本文深入解析Dubbo服务暴露过程，首先介绍了service标签如何被Spring解析成BeanDefinition，然后详细讨论ServiceBean的初始化，包括类定义、Aware接口的实现，这些都在服务启动时发挥作用。
1.标签解析
之前我们已经介绍过spring对自定义标签的解析方法，当时是以Dubbo为例的，这里就不再详细说明，Dubbo的service标签解析是通过DubboBeanDefinitionParser的parse方法来完成的。而service标签解析时，DubboBeanDefinitionParser对象的生成方式如下：
//service标签处理 服务暴露
registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
/**
* 构造方法 -- 这里会根据参数不同来解析不同的标签
* @param beanClass 带解析出的BeanDefinition对应的class
* @param required
*/
public DubboBeanDefinitionParser(Class<?> beanClass, boolean required) {
this.beanClass = beanClass;
this.required = required;
}具体的解析方法如下：
/**
* 解析节点信息
*/
@Override
public BeanDefinition parse(Element element, ParserContext parserContext) {
return parse(element, parserContext, beanClass, required);
}这里调用了另一个parse方法，如下：
@SuppressWarnings("unchecked")
private static BeanDefinition parse(Element element, ParserContext parserContext, Class<?> beanClass, boolean required) {
//创建一个RootBeanDefinition
RootBeanDefinition beanDefinition = new RootBeanDefinition();
beanDefinition.setBeanClass(beanClass); //设置对应的beanClass
beanDefinition.setLazyInit(false); //设置为非懒加载
String id = element.getAttribute("id"); //获取id
/**
* id处理
*/
if ((id == null || id.length() == 0) && required) { //未获取到id或者id为空 并且required为true
//获取name信息
String generatedBeanName = element.getAttribute("name");
if (generatedBeanName == null || generatedBeanName.length() == 0) {
//若为protocol节点处理，name未写默认为 "dubbo"
if (ProtocolConfig.class.equals(beanClass)) {
generatedBeanName = "dubbo";
} else { //其他节点未写默认为其配置的 "interface"的值 未配置则为空
generatedBeanName = element.getAttribute("interface");
}
}
//若generatedBeanName依旧为空 则直接设置为对应class的名字
if (generatedBeanName == null || generatedBeanName.length() == 0) {
generatedBeanName = beanClass.getName();
}
//生成一个id
id = generatedBeanName;
int counter = 2;
while (parserContext.getRegistry().containsBeanDefinition(id)) {
id = generatedBeanName + (counter++);
}
}
if (id != null && id.length() > 0) {
if (parserContext.getRegistry().containsBeanDefinition(id)) {
throw new IllegalStateException("Duplicate spring bean id " + id);
}
//注册id-beanDefinition到容器中
parserContext.getRegistry().registerBeanDefinition(id, beanDefinition);
//添加PropertyValue id
beanDefinition.getPropertyValues().addPropertyValue("id", id);
}
//ProtocolConfig类处理
if (ProtocolConfig.class.equals(beanClass)) {
for (String name : parserContext.getRegistry().getBeanDefinitionNames()) {
BeanDefinition definition = parserContext.getRegistry().getBeanDefinition(name);
PropertyValue property = definition.getPropertyValues().getPropertyValue("protocol");
if (property != null) {
Object value = property.getValue();
if (value instanceof ProtocolConfig && id.equals(((ProtocolConfig) value).getName())) {
definition.getPropertyValues().addPropertyValue("protocol", new RuntimeBeanReference(id));
}
}
}
} else if (ServiceBean.class.equals(beanClass)) { //ServiceBean类处理
String className = element.getAttribute("class");
if (className != null && className.length() > 0) {
RootBeanDefinition classDefinition = new RootBeanDefinition();
classDefinition.setBeanClass(ReflectUtils.forName(className));
classDefinition.setLazyInit(false);
parseProperties(element.getChildNodes(), classDefinition);
beanDefinition.getPropertyValues().addPropertyValue("ref", new BeanDefinitionHolder(classDefinition, id + "Impl"));
}
} else if (ProviderConfig.class.equals(beanClass)) { //ProviderConfig类处理
parseNested(element, parserContext, ServiceBean.class, true, "service", "provider", id, beanDefinition);
} else if (ConsumerConfig.class.equals(beanClass)) { //ConsumerConfig类处理
parseNested(element, parserContext, ReferenceBean.class, false, "reference", "consumer", id, beanDefinition);
}
Set<String> props = new HashSet<String>();
ManagedMap parameters = null;
for (Method setter : beanClass.getMethods()) {
String name = setter.getName();
if (name.length() > 3 && name.startsWith("set")
&& Modifier.isPublic(setter.getModifiers())
&& setter.getParameterTypes().length == 1) {
Class<?> type = setter.getParameterTypes()[0];
String propertyName = name.substring(3, 4).toLowerCase() + name.substring(4);
String property = StringUtils.camelToSplitName(propertyName, "-");
props.add(property);
Method getter = null;
try {
getter = beanClass.getMethod("get" + name.substring(3), new Class<?>[0]);
} catch (NoSuchMethodException e) {
try {
getter = beanClass.getMethod("is" + name.substring(3), new Class<?>[0]);
} catch (NoSuchMethodException e2) {
}
}
if (getter == null
|| !Modifier.isPublic(getter.getModifiers())
|| !type.equals(getter.getReturnType())) {
continue;
}
if ("parameters".equals(property)) {
parameters = parseParameters(element.getChildNodes(), beanDefinition);
} else if ("methods".equals(property)) {
parseMethods(id, element.getChildNodes(), beanDefinition, parserContext);
} else if ("arguments".equals(property)) {
parseArguments(id, element.getChildNodes(), beanDefinition, parserContext);
} else {
String value = element.getAttribute(property);
if (value != null) {
value = value.trim();
if (value.length() > 0) {
if ("registry".equals(property) && RegistryConfig.NO_AVAILABLE.equalsIgnoreCase(value)) {
RegistryConfig registryConfig = new RegistryConfig();
registryConfig.setAddress(RegistryConfig.NO_AVAILABLE);
beanDefinition.getPropertyValues().addPropertyValue(property, registryConfig);
} else if ("registry".equals(property) && value.indexOf(',') != -1) {
parseMultiRef("registries", value, beanDefinition, parserContext);
} else if ("provider".equals(property) && value.indexOf(',') != -1) {
parseMultiRef("providers", value, beanDefinition, parserContext);
} else if ("protocol".equals(property) && value.indexOf(',') != -1) {
parseMultiRef("protocols", value, beanDefinition, parserContext);
} else {
Object reference;
if (isPrimitive(type)) {
if ("async".equals(property) && "false".equals(value)
|| "timeout".equals(property) && "0".equals(value)
|| "delay".equals(property) && "0".equals(value)
|| "version".equals(property) && "0.0.0".equals(value)
|| "stat".equals(property) && "-1".equals(value)
|| "reliable".equals(property) && "false".equals(value)) {
// backward compatibility for the default value in old version's xsd
value = null;
}
reference = value;
} else if ("protocol".equals(property)
&& ExtensionLoader.getExtensionLoader(Protocol.class).hasExtension(value)
&& (!parserContext.getRegistry().containsBeanDefinition(value)
|| !ProtocolConfig.class.getName().equals(parserContext.getRegistry().getBeanDefinition(value).getBeanClassName()))) {
if ("dubbo:provider".equals(element.getTagName())) {
logger.warn("Recommended replace <dubbo:provider protocol=\"" + value + "\" ... /> to <dubbo:protocol name=\"" + value + "\" ... />");
}
// backward compatibility
ProtocolConfig protocol = new ProtocolConfig();
protocol.setName(value);
reference = protocol;
} else if ("onreturn".equals(property)) {
int index = value.lastIndexOf(".");
String returnRef = value.substring(0, index);
String returnMethod = value.substring(index + 1);
reference = new RuntimeBeanReference(returnRef);
beanDefinition.getPropertyValues().addPropertyValue("onreturnMethod", returnMethod);
} else if ("onthrow".equals(property)) {
int index = value.lastIndexOf(".");
String throwRef = value.substring(0, index);
String throwMethod = value.substring(index + 1);
reference = new RuntimeBeanReference(throwRef);
beanDefinition.getPropertyValues().addPropertyValue("onthrowMethod", throwMethod);
} else if ("oninvoke".equals(property)) {
int index = value.lastIndexOf(".");
String invokeRef = value.substring(0, index);
String invokeRefMethod = value.substring(index + 1);
reference = new RuntimeBeanReference(invokeRef);
beanDefinition.getPropertyValues().addPropertyValue("oninvokeMethod", invokeRefMethod);
} else {
if ("ref".equals(property) && parserContext.getRegistry().containsBeanDefinition(value)) {
BeanDefinition refBean = parserContext.getRegistry().getBeanDefinition(value);
if (!refBean.isSingleton()) {
throw new IllegalStateException("The exported service ref " + value + " must be singleton! Please set the " + value + " bean scope to singleton, eg: <bean id=\"" + value + "\" scope=\"singleton\" ...>");
}
}
reference = new RuntimeBeanReference(value);
}
beanDefinition.getPropertyValues().addPropertyValue(propertyName, reference);
}
}
}
}
}
}
NamedNodeMap attributes = element.getAttributes();
int len = attributes.getLength();
for (int i = 0; i < len; i++) {
Node node = attributes.item(i);
String name = node.getLocalName();
if (!props.contains(name)) {
if (parameters == null) {
parameters = new ManagedMap();
}
String value = node.getNodeValue();
parameters.put(name, new TypedStringValue(value, String.class));
}
}
if (parameters != null) {
//添加PropertyValue parameters
beanDefinition.getPropertyValues().addPropertyValue("parameters", parameters);
}
return beanDefinition; //返回beanDefinition
}到这里就完成了一个dubbo的service标签的解析，当然，现在只是解析标签成一个BeanDefinition，该BeanDefinition对应的class类型为ServiceBean.class，spring容器继续启动会初始化该Bean。
2.ServiceBean的初始化
由上文可知，service标签解析出来的BeanDefinition时单例非懒加载的，该BeanDefinition会在容器启动时直接初始化，下面我们来分析一下ServiceBean这个Bean的初始化过程。
2.1 ServiceBean的类定义
/**
* 继承
* ServiceConfig
* 实现
* InitializingBean --afterPropertiesSet方法 spring会在对象实例化之后调用该方法 一般用于初始化一些属性
* DisposableBean --destroy方法，spring容器关闭时调用
* ApplicationContextAware --setApplicationContext方法 会传入一个ApplicationContext的实例
* ApplicationListener --onApplicationEvent方法 添加了上下文刷新的一个监听
* BeanNameAware --setBeanName方法 设置BeanName
* ApplicationEventPublisherAware --setApplicationEventPublisher方法 设置ApplicationEventPublisher
*/
public class ServiceBean<T> extends ServiceConfig<T> implements InitializingBean, DisposableBean,
ApplicationContextAware, ApplicationListener<ContextRefreshedEvent>, BeanNameAware,
ApplicationEventPublisherAware 其继承关系入下图：
其中实现的接口有几个涉及到spring Bean的生命周期接口，这里我们分析一下具体的方法内容
2.2 Aware接口
BeanNameAware的setBeanName方法实现：
@Override
public void setBeanName(String name) {
this.beanName = name;
}ApplicationEventPublisherAware的setApplicationEventPublisher方法实现：
/**
* @param applicationEventPublisher
* @since 2.6.5
*/
@Override
public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
this.applicationEventPublisher = applicationEventPublisher;
}ApplicationContextAware的setApplicationContext方法实现：
@Override
public void setApplicationContext(ApplicationContext applicationContext) {
this.applicationContext = applicationContext; //设置applicationContext
//将applicationContext的值添加到SpringExtensionFactory中
SpringExtensionFactory.addApplicationContext(applicationContext);
//将当前类加入到Spring监听列表
supportedApplicationListener = addApplicationListener(applicationContext, this);
}InitializingBean的afterPropertiesSet方法实现：
@Override
@SuppressWarnings({ "deprecation"})
public void afterPropertiesSet() throws Exception {
//如果当前ServiceBan的provider为空
if (getProvider() == null) {
Map<String, ProviderConfig> providerConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProviderConfig.class, false, false);
if (providerConfigMap != null && providerConfigMap.size() > 0) {
Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false);
if ((protocolConfigMap == null || protocolConfigMap.size() == 0)
&& providerConfigMap.size() > 1) { // backward compatibility
List<ProviderConfig> providerConfigs = new ArrayList<ProviderConfig>();
for (ProviderConfig config : providerConfigMap.values()) {
if (config.isDefault() != null && config.isDefault().booleanValue()) {
providerConfigs.add(config);
}
}
if (!providerConfigs.isEmpty()) {
setProviders(providerConfigs);
}
} else {
ProviderConfig providerConfig = null;
for (ProviderConfig config : providerConfigMap.values()) {
if (config.isDefault() == null || config.isDefault().booleanValue()) {
if (providerConfig != null) {
throw new IllegalStateException("Duplicate provider configs: " + providerConfig + " and " + config);
}
providerConfig = config;
}
}
if (providerConfig != null) {
setProvider(providerConfig);
}
}
}
}
//如果当前ServiceBan的application为空，则为该Service设置application
if (getApplication() == null
&& (getProvider() == null || getProvider().getApplication() == null)) {
Map<String, ApplicationConfig> applicationConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ApplicationConfig.class, false, false);
if (applicationConfigMap != null && applicationConfigMap.size() > 0) {
ApplicationConfig applicationConfig = null;
for (ApplicationConfig config : applicationConfigMap.values()) {
if (config.isDefault() == null || config.isDefault().booleanValue()) {
if (applicationConfig != null) {
throw new IllegalStateException("Duplicate application configs: " + applicationConfig + " and " + config);
}
applicationConfig = config;
}
}
if (applicationConfig != null) {
setApplication(applicationConfig);
}
}
}
//如果当前ServiceBan的module为空，则为该Service设置module
if (getModule() == null
&& (getProvider() == null || getProvider().getModule() == null)) {
Map<String, ModuleConfig> moduleConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ModuleConfig.class, false, false);
if (moduleConfigMap != null && moduleConfigMap.size() > 0) {
ModuleConfig moduleConfig = null;
for (ModuleConfig config : moduleConfigMap.values()) {
if (config.isDefault() == null || config.isDefault().booleanValue()) {
if (moduleConfig != null) {
throw new IllegalStateException("Duplicate module configs: " + moduleConfig + " and " + config);
}
moduleConfig = config;
}
}
if (moduleConfig != null) {
setModule(moduleConfig);
}
}
}
//如果当前ServiceBan的Registries为空，则为该Service设置Registries
if ((getRegistries() == null || getRegistries().isEmpty())
&& (getProvider() == null || getProvider().getRegistries() == null || getProvider().getRegistries().isEmpty())
&& (getApplication() == null || getApplication().getRegistries() == null || getApplication().getRegistries().isEmpty())) {
Map<String, RegistryConfig> registryConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, RegistryConfig.class, false, false);
if (registryConfigMap != null && registryConfigMap.size() > 0) {
List<RegistryConfig> registryConfigs = new ArrayList<RegistryConfig>();
for (RegistryConfig config : registryConfigMap.values()) {
if (config.isDefault() == null || config.isDefault().booleanValue()) {
registryConfigs.add(config);
}
}
if (registryConfigs != null && !registryConfigs.isEmpty()) {
super.setRegistries(registryConfigs);
}
}
}
//如果当前ServiceBan的Monitor为空，则为该Service设置Monitor
if (getMonitor() == null
&& (getProvider() == null || getProvider().getMonitor() == null)
&& (getApplication() == null || getApplication().getMonitor() == null)) {
Map<String, MonitorConfig> monitorConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, MonitorConfig.class, false, false);
if (monitorConfigMap != null && monitorConfigMap.size() > 0) {
MonitorConfig monitorConfig = null;
for (MonitorConfig config : monitorConfigMap.values()) {
if (config.isDefault() == null || config.isDefault().booleanValue()) {
if (monitorConfig != null) {
throw new IllegalStateException("Duplicate monitor configs: " + monitorConfig + " and " + config);
}
monitorConfig = config;
}
}
if (monitorConfig != null) {
setMonitor(monitorConfig);
}
}
}
//如果当前ServiceBan的Protocol为空，则为该Service设置Protocol
if ((getProtocols() == null || getProtocols().isEmpty())
&& (getProvider() == null || getProvider().getProtocols() == null || getProvider().getProtocols().isEmpty())) {
Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false);
if (protocolConfigMap != null && protocolConfigMap.size() > 0) {
List<ProtocolConfig> protocolConfigs = new ArrayList<ProtocolConfig>();
for (ProtocolConfig config : protocolConfigMap.values()) {
if (config.isDefault() == null || config.isDefault().booleanValue()) {
protocolConfigs.add(config);
}
}
if (protocolConfigs != null && !protocolConfigs.isEmpty()) {
super.setProtocols(protocolConfigs);
}
}
}
// 设置服务名称
if (getPath() == null || getPath().length() == 0) {
if (beanName != null && beanName.length() > 0
&& getInterface() != null && getInterface().length() > 0
&& beanName.startsWith(getInterface())) {
setPath(beanName);
}
}
if (!isDelay()) { //若非延迟加载
export(); //服务暴露
}
}ApplicationListener的onApplicationEvent方法实现：
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
// 服务没有延迟加载 && 服务没有发布 && 服务没有下线过 。 满足这三个条件，则进行服务暴露
if (isDelay() && !isExported() && !isUnexported()) {
if (logger.isInfoEnabled()) {
logger.info("The service ready on spring started. service: " + getInterface());
}
export(); //进行服务暴露
}
}
private boolean isDelay() {
// 获取延迟加载的设置 ， 延迟注册服务时间(毫秒)- ，设为-1时，表示延迟到Spring容器初始化完成时暴露服务
Integer delay = getDelay();
ProviderConfig provider = getProvider();
if (delay == null && provider != null) {
delay = provider.getDelay();
}
// 加入上下文刷新监听，并且没有设置延迟加载，
return supportedApplicationListener && (delay == null || delay == -1);
}DisposableBean的destroy方法
@Override
public void destroy() throws Exception {
// no need to call unexport() here, see
// org.apache.dubbo.config.spring.extension.SpringExtensionFactory.ShutdownHookListener
}---------------------------------------------------------------分割线--------------------------------------------------------------------------------------------------
从上面的代码可以看出，Dubbo服务暴露是在afterPropertiesSet或onApplicationEvent两个方法中完成的，具体实现就是export方法，这里我们等下次再说。
扫一扫
650
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
