dubbo源码分析 config层 从@Service注解看spring bean的注册周期

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今天看到之前dubbo项目重启动的时候，遗留下来的一个bug。看了下代码被修复了，觉得自己对于dubbo的源码还不够熟练，复现该用户场景如下

假设我们有一个DemoService接口:

public interface DemoService {
    String sayHello(String name);
    String sayHello2(String name);
}

通过配置注解的parameters参数来往url上附加额外参数

@Service(
        version = "${demo.service.version}",
        application = "${dubbo.application.id}",
        protocol = "${dubbo.protocol.id}",
        registry = "${dubbo.registry.id}"
        , parameters = {"sayHello.timeout", "3100", "sayHello2.timeout", "5000"}
)
public class DefaultDemoService implements DemoService {
    @Override
    public String sayHello(String name) {
        System.out.println("get request");
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "sayHello Hello, " + name + " (from Spring Boot)";
    }
 
    @Override
    public String sayHello2(String name) {
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "sayHello2 Hello, " + name + " (from Spring Boot)";
    }
}

结果报错:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'ServiceBean:defaultDemoService:com.kingnet.blockdata.service.DemoService:${demo.service.version}': Initialization of bean failed; nested exception is org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'java.lang.String[]' to required type 'java.util.Map' for property 'parameters'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String[]' to required type 'java.util.Map' for property 'parameters': no matching editors or conversion strategy found
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:589) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:503) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:317) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$97/1279271200.getObject(Unknown Source) ~[na:na]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:315) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:760) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:869) ~[spring-context-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.0.3.RELEASE.jar:2.0.3.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759) ~[spring-boot-2.0.3.RELEASE.jar:2.0.3.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:395) ~[spring-boot-2.0.3.RELEASE.jar:2.0.3.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:327) ~[spring-boot-2.0.3.RELEASE.jar:2.0.3.RELEASE]
    at org.springframework.boot.builder.SpringApplicationBuilder.run(SpringApplicationBuilder.java:137) [spring-boot-2.0.3.RELEASE.jar:2.0.3.RELEASE]
    at com.kingnet.blockdata.DubboProviderDemo.main(DubboProviderDemo.java:20) [classes/:na]
Caused by: org.springframework.beans.ConversionNotSupportedException: Failed to convert property value of type 'java.lang.String[]' to required type 'java.util.Map' for property 'parameters'; nested exception is java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String[]' to required type 'java.util.Map' for property 'parameters': no matching editors or conversion strategy found
    at org.springframework.beans.AbstractNestablePropertyAccessor.convertIfNecessary(AbstractNestablePropertyAccessor.java:590) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.AbstractNestablePropertyAccessor.convertForProperty(AbstractNestablePropertyAccessor.java:604) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.BeanWrapperImpl.convertForProperty(BeanWrapperImpl.java:219) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.convertForProperty(AbstractAutowireCapableBeanFactory.java:1660) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1616) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1363) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:580) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    ... 15 common frames omitted
Caused by: java.lang.IllegalStateException: Cannot convert value of type 'java.lang.String[]' to required type 'java.util.Map' for property 'parameters': no matching editors or conversion strategy found
    at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(TypeConverterDelegate.java:299) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    at org.springframework.beans.AbstractNestablePropertyAccessor.convertIfNecessary(AbstractNestablePropertyAccessor.java:585) ~[spring-beans-5.0.7.RELEASE.jar:5.0.7.RELEASE]
    ... 21 common frames omitted

@Service里面的parameters是String[]类型，但是要映射到ServiceBean的parameters属性是一个Map类型，没法自动转换映射上去,

查看源码,ServiceBean是通过:
com.alibaba.dubbo.config.spring.beans.factory.annotation.ServiceAnnotationBeanPostProcessor#registerServiceBean

我们来看到修复后的dubbo bean注册源码

• 在sping bean的加载过程中，BeanDefinitionRegistry是用来注册BeanDefinition的. BeanDefinition就是Bean的配置元数据或Bean的描述信息, 比如Bean的属性值, 构造方法的参数值等. 上面的BeanFactory的BeanDefinition也是由它注册的.

• BeanDefinitionRegistryPostProcessor是BeanFactoryPostProcessor的扩展, 允许在BeanFactoryPostProcessor被调用之前对BeanDefinition做一些操作, 尤其是它可以注册BeanFactoryPostProcessor的BeanDefinition. 它提供了一个方法postProcessBeanDefinitionRegistry(), 这个方法被调用的时候, 所有的BeanDefinition已经被加载了, 但是所有的Bean还没被创建.

注意:

• 所有的Bean生成都有个顺序: 定义 --> 创建 --> 初始化.
• BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry方法在Bean被定义但还没被创建的时候执行.
• BeanFactoryPostProcessor的postProcessBeanFactory方法在Bean被创建但还没被初始化的时候执行

@Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {

        Set resolvedPackagesToScan = resolvePackagesToScan(packagesToScan);
        if (!CollectionUtils.isEmpty(resolvedPackagesToScan)) {
            registerServiceBeans(resolvedPackagesToScan, registry);
        } else {
            if (logger.isWarnEnabled()) {
                logger.warn("packagesToScan is empty , ServiceBean registry will be ignored!");
            }
        }

    }

• dubbo注册ServiceBean的方法发现是拿到所有注解的信息
• 把这个注解的信息附加到相应的注解类的属性上
• 根据注解的信息，注解的接口类，和已经注册在上下文中的这个beanName的名称新建一个Servicebean
• 之后把建立的ServiceBean注册到上下文中

private void registerServiceBean(BeanDefinitionHolder beanDefinitionHolder, BeanDefinitionRegistry registry,
                                     DubboClassPathBeanDefinitionScanner scanner) {

        Class beanClass = resolveClass(beanDefinitionHolder);

        Annotation service = findServiceAnnotation(beanClass);

        /**
         * The {@link AnnotationAttributes} of @Service annotation
         */
        AnnotationAttributes serviceAnnotationAttributes = getAnnotationAttributes(service, false, false);

        Class interfaceClass = resolveServiceInterfaceClass(serviceAnnotationAttributes, beanClass);

        String annotatedServiceBeanName = beanDefinitionHolder.getBeanName();

        AbstractBeanDefinition serviceBeanDefinition =
                buildServiceBeanDefinition(service, serviceAnnotationAttributes, interfaceClass, annotatedServiceBeanName);

        // ServiceBean Bean name
        String beanName = generateServiceBeanName(serviceAnnotationAttributes, interfaceClass);

        if (scanner.checkCandidate(beanName, serviceBeanDefinition)) { // check duplicated candidate bean
            registry.registerBeanDefinition(beanName, serviceBeanDefinition);

            if (logger.isInfoEnabled()) {
                logger.info("The BeanDefinition[" + serviceBeanDefinition +
                        "] of ServiceBean has been registered with name : " + beanName);
            }

        } else {

            if (logger.isWarnEnabled()) {
                logger.warn("The Duplicated BeanDefinition[" + serviceBeanDefinition +
                        "] of ServiceBean[ bean name : " + beanName +
                        "] was be found , Did @DubboComponentScan scan to same package in many times?");
            }

        }

    }

这里就是将之前注册的bean类型按照类型判断,为每种类型建立相应的bean

private AbstractBeanDefinition buildServiceBeanDefinition(Annotation serviceAnnotation,
                                                              AnnotationAttributes serviceAnnotationAttributes,
                                                              Class interfaceClass,
                                                              String annotatedServiceBeanName) {

        BeanDefinitionBuilder builder = rootBeanDefinition(ServiceBean.class);

        AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();

        MutablePropertyValues propertyValues = beanDefinition.getPropertyValues();

        String[] ignoreAttributeNames = of("provider", "monitor", "application", "module", "registry", "protocol",
                "interface", "interfaceName", "parameters");

        propertyValues.addPropertyValues(new AnnotationPropertyValuesAdapter(serviceAnnotation, environment, ignoreAttributeNames));

        // References "ref" property to annotated-@Service Bean
        addPropertyReference(builder, "ref", annotatedServiceBeanName);
        // Set interface
        builder.addPropertyValue("interface", interfaceClass.getName());
        // Convert parameters into map
        builder.addPropertyValue("parameters", convertParameters(serviceAnnotationAttributes.getStringArray("parameters")));
        // Add methods parameters
        List methodConfigs = convertMethodConfigs(serviceAnnotationAttributes.get("methods"));
        if (!methodConfigs.isEmpty()) {
            builder.addPropertyValue("methods", methodConfigs);
        }

       ......

        return builder.getBeanDefinition();

    }

但这些类型从哪里来呢？我们刚刚讲的是beanDefinition转换为bean
。在spring拓展Schema的时候，dubbo需要将META-INF/spring.handlers中的配置转换为beanDefinition,通过DubboNamespaceHandler获取xml文件的命名空间,对不同的节点进行解析

public class DubboNamespaceHandler extends NamespaceHandlerSupport {
    static {
        // 确保系统中只存在一份解析处理器类定义
        Version.checkDuplicate(DubboNamespaceHandler.class);
    }
    public void init() {
        // DubboBeanDefinitionParser定义了如何解析dubbo节点信息
        // DubboBeanDefinitionParser的第一个参数是beanclass
        // 配置标签解析器
    registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true));
        // 配置标签解析器
    registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true));
        //配置标签解析器
    registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true));
        //配置标签解析器
    registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true));
        //配置标签解析器
    registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true));
        //配置标签解析器
    registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true));
        //配置标签解析器
    registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true));
    //配置标签解析器
    registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
    //配置标签解析器
    registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));
    //配置标签解析器
    registerBeanDefinitionParser("annotation", new DubboBeanDefinitionParser(AnnotationBean.class, true));
    }
}