Dubbo之——改造Dubbo，使其能够兼容Spring 4注解配置

转载请注明出处：http://blog.csdn.net/l1028386804/article/details/70040928

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4.3.，今年（2017）应该会发布Spring 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：

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：

通过官方的例子，就可以看出Dubbo使用xml配置 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，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> serviceConfigs = new ConcurrentHashSet>();

    private final ConcurrentMap> referenceConfigs = new ConcurrentHashMap>();

    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