karatelabs/karate · error · JsErrorException

. is not a property (on )

Error message

. is not a property (on )

What it means

Thrown by JavaUtils.getStatic when the requested name matches no static field, no static getter method, no static method reference, and no nested class on the Java type. It means the property simply does not exist on the class: '.<name> is not a property (on <TypeName>)'.

Solutions

1. Verify the exact name of the static field/constant in the class's javadoc.
2. Check whether the member is instance-level and needs an object instead of the class handle.
3. Confirm the class/package for the constant hasn't changed across library versions.
4. Enumerate available members by inspecting the class before access.

Example fix

// before
var Math = Java.type('java.lang.Math');
var x = Math.pie;
// after
var x = Math.PI;

function hasStaticMember(clazz, name) { try { return clazz.getClass().getField(name) != null; } catch (e) { return false; } }

function safeGetStatic(clazz, name) { try { return clazz[name]; } catch (e) { return undefined; } }

try { var v = Clz.CONST; } catch (e) { if (String(e).indexOf('not a property') !== -1) { karate.log('constant missing on', Clz); v = fallback; } else { throw e; } }

When it happens

Trigger: Reading ClassName.missingField in a Karate JS block where no such static field/getter/method/nested class exists.

Common situations: Typos (Math.PII), assuming constants exist in a different class (Color.RED vs java.awt.Color variants), accessing instance members as static, version drift where a constant moved packages.

Related errors

• cannot set . (on )
• no instance property:
• toBean() needs two arguments: object and class name
• object is null
• java bridge not enabled

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/64dba3141f767461. Report an issue: GitHub.

Appendix: source

Thrown at karate-js/src/main/java/io/karatelabs/js/JavaUtils.java:129

                    } catch (Exception ex) {
                        throw JsErrorException.typeError("." + name + " is not a function (called on " + jsTypeName(clazz) + ")");
                    }
                }
                // Fall back to method reference
                for (Method m : clazz.getMethods()) {
                    if (m.getName().equals(name)) {
                        JavaType jc = new JavaType(clazz);
                        return jc.getMethod(name);
                    }
                }
                // Static nested class / enum: e.g. Foo.Bar where Bar is a member type
                for (Class<?> nested : clazz.getClasses()) {
                    if (nested.getSimpleName().equals(name)) {
                        return new JavaType(nested);
                    }
                }
            }
            throw JsErrorException.typeError("." + name + " is not a property (on " + jsTypeName(clazz) + ")");
        }
    }

    private static Method findStaticGetter(Class<?> clazz, String name) {
        String getterSuffix = name.substring(0, 1).toUpperCase() + name.substring(1);
        Method method = findStaticMethod(clazz, "get" + getterSuffix);
        if (method == null) {
            method = findStaticMethod(clazz, "is" + getterSuffix);
        }
        return method;
    }

    private static Method findStaticMethod(Class<?> clazz, String name) {
        for (Method method : clazz.getMethods()) {
            if (method.getName().equals(name) && Modifier.isStatic(method.getModifiers())
                    && method.getParameterCount() == 0) {
                return method;
            }

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