检索 ByteBuddy 生成的 Spring Bean 的问题

Question

I am making my own ORM and I'm at a point where I want to to eliminate the need to create repository classes. They currently look like this:

@Repository
public class CustomerDao extends AbstractDao<Customer, Long>
{

}

Without going too deep into the inner workings of my ORM, the AbstractDao class uses a bean which is a map containing the entity class as a key and the dao class as a value. Without bringing ByteBuddy in the mix, the declaration of that bean looks like this:

@Bean
public Map<Class<?>, AbstractDao<?, ?>> daoMap()
{
    context.getBeansWithAnnotation(Repository.class).forEach((s, c) ->
    {
        if (c instanceof AbstractDao<?, ?>) map.put(ClassUtils.getSuperClassTypeArgument(c.getClass(), 0), (AbstractDao<?, ?>) c);
    });

    return map;
}

Again this works great but it's very annoying to have to create these empty classes. I am trying to use the Reflections and ByteBuddy libraries to generate these classes at runtime and dynamically inject them into the Spring context as repository beans. Here is my modified method:

@Bean
public Map<Class<?>, AbstractDao<?, ?>> daoMap() throws InstantiationException, IllegalAccessException, IllegalArgumentException, 
    InvocationTargetException, ConstructorMissingException, AnnotationMissingException, NoSuchMethodException, SecurityException
{
    var map = new HashMap<Class<?>, AbstractDao<?, ?>>();

    var byteBuddy = new ByteBuddy();

    for (var entityClass : new Reflections("com.somepackage.entity").getSubTypesOf(Entity.class))
    {
        var daoClass = byteBuddy
            .subclass(TypeDescription.Generic.Builder.parameterizedType(AbstractDao.class, entityClass, 
                ReflectionUtils.getIdField(entityClass).getType()).build())
            .annotateType(AnnotationDescription.Builder.ofType(Repository.class).build())
            .make();

        var clazz = daoClass.load(getClass().getClassLoader()).getLoaded();

        ((GenericApplicationContext) context).registerBean(clazz, clazz.getConstructor().newInstance());
    }

    context.getBeansWithAnnotation(Repository.class).forEach((s, c) ->
    {
        if (c instanceof AbstractDao<?, ?>) map.put(ClassUtils.getSuperClassTypeArgument(c.getClass(), 0), (AbstractDao<?, ?>) c);
    });

    return map;
}

The loop that creates the classes and injects them as beans seems to work fine. It doesn't throw exceptions and affects the right classes. I am however getting an exception at the getBeansWithAnnotation line:

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.mdenis.carbon.carbon_orm.dao.AbstractDao$ByteBuddy$jzMtXq5b': Could not resolve matching constructor (hint: specify index/type/name arguments for simple parameters to avoid type ambiguities)
at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:278) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1358) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1204) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansWithAnnotation(DefaultListableBeanFactory.java:672) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.getBeansWithAnnotation(AbstractApplicationContext.java:1264) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at com.mdenis.carbon.carbon_orm.config.ORMConfig.daoMap(ORMConfig.java:55) ~[classes/:na]
at com.mdenis.carbon.carbon_orm.config.ORMConfig$$EnhancerBySpringCGLIB$$8fd9cb34.CGLIB$daoMap$1(<generated>) ~[classes/:na]
at com.mdenis.carbon.carbon_orm.config.ORMConfig$$EnhancerBySpringCGLIB$$8fd9cb34$$FastClassBySpringCGLIB$$a25eec90.invoke(<generated>) ~[classes/:na]
at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:244) ~[spring-core-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:331) ~[spring-context-5.2.6.RELEASE.jar:5.2.6.RELEASE]
at com.mdenis.carbon.carbon_orm.config.ORMConfig$$EnhancerBySpringCGLIB$$8fd9cb34.daoMap(<generated>) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) ~[spring-beans-5.2.6.RELEASE.jar:5.2.6.RELEASE]
... 85 common frames omitted

This seems to be related to Spring failing to autowire the constructor even though it technically doesn't have to. Any idea how to resolve this?

Answer 1

Your problem is not related to byte-buddy. The error also occurs if you try to register a preexisting class.

You need to register the new beans in an earlier phase of the context startup. One way of doing that is to use a BeanFactoryPostProcessor . Split your map creation into two sections. The one with the class generation into the BeanFactoryPostProcessor . The one with the Map generation you can keep in the @Bean factory method

eg:

@Configuration
public class RepositoryConfigurationBean implements BeanFactoryPostProcessor {

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
        try {
            // Replace X1.class with the one from bytebuddy
            // The name should be unique
            configurableListableBeanFactory.registerSingleton("abc", X1.class.getConstructor().newInstance());
        } catch (InstantiationException | IllegalAccessException | InvocationTargetException | NoSuchMethodException e) {
            e.printStackTrace();
        }
   }