温馨提示：本文有点长，但是满满的干货，建议耐心看完！
特别说明：由于很多网友留言自身使用的Dubbo框架版本比较低，无法兼容Spring4或Spring5的注解配置，故本文只针对低版本Dubbo如何兼容Spring4或Spring5的注解配置给出相应的解决方案，目前，高版本Dubbo已经不存在与Spring4或Spring5的注解配置的兼容性问题。
本文分析低版本Dubbo框架的源码，以找出不兼容Spring4或Spring5的注解配置的问题所在，并通过修改Dubbo源码以使其兼容Spring4或Spring5的注解配置。最后，由于直接修改Dubbo的源码对Dubbo框架的侵入性太强，文中又给出了如何以“外挂”的形式修改Dubbo源码并使其注册到Spring环境。
自从阿里重新维护Dubbo后，一路放大招，将Dubbo推上Apache的顶级开源项目，Dubbo经过不断的维护和发展，也相继发布了N多个版本，成为分布式与微服务领域中屈指可数的服务治理框架。目前， 笔者截稿前Dubbo的最新Release版本为apache-dubbo-2.7.4.1。
Dubbo的Release版本的源码Apache下载链接地址为：https://github.com/apache/dubbo/releases。
不过，目前，也有很多公司或组织内部使用的Dubbo版本比较老旧，很多网友在公众号留言咨询笔者，低版本的Dubbo如何兼容Spring4或Spring5。这里，笔者就借此机会写一些有关Dubbo服务治理框架的文章，供读者参考。
Dubbo本身就是基于Spring环境的，但是Dubbo当年Spring才2.版本。而现如今Spring 已经发展到5。
而随着Spring Boot的大热，Java-Base方式配置Spring也变得越来越流行。
Dubbo + Boot的开发模式，也是较为常见的组合方式。
但是，当使用低版本Dubbo在高版本Spring环境中使用注解方式配置时，会因为一些代码版本的原因导致整合出现问题。
1.Dubbo原生的注解配置
Dubbo本身就是基于Spring的，而且原生就提供注解配置：
服务提供方配置：
<!-- 扫描注解包路径，多个包用逗号分隔，不填pacakge表示扫描当前ApplicationContext中所有的类 --> <dubbo:annotation package="com.foo.bar.service" />
服务提供方注解：
import com.alibaba.dubbo.config.annotation.Service; @Service(version="1.0.0") public class FooServiceImpl implements FooService { // ...... }
服务消费方注解：
import com.alibaba.dubbo.config.annotation.Reference; import org.springframework.stereotype.Component; @Component public class BarAction { @Reference(version="1.0.0") private FooService fooService; }
服务消费方配置：
<!-- 扫描注解包路径，多个包用逗号分隔，不填pacakge表示扫描当前ApplicationContext中所有的类 --> <dubbo:annotation package="com.foo.bar.action" />
通过官方的例子，就可以看出Dubbo使用xml配置<dubbo:annotation /> 来开启注解配置，并提供 com.alibaba.dubbo.config.annotation.Service注解进行服务注册，提供com.alibaba.dubbo.config.annotation.Reference注解进行服务注入。
2.实现机制
可以看出，内部机制都是依托于<dubbo:annotation />标签。通过源码分析，Dubbo对于Spring xml解析处理由com.alibaba.dubbo.config.spring.schema.DubboNamespaceHandler提供：
DubboNamespaceHandler.java
package com.alibaba.dubbo.config.spring.schema; import org.springframework.beans.factory.xml.NamespaceHandlerSupport; import com.alibaba.dubbo.common.Version; import com.alibaba.dubbo.config.ApplicationConfig; import com.alibaba.dubbo.config.ConsumerConfig; import com.alibaba.dubbo.config.ModuleConfig; import com.alibaba.dubbo.config.MonitorConfig; import com.alibaba.dubbo.config.ProtocolConfig; import com.alibaba.dubbo.config.ProviderConfig; import com.alibaba.dubbo.config.RegistryConfig; import com.alibaba.dubbo.config.spring.AnnotationBean; import com.alibaba.dubbo.config.spring.ReferenceBean; import com.alibaba.dubbo.config.spring.ServiceBean; /** * DubboNamespaceHandler * * @author william.liangf * @export */ public class DubboNamespaceHandler extends NamespaceHandlerSupport { static { Version.checkDuplicate(DubboNamespaceHandler.class); } public void init() { registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true)); registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true)); registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true)); registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true)); registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true)); registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true)); registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true)); registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true)); registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false)); registerBeanDefinitionParser("annotation", new DubboBeanDefinitionParser(AnnotationBean.class, true)); }
通过上面的代码可以很直观的发现，<dubbo:annotation />标签实际是由com.alibaba.dubbo.config.spring.schema.DubboBeanDefinitionParser解析：
DubboBeanDefinitionParser.java
** * AbstractBeanDefinitionParser * * @author william.liangf * @export */ public class DubboBeanDefinitionParser implements BeanDefinitionParser { private static final Logger logger = LoggerFactory.getLogger(DubboBeanDefinitionParser.class); private final Class<?> beanClass; private final boolean required; public DubboBeanDefinitionParser(Class<?> beanClass, boolean required) { this.beanClass = beanClass; this.required = required; } public BeanDefinition parse(Element element, ParserContext parserContext) { return parse(element, parserContext, beanClass, required); } @SuppressWarnings("unchecked") private static BeanDefinition parse(Element element, ParserContext parserContext, Class<?> beanClass, boolean required) { //略 }
可以看到这个类实现了Spring的org.springframework.beans.factory.xml.BeanDefinitionParser接口，从而完成Spring Bean的解析工作。
而registerBeanDefinitionParser("annotation", new DubboBeanDefinitionParser(AnnotationBean.class, true));就是将<dubbo:annotation />标签，解析成com.alibaba.dubbo.config.spring.AnnotationBean并注册到Spring中。
3.AnnotationBean分析
先来看看源码：
AnnotationBean.java
package com.alibaba.dubbo.config.spring; /** * AnnotationBean * * @author william.liangf * @export */ public class AnnotationBean extends AbstractConfig implements DisposableBean, BeanFactoryPostProcessor, BeanPostProcessor, ApplicationContextAware { private static final long serialVersionUID = -7582802454287589552L; private static final Logger logger = LoggerFactory.getLogger(Logger.class); private String annotationPackage; private String[] annotationPackages; private final Set<ServiceConfig<?>> serviceConfigs = new ConcurrentHashSet<ServiceConfig<?>>(); private final ConcurrentMap<String, ReferenceBean<?>> referenceConfigs = new ConcurrentHashMap<String, ReferenceBean<?>>(); public String getPackage() { return annotationPackage; } public void setPackage(String annotationPackage) { this.annotationPackage = annotationPackage; this.annotationPackages = (annotationPackage == null || annotationPackage.length() == 0) ? null : Constants.COMMA_SPLIT_PATTERN.split(annotationPackage); } private ApplicationContext applicationContext; public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { this.applicationContext = applicationContext; } public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { if (annotationPackage == null || annotationPackage.length() == 0) { return; } if (beanFactory instanceof BeanDefinitionRegistry) { try { // init scanner Class<?> scannerClass = ReflectUtils.forName("org.springframework.context.annotation.ClassPathBeanDefinitionScanner"); Object scanner = scannerClass.getConstructor(new Class<?>[] {BeanDefinitionRegistry.class, boolean.class}).newInstance(new Object[] {(BeanDefinitionRegistry) beanFactory, true}); // add filter Class<?> filterClass = ReflectUtils.forName("org.springframework.core.type.filter.AnnotationTypeFilter"); Object filter = filterClass.getConstructor(Class.class).newInstance(Service.class); Method addIncludeFilter = scannerClass.getMethod("addIncludeFilter", ReflectUtils.forName("org.springframework.core.type.filter.TypeFilter")); addIncludeFilter.invoke(scanner, filter); // scan packages String[] packages = Constants.COMMA_SPLIT_PATTERN.split(annotationPackage); Method scan = scannerClass.getMethod("scan", new Class<?>[]{String[].class}); scan.invoke(scanner, new Object[] {packages}); } catch (Throwable e) { // spring 2.0 } } } public void destroy() throws Exception { for (ServiceConfig<?> serviceConfig : serviceConfigs) { try { serviceConfig.unexport(); } catch (Throwable e) { logger.error(e.getMessage(), e); } } for (ReferenceConfig<?> referenceConfig : referenceConfigs.values()) { try { referenceConfig.destroy(); } catch (Throwable e) { logger.error(e.getMessage(), e); } } } public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { if (! isMatchPackage(bean)) { return bean; } Service service = bean.getClass().getAnnotation(Service.class); if (service != null) { ServiceBean<Object> serviceConfig = new ServiceBean<Object>(service); if (void.class.equals(service.interfaceClass()) && "".equals(service.interfaceName())) { if (bean.getClass().getInterfaces().length > 0) { serviceConfig.setInterface(bean.getClass().getInterfaces()[0]); } else { throw new IllegalStateException("Failed to export remote service class " + bean.getClass().getName() + ", cause: The @Service undefined interfaceClass or interfaceName, and the service class unimplemented any interfaces."); } } if (applicationContext != null) { serviceConfig.setApplicationContext(applicationContext); if (service.registry() != null && service.registry().length > 0) { List<RegistryConfig> registryConfigs = new ArrayList<RegistryConfig>(); for (String registryId : service.registry()) { if (registryId != null && registryId.length() > 0) { registryConfigs.add((RegistryConfig)applicationContext.getBean(registryId, RegistryConfig.class)); } } serviceConfig.setRegistries(registryConfigs); } if (service.provider() != null && service.provider().length() > 0) { serviceConfig.setProvider((ProviderConfig)applicationContext.getBean(service.provider(),ProviderConfig.class)); } if (service.monitor() != null && service.monitor().length() > 0) { serviceConfig.setMonitor((MonitorConfig)applicationContext.getBean(service.monitor(), MonitorConfig.class)); } if (service.application() != null && service.application().length() > 0) { serviceConfig.setApplication((ApplicationConfig)applicationContext.getBean(service.application(), ApplicationConfig.class)); } if (service.module() != null && service.module().length() > 0) { serviceConfig.setModule((ModuleConfig)applicationContext.getBean(service.module(), ModuleConfig.class)); } if (service.provider() != null && service.provider().length() > 0) { serviceConfig.setProvider((ProviderConfig)applicationContext.getBean(service.provider(), ProviderConfig.class)); } else { } if (service.protocol() != null && service.protocol().length > 0) { List<ProtocolConfig> protocolConfigs = new ArrayList<ProtocolConfig>(); for (String protocolId : service.registry()) { if (protocolId != null && protocolId.length() > 0) { protocolConfigs.add((ProtocolConfig)applicationContext.getBean(protocolId, ProtocolConfig.class)); } } serviceConfig.setProtocols(protocolConfigs); } try { serviceConfig.afterPropertiesSet(); } catch (RuntimeException e) { throw (RuntimeException) e; } catch (Exception e) { throw new IllegalStateException(e.getMessage(), e); } } serviceConfig.setRef(bean); serviceConfigs.add(serviceConfig); serviceConfig.export(); } return bean; } public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { if (! isMatchPackage(bean)) { return bean; } Method[] methods = bean.getClass().getMethods(); for (Method method : methods) { String name = method.getName(); if (name.length() > 3 && name.startsWith("set") && method.getParameterTypes().length == 1 && Modifier.isPublic(method.getModifiers()) && ! Modifier.isStatic(method.getModifiers())) { try { Reference reference = method.getAnnotation(Reference.class); if (reference != null) { Object value = refer(reference, method.getParameterTypes()[0]); if (value != null) { method.invoke(bean, new Object[] { }); } } } catch (Throwable e) { logger.error("Failed to init remote service reference at method " + name + " in class " + bean.getClass().getName() + ", cause: " + e.getMessage(), e); } } } Field[] fields = bean.getClass().getDeclaredFields(); for (Field field : fields) { try { if (! field.isAccessible()) { field.setAccessible(true); } Reference reference = field.getAnnotation(Reference.class); if (reference != null) { Object value = refer(reference, field.getType()); if (value != null) { field.set(bean, value); } } } catch (Throwable e) { logger.error("Failed to init remote service reference at filed " + field.getName() + " in class " + bean.getClass().getName() + ", cause: " + e.getMessage(), e); } } return bean; } private Object refer(Reference reference, Class<?> referenceClass) { //method.getParameterTypes()[0] String interfaceName; if (! "".equals(reference.interfaceName())) { interfaceName = reference.interfaceName(); } else if (! void.class.equals(reference.interfaceClass())) { interfaceName = reference.interfaceClass().getName(); } else if (referenceClass.isInterface()) { interfaceName = referenceClass.getName(); } else { throw new IllegalStateException("The @Reference undefined interfaceClass or interfaceName, and the property type " + referenceClass.getName() + " is not a interface."); } String key = reference.group() + "/" + interfaceName + ":" + reference.version(); ReferenceBean<?> referenceConfig = referenceConfigs.get(key); if (referenceConfig == null) { referenceConfig = new ReferenceBean<Object>(reference); if (void.class.equals(reference.interfaceClass()) && "".equals(reference.interfaceName()) && referenceClass.isInterface()) { referenceConfig.setInterface(referenceClass); } if (applicationContext != null) { referenceConfig.setApplicationContext(applicationContext); if (reference.registry() != null && reference.registry().length > 0) { List<RegistryConfig> registryConfigs = new ArrayList<RegistryConfig>(); for (String registryId : reference.registry()) { if (registryId != null && registryId.length() > 0) { registryConfigs.add((RegistryConfig)applicationContext.getBean(registryId, RegistryConfig.class)); } } referenceConfig.setRegistries(registryConfigs); } if (reference.consumer() != null && reference.consumer().length() > 0) { referenceConfig.setConsumer((ConsumerConfig)applicationContext.getBean(reference.consumer(), ConsumerConfig.class)); } if (reference.monitor() != null && reference.monitor().length() > 0) { referenceConfig.setMonitor((MonitorConfig)applicationContext.getBean(reference.monitor(), MonitorConfig.class)); } if (reference.application() != null && reference.application().length() > 0) { referenceConfig.setApplication((ApplicationConfig)applicationContext.getBean(reference.application(), ApplicationConfig.class)); } if (reference.module() != null && reference.module().length() > 0) { referenceConfig.setModule((ModuleConfig)applicationContext.getBean(reference.module(), ModuleConfig.class)); } if (reference.consumer() != null && reference.consumer().length() > 0) { referenceConfig.setConsumer((ConsumerConfig)applicationContext.getBean(reference.consumer(), ConsumerConfig.class)); } try { referenceConfig.afterPropertiesSet(); } catch (RuntimeException e) { throw (RuntimeException) e; } catch (Exception e) { throw new IllegalStateException(e.getMessage(), e); } } referenceConfigs.putIfAbsent(key, referenceConfig); referenceConfig = referenceConfigs.get(key); } return referenceConfig.get(); } private boolean isMatchPackage(Object bean) { if (annotationPackages == null || annotationPackages.length == 0) { return true; } String beanClassName = bean.getClass().getName(); for (String pkg : annotationPackages) { if (beanClassName.startsWith(pkg)) { return true; } } return false; } }
这个AnnotationBean实现了几个Spring生命周期接口，从而完成Dubbo整合Spring 的操作。
org.springframework.beans.factory.config.BeanFactoryPostProcessor
先来看看Spring文档中的介绍：
BeanFactoryPostProcessor operates on the bean configuration metadata; that is, the Spring IoC container allows a BeanFactoryPostProcessor to read the configuration metadata and potentially change it before the container instantiates any beans other than BeanFactoryPostProcessors.
翻译成中文就是：BeanFactoryPostProcessor可以用于在Spring IoC容器实例化Bean之前，对Spring Bean配置信息进行一些操作
通过Spring文档，可以清楚这个接口的功能，那再来看看Dubbo的AnnotationBean是如何实现这个接口的：
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { if (annotationPackage == null || annotationPackage.length() == 0) { return; } if (beanFactory instanceof BeanDefinitionRegistry) { try { // init scanner Class<?> scannerClass = ReflectUtils.forName("org.springframework.context.annotation.ClassPathBeanDefinitionScanner"); Object scanner = scannerClass.getConstructor(new Class<?>[] {BeanDefinitionRegistry.class, boolean.class}).newInstance(new Object[] {(BeanDefinitionRegistry) beanFactory, true}); // add filter Class<?> filterClass = ReflectUtils.forName("org.springframework.core.type.filter.AnnotationTypeFilter"); Object filter = filterClass.getConstructor(Class.class).newInstance(Service.class); Method addIncludeFilter = scannerClass.getMethod("addIncludeFilter", ReflectUtils.forName("org.springframework.core.type.filter.TypeFilter")); addIncludeFilter.invoke(scanner, filter); // scan packages String[] packages = Constants.COMMA_SPLIT_PATTERN.split(annotationPackage); Method scan = scannerClass.getMethod("scan", new Class<?>[]{String[].class}); scan.invoke(scanner, new Object[] {packages}); } catch (Throwable e) { // spring 2.0 } }
源码中已经标出了，Dubbo做了以下几件事：
- 增加了一个class扫描器，用于处理Dubbo服务类的扫描
- 增加过滤器，只扫描带有com.alibaba.dubbo.config.annotation.Service注解的class
- 指定扫描的包，对应这<dubbo:annotation package="com.foo.bar.service" />标签中的package属性。
这个扫描器，就是将那些带有com.alibaba.dubbo.config.annotation.Service注解的class纳入Spring容器中，而这些Dubbo服务类上不需要单独加上Spring的注解，也不需要额外配置Spring Bean定义。
org.springframework.beans.factory.DisposableBean
再来看看这个接口，还是先看看Spring文档：
Implementing the org.springframework.beans.factory.DisposableBean interface allows a bean to get a callback when the container containing it is destroyed. The DisposableBean interface specifies a single method:void destroy() throws Exception;
这个接口实际上就是当Spring容器要销毁时的一个回调接口。
那再来看看Dubbo是如何实现的：
public void destroy() throws Exception { for (ServiceConfig<?> serviceConfig : serviceConfigs) { try { serviceConfig.unexport(); } catch (Throwable e) { logger.error(e.getMessage(), e); } } for (ReferenceConfig<?> referenceConfig : referenceConfigs.values()) { try { referenceConfig.destroy(); } catch (Throwable e) { logger.error(e.getMessage(), e); } } }
也比较简单，实际上就是当Spring容器销毁时，对Dubbo服务进行反注册操作。
org.springframework.beans.factory.config.BeanPostProcessor
最后来看看这个接口，照例先看看Spring文档：
The BeanPostProcessor interface defines callback methods that you can implement to provide your own (or override the container’s default) instantiation logic, dependency-resolution logic, and so forth. If you want to implement some custom logic after the Spring container finishes instantiating, configuring, and initializing a bean, you can plug in one or more BeanPostProcessor implementations.
这个接口也是一个回调接口，只是回调时机不同，它发生在Spring容器初始化过程中，Bean实例化前后之时。也可以理解为Spring容器初始化完成后，Bean实例化前后但还没有给容器外使用前。
再来看看Dubbbo在这个时间点上做了什么：
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { if (! isMatchPackage(bean)) { return bean; } Method[] methods = bean.getClass().getMethods(); for (Method method : methods) { String name = method.getName(); if (name.length() > 3 && name.startsWith("set") && method.getParameterTypes().length == 1 && Modifier.isPublic(method.getModifiers()) && ! Modifier.isStatic(method.getModifiers())) { try { Reference reference = method.getAnnotation(Reference.class); if (reference != null) { Object value = refer(reference, method.getParameterTypes()[0]); if (value != null) { method.invoke(bean, new Object[] { }); } } } catch (Throwable e) { logger.error("Failed to init remote service reference at method " + name + " in class " + bean.getClass().getName() + ", cause: " + e.getMessage(), e); } } } Field[] fields = bean.getClass().getDeclaredFields(); for (Field field : fields) { try { if (! field.isAccessible()) { field.setAccessible(true); } Reference reference = field.getAnnotation(Reference.class); if (reference != null) { Object value = refer(reference, field.getType()); if (value != null) { field.set(bean, value); } } } catch (Throwable e) { logger.error("Failed to init remote service reference at filed " + field.getName() + " in class " + bean.getClass().getName() + ", cause: " + e.getMessage(), e); } } return bean; }
postProcessBeforeInitialization方法，顾名思义，发生Bean实例化之前。通过源码就可以发现，主要用于处理Bean中的com.alibaba.dubbo.config.annotation.Reference注解，从而让Dubbo服务能够注入到Bean中。期间利用JAVA反射机制对Bean的方法和属性进行注入。
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { if (! isMatchPackage(bean)) { return bean; } Service service = bean.getClass().getAnnotation(Service.class); if (service != null) { ServiceBean<Object> serviceConfig = new ServiceBean<Object>(service); if (void.class.equals(service.interfaceClass()) && "".equals(service.interfaceName())) { if (bean.getClass().getInterfaces().length > 0) { serviceConfig.setInterface(bean.getClass().getInterfaces()[0]); } else { throw new IllegalStateException("Failed to export remote service class " + bean.getClass().getName() + ", cause: The @Service undefined interfaceClass or interfaceName, and the service class unimplemented any interfaces."); } } if (applicationContext != null) { serviceConfig.setApplicationContext(applicationContext); if (service.registry() != null && service.registry().length > 0) { List<RegistryConfig> registryConfigs = new ArrayList<RegistryConfig>(); for (String registryId : service.registry()) { if (registryId != null && registryId.length() > 0) { registryConfigs.add((RegistryConfig)applicationContext.getBean(registryId, RegistryConfig.class)); } } serviceConfig.setRegistries(registryConfigs); } if (service.provider() != null && service.provider().length() > 0) { serviceConfig.setProvider((ProviderConfig)applicationContext.getBean(service.provider(),ProviderConfig.class)); } if (service.monitor() != null && service.monitor().length() > 0) { serviceConfig.setMonitor((MonitorConfig)applicationContext.getBean(service.monitor(), MonitorConfig.class)); } if (service.application() != null && service.application().length() > 0) { serviceConfig.setApplication((ApplicationConfig)applicationContext.getBean(service.application(), ApplicationConfig.class)); } if (service.module() != null && service.module().length() > 0) { serviceConfig.setModule((ModuleConfig)applicationContext.getBean(service.module(), ModuleConfig.class)); } if (service.provider() != null && service.provider().length() > 0) { serviceConfig.setProvider((ProviderConfig)applicationContext.getBean(service.provider(), ProviderConfig.class)); } else { } if (service.protocol() != null && service.protocol().length > 0) { List<ProtocolConfig> protocolConfigs = new ArrayList<ProtocolConfig>(); for (String protocolId : service.registry()) { if (protocolId != null && protocolId.length() > 0) { protocolConfigs.add((ProtocolConfig)applicationContext.getBean(protocolId, ProtocolConfig.class)); } } serviceConfig.setProtocols(protocolConfigs); } try { serviceConfig.afterPropertiesSet(); } catch (RuntimeException e) { throw (RuntimeException) e; } catch (Exception e) { throw new IllegalStateException(e.getMessage(), e); } } serviceConfig.setRef(bean); serviceConfigs.add(serviceConfig); serviceConfig.export(); } return bean; }
postProcessAfterInitialization方法，同样从名字就能看出，其发生在Bean实例化之后。通过源码就能发现，其作用就是将带有com.alibaba.dubbo.config.annotation.Service注解的Bean自动注册到Dubbo的注册中心，完成服务注册动作。
4.问题分析
通过上面的分析，对于Dubbo注解方式整合到Spring已经比较清楚了。而在使用高版本Spring时，上面的AnnotationBean会出现一些问题。
问题主要集中在：
- Dubbo的注解Service有时不能进行服务注册
- Dubbo的注解Reference有时不能注入服务
从代码分析问题主要集中在postProcessBeforeInitialization和postProcessAfterInitialization方法上。
Service service = bean.getClass().getAnnotation(Service.class);
Method[] methods = bean.getClass().getMethods();
方法中都是利用Java反射来处理Bean的Class。
众所周知，Spring有两大利器IOC和AOP。在早期AOP基本都是利用JAVA动态代理实现的，而随着字节码技术的发展，现在Spring已经基本以ASM为代表的字节码增强框架为基础实现AOP,以及一些Bean的代理。
有兴趣的小伙伴可以打开spring-core-x.x.x.jar,会发现spring已经内嵌了asm以及cglib （org.springframework.asm）（org.springframework.cglib）
而在Spring环境中大量出现经过Cglib增强的Class，这些Class不再是简单的基于接口的代理机制了，其内部大量使用委派方式，以及访问器模式。最常见的就是Spring的事物，对于使用了@Transactional的Bean，都是以这种方式来增加事物处理能力的。
那基于这种方式扩展的Class，再通过反射getClass得到的是经过cglib改写后的class。在这些class上getAnnotation以及getMethods都不再是预期中的结果了。
所以，这也也就导致了上面罗列的两个问题。
5. 解决方案
经过对问题的分析，可以发现，问题主要是集中在Dubbo获取Bean的class上。
在Spring中，提供了很多Utils类。其中org.springframework.aop.support.AopUtils就可以用来对Aop代理的类进行操作的API。
于是，我们可以利用这个类来完成Class的获取。
private Class<?> getBeanClass(Object bean) { Class<?> clazz = bean.getClass(); if (AopUtils.isAopProxy(bean)) { clazz = AopUtils.getTargetClass(bean); } return clazz; }
这样获取Class就可以这样：
Class<?> clazz = getBeanClass(bean); Service service = clazz.getAnnotation(Service.class);
Class<?> clazz = getBeanClass(bean);
修改后完整的代码：
AnnotationBean.java
/* * Copyright 1999-2012 Alibaba Group. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.roc.dubbo.config.spring; import java.lang.reflect.Field; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.util.ArrayList; import java.util.List; import java.util.Set; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; import org.springframework.aop.support.AopUtils; import org.springframework.beans.BeansException; import org.springframework.beans.factory.DisposableBean; import org.springframework.beans.factory.config.BeanFactoryPostProcessor; import org.springframework.beans.factory.config.BeanPostProcessor; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; import org.springframework.beans.factory.support.BeanDefinitionRegistry; import org.springframework.context.ApplicationContext; import org.springframework.context.ApplicationContextAware; import com.alibaba.dubbo.common.Constants; import com.alibaba.dubbo.common.logger.Logger; import com.alibaba.dubbo.common.logger.LoggerFactory; import com.alibaba.dubbo.common.utils.ConcurrentHashSet; import com.alibaba.dubbo.common.utils.ReflectUtils; import com.alibaba.dubbo.config.AbstractConfig; import com.alibaba.dubbo.config.ApplicationConfig; import com.alibaba.dubbo.config.ConsumerConfig; import com.alibaba.dubbo.config.ModuleConfig; import com.alibaba.dubbo.config.MonitorConfig; import com.alibaba.dubbo.config.ProtocolConfig; import com.alibaba.dubbo.config.ProviderConfig; import com.alibaba.dubbo.config.ReferenceConfig; import com.alibaba.dubbo.config.RegistryConfig; import com.alibaba.dubbo.config.ServiceConfig; import com.alibaba.dubbo.config.annotation.Reference; import com.alibaba.dubbo.config.annotation.Service; import com.alibaba.dubbo.config.spring.ReferenceBean; import com.alibaba.dubbo.config.spring.ServiceBean; /** * AnnotationBean * * @author william.liangf * @export * * >>>修复@com.alibaba.dubbo.config.annotation.Service * 与Spring @Transactional 冲突 */ public class AnnotationBean extends AbstractConfig implements DisposableBean, BeanFactoryPostProcessor, BeanPostProcessor, ApplicationContextAware { private static final long serialVersionUID = -7582802454287589552L; private static final Logger logger = LoggerFactory.getLogger(Logger.class); private String annotationPackage; private String[] annotationPackages; private final Set<ServiceConfig<?>> serviceConfigs = new ConcurrentHashSet<ServiceConfig<?>>(); private final ConcurrentMap<String, ReferenceBean<?>> referenceConfigs = new ConcurrentHashMap<String, ReferenceBean<?>>(); public String getPackage() { return annotationPackage; } public void setPackage(String annotationPackage) { this.annotationPackage = annotationPackage; this.annotationPackages = (annotationPackage == null || annotationPackage.length() == 0) ? null : Constants.COMMA_SPLIT_PATTERN.split(annotationPackage); } private ApplicationContext applicationContext; public void setApplicationContext(ApplicationContext applicationContext) throws BeansException { this.applicationContext = applicationContext; } public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { if (annotationPackage == null || annotationPackage.length() == 0) { logger.debug("未定义注解扫描包"); return; } logger.info("扫描：" + annotationPackage); if (beanFactory instanceof BeanDefinitionRegistry) { try { // init scanner Class<?> scannerClass = ReflectUtils .forName("org.springframework.context.annotation.ClassPathBeanDefinitionScanner"); Object scanner = scannerClass .getConstructor(new Class<?>[] { BeanDefinitionRegistry.class, boolean.class }) .newInstance(new Object[] { (BeanDefinitionRegistry) beanFactory, true }); // add filter Class<?> filterClass = ReflectUtils .forName("org.springframework.core.type.filter.AnnotationTypeFilter"); Object filter = filterClass.getConstructor(Class.class).newInstance(Service.class); Method addIncludeFilter = scannerClass.getMethod("addIncludeFilter", ReflectUtils.forName("org.springframework.core.type.filter.TypeFilter")); addIncludeFilter.invoke(scanner, filter); // scan packages String[] packages = Constants.COMMA_SPLIT_PATTERN.split(annotationPackage); Method scan = scannerClass.getMethod("scan", new Class<?>[] { String[].class }); scan.invoke(scanner, new Object[] { packages }); } catch (Throwable e) { // spring 2.0 } } } public void destroy() throws Exception { for (ServiceConfig<?> serviceConfig : serviceConfigs) { try { serviceConfig.unexport(); } catch (Throwable e) { logger.error(e.getMessage(), e); } } for (ReferenceConfig<?> referenceConfig : referenceConfigs.values()) { try { referenceConfig.destroy(); } catch (Throwable e) { logger.error(e.getMessage(), e); } } } public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { if (!isMatchPackage(bean)) { return bean; } Class<?> clazz = getBeanClass(bean); Service service = clazz.getAnnotation(Service.class); // >>>>>>>>>>>>>>>>>> if (service != null) { ServiceBean<Object> serviceConfig = new ServiceBean<Object>(service); if (void.class.equals(service.interfaceClass()) && "".equals(service.interfaceName())) { if (bean.getClass().getInterfaces().length > 0) { serviceConfig.setInterface(bean.getClass().getInterfaces()[0]); } else { throw new IllegalStateException("Failed to export remote service class " + bean.getClass().getName() + ", cause: The @Service undefined interfaceClass or interfaceName, and the service class unimplemented any interfaces."); } } if (applicationContext != null) { serviceConfig.setApplicationContext(applicationContext); if (service.registry() != null && service.registry().length > 0) { List<RegistryConfig> registryConfigs = new ArrayList<RegistryConfig>(); for (String registryId : service.registry()) { if (registryId != null && registryId.length() > 0) { registryConfigs .add((RegistryConfig) applicationContext.getBean(registryId, RegistryConfig.class)); } } serviceConfig.setRegistries(registryConfigs); } if (service.provider() != null && service.provider().length() > 0) { serviceConfig.setProvider( (ProviderConfig) applicationContext.getBean(service.provider(), ProviderConfig.class)); } if (service.monitor() != null && service.monitor().length() > 0) { serviceConfig.setMonitor( (MonitorConfig) applicationContext.getBean(service.monitor(), MonitorConfig.class)); } if (service.application() != null && service.application().length() > 0) { serviceConfig.setApplication((ApplicationConfig) applicationContext.getBean(service.application(), ApplicationConfig.class)); } if (service.module() != null && service.module().length() > 0) { serviceConfig .setModule((ModuleConfig) applicationContext.getBean(service.module(), ModuleConfig.class)); } if (service.provider() != null && service.provider().length() > 0) { serviceConfig.setProvider( (ProviderConfig) applicationContext.getBean(service.provider(), ProviderConfig.class)); } else { } if (service.protocol() != null && service.protocol().length > 0) { List<ProtocolConfig> protocolConfigs = new ArrayList<ProtocolConfig>(); for (String protocolId : service.registry()) { if (protocolId != null && protocolId.length() > 0) { protocolConfigs .add((ProtocolConfig) applicationContext.getBean(protocolId, ProtocolConfig.class)); } } serviceConfig.setProtocols(protocolConfigs); } try { serviceConfig.afterPropertiesSet(); } catch (RuntimeException e) { throw (RuntimeException) e; } catch (Exception e) { throw new IllegalStateException(e.getMessage(), e); } } serviceConfig.setRef(bean); serviceConfigs.add(serviceConfig); serviceConfig.export(); } return bean; } public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { // logger.debug("扫描bean:"+bean); // System.out.println("扫描bean:"+bean); if (!isMatchPackage(bean)) { return bean; } // >>>>>>>>>>>>>>>>>>>>>>>> Class<?> clazz = getBeanClass(bean); // >>>>>>>>>>>>>>>>>>>>>>>> Method[] methods = clazz.getMethods(); for (Method method : methods) { String name = method.getName(); if (name.length() > 3 && name.startsWith("set") && method.getParameterTypes().length == 1 && Modifier.isPublic(method.getModifiers()) && !Modifier.isStatic(method.getModifiers())) { try { Reference reference = method.getAnnotation(Reference.class); if (reference != null) { Object value = refer(reference, method.getParameterTypes()[0]); if (value != null) { method.invoke(bean, new Object[] {}); } } } catch (Throwable e) { logger.error("Failed to init remote service reference at method " + name + " in class " + bean.getClass().getName() + ", cause: " + e.getMessage(), e); } } } // >>>>>>>>>>>>>>>>>>>>>>>> Field[] fields = clazz.getDeclaredFields(); for (Field field : fields) { try { if (!field.isAccessible()) { field.setAccessible(true); } Reference reference = field.getAnnotation(Reference.class); if (reference != null) { Object value = refer(reference, field.getType()); if (value != null) { field.set(bean, value); } } } catch (Throwable e) { logger.error("Failed to init remote service reference at filed " + field.getName() + " in class " + bean.getClass().getName() + ", cause: " + e.getMessage(), e); } } return bean; } private Object refer(Reference reference, Class<?> referenceClass) { // method.getParameterTypes()[0] String interfaceName; if (!"".equals(reference.interfaceName())) { interfaceName = reference.interfaceName(); } else if (!void.class.equals(reference.interfaceClass())) { interfaceName = reference.interfaceClass().getName(); } else if (referenceClass.isInterface()) { interfaceName = referenceClass.getName(); } else { throw new IllegalStateException( "The @Reference undefined interfaceClass or interfaceName, and the property type " + referenceClass.getName() + " is not a interface."); } String key = reference.group() + "/" + interfaceName + ":" + reference.version(); ReferenceBean<?> referenceConfig = referenceConfigs.get(key); if (referenceConfig == null) { referenceConfig = new ReferenceBean<Object>(reference); if (void.class.equals(reference.interfaceClass()) && "".equals(reference.interfaceName()) && referenceClass.isInterface()) { referenceConfig.setInterface(referenceClass); } if (applicationContext != null) { referenceConfig.setApplicationContext(applicationContext); if (reference.registry() != null && reference.registry().length > 0) { List<RegistryConfig> registryConfigs = new ArrayList<RegistryConfig>(); for (String registryId : reference.registry()) { if (registryId != null && registryId.length() > 0) { registryConfigs .add((RegistryConfig) applicationContext.getBean(registryId, RegistryConfig.class)); } } referenceConfig.setRegistries(registryConfigs); } if (reference.consumer() != null && reference.consumer().length() > 0) { referenceConfig.setConsumer( (ConsumerConfig) applicationContext.getBean(reference.consumer(), ConsumerConfig.class)); } if (reference.monitor() != null && reference.monitor().length() > 0) { referenceConfig.setMonitor( (MonitorConfig) applicationContext.getBean(reference.monitor(), MonitorConfig.class)); } if (reference.application() != null && reference.application().length() > 0) { referenceConfig.setApplication((ApplicationConfig) applicationContext .getBean(reference.application(), ApplicationConfig.class)); } if (reference.module() != null && reference.module().length() > 0) { referenceConfig.setModule( (ModuleConfig) applicationContext.getBean(reference.module(), ModuleConfig.class)); } if (reference.consumer() != null && reference.consumer().length() > 0) { referenceConfig.setConsumer( (ConsumerConfig) applicationContext.getBean(reference.consumer(), ConsumerConfig.class)); } try { referenceConfig.afterPropertiesSet(); } catch (RuntimeException e) { throw (RuntimeException) e; } catch (Exception e) { throw new IllegalStateException(e.getMessage(), e); } } referenceConfigs.putIfAbsent(key, referenceConfig); referenceConfig = referenceConfigs.get(key); } return referenceConfig.get(); } private boolean isMatchPackage(Object bean) { if (annotationPackages == null || annotationPackages.length == 0) { return true; } Class<?> clazz = getBeanClass(bean); String beanClassName = clazz.getName(); for (String pkg : annotationPackages) { if (beanClassName.startsWith(pkg)) { return true; } } return false; } private Class<?> getBeanClass(Object bean) { Class<?> clazz = bean.getClass(); if (AopUtils.isAopProxy(bean)) { clazz = AopUtils.getTargetClass(bean); } return clazz; }
6. 整合
同样，我不太赞同自己修改Dubbo源码，然后打包。侵入性太强。通过前面几节的分析发现，其实只要AnnotationBean能够注册到Spring环境就行。而AnnotationBean无所谓放在哪个jar中。
所以，完全可以把修改后的AnnotationBean打入到自己写的jar中，然后注入Spring环境，以外挂的方式完成修改。
下面示例代码展示了，在Spring Boot中以外挂方式整合：
package com.roc.dubbo.boot.configuration; import org.apache.logging.log4j.LogManager; import org.apache.logging.log4j.Logger; import com.roc.dubbo.config.spring.AnnotationBean; import org.springframework.boot.autoconfigure.AutoConfigureAfter; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.Import; /** * @author binghe * @description 以外挂方式整合修改后的Dubbo源码 */ @Configuration @Import(DubboBasicConfiguration.class) @AutoConfigureAfter(DubboBasicConfiguration.class) public class DubboConfiguration { private final Logger logger = LogManager.getLogger(getClass()); @Bean // @DependsOn("dubboConfiguration") public AnnotationBean dubboAnnotationBean() { AnnotationBean annotationBean = new AnnotationBean(); // annotationBean.setApplicationContext(applicationContext); // annotationBean.setPackage(dubboProperties.getAnnotationPackage()); // annotationBean.setPackage("com.roc.pay"); logger.info("加入自定义" + annotationBean); return annotationBean; } }
