked methods before the actual call.

Source

Thrown at independent-projects/arc/runtime/src/main/java/io/quarkus/arc/impl/AbstractInvocationContext.java:73

        return found;
    }

    static void validateParameters(Executable executable, Object[] params) {
        int newParametersCount = Objects.requireNonNull(params).length;
        Class<?>[] parameterTypes = executable.getParameterTypes();
        if (parameterTypes.length != newParametersCount) {
            throw new IllegalArgumentException(
                    "Wrong number of parameters - method has " + Arrays.toString(parameterTypes) + ", attempting to set "
                            + Arrays.toString(params));
        }
        for (int i = 0; i < params.length; i++) {
            if (parameterTypes[i].isPrimitive() && params[i] == null) {
                throw new IllegalArgumentException("Trying to set a null value to a primitive parameter [position: " + i
                        + ", type: " + parameterTypes[i] + "]");
            }
            if (params[i] != null) {
                if (!Types.boxedClass(parameterTypes[i]).isAssignableFrom(Types.boxedClass(params[i].getClass()))) {
                    throw new IllegalArgumentException("The parameter type [" + params[i].getClass()
                            + "] can not be assigned to the type for the target method [" + parameterTypes[i] + "]");
                }
            }
        }
    }

    @Override
    public Method getMethod() {
        return null;
    }

    @Override
    public Object getTarget() {
        return target;
    }

    @Override
    public Object getTimer() {

View on GitHub (pinned to e1c734241f)

Solutions

1. Cast/convert the argument to the declared parameter type before invocation
2. Use converters (e.g. Number conversion) when values come from text/config sources
3. Verify the method signature hasn't changed and callers pass matching types
4. Validate assignability with Types.boxedClass(paramType).isInstance(value) beforehand

Example fix

// before
ctx.setParameters(new Object[] { "42" }); // param is Integer
// after
ctx.setParameters(new Object[] { Integer.valueOf("42") });

for (int i = 0; i < params.length; i++) {
  Class<?> declared = Types.boxedClass(method.getParameterTypes()[i]);
  if (params[i] != null && !declared.isAssignableFrom(Types.boxedClass(params[i].getClass()))) params[i] = convert(params[i], declared);
}

try { ctx.setParameters(args); } catch (IllegalArgumentException e) { log.warnf("Type mismatch: %s", e.getMessage()); }

When it happens

Trigger: Passing an argument whose runtime class cannot be assigned to the declared parameter's boxed class — e.g. passing String where Integer is expected, or an unrelated subtype not in the hierarchy.

Common situations: Hand-built invocation arrays from deserialized JSON (numbers become String or BigDecimal); generic Object wiring in interceptors; changed method signature with stale callers; int vs long confusion.

Related errors

• Cache key generator instantiation failed
• Cannot instantiate JSON-B component:
• Unable to instantiate the class:
• Wrong number of parameters - method has " + Arrays.toString(
• Trying to set a null value to a primitive parameter [positio

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/f3ad1571093e584d. Report an issue: GitHub.