1.Dubbo服務(wù)架構(gòu)圖
圖1--Dubbo原理圖
名詞解釋
Provider：暴露服務(wù)的服務(wù)提供方
Container：服務(wù)運行容器(可以理解為Spring容器)
Registry：服務(wù)注冊與發(fā)現(xiàn)的注冊中心
Consumer：調(diào)用遠程服務(wù)的消費者(一般為Web應(yīng)用)
Monitor：統(tǒng)計服務(wù)的調(diào)用次數(shù)喝調(diào)用時間的監(jiān)控中心
Container詳解
Dubbo的Container是一個獨立的容器毙沾，因為Dubbo服務(wù)通常不需要部署在Web容器(如Tomcat归形、JBoss等)中挺峡，沒有必要用Web容器去加載服務(wù)葵孤，服務(wù)容器只是一個簡單的Main方法，并且在一個簡單的Spring容器用于暴露服務(wù)橱赠。
org.apache.dubbo.container.Container是服務(wù)啟動的主類源碼：
package org.apache.dubbo.container;
import org.apache.dubbo.common.extension.SPI;
/**
* Container. (SPI, Singleton, ThreadSafe)
*/
@SPI("spring")
public interface Container {
/**
* start method to load the container.
*/
void start();
/**
* stop method to unload the container.
*/
void stop();
}
通過以上代碼可以看到尤仍，這個接口有兩個方法，start()方法和stop()方法狭姨，它的實現(xiàn)類有Log4jContainer宰啦、LogBackContainer和SpringContainer，由于該接口上有@SPI(“spring”)注解饼拍，所以默認調(diào)用SpringContainer赡模。
那么接下來看一下SpringContainer的源碼：
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.dubbo.container.spring;
import org.apache.dubbo.common.logger.Logger;
import org.apache.dubbo.common.logger.LoggerFactory;
import org.apache.dubbo.common.utils.ConfigUtils;
import org.apache.dubbo.common.utils.StringUtils;
import org.apache.dubbo.container.Container;
import org.springframework.context.support.ClassPathXmlApplicationContext;
/**
* SpringContainer. (SPI, Singleton, ThreadSafe)
*
* The container class implementation for Spring
*/
public class SpringContainer implements Container {
/**讀取dubbo.properties配置文件中dubbo.spring.config”的參數(shù)*/
public static final String SPRING_CONFIG = "dubbo.spring.config”;
/**默認加載的Spring配置文件路徑*/
public static final String DEFAULT_SPRING_CONFIG = "classpath*:META-INF/spring/*.xml";
private static final Logger logger = LoggerFactory.getLogger(SpringContainer.class);
static ClassPathXmlApplicationContext context;
public static ClassPathXmlApplicationContext getContext() {
return context;
}
@Override
public void start() {
String configPath = ConfigUtils.getProperty(SPRING_CONFIG);
/**如果參數(shù)為空，則默認加載META-INF/spring路徑下的所有配置文件*/
if (StringUtils.isEmpty(configPath)) {
configPath = DEFAULT_SPRING_CONFIG;
}
context = new ClassPathXmlApplicationContext(configPath.split("[,\\s]+"), false);
context.refresh();
//加載完配置文件之后师抄，Spring容器開始啟動
context.start();
}
@Override
public void stop() {
try {
if (context != null) {
context.stop();
context.close();
context = null;
}
} catch (Throwable e) {
logger.error(e.getMessage(), e);
}
}
}
容器在啟動時漓柑，先去讀取dubbo.properties文件，如果dubbo.properties文件中沒有配置dubbo.spring.config 參數(shù)叨吮，則默認加載META-INF/spring下的全部Spring配置文件辆布。
圖2--Dubbo--provider示例代碼結(jié)構(gòu).png
SpringContainer加載完配置文件之后，Spring容器開始啟動茶鉴，此時Dubbo服務(wù)的整個啟動過程結(jié)束锋玲。
2. Dubbo-provider服務(wù)的配置文件：
由圖2我們可以看出Dubbo服務(wù)的項目結(jié)構(gòu)圖，在resources目錄下涵叮，重點需要兩個配置文件：
1惭蹂、dubbo-consumer.xml
2、dubbo.properties
在項目啟動時围肥，Spring容器會加載這兩個配置文件剿干，Dubbo框架中的dubbo-config模塊會解析這些配置文件，并且解析成對應(yīng)的Bean定義穆刻，并注冊到Spring上下文中置尔。那么接下來我們分析，這些配置文件到底是怎么被解析成對應(yīng)的Bean氢伟，并且注冊到Spring的上下文當中的榜轿。
3.Dubbo服務(wù)的啟動類：
想要了解配置文件被加載的過程幽歼，那么我們首先從項目啟動的入口著手進行分析。接下來谬盐，我們看下Dubbo服務(wù)啟動類的代碼：
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.dubbo.demo.provider;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Application {
public static void main(String[] args) throws Exception {
/**創(chuàng)建Spring IOC容器*/
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("spring/dubbo-provider.xml");
context.start();
System.in.read();
}
}
啟動類的關(guān)鍵代碼甸私，加載Sring的IOC容器，并且指定dubbo的配置文件飞傀，那么當Spring容器啟動的時候皇型，會加載dubb-provider.xml文件。
關(guān)于ClassPathXmlApplicationContext的加載過程有篇博客介紹的非常詳細砸烦，博客地址： ClassPathXmlApplicationContext加載過程 那么當Spring容器加載完dubbo.provider.xml文件之后弃鸦，又怎么將配置文件解析并且獲取到里面的一些參數(shù)呢，接下來我們看一下dubbo-config模塊的代碼幢痘，看下具體解析唬格。
4.Dubbu服務(wù)配置文件的加載過程
首先我們來看一下dubbo-config模塊的整體架構(gòu)：
圖3--Dubbo-config模塊結(jié)構(gòu)
如圖3所示，dubbo-config模塊分為兩塊颜说，一個是dubbon-config-api和dubbo-config-spring购岗，其中dubbo-config-api提供了一些接口和封裝了一些實體類，dubbo-config-spring重點實現(xiàn)的是在spring容器啟動時门粪，加載并且解析dubbo項目的配置文件喊积。
基于schema設(shè)計解析：
dubbo-config-spring的META-INF下有三個配置文件： dubbo.xsd、spring.handlers玄妈、spring.schemas文件注服。那么我們分別看下這三個配置文件的作用：
dubbo.xsd文件：規(guī)范了在編寫xml文件時需要有哪些元素，以及元素的節(jié)點是什么措近，也就是對我們的provider服務(wù)中的dubbo-provider.xml文件做了一個約束溶弟。
spring.schemas文件：
http\://dubbo.apache.org/schema/dubbo/dubbo.xsd=META-INF/dubbo.xsd
http\://code.alibabatech.com/schema/dubbo/dubbo.xsd=META-INF/compat/dubbo.xsd
文件中指定了dubbo的約束文件，Spring框架通過spring.handlers中的配置來解析用戶的自定義配置瞭郑，而dubbo.xsd文件正是用戶自定義的一種約束規(guī)范辜御，所以在此指定dubbo.xsd文件 Spring就可以解析xsd文件中配置的節(jié)點。
spring.handlers文件：
http\://dubbo.apache.org/schema/dubbo=org.apache.dubbo.config.spring.schema.DubboNamespaceHandler
http\://code.alibabatech.com/schema/dubbo=org.apache.dubbo.config.spring.schema.DubboNamespaceHandler
指定了解析配置文件中標簽的解析類屈张。
Spring解析項目中dubbo-provider.xml的過程可以這么理解：
1擒权、加載dubbo-provider.xml
2、解析到自定義的namespace(如 <dubbo:service>標簽)時查找對應(yīng)的spring.schemas和spring.handlers文件
3阁谆、spring.schemas文件指定了約束文件碳抄，spring.handlers指定了解析標簽的類及DubboNamespaceHandler來進行初始化和解析。
dubbo.xsd文件中定義了很多模塊场绿，這些模塊基本可以滿足大多數(shù)使用場景剖效。
基于XML配置解析原理：
通過以上分析我們可以得知，最終解析xml文件的是DubboNamespaceHandler這個類，接下來我們看下DubboNamespaceHandler的實現(xiàn)：
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.dubbo.config.spring.schema;
import org.apache.dubbo.common.Version;
import org.apache.dubbo.config.ApplicationConfig;
import org.apache.dubbo.config.MetadataReportConfig;
import org.apache.dubbo.config.ModuleConfig;
import org.apache.dubbo.config.RegistryConfig;
import org.apache.dubbo.config.MonitorConfig;
import org.apache.dubbo.config.MetricsConfig;
import org.apache.dubbo.config.ProviderConfig;
import org.apache.dubbo.config.ConsumerConfig;
import org.apache.dubbo.config.ProtocolConfig;
import org.apache.dubbo.config.spring.ConfigCenterBean;
import org.apache.dubbo.config.spring.ReferenceBean;
import org.apache.dubbo.config.spring.ServiceBean;
import org.springframework.beans.factory.xml.NamespaceHandlerSupport;
/**
* DubboNamespaceHandler
*
* @export
*/
public class DubboNamespaceHandler extends NamespaceHandlerSupport {
static {
Version.checkDuplicate(DubboNamespaceHandler.class);
}
@Override
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("config-center", new DubboBeanDefinitionParser(ConfigCenterBean.class, true));
registerBeanDefinitionParser("metadata-report", new DubboBeanDefinitionParser(MetadataReportConfig.class, true));
registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true));
registerBeanDefinitionParser("metrics", new DubboBeanDefinitionParser(MetricsConfig.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 AnnotationBeanDefinitionParser());
}
}
DubboNamespaceHandler的繼承圖：
圖4--DubboNamespaceHandler繼承結(jié)構(gòu)
DubboNamespaceHandler集成了NamespaceHandlerSupport璧尸，因此不需要實現(xiàn)全部的解析工作咒林，只需要將自定義schema中的元素解析器注冊進來就可以。
DubboBeanDefinitionParser類實現(xiàn)了BeanDefinitionParser這個接口爷光，負責(zé)將標簽轉(zhuǎn)換成bean定義對象BeanDefinition垫竞。
我們接下來看一下DubboBeanDefinitionParser的parser方法解析步驟：
private static BeanDefinition parse(Element element, ParserContext parserContext, Class<?> beanClass, boolean required) {
/**初始化RootBeanDefinition，生成Spring的bean定義蛀序，指定beanClass交給Spring反射創(chuàng)建實例*/
RootBeanDefinition beanDefinition = new RootBeanDefinition();
beanDefinition.setBeanClass(beanClass);
beanDefinition.setLazyInit(false);
String id = element.getAttribute("id”);
/**確保Spring容器中沒有重復(fù)的Bean定義*/
if (StringUtils.isEmpty(id) && required) {
/**依次嘗試獲取XML文件配置標簽的name和interface屬性做為Bean的唯一Id*/
String generatedBeanName = element.getAttribute("name");
if (StringUtils.isEmpty(generatedBeanName)) {
/**如果協(xié)議中沒有指定名稱欢瞪，則默認為Dubbo*/
if (ProtocolConfig.class.equals(beanClass)) {
generatedBeanName = "dubbo";
} else {
generatedBeanName = element.getAttribute("interface");
}
}
if (StringUtils.isEmpty(generatedBeanName)) {
generatedBeanName = beanClass.getName();
}
id = generatedBeanName;
int counter = 2;
while (parserContext.getRegistry().containsBeanDefinition(id)) {
id = generatedBeanName + (counter++);
}
}
if (StringUtils.isNotEmpty(id)) {
if (parserContext.getRegistry().containsBeanDefinition(id)) {
throw new IllegalStateException("Duplicate spring bean id " + id);
}
/**每次解析回想Sring注冊心的BeanDefinition，后續(xù)會追加屬性*/
parserContext.getRegistry().registerBeanDefinition(id, beanDefinition);
beanDefinition.getPropertyValues().addPropertyValue("id", id);
}
/**<dubbo:protocol>標簽解析*/
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));
}
}
}
}
/**<dubbo:service>標簽解析*/
else if (ServiceBean.class.equals(beanClass)) {
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"));
}
}
/**<dubbo:provider>標簽解析*/
else if (ProviderConfig.class.equals(beanClass)) {
parseNested(element, parserContext, ServiceBean.class, true, "service", "provider", id, beanDefinition);
}
/**<dubbo:consumer>標簽解析*/
else if (ConsumerConfig.class.equals(beanClass)) {
parseNested(element, parserContext, ReferenceBean.class, false, "reference", "consumer", id, beanDefinition);
}
Set<String> props = new HashSet<>();
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 beanProperty = name.substring(3, 4).toLowerCase() + name.substring(4);
String property = StringUtils.camelToSplitName(beanProperty, "-");
props.add(property);
// check the setter/getter whether match
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) {
// ignore, there is no need any log here since some class implement the interface: EnvironmentAware,
// ApplicationAware, etc. They only have setter method, otherwise will cause the error log during application start up.
}
}
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(beanProperty, registryConfig);
} else if ("provider".equals(property) || "registry".equals(property) || ("protocol".equals(property) && ServiceBean.class.equals(beanClass))) {
/**
* For 'provider' 'protocol' 'registry', keep literal value (should be id/name) and set the value to 'registryIds' 'providerIds' protocolIds'
* The following process should make sure each id refers to the corresponding instance, here's how to find the instance for different use cases:
* 1. Spring, check existing bean by id, see{@link ServiceBean#afterPropertiesSet()}; then try to use id to find configs defined in remote Config Center
* 2. API, directly use id to find configs defined in remote Config Center; if all config instances are defined locally, please use {@link org.apache.dubbo.config.ServiceConfig#setRegistries(List)}
*/
beanDefinition.getPropertyValues().addPropertyValue(beanProperty + "Ids", value);
} 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(ONRETURN.equals(property) || ONTHROW.equals(property) || ONINVOKE.equals(property)) {
int index = value.lastIndexOf(".");
String ref = value.substring(0, index);
String method = value.substring(index + 1);
reference = new RuntimeBeanReference(ref);
beanDefinition.getPropertyValues().addPropertyValue(property + METHOD, method);
} 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(beanProperty, 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) {
beanDefinition.getPropertyValues().addPropertyValue("parameters", parameters);
}
return beanDefinition;
}
Dubbo通過parse方法解析配置文件徐裸，并將配置文件的各個參數(shù)映射到對應(yīng)的JavaBean引有。
我是割草的小豬頭，不斷學(xué)習(xí)倦逐，不斷進步，后續(xù)陸續(xù)更新Dubbo系列的文章宫补，如您有興趣一起了解檬姥，歡迎關(guān)注，如文章中有不妥之處粉怕，歡迎指正健民！
