apache/flink · critical · RuntimeException

Cannot create Hadoop WritableTypeInfo.

Error message

Cannot create Hadoop WritableTypeInfo.

What it means

Thrown by TypeExtractor.createHadoopWritableTypeInfo when invoking the HadoopWritableTypeInfo constructor throws an InvocationTargetException — meaning the constructor itself was found and accessible but threw an exception during instantiation. This wraps the target exception from the constructor.

Source

Thrown at flink-core/src/main/java/org/apache/flink/api/java/typeutils/TypeExtractor.java:2477

                            Thread.currentThread().getContextClassLoader());
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(
                    "Could not load the TypeInformation for the class '"
                            + HADOOP_WRITABLE_CLASS
                            + "'. You may be missing the 'flink-hadoop-compatibility' dependency.");
        }

        try {
            Constructor<?> constr = typeInfoClass.getConstructor(Class.class);

            @SuppressWarnings("unchecked")
            TypeInformation<T> typeInfo = (TypeInformation<T>) constr.newInstance(clazz);
            return typeInfo;
        } catch (NoSuchMethodException | IllegalAccessException | InstantiationException e) {
            throw new RuntimeException(
                    "Incompatible versions of the Hadoop Compatibility classes found.");
        } catch (InvocationTargetException e) {
            throw new RuntimeException(
                    "Cannot create Hadoop WritableTypeInfo.", e.getTargetException());
        }
    }

    // visible for testing
    static void validateIfWritable(TypeInformation<?> typeInfo, Type type) {
        try {
            // try to load the writable type info

            Class<?> writableTypeInfoClass =
                    Class.forName(
                            HADOOP_WRITABLE_TYPEINFO_CLASS,
                            false,
                            typeInfo.getClass().getClassLoader());

            if (writableTypeInfoClass.isAssignableFrom(typeInfo.getClass())) {
                // this is actually a writable type info
                // check if the type is a writable

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Inspect the wrapped target exception (e.getCause() or e.getTargetException()) for the root cause.
2. Ensure the Writable class has a public no-arg constructor as required by Hadoop Writable contract.
3. Verify the class is a concrete class (not abstract or interface) implementing org.apache.hadoop.io.Writable.
4. Check for security manager or classloader restrictions that might block reflective instantiation.

Example fix

// before
public class MyWritable implements Writable {
    // missing no-arg constructor, has only MyWritable(String s)
}

// after
public class MyWritable implements Writable {
    public MyWritable() {} // required no-arg constructor
    public MyWritable(String s) { ... }
    public void write(DataOutput out) { ... }
    public void readFields(DataInput in) { ... }
}

// Verify the Writable class has a no-arg constructor before type extraction
try {
    myWritableClass.getConstructor();
    // OK
} catch (NoSuchMethodException e) {
    // Writable class missing no-arg constructor; fix the class
}

static boolean hasValidWritableConstructor(Class<?> clazz) {
    try {
        clazz.getConstructor();
        return true;
    } catch (NoSuchMethodException e) {
        return false;
    }
}

try {
    TypeInformation<?> ti = TypeExtractor.createHadoopWritableTypeInfo(MyWritable.class);
} catch (RuntimeException e) {
    if (e.getCause() != null) {
        // inspect e.getCause() for the constructor's target exception
    }
}

When it happens

Trigger: Called during createHadoopWritableTypeInfo after constructor lookup succeeds, but constr.newInstance(clazz) throws InvocationTargetException. The HadoopWritableTypeInfo constructor threw an exception, possibly because the passed Writable class is invalid, has security restrictions, or failed internal validation.

Common situations: Passing a class to createHadoopWritableTypeInfo that does not properly implement Hadoop's Writable interface. Security manager restrictions preventing instantiation. Constructor internal validation rejecting the class (e.g., missing no-arg constructor on the Writable type, or the class is abstract).

Related errors

• InputSplit must implement Writable interface.
• Cannot create Comparator for {typeClass.getCanonicalName()}.
• The given class is no subclass of {Writable.class.getName()}
• Could not load the TypeInformation for the class '{}'. You m
• Incompatible versions of the Hadoop Compatibility classes fo

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/7da8b3e6013dca1d. Report an issue: GitHub.