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服务暴露前的准备-ServiceBean的装配
勿忘初心2018-11-18 11:58此文已由作者赵计刚薪授权网易云社区发布。
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dubbo的服务暴露以第一章 第一个dubbo项目中的dubbo-demo-provider来讲述。
列出dubbo-demo-provider的xml配置：
1 <?xml version="1.0" encoding="UTF-8"?> 2 <beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 3 xmlns:dubbo="http://code.alibabatech.com/schema/dubbo" 4 xmlns="http://www.springframework.org/schema/beans" 5 xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd 6 http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd"> 7 8 <!-- 提供方应用信息，用于计算依赖关系 --> 9 <dubbo:application name="demo-provider"/> 10 11 <!-- 使用zookeeper注册中心，并使用curator客户端 --> 12 <dubbo:registry protocol="zookeeper" address="10.211.55.5:2181" client="curator"/> 13 14 <!-- 用dubbo协议在20880端口暴露服务 --> 15 <dubbo:protocol name="dubbo" port="20880"/> 16 17 <!-- 和本地bean一样实现服务 --> 18 <bean id="demoService" class="com.alibaba.dubbo.demo.provider.DemoServiceImpl"/> 19 <!--<bean id="demo2Service"/>--> 20 21 <!-- 声明需要暴露的服务接口 --> 22 <dubbo:service interface="com.alibaba.dubbo.demo.DemoService" ref="demoService"/> 23 <!--<dubbo:service interface="com.alibaba.dubbo.demo.Demo2Service" ref="demo2Service"/>--> 24 </beans>
服务暴露是由com.alibaba.dubbo.config.spring.ServiceBean这个类来实现的，这个类是spring通过解析<dubbo:service>节点创建的单例Bean，每一个<dubbo:service>都会创建一个ServiceBean。先看一下ServiceBean的继承类图：
看一下ServiceBean的源码：
1 package com.alibaba.dubbo.config.spring;
2
3 import com.alibaba.dubbo.config.ApplicationConfig;
4 import com.alibaba.dubbo.config.ModuleConfig;
5 import com.alibaba.dubbo.config.MonitorConfig;
6 import com.alibaba.dubbo.config.ProtocolConfig;
7 import com.alibaba.dubbo.config.ProviderConfig;
8 import com.alibaba.dubbo.config.RegistryConfig;
9 import com.alibaba.dubbo.config.ServiceConfig;
10 import com.alibaba.dubbo.config.annotation.Service;
11 import com.alibaba.dubbo.config.spring.extension.SpringExtensionFactory;
12
13 import org.springframework.beans.factory.BeanFactoryUtils;
14 import org.springframework.beans.factory.BeanNameAware;
15 import org.springframework.beans.factory.DisposableBean;
16 import org.springframework.beans.factory.InitializingBean;
17 import org.springframework.context.ApplicationContext;
18 import org.springframework.context.ApplicationContextAware;
19 import org.springframework.context.ApplicationEvent;
20 import org.springframework.context.ApplicationListener;
21 import org.springframework.context.event.ContextRefreshedEvent;
22 import org.springframework.context.support.AbstractApplicationContext;
23
24 import java.lang.reflect.Method;
25 import java.util.ArrayList;
26 import java.util.List;
27 import java.util.Map;
28
29 /**
30 * ServiceFactoryBean
31 */
32 public class ServiceBean<T> extends ServiceConfig<T> implements InitializingBean, DisposableBean, ApplicationContextAware, ApplicationListener, BeanNameAware {
33 private static final long serialVersionUID = 213195494150089726L;
34
35 private static transient ApplicationContext SPRING_CONTEXT;
36
37 private transient ApplicationContext applicationContext;
38
39 private transient String beanName;
40
41 private transient boolean supportedApplicationListener;
42
43 public ServiceBean() {
44 super();
45 }
46
47 public ServiceBean(Service service) {
48 super(service);
49 }
50
51 public static ApplicationContext getSpringContext() {
52 return SPRING_CONTEXT;
53 }
54
55 /**
56 * ApplicationContextAware接口的方法
57 * Set the ApplicationContext that this object runs in.
58 * Invoked after population of normal bean properties but before an init callback such
59 * as {@link org.springframework.beans.factory.InitializingBean#afterPropertiesSet()}
60 * or a custom init-method.
61 *
62 * 流程：
63 * 1 将applicationContext设置到SpringExtensionFactory中,用于后续从SpringExtensionFactory中获取Bean
64 * 2 获取方法addApplicationListener(ApplicationListener<?> listener),之后将当前类（因为当前类监听了ContextRefreshedEvent事件）加入spring的监听器列表
65 */
66 @Override
67 public void setApplicationContext(ApplicationContext applicationContext) {
68 this.applicationContext = applicationContext;
69 SpringExtensionFactory.addApplicationContext(applicationContext);
70 if (applicationContext != null) {
71 SPRING_CONTEXT = applicationContext;
72 try {
73 /** */
74 Method method = applicationContext.getClass().getMethod("addApplicationListener", new Class<?>[]{ApplicationListener.class}); // 兼容Spring2.0.1
75 method.invoke(applicationContext, new Object[]{this});
76 supportedApplicationListener = true;
77 } catch (Throwable t) {
78 if (applicationContext instanceof AbstractApplicationContext) {
79 try {
80 Method method = AbstractApplicationContext.class.getDeclaredMethod("addListener", new Class<?>[]{ApplicationListener.class}); // 兼容Spring2.0.1
81 if (!method.isAccessible()) {
82 method.setAccessible(true);
83 }
84 method.invoke(applicationContext, new Object[]{this});
85 supportedApplicationListener = true;
86 } catch (Throwable t2) {
87 }
88 }
89 }
90 }
91 }
92
93 /**
94 * BeanNameAware接口的方法
95 * Set the name of the bean in the bean factory that created this bean.
96 * Invoked after population of normal bean properties but before an
97 * init callback such as {@link InitializingBean#afterPropertiesSet()}
98 * or a custom init-method.
99 */
100 @Override
101 public void setBeanName(String name) {
102 this.beanName = name;
103 }
104
105 /**
106 * ApplicationListener接口的方法
107 * delay没有设置或者是-1 && 服务没有暴露 && 服务没有反注册，则进行服务暴露
108 */
109 @Override
110 public void onApplicationEvent(ApplicationEvent event) {
111 if (ContextRefreshedEvent.class.getName().equals(event.getClass().getName())) {
112 if (isDelay() && !isExported() && !isUnexported()) {
113 if (logger.isInfoEnabled()) {
114 logger.info("The service ready on spring started. service: " + getInterface());
115 }
116 export();
117 }
118 }
119 }
120
121 private boolean isDelay() {
122 Integer delay = getDelay();
123 ProviderConfig provider = getProvider();
124 if (delay == null && provider != null) {
125 delay = provider.getDelay();
126 }
127 return supportedApplicationListener && (delay == null || delay.intValue() == -1);
128 }
129
130 /**
131 * InitializingBean接口的方法：
132 * This method allows the bean instance to perform initialization only
133 * possible when all bean properties have been set
134 *
135 * 流程：
136 * 1 检查ServiceBean的ProviderConfig provider，如果为空，从applicationContext获取ProviderConfig类型的bean（这里查找的过程其实就是看有没有配置<dubbo:provider>），如果获取到了，进行设置
137 * 2 后续会参照1分别进行
138 * -- ApplicationConfig application
139 * -- ModuleConfig module
140 * -- List<RegistryConfig> registries
141 * -- MonitorConfig monitor
142 * -- List<ProtocolConfig> protocols
143 * -- String path：服务名称
144 * 3 判断延迟的事件是否大于0，如果是，执行export()，进行服务暴露，如果不是，结束（这种情况下服务暴露，会发生在发布上下文刷新事件的时候）
145 */
146 @Override
147 @SuppressWarnings({"unchecked", "deprecation"})
148 public void afterPropertiesSet() throws Exception {
149 if (getProvider() == null) {
150 Map<String, ProviderConfig> providerConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProviderConfig.class, false, false);
151 if (providerConfigMap != null && providerConfigMap.size() > 0) {
152 Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false);
153 if ((protocolConfigMap == null || protocolConfigMap.size() == 0)
154 && providerConfigMap.size() > 1) { // 兼容旧版本
155 List<ProviderConfig> providerConfigs = new ArrayList<ProviderConfig>();
156 for (ProviderConfig config : providerConfigMap.values()) {
157 if (config.isDefault() != null && config.isDefault().booleanValue()) {
158 providerConfigs.add(config);
159 }
160 }
161 if (providerConfigs.size() > 0) {
162 setProviders(providerConfigs);
163 }
164 } else {
165 ProviderConfig providerConfig = null;
166 for (ProviderConfig config : providerConfigMap.values()) {
167 if (config.isDefault() == null || config.isDefault().booleanValue()) {
168 if (providerConfig != null) {
169 throw new IllegalStateException("Duplicate provider configs: " + providerConfig + " and " + config);
170 }
171 providerConfig = config;
172 }
173 }
174 if (providerConfig != null) {
175 setProvider(providerConfig);
176 }
177 }
178 }
179 }
180 if (getApplication() == null
181 && (getProvider() == null || getProvider().getApplication() == null)) {
182 Map<String, ApplicationConfig> applicationConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ApplicationConfig.class, false, false);
183 if (applicationConfigMap != null && applicationConfigMap.size() > 0) {
184 ApplicationConfig applicationConfig = null;
185 for (ApplicationConfig config : applicationConfigMap.values()) {
186 if (config.isDefault() == null || config.isDefault().booleanValue()) {
187 if (applicationConfig != null) {
188 throw new IllegalStateException("Duplicate application configs: " + applicationConfig + " and " + config);
189 }
190 applicationConfig = config;
191 }
192 }
193 if (applicationConfig != null) {
194 setApplication(applicationConfig);
195 }
196 }
197 }
198 if (getModule() == null
199 && (getProvider() == null || getProvider().getModule() == null)) {
200 Map<String, ModuleConfig> moduleConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ModuleConfig.class, false, false);
201 if (moduleConfigMap != null && moduleConfigMap.size() > 0) {
202 ModuleConfig moduleConfig = null;
203 for (ModuleConfig config : moduleConfigMap.values()) {
204 if (config.isDefault() == null || config.isDefault().booleanValue()) {
205 if (moduleConfig != null) {
206 throw new IllegalStateException("Duplicate module configs: " + moduleConfig + " and " + config);
207 }
208 moduleConfig = config;
209 }
210 }
211 if (moduleConfig != null) {
212 setModule(moduleConfig);
213 }
214 }
215 }
216 if ((getRegistries() == null || getRegistries().size() == 0)
217 && (getProvider() == null || getProvider().getRegistries() == null || getProvider().getRegistries().size() == 0)
218 && (getApplication() == null || getApplication().getRegistries() == null || getApplication().getRegistries().size() == 0)) {
219 Map<String, RegistryConfig> registryConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, RegistryConfig.class, false, false);
220 if (registryConfigMap != null && registryConfigMap.size() > 0) {
221 List<RegistryConfig> registryConfigs = new ArrayList<RegistryConfig>();
222 for (RegistryConfig config : registryConfigMap.values()) {
223 if (config.isDefault() == null || config.isDefault().booleanValue()) {
224 registryConfigs.add(config);
225 }
226 }
227 if (registryConfigs != null && registryConfigs.size() > 0) {
228 super.setRegistries(registryConfigs);
229 }
230 }
231 }
232 if (getMonitor() == null
233 && (getProvider() == null || getProvider().getMonitor() == null)
234 && (getApplication() == null || getApplication().getMonitor() == null)) {
235 Map<String, MonitorConfig> monitorConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, MonitorConfig.class, false, false);
236 if (monitorConfigMap != null && monitorConfigMap.size() > 0) {
237 MonitorConfig monitorConfig = null;
238 for (MonitorConfig config : monitorConfigMap.values()) {
239 if (config.isDefault() == null || config.isDefault().booleanValue()) {
240 if (monitorConfig != null) {
241 throw new IllegalStateException("Duplicate monitor configs: " + monitorConfig + " and " + config);
242 }
243 monitorConfig = config;
244 }
245 }
246 if (monitorConfig != null) {
247 setMonitor(monitorConfig);
248 }
249 }
250 }
251 if ((getProtocols() == null || getProtocols().size() == 0)
252 && (getProvider() == null || getProvider().getProtocols() == null || getProvider().getProtocols().size() == 0)) {
253 Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false);
254 if (protocolConfigMap != null && protocolConfigMap.size() > 0) {
255 List<ProtocolConfig> protocolConfigs = new ArrayList<ProtocolConfig>();
256 for (ProtocolConfig config : protocolConfigMap.values()) {
257 if (config.isDefault() == null || config.isDefault().booleanValue()) {
258 protocolConfigs.add(config);
259 }
260 }
261 if (protocolConfigs != null && protocolConfigs.size() > 0) {
262 super.setProtocols(protocolConfigs);
263 }
264 }
265 }
266 if (getPath() == null || getPath().length() == 0) {
267 if (beanName != null && beanName.length() > 0
268 && getInterface() != null && getInterface().length() > 0
269 && beanName.startsWith(getInterface())) {
270 setPath(beanName);
271 }
272 }
273 if (!isDelay()) {//设置的延迟时间大于0
274 export();
275 }
276 }
277
278 /**
279 * DisposableBean接口的方法
280 */
281 @Override
282 public void destroy() throws Exception {
283 unexport();
284 }
285 }
这里最重要的两个方法：afterPropertiesSet()和onApplicationEvent(ApplicationEvent event)。
一 设置属性与服务暴露
当所有的Bean的属性被设置好之后，执行afterPropertiesSet()。该方法的流程：
1 设置属性
检查ServiceBean的某个属性（这里的属性包含如下6个）是否为空，如果为空，从applicationContext获取相应类型的bean，如果获取到了，则进行相应的设置。
- ProviderConfig provider：其实就是看有没有配置<dubbo:provider>
- ApplicationConfig application：其实就是看有没有配置<dubbo:application>
- ModuleConfig module：其实就是看有没有配置<dubbo:module>
- List<RegistryConfig> registries：其实就是看有没有配置<dubbo:registry>
- MonitorConfig monitor：其实就是看有没有配置<dubbo:monitor>
- List<ProtocolConfig> protocols：其实就是看有没有配置<dubbo:protocol>
- String path：服务名称
2 是否暴露服务
之后判断延迟的时间是否大于0，如果是，执行export()，进行服务暴露，如果不是，结束（这种情况下服务暴露会发生在容器发布上下文刷新事件的时候）。在这里，我们并没有指定delay，所以delay==null，服务暴露会发生在容器发布上下文刷新事件的时候。
当afterPropertiesSet()结束之后，来看一下此时的ServiceBean实例，实例的私有属性如下：（没有值的暂时不说）
1 id = com.alibaba.dubbo.demo.DemoService 2 applicationContext = ClassPathXmlApplicationContext实例 3 beanName = com.alibaba.dubbo.demo.DemoService 4 interfaceName = com.alibaba.dubbo.demo.DemoService 5 supportedApplicationListener = true 6 ref = DemoServiceImpl实例 7 path = com.alibaba.dubbo.demo.DemoService 8 9 application: 10 -- id = demo-provider 11 -- name = demo-provider 12 13 registries = [ 14 RegistryConfig: 15 -- id = com.alibaba.dubbo.config.RegistryConfig 16 -- protocol = zookeeper 17 -- address = 10.211.55.5:2181 18 -- client = curator 19 ] 20 21 protocols = [ 22 ProtocolConfig: 23 -- id = dubbo 24 -- name = dubbo 25 -- port = 20880 26 ]
实际上在创建ServiceBean实例的时候，也会初始化其父类ServiceConfig的静态属性：
1 private static final Protocol protocol = ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension(); 2 private static final ProxyFactory proxyFactory = ExtensionLoader.getExtensionLoader(ProxyFactory.class).getAdaptiveExtension();
其中protocol的实例是：Protocol$Adaptive实例，Protocol$Adaptive类的代码在5.2 dubbo-compiler源码解析已经列出。
下边来看一下第二句代码的源码。首先，看一下ProxyFactory的定义：
1 package com.alibaba.dubbo.rpc;
2
3 import com.alibaba.dubbo.common.Constants;
4 import com.alibaba.dubbo.common.URL;
5 import com.alibaba.dubbo.common.extension.Adaptive;
6 import com.alibaba.dubbo.common.extension.SPI;
7
8 /**
9 * ProxyFactory. (API/SPI, Singleton, ThreadSafe)
10 */
11 @SPI("javassist")
12 public interface ProxyFactory {
13 /**
14 * create proxy.
15 */
16 @Adaptive({Constants.PROXY_KEY})
17 <T> T getProxy(Invoker<T> invoker) throws RpcException;
18
19 /**
20 * create invoker.
21 */
22 @Adaptive({Constants.PROXY_KEY})
23 <T> Invoker<T> getInvoker(T proxy, Class<T> type, URL url) throws RpcException;
24 }
ExtensionLoader.getExtensionLoader(ProxyFactory.class)的实现结果还是：
ExtensionLoader<com.alibaba.dubbo.rpc.ProxyFactory> loader，最终的loader包含如下属性：
- Class<?> type = interface com.alibaba.dubbo.rpc.ProxyFactory
- ExtensionFactory objectFactory = AdaptiveExtensionFactory（适配类）
- factories = [SpringExtensionFactory实例, SpiExtensionFactory实例]
之后，执行getAdaptiveExtension()。
来看一下：META-INF/dubbo/internal/com.alibaba.dubbo.rpc.ProxyFactory的内容：
1 stub=com.alibaba.dubbo.rpc.proxy.wrapper.StubProxyFactoryWrapper 2 jdk=com.alibaba.dubbo.rpc.proxy.jdk.JdkProxyFactory 3 javassist=com.alibaba.dubbo.rpc.proxy.javassist.JavassistProxyFactory
从ProxyFactory的@SPI("javassist")，默认选用的实现是com.alibaba.dubbo.rpc.proxy.javassist.JavassistProxyFactory。com.alibaba.dubbo.rpc.proxy.wrapper.StubProxyFactoryWrapper是一个wrapper类，但是wrapper类只在getExtension("xxx")中会实现aop，而在getAdaptiveExtension()不会进行aop包裹。
这里的三个实现类没有一个类上带有@Adaptive注解，所以会动态创建类。动态生成的类ProxyFactory$Adaptive代码如下：
1 package com.alibaba.dubbo.rpc;
2 import com.alibaba.dubbo.common.extension.ExtensionLoader;
3
4 public class ProxyFactory$Adaptive implements com.alibaba.dubbo.rpc.ProxyFactory {
5 public com.alibaba.dubbo.rpc.Invoker getInvoker(java.lang.Object arg0, java.lang.Class arg1, com.alibaba.dubbo.common.URL arg2) throws com.alibaba.dubbo.rpc.RpcException {
6 if (arg2 == null)
7 throw new IllegalArgumentException("url == null");
8 com.alibaba.dubbo.common.URL url = arg2;
9 String extName = url.getParameter("proxy", "javassist");
10 if(extName == null)
11 throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.ProxyFactory) name from url(" + url.toString() + ") use keys([proxy])");
12 com.alibaba.dubbo.rpc.ProxyFactory extension = (com.alibaba.dubbo.rpc.ProxyFactory)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.ProxyFactory.class).getExtension(extName);
13 return extension.getInvoker(arg0, arg1, arg2);
14 }
15
16 public java.lang.Object getProxy(com.alibaba.dubbo.rpc.Invoker arg0) throws com.alibaba.dubbo.rpc.RpcException {
17 if (arg0 == null)
18 throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument == null");
19 if (arg0.getUrl() == null)
20 throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument getUrl() == null");com.alibaba.dubbo.common.URL url = arg0.getUrl();
21 String extName = url.getParameter("proxy", "javassist");
22 if(extName == null)
23 throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.ProxyFactory) name from url(" + url.toString() + ") use keys([proxy])");
24 com.alibaba.dubbo.rpc.ProxyFactory extension = (com.alibaba.dubbo.rpc.ProxyFactory)ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.ProxyFactory.class).getExtension(extName);
25 return extension.getProxy(arg0);
26 }
27 }
所以ServiceConfig中的静态属性proxyFactory为ProxyFactory$Adaptive实例。
至此，一个ServiceBean实例完成了。
二 在上下文刷新时进行初始化
1 /**
2 * ApplicationListener接口的方法
3 * delay没有设置或者是-1 && 服务没有暴露 && 服务没有反注册，则进行服务暴露
4 */
5 @Override
6 public void onApplicationEvent(ApplicationEvent event) {
7 if (ContextRefreshedEvent.class.getName().equals(event.getClass().getName())) {
8 if (isDelay() && !isExported() && !isUnexported()) {
9 if (logger.isInfoEnabled()) {
10 logger.info("The service ready on spring started. service: " + getInterface());
11 }
12 export();
13 }
14 }
15 }
一切准备好之后，就在这里开始进行服务暴露！export()！！！
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