apache/dubbo · error · IllegalStateException

No such extension name for the class {} in the config {}

Error message

No such extension name for the class {} in the config {}

What it means

Thrown by loadClass() when an SPI config line has no name component and the class also lacks a derivable name from its @Extension annotation (via findAnnotationName). SPI config lines are normally 'name=com.example.Impl'; if only the class is given with no name prefix, and the class has no annotation providing a name, Dubbo cannot register it and throws.

Source

Thrown at dubbo-common/src/main/java/org/apache/dubbo/common/extension/ExtensionLoader.java:1293

                    "Error occurred when loading extension class (interface: " + type + ", class line: "
                            + clazz.getName() + "), class " + clazz.getName() + " is not subtype of interface.");
        }

        boolean isActive = loadClassIfActive(classLoader, clazz);

        if (!isActive) {
            return;
        }

        if (clazz.isAnnotationPresent(Adaptive.class)) {
            cacheAdaptiveClass(clazz, overridden);
        } else if (isWrapperClass(clazz)) {
            cacheWrapperClass(clazz);
        } else {
            if (StringUtils.isEmpty(name)) {
                name = findAnnotationName(clazz);
                if (name.length() == 0) {
                    throw new IllegalStateException("No such extension name for the class " + clazz.getName()
                            + " in the config " + resourceURL);
                }
            }

            String[] names = NAME_SEPARATOR.split(name);
            if (ArrayUtils.isNotEmpty(names)) {
                cacheActivateClass(clazz, names[0]);
                for (String n : names) {
                    cacheName(clazz, n);
                    saveInExtensionClass(extensionClasses, clazz, n, overridden);
                }
            }
        }
    }

    private boolean loadClassIfActive(ClassLoader classLoader, Class<?> clazz) {
        Activate activate = clazz.getAnnotation(Activate.class);

View on GitHub (pinned to 3a3043227f)

Solutions

1. Edit the SPI config line to include a name: 'myName=com.example.Impl'.
2. Alternatively, annotate the implementation class so Dubbo can derive the name automatically (the @Extension annotation or package/class naming convention).
3. Validate every line in your META-INF SPI files has the 'name=FQN' format before packaging.

Example fix

# before: META-INF/dubbo/org.apache.dubbo.rpc.Protocol
com.example.MyProtocol
# throws [147]

# after
myproto=com.example.MyProtocol

// Build-time check: every SPI config line must be 'name=FQN' or the class must be annotated
for (String line : readSpiConfig(resourceUrl)) {
    String trimmed = line.trim();
    if (trimmed.isEmpty() || trimmed.startsWith("#")) continue;
    if (!trimmed.contains("=")) {
        // ensure the class has an @Extension annotation providing a name
        Class<?> c = Class.forName(trimmed);
        // else fail with a clear message
    }
}

When it happens

Trigger: A META-INF SPI config line is written as '=com.example.Impl' (empty name) or as 'com.example.Impl' with no name= prefix and the class has no @Extension/@SPI-derivable annotation. findAnnotationName() returns an empty string, triggering the check at name.length() == 0.

Common situations: Hand-edited SPI config file missing the name= prefix; migration from java ServiceLoader format (which has no names) into Dubbo SPI format without adding the name; a class that previously had an @Extension annotation providing the name but the annotation was removed during refactor.

Related errors

• Error occurred when loading extension class (interface: {},
• Extension instance (name: {}, class: {}) couldn't be instant
• Extension type == null
• Exception occurred when loading extension class (interface:
• More than 1 default extension name on extension {}: {}

AI-assisted analysis of apache/dubbo@3a3043227f (2026-08-14). Data as JSON: /api/errors/3e1e9f394595a8a1. Report an issue: GitHub.