dubbo消费端源码分析
这篇文章主要是讲述dubbo的消费者初始化发生的事情，比如：怎么注入和注入什么对象到带有@DubboReference和@Reference注解的成员变量里，怎么去建立dubbo的连接，怎么获取注册中心里提供者的地址等等
消费端的入口-DubboAutoConfiguration
因为根据spring-boot的自动装载策略，至于为什么会触发自动转载，这里我就不去说了。只要知道他会注入DubboAutoConfiguration这个对象就行了
@ConditionalOnProperty(
prefix = "dubbo",
name = {"enabled"},
matchIfMissing = true
)
@Configuration
@AutoConfigureAfter({DubboRelaxedBindingAutoConfiguration.class})
@EnableConfigurationProperties({DubboConfigurationProperties.class})
public class DubboAutoConfiguration {
public DubboAutoConfiguration() {
}
...
//注入ReferenceAnnotationBeanPostProcessor对象
@ConditionalOnMissingBean
@Bean(
name = {"referenceAnnotationBeanPostProcessor"}
)
public ReferenceAnnotationBeanPostProcessor referenceAnnotationBeanPostProcessor() {
return new ReferenceAnnotationBeanPostProcessor();
}
...
}
public class ReferenceAnnotationBeanPostProcessor extends AbstractAnnotationBeanPostProcessor implements ApplicationContextAware {
public static final String BEAN_NAME = "referenceAnnotationBeanPostProcessor";
private static final int CACHE_SIZE = Integer.getInteger("referenceAnnotationBeanPostProcessor.cache.size", 32);
private final ConcurrentMap<String, ReferenceBean<?>> referenceBeanCache;
private final ConcurrentMap<InjectedElement, ReferenceBean<?>> injectedFieldReferenceBeanCache;
private final ConcurrentMap<InjectedElement, ReferenceBean<?>> injectedMethodReferenceBeanCache;
private ApplicationContext applicationContext;
public ReferenceAnnotationBeanPostProcessor() {
super(new Class[]{DubboReference.class, Reference.class, com.alibaba.dubbo.config.annotation.Reference.class});
this.referenceBeanCache = new ConcurrentHashMap(CACHE_SIZE);
this.injectedFieldReferenceBeanCache = new ConcurrentHashMap(CACHE_SIZE);
this.injectedMethodReferenceBeanCache = new ConcurrentHashMap(CACHE_SIZE);
}
}
DubboAutoConfiguration作用就是注入了ReferenceAnnotationBeanPostProcessor对象，那ReferenceAnnotationBeanPostProcessor有什么特别之处呢？不妨看看它的结构图
可以看到ReferenceAnnotationBeanPostProcessor是InstantiationAwareBeanPostProcessorAdapter的子类还有是MergedBeanDefinitionPostProcessor的实现类。
所以初始化的时候会触发postProcessMergedBeanDefinition的方法和postProcessPropertyValues的方法。
- postProcessPropertyValues：从名字上来看，应该是给对象做依赖注入吧。
- postProcessMergedBeanDefinition： 这个应该是对象合并触发的。这个会比postProcessPropertyValues执行时机要靠前
因为ReferenceAnnotationBeanPostProcessor是AbstractAnnotationBeanPostProcessor的子类，postProcessPropertyValues和postProcessMergedBeanDefinition的实现都在AbstractAnnotationBeanPostProcessor（注意这个类是：阿里巴巴包下的类）这里面的实现。接下来我们看一下：
public abstract class AbstractAnnotationBeanPostProcessor extends InstantiationAwareBeanPostProcessorAdapter implements MergedBeanDefinitionPostProcessor, PriorityOrdered, BeanFactoryAware, BeanClassLoaderAware, EnvironmentAware, DisposableBean {
public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
if (beanType != null) {
//发现需要依赖注入的对象，即带有：@Reference和@DubboReference
InjectionMetadata metadata = this.findInjectionMetadata(beanName, beanType, (PropertyValues)null);
metadata.checkConfigMembers(beanDefinition);
}
}
public PropertyValues postProcessPropertyValues(PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeanCreationException {
//发现需要依赖注入的对象，即带有：@Reference和@DubboReference
InjectionMetadata metadata = this.findInjectionMetadata(beanName, bean.getClass(), pvs);
try {
//依赖注入
metadata.inject(bean, beanName, pvs);
return pvs;
} catch (Exception var7) {
throw var7;
}
}
}
postProcessPropertyValues和postProcessMergedBeanDefinition都使用findInjectionMetadata，功能是：发现需要依赖注入的对象
下面分析一下AbstractAnnotationBeanPostProcessor.findInjectionMetadata方法
findInjectionMetadata发现需要依赖注入的对象
public abstract class AbstractAnnotationBeanPostProcessor extends InstantiationAwareBeanPostProcessorAdapter implements MergedBeanDefinitionPostProcessor, PriorityOrdered, BeanFactoryAware, BeanClassLoaderAware, EnvironmentAware, DisposableBean {
private InjectionMetadata findInjectionMetadata(String beanName, Class<?> clazz, PropertyValues pvs) {
//下面这一部分都是是否需要读换存的不用理，主要看buildAnnotatedMetadata，这个方法去
String cacheKey = StringUtils.hasLength(beanName) ? beanName : clazz.getName();
AbstractAnnotationBeanPostProcessor.AnnotatedInjectionMetadata metadata = (AbstractAnnotationBeanPostProcessor.AnnotatedInjectionMetadata)this.injectionMetadataCache.get(cacheKey);
if (InjectionMetadata.needsRefresh(metadata, clazz)) {
ConcurrentMap var6 = this.injectionMetadataCache;
synchronized(this.injectionMetadataCache) {
metadata = (AbstractAnnotationBeanPostProcessor.AnnotatedInjectionMetadata)this.injectionMetadataCache.get(cacheKey);
if (InjectionMetadata.needsRefresh(metadata, clazz)) {
if (metadata != null) {
metadata.clear(pvs);
}
try {
metadata = this.buildAnnotatedMetadata(clazz);
this.injectionMetadataCache.put(cacheKey, metadata);
} catch (NoClassDefFoundError var9) {
throw new IllegalStateException("Failed to introspect object class [" + clazz.getName() + "] for annotation metadata: could not find class that it depends on", var9);
}
}
}
}
return metadata;
}
private AbstractAnnotationBeanPostProcessor.AnnotatedInjectionMetadata buildAnnotatedMetadata(Class<?> beanClass) {
//找到类下的成员变量
Collection<AbstractAnnotationBeanPostProcessor.AnnotatedFieldElement> fieldElements =
this.findFieldAnnotationMetadata(beanClass);
//找到类下的方法--方法就不贴出来讨论了
Collection<AbstractAnnotationBeanPostProcessor.AnnotatedMethodElement> methodElements =
this.findAnnotatedMethodMetadata(beanClass);
return new AbstractAnnotationBeanPostProcessor.AnnotatedInjectionMetadata(beanClass, fieldElements, methodElements);
}
private List<AbstractAnnotationBeanPostProcessor.AnnotatedFieldElement> findFieldAnnotationMetadata(Class<?> beanClass) {
final List<AbstractAnnotationBeanPostProcessor.AnnotatedFieldElement> elements = new LinkedList();
ReflectionUtils.doWithFields(beanClass, new FieldCallback() {
public void doWith(Field field) throws IllegalArgumentException, IllegalAccessException {
//获取符合条件的注解,即：DubboReference.class, Reference.class, com.alibaba.dubbo.config.annotation.Reference.class
Class[] var2 = AbstractAnnotationBeanPostProcessor.this.getAnnotationTypes();
int var3 = var2.length;
for(int var4 = 0; var4 < var3; ++var4) {
Class<? extends Annotation> annotationType = var2[var4];
AnnotationAttributes attributes = AnnotationUtils.getAnnotationAttributes(field, annotationType, AbstractAnnotationBeanPostProcessor.this.getEnvironment(), true, true, new String[0]);
if (attributes != null) {
//is not supported on static fields:
if (Modifier.isStatic(field.getModifiers())) {
return;
}
elements.add(AbstractAnnotationBeanPostProcessor.this.new AnnotatedFieldElement(field, attributes));
}
}
}
});
return elements;
}
//构造方法
public AbstractAnnotationBeanPostProcessor(Class<? extends Annotation>... annotationTypes) {
this.injectionMetadataCache = new ConcurrentHashMap(CACHE_SIZE);
this.injectedObjectsCache = new ConcurrentHashMap(CACHE_SIZE);
this.order = 2147483644;
this.annotationTypes = annotationTypes;
}
}
//buildAnnotatedMetadata构造返回的结果类
private class AnnotatedInjectionMetadata extends InjectionMetadata {
private final Collection<AbstractAnnotationBeanPostProcessor.AnnotatedFieldElement> fieldElements;
private final Collection<AbstractAnnotationBeanPostProcessor.AnnotatedMethodElement> methodElements;
public AnnotatedInjectionMetadata(Class<?> targetClass, Collection<AbstractAnnotationBeanPostProcessor.AnnotatedFieldElement> fieldElements, Collection<AbstractAnnotationBeanPostProcessor.AnnotatedMethodElement> methodElements) {
super(targetClass, AbstractAnnotationBeanPostProcessor.combine(fieldElements, methodElements));
this.fieldElements = fieldElements;
this.methodElements = methodElements;
}
}
public class InjectionMetadata {
public InjectionMetadata(Class<?> targetClass, Collection<InjectionMetadata.InjectedElement> elements) {
this.targetClass = targetClass;
this.injectedElements = elements;
}
}
public class ReferenceAnnotationBeanPostProcessor extends AbstractAnnotationBeanPostProcessor implements
ApplicationContextAware {
public ReferenceAnnotationBeanPostProcessor() {
//注入注解的位置
super(DubboReference.class, Reference.class, com.alibaba.dubbo.config.annotation.Reference.class);
}
}
-
findInjectionMetadata: 首先读取缓存有没有相应的信息（通过beanName为key），没有的话就调用buildAnnotatedMetadata来进行创建 -
buildAnnotatedMetadata: 调用findFieldAnnotationMetadata去查找带有相应注解的成员变量，调用findAnnotatedMethodMetadata应该也是查找带有相应注解的方法。 这里我们只研究findFieldAnnotationMetadata，最后构造AbstractAnnotationBeanPostProcessor.AnnotatedInjectionMetadata返回，里面带有的信息有，beanClass,符合条件成员变量的集合，符合条件方法的集合 -
findFieldAnnotationMetadata： ReflectionUtils.doWithFields里面实现其实就是遍历类下的所有的成员变量，得到成员变量后通过new FieldCallback()来做一个回调，看看回调里的信息：AbstractAnnotationBeanPostProcessor.this.getAnnotationTypes()得到的是以下这些注解：DubboReference.class, Reference.class, com.alibaba.dubbo.config.annotation.Reference.class。然后再通过AnnotationUtils.getAnnotationAttributes方法去获取带有这些注解的成员变量的属性，如果带有这些注解的话，就加入到集合中返回。问题：
DubboReference.class, Reference.class, com.alibaba.dubbo.config.annotation.Reference.class这些注解的引入位置？因为在构造
ReferenceAnnotationBeanPostProcessor这个类时调用了super(DubboReference.class, Reference.class, com.alibaba.dubbo.config.annotation.Reference.class);这个方法。然后在看到AbstractAnnotationBeanPostProcessor的构造方法可以看到this.annotationTypes = annotationTypes;
AbstractAnnotationBeanPostProcessor.postProcessMergedBeanDefinition
public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
if (beanType != null) {
InjectionMetadata metadata = this.findInjectionMetadata(beanName, beanType, (PropertyValues)null);
metadata.checkConfigMembers(beanDefinition);
}
}
public class InjectionMetadata {
public void checkConfigMembers(RootBeanDefinition beanDefinition) {
Set<InjectionMetadata.InjectedElement> checkedElements = new LinkedHashSet(this.injectedElements.size());
Iterator var3 = this.injectedElements.iterator();
while(var3.hasNext()) {
//这里得到的是findInjectionMetadata方法执行得到的成员变量信息和方法信息
InjectionMetadata.InjectedElement element = (InjectionMetadata.InjectedElement)var3.next();
Member member = element.getMember();
if (!beanDefinition.isExternallyManagedConfigMember(member)) {
beanDefinition.registerExternallyManagedConfigMember(member);
checkedElements.add(element);
if (logger.isTraceEnabled()) {
logger.trace("Registered injected element on class [" + this.targetClass.getName() + "]: " + element);
}
}
}
//通过检查后放入到checkedElements
this.checkedElements = checkedElements;
}
}
findInjectionMetadata上面已经分析了。checkConfigMembers其实就是检查一下通过findInjectionMetadata方法执行得到的成员变量信息和方法信息，符合条件就加入到 InjectionMetadata.checkedElements中
AbstractAnnotationBeanPostProcessor.postProcessPropertyValues
public PropertyValues postProcessPropertyValues(PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeanCreationException {
InjectionMetadata metadata = this.findInjectionMetadata(beanName, bean.getClass(), pvs);
try {
metadata.inject(bean, beanName, pvs);
return pvs;
} catch (Exception var7) {
throw var7;
}
}
public class InjectionMetadata {
public void inject(Object target, @Nullable String beanName, @Nullable PropertyValues pvs) throws Throwable {
//引入的位置postProcessMergedBeanDefinition
Collection<InjectionMetadata.InjectedElement> checkedElements = this.checkedElements;
//如果没有检查过的属性，就用没有检查过的
Collection<InjectionMetadata.InjectedElement> elementsToIterate = checkedElements != null ? checkedElements : this.injectedElements;
//elementsToIterate就是带有@DubboReference等等的成员变量或方法
InjectionMetadata.InjectedElement element;
if (!((Collection)elementsToIterate).isEmpty()) {
for(Iterator var6 = ((Collection)elementsToIterate).iterator(); var6.hasNext(); element.inject(target, beanName, pvs)) {
element = (InjectionMetadata.InjectedElement)var6.next();
}
}
}
}
public abstract class AbstractAnnotationBeanPostProcessor extends InstantiationAwareBeanPostProcessorAdapter implements MergedBeanDefinitionPostProcessor, PriorityOrdered, BeanFactoryAware, BeanClassLoaderAware, EnvironmentAware, DisposableBean {
protected Object getInjectedObject(AnnotationAttributes attributes, Object bean, String beanName, Class<?> injectedType, InjectedElement injectedElement) throws Exception {
String cacheKey = this.buildInjectedObjectCacheKey(attributes, bean, beanName, injectedType, injectedElement);
Object injectedObject = this.injectedObjectsCache.get(cacheKey);
if (injectedObject == null) {
injectedObject = this.doGetInjectedBean(attributes, bean, beanName, injectedType, injectedElement);
this.injectedObjectsCache.putIfAbsent(cacheKey, injectedObject);
}
return injectedObject;
}
public class AnnotatedFieldElement extends InjectedElement {
private final Field field;
private final AnnotationAttributes attributes;
private volatile Object bean;
protected AnnotatedFieldElement(Field field, AnnotationAttributes attributes) {
super(field, (PropertyDescriptor)null);
this.field = field;
this.attributes = attributes;
}
protected void inject(Object bean, String beanName, PropertyValues pvs) throws Throwable {
Class<?> injectedType = this.field.getType();
Object injectedObject = AbstractAnnotationBeanPostProcessor.this.getInjectedObject(this.attributes, bean, beanName, injectedType, this);
ReflectionUtils.makeAccessible(this.field);
this.field.set(bean, injectedObject);
}
}
}
public class ReferenceAnnotationBeanPostProcessor extends AbstractAnnotationBeanPostProcessor implements
ApplicationContextAware {
@Override
protected Object doGetInjectedBean(AnnotationAttributes attributes, Object bean, String beanName, Class<?> injectedType,
InjectionMetadata.InjectedElement injectedElement) throws Exception {
/**
* The name of bean that annotated Dubbo's {@link Service @Service} in local Spring {@link ApplicationContext}
*/
String referencedBeanName = buildReferencedBeanName(attributes, injectedType);
/**
* The name of bean that is declared by {@link Reference @Reference} annotation injection
*/
String referenceBeanName = getReferenceBeanName(attributes, injectedType);
ReferenceBean referenceBean = buildReferenceBeanIfAbsent(referenceBeanName, attributes, injectedType);
boolean localServiceBean = isLocalServiceBean(referencedBeanName, referenceBean, attributes);
prepareReferenceBean(referencedBeanName, referenceBean, localServiceBean);
registerReferenceBean(referencedBeanName, referenceBean, attributes, localServiceBean, injectedType);
cacheInjectedReferenceBean(referenceBean, injectedElement);
return referenceBean.get();
}
}
AbstractAnnotationBeanPostProcessor.postProcessPropertyValues：
this.findInjectionMetadata: 上面已经分析了，就是获取需要注入的成员变量和方法metadata.inject(bean, beanName, pvs)： 依赖注入
InjectionMetadata.inject
this.checkedElements != null ? this.checkedElements : this.injectedElements: 如果有检查过的checkedElements 就用有检查过的，没有就使用没有检查过的injectedElements。- 遍历需要注入的成员变量和方法嗲用：
element.inject
AbstractAnnotationBeanPostProcessor.AnnotatedFieldElement.inject
- AbstractAnnotationBeanPostProcessor.this.getInjectedObject: 构建一个对象
- this.field.set(bean, injectedObject)： 把构建的对象，设置到成员变量里面
AbstractAnnotationBeanPostProcessor.getInjectedObject
- 调用this.doGetInjectedBean , 因为
AbstractAnnotationBeanPostProcessor.doGetInjectedBean是一个抽象的方法，最后回调用字类的方法。即：ReferenceAnnotationBeanPostProcessor.doGetInjectedBean
ReferenceAnnotationBeanPostProcessor.doGetInjectedBean： 这里直接看referenceBean.get()，只需要着重看返回的对象是什么就好了。
ReferenceConfig解析
ReferenceConfig.init()初始化
public class ReferenceConfig<T> extends ReferenceConfigBase<T> {
private transient volatile T ref;
public synchronized T get() {
if (destroyed) {
throw new IllegalStateException("The invoker of ReferenceConfig(" + url + ") has already destroyed!");
}
if (ref == null) {
init();
}
return ref;
}
public synchronized void init() {
if (initialized) {
return;
}
if (bootstrap == null) {
bootstrap = DubboBootstrap.getInstance();
bootstrap.init();
}
checkAndUpdateSubConfigs();
checkStubAndLocal(interfaceClass);
ConfigValidationUtils.checkMock(interfaceClass, this);
//构建map，这个跟提供者差不多
Map<String, String> map = new HashMap<String, String>();
map.put(SIDE_KEY, CONSUMER_SIDE);
ReferenceConfigBase.appendRuntimeParameters(map);
if (!ProtocolUtils.isGeneric(generic)) {
String revision = Version.getVersion(interfaceClass, version);
if (revision != null && revision.length() > 0) {
map.put(REVISION_KEY, revision);
}
String[] methods = Wrapper.getWrapper(interfaceClass).getMethodNames();
if (methods.length == 0) {
logger.warn("No method found in service interface " + interfaceClass.getName());
map.put(METHODS_KEY, ANY_VALUE);
} else {
map.put(METHODS_KEY, StringUtils.join(new HashSet<String>(Arrays.asList(methods)), COMMA_SEPARATOR));
}
}
map.put(INTERFACE_KEY, interfaceName);
AbstractConfig.appendParameters(map, getMetrics());
AbstractConfig.appendParameters(map, getApplication());
AbstractConfig.appendParameters(map, getModule());
// remove 'default.' prefix for configs from ConsumerConfig
// appendParameters(map, consumer, Constants.DEFAULT_KEY);
AbstractConfig.appendParameters(map, consumer);
AbstractConfig.appendParameters(map, this);
MetadataReportConfig metadataReportConfig = getMetadataReportConfig();
if (metadataReportConfig != null && metadataReportConfig.isValid()) {
map.putIfAbsent(METADATA_KEY, REMOTE_METADATA_STORAGE_TYPE);
}
Map<String, AsyncMethodInfo> attributes = null;
if (CollectionUtils.isNotEmpty(getMethods())) {
attributes = new HashMap<>();
for (MethodConfig methodConfig : getMethods()) {
AbstractConfig.appendParameters(map, methodConfig, methodConfig.getName());
String retryKey = methodConfig.getName() + ".retry";
if (map.containsKey(retryKey)) {
String retryValue = map.remove(retryKey);
if ("false".equals(retryValue)) {
map.put(methodConfig.getName() + ".retries", "0");
}
}
AsyncMethodInfo asyncMethodInfo = AbstractConfig.convertMethodConfig2AsyncInfo(methodConfig);
if (asyncMethodInfo != null) {
// consumerModel.getMethodModel(methodConfig.getName()).addAttribute(ASYNC_KEY, asyncMethodInfo);
attributes.put(methodConfig.getName(), asyncMethodInfo);
}
}
}
String hostToRegistry = ConfigUtils.getSystemProperty(DUBBO_IP_TO_REGISTRY);
if (StringUtils.isEmpty(hostToRegistry)) {
hostToRegistry = NetUtils.getLocalHost();
} else if (isInvalidLocalHost(hostToRegistry)) {
throw new IllegalArgumentException("Specified invalid registry ip from property:" + DUBBO_IP_TO_REGISTRY + ", value:" + hostToRegistry);
}
map.put(REGISTER_IP_KEY, hostToRegistry);
serviceMetadata.getAttachments().putAll(map);
ref = createProxy(map);
serviceMetadata.setTarget(ref);
serviceMetadata.addAttribute(PROXY_CLASS_REF, ref);
ConsumerModel consumerModel = repository.lookupReferredService(serviceMetadata.getServiceKey());
consumerModel.setProxyObject(ref);
consumerModel.init(attributes);
initialized = true;
checkInvokerAvailable();
// dispatch a ReferenceConfigInitializedEvent since 2.7.4
dispatch(new ReferenceConfigInitializedEvent(this, invoker));
}
}
ReferenceConfig.get(): 判断this.ref是否是空，不是的话，进行init()初始化。
ReferenceConfig.init()初始化：
- 构建map，这个跟提供者差不多，构建出来的map如下：
createProxy(map)： 创建代理类
createProxy(map)创建代理对象
public class ReferenceConfig<T> extends ReferenceConfigBase<T> {
private T createProxy(Map<String, String> map) {
//判断是否是本地的refer,本地绑定，这里就不看了。只看远程的
if (shouldJvmRefer(map)) {
URL url = new URL(LOCAL_PROTOCOL, LOCALHOST_VALUE, 0, interfaceClass.getName()).addParameters(map);
invoker = REF_PROTOCOL.refer(interfaceClass, url);
if (logger.isInfoEnabled()) {
logger.info("Using injvm service " + interfaceClass.getName());
}
} else {
urls.clear();
//这种情况是类似于： <dubbo:reference id="orderService" interface="com.onion.service.IOrderService" url="dubbo://127.0.0.1:20881/com.onion.service.IOrderService" /> 这种指定url就会进入if语句里面。，这里我们也是只是看注册中心获取的。
if (url != null && url.length() > 0) { // user specified URL, could be peer-to-peer address, or register center's address.
String[] us = SEMICOLON_SPLIT_PATTERN.split(url);
if (us != null && us.length > 0) {
for (String u : us) {
URL url = URL.valueOf(u);
if (StringUtils.isEmpty(url.getPath())) {
url = url.setPath(interfaceName);
}
if (UrlUtils.isRegistry(url)) {
urls.add(url.addParameterAndEncoded(REFER_KEY, StringUtils.toQueryString(map)));
} else {
urls.add(ClusterUtils.mergeUrl(url, map));
}
}
}
} else { // assemble URL from register center's configuration
// if protocols not injvm checkRegistry
if (!LOCAL_PROTOCOL.equalsIgnoreCase(getProtocol())) {
checkRegistry();
List<URL> us = ConfigValidationUtils.loadRegistries(this, false);
...遍历us，判断有没有monitorUrl，需要的话加入到url的参数中： monitor=monitorUrl...
if (urls.isEmpty()) {
....抛错.....
}
}
}
//urls就是注册中心地址，如果只有一个注册中心，就直接获取invoker
if (urls.size() == 1) {
invoker = REF_PROTOCOL.refer(interfaceClass, urls.get(0));
} else {
List<Invoker<?>> invokers = new ArrayList<Invoker<?>>();
URL registryURL = null;
for (URL url : urls) {
invokers.add(REF_PROTOCOL.refer(interfaceClass, url));
if (UrlUtils.isRegistry(url)) {
registryURL = url; // use last registry url
}
}
//选择容错的策略
if (registryURL != null) { // registry url is available
// for multi-subscription scenario, use 'zone-aware' policy by default
String cluster = registryURL.getParameter("cluster", "zone-aware");
// The invoker wrap sequence would be: ZoneAwareClusterInvoker(StaticDirectory) -> FailoverClusterInvoker(RegistryDirectory, routing happens here) -> Invoker
invoker = Cluster.getCluster(cluster, false).join(new StaticDirectory(registryURL, invokers));
} else { // not a registry url, must be direct invoke.
String cluster = CollectionUtils.isNotEmpty(invokers)
? (invokers.get(0).getUrl() != null ? invokers.get(0).getUrl().getParameter("cluster", "zone-aware") : "failover")
:"failover";
invoker = Cluster.getCluster(cluster).join(new StaticDirectory(invokers));
}
}
}
if (logger.isInfoEnabled()) {
logger.info("Refer dubbo service " + interfaceClass.getName() + " from url " + invoker.getUrl());
}
/**
* @since 2.7.0
* ServiceData Store
*/
String metadata = map.get(METADATA_KEY);
WritableMetadataService metadataService = WritableMetadataService.getExtension(metadata == null ? DEFAULT_METADATA_STORAGE_TYPE : metadata);
if (metadataService != null) {
URL consumerURL = new URL(CONSUMER_PROTOCOL, map.remove(REGISTER_IP_KEY), 0, map.get(INTERFACE_KEY), map);
metadataService.publishServiceDefinition(consumerURL);
}
// create service proxy
return (T) PROXY_FACTORY.getProxy(invoker, ProtocolUtils.isGeneric(generic));
}
}
createProxy做的事情：
-
shouldJvmRefer(map): 判断是否连接本地信息，这里我们只考虑远程的。 -
判断接口是否指定了url地址，如果是的话，直接利用url上面的地址直接构建。 比如是：
<dubbo:reference id="orderService" interface="com.onion.service.IOrderService" url="dubbo://127.0.0.1:20881/com.onion.service.IOrderService" />这种就会直接利用url上面的地址直接构建了
-
利用
ConfigValidationUtils.loadRegistries获取注册中心地址，这个会得到的注册中心地址为： registry://127.0.0.1:8848?registry=nacos，这个跟提供者里的loadRegistries是一样的，如果想知道为什么会变成 registry://127.0.0.1:8848?registry=nacos，可以去看我上一个文章。 -
如果是多个注册中心，就会进行容错的处理，这里我们只看一个的把。
REF_PROTOCOL.refer(interfaceClass, urls.get(0))直接构建Invoker。 -
PROXY_FACTORY.getProxy(invoker, ProtocolUtils.isGeneric(generic))： 把得到invoker作为参数构造一个代理类返回
REF_PROTOCOL是ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension()，因为根据自适应的扩展点的功能得到的是Protocol$Adaptive,又因为url协议为registry，所以最后会调用RegistryProtocol.ref
RegistryProtocol.refer 构造invoker
public class RegistryProtocol implements Protocol {
private static final ConsumerConfigurationListener CONSUMER_CONFIGURATION_LISTENER = new ConsumerConfigurationListener();
@Override
@SuppressWarnings("unchecked")
public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
url = getRegistryUrl(url);
Registry registry = registryFactory.getRegistry(url);
if (RegistryService.class.equals(type)) {
return proxyFactory.getInvoker((T) registry, type, url);
}
// group="a,b" or group="*"
Map<String, String> qs = StringUtils.parseQueryString(url.getParameterAndDecoded(REFER_KEY));
String group = qs.get(GROUP_KEY);
if (group != null && group.length() > 0) {
if ((COMMA_SPLIT_PATTERN.split(group)).length > 1 || "*".equals(group)) {
return doRefer(Cluster.getCluster(MergeableCluster.NAME), registry, type, url);
}
}
Cluster cluster = Cluster.getCluster(qs.get(CLUSTER_KEY));
return doRefer(cluster, registry, type, url);
}
private <T> Invoker<T> doRefer(Cluster cluster, Registry registry, Class<T> type, URL url) {
RegistryDirectory<T> directory = new RegistryDirectory<T>(type, url);
directory.setRegistry(registry);
directory.setProtocol(protocol);
// all attributes of REFER_KEY
Map<String, String> parameters = new HashMap<String, String>(directory.getConsumerUrl().getParameters());
URL subscribeUrl = new URL("consumer", parameters.remove("register.ip"), 0, type.getName(), parameters);
if (directory.isShouldRegister()) {
directory.setRegisteredConsumerUrl(subscribeUrl);
registry.register(directory.getRegisteredConsumerUrl());
}
directory.buildRouterChain(subscribeUrl);
directory.subscribe(toSubscribeUrl(subscribeUrl));
Invoker<T> invoker = cluster.join(directory);
List<RegistryProtocolListener> listeners = findRegistryProtocolListeners(url);
if (CollectionUtils.isEmpty(listeners)) {
return invoker;
}
RegistryInvokerWrapper<T> registryInvokerWrapper = new RegistryInvokerWrapper<>(directory, cluster, invoker);
for (RegistryProtocolListener listener : listeners) {
listener.onRefer(this, registryInvokerWrapper);
}
return registryInvokerWrapper;
}
protected URL getRegistryUrl(URL url) {
return URLBuilder.from(url)
.setProtocol(url.getParameter(REGISTRY_KEY, DEFAULT_REGISTRY))
.removeParameter(REGISTRY_KEY)
.build();
}
public void subscribe(URL url) {
setConsumerUrl(url);
//把当前RegistryDirectory作为listener，去监听节点的变化
CONSUMER_CONFIGURATION_LISTENER.addNotifyListener(this);
serviceConfigurationListener = new ReferenceConfigurationListener(this, url);
registry.subscribe(url, this);
}
}
RegistryProtocol.refer:
-
getRegistryUrl： 获取注册中心的地址传入传入url:registry://127.0.0.1:8848?export=dubbo://127.0.0.1:20880®istry=nacos
返回：nacos://127.0.0.1:8848?export=dubbo://127.0.0.1:20880
-
registryFactory.getRegistry(url): 通过url的协议。得到相应的registry,这里我是nacos,所以得到的就是nacosRegistry
-
Cluster.getCluster(qs.get("cluster"))： 获取相应的Cluster，默认使用的是：
"failover" -
最后调用doRefer(cluster, registry, type, url)
doRefer：
-
构造一个
RegistryDirectory RegistryDirectory是Dubbo中的服务目录，从名字上来看，也比较容易理解，服务目录中存储了一些和服务提供者有关的信息，通过服务目录，服务消费者可获取到服务提供者的信息，比如 ip、端口、服务协议等。通过这些信息，服务消费者就可通过 Netty 等客户端进行远程调用
-
new URL("consumer", parameters.remove("register.ip"), 0, type.getName(), parameters)： 构建一个发布地址，地址格式如下： consumer://192.168.56.1/com.onion.service.IUserService?...参数...
-
registry.register(directory.getRegisteredConsumerUrl())：发布该地址去注册中心。
-
directory.subscribe(toSubscribeUrl(subscribeUrl));
- toSubscribeUrl： 往url中添加 category=providers,configurators,routers 这个参数。
providers,configurators,routers这个是需要监听的属性 directory.subscribe：把当前RegistryDirectory作为listener，去监听节点的变化，然后调用registry.subscribe(url, this)，这里的registry是NacosRegistry,又因为它是FailbackRegistry的子类，所以会调用FailbackRegistry.subscribe。
- toSubscribeUrl： 往url中添加 category=providers,configurators,routers 这个参数。
注意：FailbackRegistry是全类名称是org.apache.dubbo.registry.support.FailbackRegistry
registry.register 注册到注册中心
因为我是使用nacos为注册中心，所以reigstry是nacosRegistry，又因为FailbackRegistry是nacosRegistry的父类，所以会调用FailbackRegistry.register
public abstract class FailbackRegistry extends AbstractRegistry {
@Override
public void register(URL url) {
if (!acceptable(url)) {
return;
}
super.register(url);
removeFailedRegistered(url);
removeFailedUnregistered(url);
try {
// Sending a registration request to the server side
//调用真正的NacosRegistry
doRegister(url);
} catch (Exception e) {
Throwable t = e;
....
}
}
}
public class NacosRegistry extends FailbackRegistry {
@Override
public void doRegister(URL url) {
execute(namingService -> namingService.registerInstance(serviceName,
getUrl().getParameter(GROUP_KEY, Constants.DEFAULT_GROUP), instance));
}
}
FailbackRegistry.register方法里面会调用NacosRegistry.doRegister。 这里就是注册的步骤了
FailbackRegistry.subscribe 获取节点信息和订阅节点信息
public abstract class FailbackRegistry extends AbstractRegistry {
@Override
public void subscribe(URL url, NotifyListener listener) {
super.subscribe(url, listener);
//移除失效的节点
removeFailedSubscribed(url, listener);
try {
// Sending a subscription request to the server side
//重新订阅节点
doSubscribe(url, listener);
} catch (Exception e) {
Throwable t = e;
List<URL> urls = getCacheUrls(url);
if (CollectionUtils.isNotEmpty(urls)) {
notify(url, listener, urls);
} else {
// If the startup detection is opened, the Exception is thrown directly.
boolean check = getUrl().getParameter(Constants.CHECK_KEY, true)
&& url.getParameter(Constants.CHECK_KEY, true);
boolean skipFailback = t instanceof SkipFailbackWrapperException;
if (check || skipFailback) {
if (skipFailback) {
t = t.getCause();
}
throw new IllegalStateException("Failed to subscribe " + url + ", cause: " + t.getMessage(), t);
} else {
logger.error("Failed to subscribe " + url + ", waiting for retry, cause: " + t.getMessage(), t);
}
}
// Record a failed registration request to a failed list, retry regularly
addFailedSubscribed(url, listener);
}
}
}
public class NacosRegistry extends FailbackRegistry {
@Override
public void doSubscribe(final URL url, final NotifyListener listener) {
Set<String> serviceNames = getServiceNames(url, listener);
//Set corresponding serviceNames for easy search later
if (isServiceNamesWithCompatibleMode(url)) {
for (String serviceName : serviceNames) {
NacosInstanceManageUtil.setCorrespondingServiceNames(serviceName, serviceNames);
}
}
doSubscribe(url, listener, serviceNames);
}
private void doSubscribe(final URL url, final NotifyListener listener, final Set<String> serviceNames) {
execute(namingService -> {
//是否普通 serviceInterface 订阅
if (isServiceNamesWithCompatibleMode(url)) {
List<Instance> allCorrespondingInstanceList = Lists.newArrayList();
for (String serviceName : serviceNames) {
List<Instance> instances = namingService.getAllInstances(serviceName,
getUrl().getParameter(GROUP_KEY, Constants.DEFAULT_GROUP));
NacosInstanceManageUtil.initOrRefreshServiceInstanceList(serviceName, instances);
allCorrespondingInstanceList.addAll(instances);
}
notifySubscriber(url, listener, allCorrespondingInstanceList);
for (String serviceName : serviceNames) {
//订阅。
subscribeEventListener(serviceName, url, listener);
}
} else {
....
}
});
}
}
doSubscribe(url, listener):
getServiceNames得到的集合如下显示：(serviceNames)
0 = "providers:com.onion.service.IUserService::"
1 = "providers:com.onion.service.IUserService"
然后调用 doSubscribe(url, listener, serviceNames); 进行订阅
doSubscribe(url, listener, serviceNames):
-
namingService.getAllInstances:通过serviceName作为参数得到instances，instances就是提供者的节点信息。 -
把得到的instance节点都放到allCorrespondingInstanceList集合里面，集合数据如下：
-
notifySubscriber：更新缓存中提供者的节点信息。 -
subscribeEventListener： 监听serviceName的节点的变化。
NacosRegistry.notifySubscriber更新节点信息
public class NacosRegistry extends FailbackRegistry {
private void notifySubscriber(URL url, NotifyListener listener, Collection<Instance> instances) {
List<Instance> healthyInstances = new LinkedList<>(instances);
if (healthyInstances.size() > 0) {
filterHealthyInstances(healthyInstances);
}
List<URL> urls = toUrlWithEmpty(url, healthyInstances);
NacosRegistry.this.notify(url, listener, urls);
}
}
public abstract class FailbackRegistry extends AbstractRegistry {
@Override
protected void notify(URL url, NotifyListener listener, List<URL> urls) {
try {
doNotify(url, listener, urls);
} catch (Exception t) {
// Record a failed registration request to a failed list, retry regularly
addFailedNotified(url, listener, urls);
logger.error("Failed to notify for subscribe " + url + ", waiting for retry, cause: " + t.getMessage(), t);
}
}
protected void doNotify(URL url, NotifyListener listener, List<URL> urls) {
super.notify(url, listener, urls);
}
}
public abstract class AbstractRegistry implements Registry {
protected void notify(URL url, NotifyListener listener, List<URL> urls) {
Map<String, List<URL>> result = new HashMap<>();
for (URL u : urls) {
//urls是从注册中心获取到的地址，u是消费者的地址
//拿到符合匹配的地址放到categoryList
if (UrlUtils.isMatch(url, u)) {
String category = u.getParameter(CATEGORY_KEY, DEFAULT_CATEGORY);
List<URL> categoryList = result.computeIfAbsent(category, k -> new ArrayList<>());
categoryList.add(u);
}
}
if (result.size() == 0) {
return;
}
Map<String, List<URL>> categoryNotified = notified.computeIfAbsent(url, u -> new ConcurrentHashMap<>());
//
for (Map.Entry<String, List<URL>> entry : result.entrySet()) {
String category = entry.getKey();
List<URL> categoryList = entry.getValue();
categoryNotified.put(category, categoryList);
//listener就是RegistryDirectory，进行更新
listener.notify(categoryList);
// We will update our cache file after each notification.
// When our Registry has a subscribe failure due to network jitter, we can return at least the existing cache URL.
//把这个url保存到本地文件中
saveProperties(url);
}
}
}
调用顺序NacosRegistry.notifySubscriber -> FailbackRegistry.doNotify -> AbstractRegistry.notify ,
AbstractRegistry.notify ：
- 把注册中心获取到的地址和消费者的地址进行一个匹配，符合规则的返回categoryList
- 把得到的categoryList保存到notified中。这个notified在saveProperties用到
listener.notify： 这里的listener就是RegistryDirectory，RegistryDirectory.notify- saveProperties: 把注册信息保存到本地系统中.下面有介绍请看标题
RegistryDirectory.notify
public class RegistryDirectory<T> extends AbstractDirectory<T> implements NotifyListener {
@Override
public synchronized void notify(List<URL> urls) {
Map<String, List<URL>> categoryUrls = urls.stream()
.filter(Objects::nonNull)
.filter(this::isValidCategory)
.filter(this::isNotCompatibleFor26x)
.collect(Collectors.groupingBy(this::judgeCategory));
List<URL> configuratorURLs = categoryUrls.getOrDefault("configurators", Collections.emptyList());
this.configurators = Configurator.toConfigurators(configuratorURLs).orElse(this.configurators);
List<URL> routerURLs = categoryUrls.getOrDefault("routers", Collections.emptyList());
toRouters(routerURLs).ifPresent(this::addRouters);
// providers
List<URL> providerURLs = categoryUrls.getOrDefault("providers", Collections.emptyList());
/**
* 3.x added for extend URL address
*/
...
refreshOverrideAndInvoker(providerURLs);
}
private void refreshOverrideAndInvoker(List<URL> urls) {
// mock zookeeper://xxx?mock=return null
//逐个调用注册中心里面的配置，覆盖原来的url，组成最新的url 放入overrideDirectoryUrl 存储，
//此时我们没有在dubbo-admin中修改任何配置，所以这里没必要去分析
overrideDirectoryUrl();
refreshInvoker(urls);
}
private void refreshInvoker(List<URL> invokerUrls) {
if (invokerUrls.size() == 1
&& invokerUrls.get(0) != null
&& EMPTY_PROTOCOL.equals(invokerUrls.get(0).getProtocol())) {
....
} else {
...
//通过urls生成newUrlInvokerMap
Map<String, Invoker<T>> newUrlInvokerMap = toInvokers(invokerUrls);//
//赋值
List<Invoker<T>> newInvokers = Collections.unmodifiableList(new ArrayList<>(newUrlInvokerMap.values()));
routerChain.setInvokers(newInvokers);
this.invokers = multiGroup ? toMergeInvokerList(newInvokers) : newInvokers;
this.urlInvokerMap = newUrlInvokerMap;
....
}
}
}
private Map<String, Invoker<T>> toInvokers(List<URL> urls) {
Map<String, Invoker<T>> newUrlInvokerMap = new HashMap<>();
if (urls == null || urls.isEmpty()) {
return newUrlInvokerMap;
}
Set<String> keys = new HashSet<>();
String queryProtocols = this.queryMap.get(PROTOCOL_KEY);
for (URL providerUrl : urls) {
....
//构建一个新的url
URL url = mergeUrl(providerUrl);
String key = url.toFullString(); // The parameter urls are sorted
if (keys.contains(key)) { // Repeated url
continue;
}
keys.add(key);
...
if (invoker == null) { // Not in the cache, refer again
try {
...
//新建invoker
invoker = new InvokerDelegate<>(protocol.refer(serviceType, url), url, providerUrl);
} catch (Throwable t) {
. ...
}
if (invoker != null) { // Put new invoker in cache
newUrlInvokerMap.put(key, invoker);
}
} else {
newUrlInvokerMap.put(key, invoker);
}
}
keys.clear();
return newUrlInvokerMap;
}
//把提供者的url和我的消费者的配置做一个整合
private URL mergeUrl(URL providerUrl) {
//queryMap是消费者的配置信息比如：application -> spring-boot-dubbo-consumer ，
//methods -> loginUser,getUser
providerUrl = ClusterUtils.mergeUrl(providerUrl, queryMap); // Merge the consumer side parameters
providerUrl = overrideWithConfigurator(providerUrl);
providerUrl = providerUrl.addParameter(Constants.CHECK_KEY, String.valueOf(false)); // Do not check whether the connection is successful or not, always create Invoker!
// The combination of directoryUrl and override is at the end of notify, which can't be handled here
this.overrideDirectoryUrl = this.overrideDirectoryUrl.addParametersIfAbsent(providerUrl.getParameters()); // Merge the provider side parameters
if ((providerUrl.getPath() == null || providerUrl.getPath()
.length() == 0) && DUBBO_PROTOCOL.equals(providerUrl.getProtocol())) { // Compatible version 1.0
//fix by tony.chenl DUBBO-44
String path = directoryUrl.getParameter(INTERFACE_KEY);
if (path != null) {
int i = path.indexOf('/');
if (i >= 0) {
path = path.substring(i + 1);
}
i = path.lastIndexOf(':');
if (i >= 0) {
path = path.substring(0, i);
}
providerUrl = providerUrl.setPath(path);
}
}
return providerUrl;
}
RegistryDirectory.notify:
-
获取urls中的参数为"configurators"，"routers"，"providers"的值
-
refreshOverrideAndInvoker(providerURLs): 是providerURLs是urls中的"providers"的参数值
refreshOverrideAndInvoker：
- overrideDirectoryUrl： 逐个调用注册中心里面的配置，覆盖原来的url，组成最新的url 放入overrideDirectoryUrl 存储，此时我们没有在dubbo-admin中修改任何配置，所以这里没必要去分析
- refreshInvoker： 刷新Invoker
refreshInvoker:
- 通过 toInvokers(invokerUrls)方法把url生成Invoker集合Map。名字为：newUrlInvokerMap
- 把生成的newUrlInvokerMap给
this.invokers，this.urlInvokerMap赋值
toInvokers:
- 遍历所有的提供者的地址
mergeUrl(providerUrl)：把提供者的url和我的消费者的配置做一个整合。ClusterUtils.mergeUrl(providerUrl, queryMap)里面的queryMap的数据如下：
new InvokerDelegate<>(protocol.refer(serviceType, url), url, providerUrl): 新建invoker- 构造newUrlInvokerMap返回
protocol.refer(serviceType, url)
url的地址协议是dubbo，这里应该是调用DubboProtocol.refer。（AbstractProtocol是DubboProtocol的父类）
public abstract class AbstractProtocol implements Protocol {
public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
//把返回的invoker再包装一层返回
return new AsyncToSyncInvoker(this.protocolBindingRefer(type, url));
}
}
public class DubboProtocol extends AbstractProtocol {
public <T> Invoker<T> protocolBindingRefer(Class<T> serviceType, URL url) throws RpcException {
this.optimizeSerialization(url);
DubboInvoker<T> invoker = new DubboInvoker(serviceType, url, this.getClients(url), this.invokers);
this.invokers.add(invoker);
return invoker;
}
private ExchangeClient[] getClients(URL url) {
boolean useShareConnect = false;
int connections = url.getParameter("connections", 0);
...一些connections判断...
ExchangeClient[] clients = new ExchangeClient[connections];
for(int i = 0; i < clients.length; ++i) {
if (useShareConnect) {
clients[i] = (ExchangeClient)shareClients.get(i);
} else {
//初始化客户端
clients[i] = this.initClient(url);
}
}
return clients;
}
private ExchangeClient initClient(URL url) {
try {
Object client;
if (url.getParameter("lazy", false)) {
client = new LazyConnectExchangeClient(url, this.requestHandler);
} else {
//链接提供者
client = Exchangers.connect(url, this.requestHandler);
}
return (ExchangeClient)client;
} catch (RemotingException var5) {
throw new RpcException("Fail to create remoting client for service(" + url + "): " + var5.getMessage(), var5);
}
}
}
}
执行的过程： AbstractProtocol.refer -> DubboProtocol.protocolBindingRefer
DubboProtocol.protocolBindingRefer: 会首先调用initClient 得到客户端信息的信息，然后构建DubboInvoker，最后返回DubboInvoker。
initClient： 就是获取相应的Exchangers。去做连接 Exchangers.connect(url, this.requestHandler);
Exchangers继续往下执行连接：
public class Exchangers {
public static ExchangeClient connect(URL url, ExchangeHandler handler) throws RemotingException {
url = url.addParameterIfAbsent("codec", "exchange");
return getExchanger(url).connect(url, handler);
}
}
public class HeaderExchanger implements Exchanger {
public static final String NAME = "header";
public HeaderExchanger() {
}
public ExchangeClient connect(URL url, ExchangeHandler handler) throws RemotingException {
return new HeaderExchangeClient(Transporters.connect(url, new ChannelHandler[]{new DecodeHandler(new HeaderExchangeHandler(handler))}), true);
}
}
public class Transporters {
static {
// check duplicate jar package
Version.checkDuplicate(Transporters.class);
Version.checkDuplicate(RemotingException.class);
}
private Transporters() {
}
public static Client connect(URL url, ChannelHandler... handlers) throws RemotingException {
return getTransporter().connect(url, handler);
}
public static Transporter getTransporter() {
return ExtensionLoader.getExtensionLoader(Transporter.class).getAdaptiveExtension();
}
}
public class NettyTransporter implements Transporter {
public static final String NAME = "netty";
@Override
public Client connect(URL url, ChannelHandler handler) throws RemotingException {
return new NettyClient(url, handler);
}
}
public class NettyClient extends AbstractClient {
public NettyClient(final URL url, final ChannelHandler handler) throws RemotingException {
super(url, wrapChannelHandler(url, handler));
}
}
public abstract class AbstractClient extends AbstractEndpoint implements Client {
protected static final String CLIENT_THREAD_POOL_NAME = "DubboClientHandler";
private static final Logger logger = LoggerFactory.getLogger(AbstractClient.class);
private final Lock connectLock = new ReentrantLock();
private final boolean needReconnect;
protected volatile ExecutorService executor;
private ExecutorRepository executorRepository = ExtensionLoader.getExtensionLoader(ExecutorRepository.class).getDefaultExtension();
public AbstractClient(URL url, ChannelHandler handler) throws RemotingException {
super(url, handler);
needReconnect = url.getParameter(Constants.SEND_RECONNECT_KEY, false);
initExecutor(url);
try {
doOpen();
} catch (Throwable t) {
close();
}
try {
// connect.
connect();
...
}
}
Exchangers.connect -> Transporters.connect ->NettyTransporter.connect -> 新建NettyClient对象 。
NettyClient的构建方法：doOpen() --- connect()
AbstractRegistry.saveProperties保存提供者信息到文件系统
public abstract class AbstractRegistry implements Registry {
private final ExecutorService registryCacheExecutor = Executors.newFixedThreadPool(1, new NamedThreadFactory("DubboSaveRegistryCache", true));
public AbstractRegistry(URL url) {
setUrl(url);
if (url.getParameter("file.cache", true)) {
// Start file save timer
syncSaveFile = url.getParameter("file.cache", false);
//默认为的文件名字
String defaultFilename = System.getProperty("user.home") + "/.dubbo/dubbo-registry-" + url.getParameter("application") + "-" + url.getAddress().replaceAll(":", "-") + ".cache";
String filename = url.getParameter("file", defaultFilename);
File file = null;
if (ConfigUtils.isNotEmpty(filename)) {
file = new File(filename);
//判断文件是否有效。。
}
this.file = file;
// When starting the subscription center,
// we need to read the local cache file for future Registry fault tolerance processing.
loadProperties();
notify(url.getBackupUrls());
}
}
private void saveProperties(URL url) {
if (file == null) {
return;
}
try {
StringBuilder buf = new StringBuilder();
//AbstractRegistry.notify引用位置，获取提供者的map列表
Map<String, List<URL>> categoryNotified = notified.get(url);
if (categoryNotified != null) {
for (List<URL> us : categoryNotified.values()) {
for (URL u : us) {
if (buf.length() > 0) {
buf.append(URL_SEPARATOR);
}
buf.append(u.toFullString());
}
}
}
properties.setProperty(url.getServiceKey(), buf.toString());
long version = lastCacheChanged.incrementAndGet();
//是否要同步保存到文件里
if (syncSaveFile) {
doSaveProperties(version);
} else {
//异步保存到文件，registryCacheExecutor线程池，开一个线程来执行doSaveProperties(version)
registryCacheExecutor.execute(new SaveProperties(version));
}
} catch (Throwable t) {
logger.warn(t.getMessage(), t);
}
}
private class SaveProperties implements Runnable {
private long version;
private SaveProperties(long version) {
this.version = version;
}
@Override
public void run() {
doSaveProperties(version);
}
}
}
AbstractRegistry构造的时候：会从url参数中获取"file.cache"的值来判断是否要把提供者的信息保存到文件中，需要的话默认路径为：
默认路径：
System.getProperty("user.home") + "/.dubbo/dubbo-registry-" + url.getParameter("application") + "-" + url.getAddress().replaceAll(":", "-") + ".cache";
为了更好理解，我用debug把路径打印出来如下：
C:\Users\p\.dubbo\dubbo-registry-spring-boot-dubbo-consumer-127.0.0.1-8848.cache
也可以自己指定文件的路径，只需要在url中加入file参数就行，比如：file=/tmp/spring-boot-dubbo-consumer.cache
saveProperties：notified.get(url)获取提供者的信息，然后拼接成字符串，最后执行doSaveProperties(version);把拼接的字符串保存到文件里面。
notified.get(url)引用的位置：AbstractRegistry.notify
保存起来的文件如下：
#Dubbo Registry Cache
#Tue Nov 10 17:19:26 CST 2020
com.onion.service.IUserService=dubbo\://192.168.56.1\:20880/com.onion.service.IUserService?anyhost\=true&application\=spring-boot-dubbo-provider&category\=providers&deprecated\=false&dubbo\=2.0.2&dynamic\=true&generic\=false&getUser.retries\=2&getUser.return\=true&interface\=com.onion.service.IUserService&metadata-type\=remote&methods\=loginUser,getUser&path\=com.onion.service.IUserService&pid\=23732&protocol\=dubbo&release\=2.7.8&side\=provider×tamp\=1604998712794
subscribeEventListener订阅节点信息
public class NacosRegistry extends FailbackRegistry {
private void subscribeEventListener(String serviceName, final URL url, final NotifyListener listener)
throws NacosException {
EventListener eventListener = event -> {
if (event instanceof NamingEvent) {
NamingEvent e = (NamingEvent) event;
List<Instance> instances = e.getInstances();
if (isServiceNamesWithCompatibleMode(url)) {
NacosInstanceManageUtil.initOrRefreshServiceInstanceList(serviceName, instances);
instances = NacosInstanceManageUtil.getAllCorrespondingServiceInstanceList(serviceName);
}
notifySubscriber(url, listener, instances);
}
};
namingService.subscribe(serviceName,
getUrl().getParameter("group", "DEFAULT_GROUP"),
eventListener);
}
}
NacosNamingService是com.alibaba.nacos.client.naming包下的，象征着终于使用了nacos-client的相关类了，到这里就是nacos订阅的内容，我就不再往下走了
public class NacosNamingService implements NamingService {
public void subscribe(String serviceName, String groupName, EventListener listener) throws NacosException {
this.subscribe(serviceName, groupName, new ArrayList(), listener);
}
NacosRegistry.subscribeEventListener:
- namingService.subscribe: 订阅nacos中的节点的变化，如果节点发生变化
eventListener监听器 - eventListener：回调的监听器的时候，调用notifySubscriber(url, listener, instances)，instances就是变化的节点信息，这个方法上面已经说过了，功能就是更新节点的信息
结尾：
还有PROXY_FACTORY.getProxy构建代理类没有讲，下一篇主要是讲PROXY_FACTORY.getProxy的构建，和依赖注入对象的调用过程
附上一个消费端的高清图：
图片下载地址：https://gitee.com/gzgyc/blogimage/raw/master/dubbo服务消费.png
