Dubbo介绍2- 源码分析，通过schema启动服务

前言

spring2.5以后，spring支持自定义schema扩展xml配置。具体的spring schema细节，本文就不多说了。这篇文章就拿provider为例，介绍dubbo是如何启动服务的。

正文

首先，再把HelloWolrd例子中的 provider.xml的源码放上来

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd ">
<dubbo:application name="hello-world-app" />
<dubbo:registry  protocol="zookeeper" address="10.125.195.174:2181" />
<dubbo:protocol name="dubbo" port="20880" />
<dubbo:service interface="demo.service.DemoService"
ref="demoService" />       <!-- 和本地bean一样实现服务 -->
<bean id="demoService" class="demo.service.DemoServiceImpl" />
</beans>

对应的自定义schema文件，就不解释了。直接在dubbo-{version}.jar 中 META-INF目录下找到对应的handler配置

spring.handlers 写道

http\://code.alibabatech.com/schema/dubbo=com.alibaba.dubbo.config.spring.schema.DubboNamespaceHandler

可以看到，对应的handler是 DubboNamespaceHandler。对应的源码如下

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));
}

}

从这里也可以看到，对应的支持的标签其实不多。所有的Parser都封装到了DubboBeanDefinitionParser中。对应的class，就是传入的beanClass。比如application的就是ApplicationConfig。module的就是ModuleConfig。经过Parser的转换，provider.xml大概可以变成如下的样子(具体的解析不多解释了)

<bean id="hello-world-app" class="com.alibaba.dubbo.config.ApplicationConfig"/>
<bean id="registryConfig" class="com.alibaba.dubbo.config.RegistryConfig">
<property name="address" value="10.125.195.174:2181"/>
<property name="protocol" value="zookeeper"/>
</bean>
<bean id="dubbo" class="com.alibaba.dubbo.config.ProtocolConfig">
<property name="port" value="20880"/>
</bean>
<bean id="demo.service.DemoService" class="com.alibaba.dubbo.config.spring.ServiceBean">
<property name="interface" value="demo.service.DemoService"/>
<property name="ref" ref="demoService"/>
</bean>
<bean id="demoService" class="demo.service.DemoServiceImpl" />

分别看每一个bean的内容。由于篇幅原因，我就不把每个代码放上来了。总结一下就是

写道

ApplicationConfig，RegistryConfig，ProtocolConfig都只是普通的pojo。负责接收数据。真正的处理逻辑在ServiceBean中

看具体的代码

public class ServiceBean<T> extends ServiceConfig<T> implements InitializingBean, DisposableBean, ApplicationContextAware, ApplicationListener, BeanNameAware {

private static final long serialVersionUID = 213195494150089726L;

private static transient ApplicationContext SPRING_CONTEXT;

private transient ApplicationContext applicationContext;

private transient String beanName;

private transient boolean supportedApplicationListener;

public ServiceBean() {
super();
}

public ServiceBean(Service service) {
super(service);
}

public static ApplicationContext getSpringContext() {
return SPRING_CONTEXT;
}
//设置对应的applicationConext
public void setApplicationContext(ApplicationContext applicationContext) {
this.applicationContext = applicationContext;
SpringExtensionFactory.addApplicationContext(applicationContext);
if (applicationContext != null) {
SPRING_CONTEXT = applicationContext;
try {
Method method = applicationContext.getClass().getMethod("addApplicationListener", new Class<?>[]{ApplicationListener.class}); // 兼容Spring2.0.1
method.invoke(applicationContext, new Object[] {this});
supportedApplicationListener = true;
} catch (Throwable t) {
if (applicationContext instanceof AbstractApplicationContext) {
try {
Method method = AbstractApplicationContext.class.getDeclaredMethod("addListener", new Class<?>[]{ApplicationListener.class}); // 兼容Spring2.0.1
if (! method.isAccessible()) {
method.setAccessible(true);
}
method.invoke(applicationContext, new Object[] {this});
supportedApplicationListener = true;
} catch (Throwable t2) {
}
}
}
}
}

public void setBeanName(String name) {
this.beanName = name;
}

public void onApplicationEvent(ApplicationEvent event) {
//如果容器加载完成以后当前的provider还没export，那么调用一次export方法（这个针对那种延迟export的情况）
if (ContextRefreshedEvent.class.getName().equals(event.getClass().getName())) {
if (isDelay() && ! isExported() && ! isUnexported()) {
if (logger.isInfoEnabled()) {
logger.info("The service ready on spring started. service: " + getInterface());
}
export();
}
}
}
//是否延迟export
private boolean isDelay() {
Integer delay = getDelay();
ProviderConfig provider = getProvider();
if (delay == null && provider != null) {
delay = provider.getDelay();
}
return supportedApplicationListener && (delay == null || delay.intValue() == -1);
}

@SuppressWarnings({ "unchecked", "deprecation" })
public void afterPropertiesSet() throws Exception {
//这里的Provider其实就是ProviderConfig对象。如果provider为空，表示spring在创建 当前bean的时候还没有初始化ProtocolConfig bean。这里就是做一个前后顺序保证
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) { // 兼容旧版本
List<ProviderConfig> providerConfigs = new ArrayList<ProviderConfig>();
for (ProviderConfig config : providerConfigMap.values()) {
if (config.isDefault() != null && config.isDefault().booleanValue()) {
providerConfigs.add(config);
}
}
if (providerConfigs.size() > 0) {
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);
}
}
}
}
//这里和上面同样，手动创建ApplicationConfig bean
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);
}
}
}
//如果没有创建module，则手动创建 module。 在HelloWorld例子中，没有用到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);
}
}
}
//初始化registiry
if ((getRegistries() == null || getRegistries().size() == 0)
&& (getProvider() == null || getProvider().getRegistries() == null || getProvider().getRegistries().size() == 0)
&& (getApplication() == null || getApplication().getRegistries() == null || getApplication().getRegistries().size() == 0)) {
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.size() > 0) {
super.setRegistries(registryConfigs);
}
}
}
//初始化monitor （HelloWorld例子中没有用到）
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);
}
}
}
//初始化protocol
if ((getProtocols() == null || getProtocols().size() == 0)
&& (getProvider() == null || getProvider().getProtocols() == null || getProvider().getProtocols().size() == 0)) {
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.size() > 0) {
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);
}
}
//调用export
if (! isDelay()) {
export();
}
}
//调用unexport
public void destroy() throws Exception {
unexport();
}

}

代码里面已经加了一些注释。虽然很长，逻辑还是很简单的。其中用到了spring的很多特性。非常值得我们学习。

很明显，下一篇就要介绍 核心的 export 和unexport方法了。