karatelabs/karate · error · java.lang.RuntimeException

no such method

Error message

no such method: <setterName>

What it means

JavaUtils.set assigns a Java bean property from JS by constructing the setter name ('set' + capitalized field) and reflectively finding it. If no matching setter method exists it throws 'no such method: <setterName>', which is then converted to a JS typeError 'cannot set .<name>'.

Solutions

1. Add a standard bean setter (setXxx) to the Java class, or use an existing mutator method explicitly
2. Call the mutation method directly from JS instead of property assignment syntax
3. Check property-name capitalization — the setter name is derived from the first letter capitalized
4. If the object is meant to be immutable, construct a new instance with the desired value instead

Example fix

// before
obj.name = 'x'; // no such method: setName
// after
obj.setName('x'); // or add setName to the class

function hasSetter(obj, prop) {
  var setter = 'set' + prop.charAt(0).toUpperCase() + prop.slice(1);
  return obj[setter] !== undefined;
}
// call only if hasSetter(obj, 'name')

try {
  obj.name = value;
} catch (e) {
  if (String(e).includes('cannot set')) karate.log('no bean setter for', 'name');
  else throw e;
}

When it happens

Trigger: Setting a property on a Java object from JS where the bean has no setter for that name — e.g. `obj.someField = value` on a Java instance whose class lacks setSomeField, or the field is read-only/final.

Common situations: Assuming JS property assignment works like direct field access on Java objects; Java classes with fluent/builder APIs instead of bean setters; property name casing mismatches; records or immutable objects without setters.

Related errors

• <cause message>
• is not a constructor
• . is not a function (called on )
• no instance property:
• cannot get . (on )

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/6518100a12d3246f. Report an issue: GitHub.

Appendix: source

Thrown at karate-js/src/main/java/io/karatelabs/js/JavaUtils.java:267

            return new JavaObject(object).getMethod(name);
        }
        try {
            if (member instanceof Field field) {
                return field.get(object);
            }
            return ((Method) member).invoke(object, EMPTY);
        } catch (Exception e) {
            throw JsErrorException.typeError("cannot get ." + name + " (on " + jsTypeName(object.getClass()) + ")");
        }
    }

    static void set(Object object, String name, Object value) {
        String setterName = "set" + name.substring(0, 1).toUpperCase() + name.substring(1);
        Object[] args = new Object[]{value};
        try {
            Method method = findMethod(object.getClass(), setterName, args);
            if (method == null) {
                throw new RuntimeException("no such method: " + setterName);
            }
            method.invoke(object, args);
        } catch (Exception e) {
            throw JsErrorException.typeError("cannot set ." + name + " (on " + jsTypeName(object.getClass()) + ")");
        }
    }

    //==================================================================================================================
    //
    static final Object[] EMPTY = new Object[0];

    private static Class<?>[] paramTypes(Object[] args) {
        Class<?>[] paramTypes = new Class[args.length];
        for (int i = 0; i < args.length; i++) {
            Object arg = args[i];
            paramTypes[i] = arg == null ? Object.class : arg.getClass();
        }
        return paramTypes;

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