SpringCloud @RefreshScope刷新机制是什么

今天小编给大家分享一下SpringCloud @RefreshScope刷新机制是什么的相关知识点，内容详细，逻辑清晰，相信大部分人都还太了解这方面的知识，所以分享这篇文章给大家参考一下，希望大家阅读完这篇文章后有所收获，下面我们一起来了解一下吧。

在学习 nacos 的配置修改发现用到了 @RefreshScope 注解，将 spring boot 的日志调整如下

logging:
  level:
    com:
      alibaba:
        cloud: debug
    org:
      springframework:
        context: debug
        cloud: debug

调用 nacos 的配置修改，看到如下信息

2023-03-10 15:48:15.332 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] com.alibaba.nacos.client.config.impl.ClientWorker Caller+0     at com.alibaba.nacos.client.config.impl.ClientWorker.parseUpdateDataIdResponse(ClientWorker.java:486)
 - [fixed-node1.hahaou.cn_8848] [polling-resp] config changed. dataId=soft-jraft-apache-derby-config-test.yaml, group=DEFAULT_GROUP
2023-03-10 15:48:15.333 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] com.alibaba.nacos.client.config.impl.ClientWorker Caller+0     at com.alibaba.nacos.client.config.impl.ClientWorker$LongPollingRunnable.run(ClientWorker.java:598)
 - get changedGroupKeys:[soft-jraft-apache-derby-config-test.yaml+DEFAULT_GROUP]
2023-03-10 15:48:15.400 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] com.alibaba.nacos.client.config.impl.ClientWorker Caller+0     at com.alibaba.nacos.client.config.impl.ClientWorker$LongPollingRunnable.run(ClientWorker.java:616)
 - [fixed-node1.hahaou.cn_8848] [data-received] dataId=soft-jraft-apache-derby-config-test.yaml, group=DEFAULT_GROUP, tenant=null, md5=5f214678315ac83144e77f4c4b3b3416, content=spring:
  youxia:
    config:
      name: test, type=
2023-03-10 15:48:15.400 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] com.alibaba.nacos.client.config.impl.CacheData Caller+0     at com.alibaba.nacos.client.config.impl.CacheData$1.run(CacheData.java:199)
 - [fixed-node1.hahaou.cn_8848] [notify-context] dataId=soft-jraft-apache-derby-config-test.yaml, group=DEFAULT_GROUP, md5=5f214678315ac83144e77f4c4b3b3416
2023-03-10 15:48:15.401 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.cloud.endpoint.event.RefreshEventListener Caller+0     at org.springframework.cloud.endpoint.event.RefreshEventListener.handle(RefreshEventListener.java:71)
 - Event received Refresh Nacos config
2023-03-10 15:48:17.002 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.c.a.AnnotationConfigApplicationContext Caller+0     at org.springframework.context.support.AbstractApplicationContext.prepareRefresh(AbstractApplicationContext.java:596)
 - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@653cd99a
2023-03-10 15:48:18.632 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] c.a.cloud.nacos.client.NacosPropertySourceBuilder Caller+0     at com.alibaba.cloud.nacos.client.NacosPropertySourceBuilder.loadNacosData(NacosPropertySourceBuilder.java:93)
 - Loading nacos data, dataId: 'soft-jraft-apache-derby-config-test.yaml', group: 'DEFAULT_GROUP', data: spring:
  youxia:
    config:
      name: test
2023-03-10 15:48:18.706 WARN [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] c.a.cloud.nacos.client.NacosPropertySourceBuilder Caller+0     at com.alibaba.cloud.nacos.client.NacosPropertySourceBuilder.loadNacosData(NacosPropertySourceBuilder.java:87)
 - Ignore the empty nacos configuration and get it based on dataId[soft-jraft-apache-derby-config] & group[DEFAULT_GROUP]
2023-03-10 15:48:18.789 WARN [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] c.a.cloud.nacos.client.NacosPropertySourceBuilder Caller+0     at com.alibaba.cloud.nacos.client.NacosPropertySourceBuilder.loadNacosData(NacosPropertySourceBuilder.java:87)
 - Ignore the empty nacos configuration and get it based on dataId[soft-jraft-apache-derby-config.properties] & group[DEFAULT_GROUP]
2023-03-10 15:48:18.790 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.c.b.c.PropertySourceBootstrapConfiguration Caller+0     at org.springframework.cloud.bootstrap.config.PropertySourceBootstrapConfiguration.initialize(PropertySourceBootstrapConfiguration.java:112)
 - Located property source: [BootstrapPropertySource@1783236684 {name='bootstrapProperties-soft-jraft-apache-derby-config.properties,DEFAULT_GROUP', properties={}}, BootstrapPropertySource@942001677 {name='bootstrapProperties-soft-jraft-apache-derby-config,DEFAULT_GROUP', properties={}}, BootstrapPropertySource@1637255792 {name='bootstrapProperties-soft-jraft-apache-derby-config-test.yaml,DEFAULT_GROUP', properties={spring.youxia.config.name=test}}]
2023-03-10 15:48:18.800 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] org.springframework.boot.SpringApplication Caller+0     at org.springframework.boot.SpringApplication.logStartupProfileInfo(SpringApplication.java:651)
 - No active profile set, falling back to default profiles: default
2023-03-10 15:48:18.801 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.c.a.AnnotationConfigApplicationContext Caller+0     at org.springframework.context.support.AbstractApplicationContext.prepareRefresh(AbstractApplicationContext.java:596)
 - Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@6709b8b
2023-03-10 15:48:18.806 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] org.springframework.boot.SpringApplication Caller+0     at org.springframework.boot.StartupInfoLogger.logStarted(StartupInfoLogger.java:61)
 - Started application in 3.403 seconds (JVM running for 54.758)
2023-03-10 15:48:18.807 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.c.a.AnnotationConfigApplicationContext Caller+0     at org.springframework.context.support.AbstractApplicationContext.doClose(AbstractApplicationContext.java:1006)
 - Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@6709b8b, started on Fri Mar 10 15:48:18 CST 2023, parent: org.springframework.context.annotation.AnnotationConfigApplicationContext@653cd99a
2023-03-10 15:48:18.808 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.c.a.AnnotationConfigApplicationContext Caller+0     at org.springframework.context.support.AbstractApplicationContext.doClose(AbstractApplicationContext.java:1006)
 - Closing org.springframework.context.annotation.AnnotationConfigApplicationContext@653cd99a, started on Fri Mar 10 15:48:17 CST 2023
2023-03-10 15:48:18.819 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] o.s.cloud.endpoint.event.RefreshEventListener Caller+0     at org.springframework.cloud.endpoint.event.RefreshEventListener.handle(RefreshEventListener.java:73)
 - Refresh keys changed: [spring.youxia.config.name]
2023-03-10 15:48:18.820 DEBUG [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] c.a.cloud.nacos.refresh.NacosContextRefresher Caller+0     at com.alibaba.cloud.nacos.refresh.NacosContextRefresher$1.innerReceive(NacosContextRefresher.java:136)
 - Refresh Nacos config group=DEFAULT_GROUP,dataId=soft-jraft-apache-derby-config-test.yaml,configInfo=spring:
  youxia:
    config:
      name: test
2023-03-10 15:48:18.820 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] com.alibaba.nacos.client.config.impl.CacheData Caller+0     at com.alibaba.nacos.client.config.impl.CacheData$1.run(CacheData.java:222)
 - [fixed-node1.hahaou.cn_8848] [notify-ok] dataId=soft-jraft-apache-derby-config-test.yaml, group=DEFAULT_GROUP, md5=5f214678315ac83144e77f4c4b3b3416, listener=com.alibaba.cloud.nacos.refresh.NacosContextRefresher$1@59af462e 
2023-03-10 15:48:18.820 INFO [com.alibaba.nacos.client.Worker.longPolling.fixed-node1.hahaou.cn_8848] com.alibaba.nacos.client.config.impl.CacheData Caller+0     at com.alibaba.nacos.client.config.impl.CacheData.safeNotifyListener(CacheData.java:248)
 - [fixed-node1.hahaou.cn_8848] [notify-listener] time cost=3420ms in ClientWorker, dataId=soft-jraft-apache-derby-config-test.yaml, group=DEFAULT_GROUP, md5=5f214678315ac83144e77f4c4b3b3416, listener=com.alibaba.cloud.nacos.refresh.NacosContextRefresher$1@59af462e 
使用Spring Cloud Alibaba接入Nacos配置中心，获取配置信息name为：test
使用Spring Cloud Alibaba接入Nacos配置中心，获取配置信息value为：null

得知保存配置后进行了 jvm 重启。

梳理过程如下

@RefreshScope

package org.springframework.cloud.context.config.annotation;import java.lang.annotation.Documented;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;import org.springframework.context.annotation.Scope;import org.springframework.context.annotation.ScopedProxyMode;@Target({ ElementType.TYPE, ElementType.METHOD })@Retention(RetentionPolicy.RUNTIME)@Scope("refresh")@Documentedpublic @interface RefreshScope {        ScopedProxyMode proxyMode() default ScopedProxyMode.TARGET_CLASS;}

可以得知，@RefreshScope 是一个 scopeName 为 refresh 的 @Scope。

ScopedProxyMode

package org.springframework.context.annotation;public enum ScopedProxyMode {        DEFAULT,        NO,        INTERFACES,        TARGET_CLASS}

由枚举 ScopedProxyMode 得知，ScopedProxyMode.TARGET_CLASS 通过 cglib 生成一个代理类进行字节码增强

RefreshAutoConfiguration

部分源码如下

package org.springframework.cloud.autoconfigure;import java.util.HashSet;import java.util.Set;import javax.annotation.PostConstruct;import org.springframework.aop.scope.ScopedProxyUtils;import org.springframework.beans.BeansException;import org.springframework.beans.factory.BeanFactory;import org.springframework.beans.factory.ListableBeanFactory;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.beans.factory.config.BeanDefinition;import org.springframework.beans.factory.config.BeanDefinitionHolder;import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;import org.springframework.beans.factory.support.BeanDefinitionRegistry;import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;import org.springframework.boot.autoconfigure.AutoConfigureBefore;import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;import org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration;import org.springframework.boot.context.properties.bind.Bindable;import org.springframework.boot.context.properties.bind.Binder;import org.springframework.cloud.context.refresh.ContextRefresher;import org.springframework.cloud.context.scope.refresh.RefreshScope;import org.springframework.cloud.endpoint.event.RefreshEventListener;import org.springframework.cloud.logging.LoggingRebinder;import org.springframework.context.ConfigurableApplicationContext;import org.springframework.context.EnvironmentAware;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.context.weaving.LoadTimeWeaverAware;import org.springframework.core.env.Environment;import org.springframework.core.env.StandardEnvironment;import org.springframework.instrument.classloading.LoadTimeWeaver;import org.springframework.stereotype.Component;import org.springframework.util.StringUtils;@Configuration(proxyBeanMethods = false)@ConditionalOnClass(RefreshScope.class)@ConditionalOnProperty(name = RefreshAutoConfiguration.REFRESH_SCOPE_ENABLED,        matchIfMissing = true)@AutoConfigureBefore(HibernateJpaAutoConfiguration.class)public class RefreshAutoConfiguration {        public static final String REFRESH_SCOPE_NAME = "refresh";        public static final String REFRESH_SCOPE_PREFIX = "spring.cloud.refresh";        public static final String REFRESH_SCOPE_ENABLED = REFRESH_SCOPE_PREFIX + ".enabled";    @Bean    @ConditionalOnMissingBean(RefreshScope.class)    public static RefreshScope refreshScope() {        return new RefreshScope();    }    @Bean    @ConditionalOnMissingBean    public static LoggingRebinder loggingRebinder() {        return new LoggingRebinder();    }    @Bean    @ConditionalOnMissingBean    public ContextRefresher contextRefresher(ConfigurableApplicationContext context,            RefreshScope scope) {        return new ContextRefresher(context, scope);    }    @Bean    public RefreshEventListener refreshEventListener(ContextRefresher contextRefresher) {        return new RefreshEventListener(contextRefresher);    }}

@ConditionalOnProperty(name = RefreshAutoConfiguration.REFRESH_SCOPE_ENABLED,        matchIfMissing = true)

通过上面的注解得知，自动刷新在 spring cloud 中默认启用

nacos中添加配置

NacosConfigService

public NacosConfigService(Properties properties) throws NacosException {    ValidatorUtils.checkInitParam(properties);    String encodeTmp = properties.getProperty(PropertyKeyConst.ENCODE);    if (StringUtils.isBlank(encodeTmp)) {        this.encode = Constants.ENCODE;    } else {        this.encode = encodeTmp.trim();    }    initNamespace(properties);    this.agent = new MetricsHttpAgent(new ServerHttpAgent(properties));    this.agent.start();    this.worker = new ClientWorker(this.agent, this.configFilterChainManager, properties);}

NacosConfigService 构造器创建 ClientWorker 对象

ClientWorker

public ClientWorker(final HttpAgent agent, final ConfigFilterChainManager configFilterChainManager,        final Properties properties) {    this.agent = agent;    this.configFilterChainManager = configFilterChainManager;    // Initialize the timeout parameter    init(properties);    this.executor = Executors.newScheduledThreadPool(1, new ThreadFactory() {        @Override        public Thread newThread(Runnable r) {            Thread t = new Thread(r);            t.setName("com.alibaba.nacos.client.Worker." + agent.getName());            t.setDaemon(true);            return t;        }    });    this.executorService = Executors            .newScheduledThreadPool(Runtime.getRuntime().availableProcessors(), new ThreadFactory() {                @Override                public Thread newThread(Runnable r) {                    Thread t = new Thread(r);                    t.setName("com.alibaba.nacos.client.Worker.longPolling." + agent.getName());                    t.setDaemon(true);                    return t;                }            });    this.executor.scheduleWithFixedDelay(new Runnable() {        @Override        public void run() {            try {                checkConfigInfo();            } catch (Throwable e) {                LOGGER.error("[" + agent.getName() + "] [sub-check] rotate check error", e);            }        }    }, 1L, 10L, TimeUnit.MILLISECONDS);}public void checkConfigInfo() {    // Dispatch taskes.    int listenerSize = cacheMap.size();    // Round up the longingTaskCount.    int longingTaskCount = (int) Math.ceil(listenerSize / ParamUtil.getPerTaskConfigSize());    if (longingTaskCount > currentLongingTaskCount) {        for (int i = (int) currentLongingTaskCount; i < longingTaskCount; i++) {            // The task list is no order.So it maybe has issues when changing.            executorService.execute(new LongPollingRunnable(i));        }        currentLongingTaskCount = longingTaskCount;    }}class LongPollingRunnable implements Runnable {    private final int taskId;    public LongPollingRunnable(int taskId) {        this.taskId = taskId;    }    @Override    public void run() {        List<CacheData> cacheDatas = new ArrayList<CacheData>();        List<String> inInitializingCacheList = new ArrayList<String>();        try {            // check failover config            for (CacheData cacheData : cacheMap.values()) {                if (cacheData.getTaskId() == taskId) {                    cacheDatas.add(cacheData);                    try {                        checkLocalConfig(cacheData);                        if (cacheData.isUseLocalConfigInfo()) {                            cacheData.checkListenerMd5();                        }                    } catch (Exception e) {                        LOGGER.error("get local config info error", e);                    }                }            }            // check server config            List<String> changedGroupKeys = checkUpdateDataIds(cacheDatas, inInitializingCacheList);            if (!CollectionUtils.isEmpty(changedGroupKeys)) {                LOGGER.info("get changedGroupKeys:" + changedGroupKeys);            }            for (String groupKey : changedGroupKeys) {                String[] key = GroupKey.parseKey(groupKey);                String dataId = key[0];                String group = key[1];                String tenant = null;                if (key.length == 3) {                    tenant = key[2];                }                try {                    String[] ct = getServerConfig(dataId, group, tenant, 3000L);                    CacheData cache = cacheMap.get(GroupKey.getKeyTenant(dataId, group, tenant));                    cache.setContent(ct[0]);                    if (null != ct[1]) {                        cache.setType(ct[1]);                    }                    LOGGER.info("[{}] [data-received] dataId={}, group={}, tenant={}, md5={}, content={}, type={}",                            agent.getName(), dataId, group, tenant, cache.getMd5(),                            ContentUtils.truncateContent(ct[0]), ct[1]);                } catch (NacosException ioe) {                    String message = String                            .format("[%s] [get-update] get changed config exception. dataId=%s, group=%s, tenant=%s",                                    agent.getName(), dataId, group, tenant);                    LOGGER.error(message, ioe);                }            }            for (CacheData cacheData : cacheDatas) {                if (!cacheData.isInitializing() || inInitializingCacheList                        .contains(GroupKey.getKeyTenant(cacheData.dataId, cacheData.group, cacheData.tenant))) {                    cacheData.checkListenerMd5();                    cacheData.setInitializing(false);                }            }            inInitializingCacheList.clear();            executorService.execute(this);        } catch (Throwable e) {            // If the rotation training task is abnormal, the next execution time of the task will be punished            LOGGER.error("longPolling error : ", e);            executorService.schedule(this, taskPenaltyTime, TimeUnit.MILLISECONDS);        }    }}

ClientWorker checkConfigInfo() 中通过线程池创建 LongPollingRunnable 对象，线程池名称前缀为 com.alibaba.nacos.client.Worker.longPolling

CacheData

void checkListenerMd5() {    for (ManagerListenerWrap wrap : listeners) {        if (!md5.equals(wrap.lastCallMd5)) {            safeNotifyListener(dataId, group, content, type, md5, wrap);        }    }}private void safeNotifyListener(final String dataId, final String group, final String content, final String type,        final String md5, final ManagerListenerWrap listenerWrap) {    final Listener listener = listenerWrap.listener;    Runnable job = new Runnable() {        @Override        public void run() {            ClassLoader myClassLoader = Thread.currentThread().getContextClassLoader();            ClassLoader appClassLoader = listener.getClass().getClassLoader();            try {                if (listener instanceof AbstractSharedListener) {                    AbstractSharedListener adapter = (AbstractSharedListener) listener;                    adapter.fillContext(dataId, group);                    LOGGER.info("[{}] [notify-context] dataId={}, group={}, md5={}", name, dataId, group, md5);                }                // 执行回调之前先将线程classloader设置为具体webapp的classloader，以免回调方法中调用spi接口是出现异常或错用（多应用部署才会有该问题）。                Thread.currentThread().setContextClassLoader(appClassLoader);                ConfigResponse cr = new ConfigResponse();                cr.setDataId(dataId);                cr.setGroup(group);                cr.setContent(content);                configFilterChainManager.doFilter(null, cr);                String contentTmp = cr.getContent();                listener.receiveConfigInfo(contentTmp);                // compare lastContent and content                if (listener instanceof AbstractConfigChangeListener) {                    Map data = ConfigChangeHandler.getInstance()                            .parseChangeData(listenerWrap.lastContent, content, type);                    ConfigChangeEvent event = new ConfigChangeEvent(data);                    ((AbstractConfigChangeListener) listener).receiveConfigChange(event);                    listenerWrap.lastContent = content;                }                listenerWrap.lastCallMd5 = md5;                LOGGER.info("[{}] [notify-ok] dataId={}, group={}, md5={}, listener={} ", name, dataId, group, md5,                        listener);            } catch (NacosException ex) {                LOGGER.error("[{}] [notify-error] dataId={}, group={}, md5={}, listener={} errCode={} errMsg={}",                        name, dataId, group, md5, listener, ex.getErrCode(), ex.getErrMsg());            } catch (Throwable t) {                LOGGER.error("[{}] [notify-error] dataId={}, group={}, md5={}, listener={} tx={}", name, dataId,                        group, md5, listener, t.getCause());            } finally {                Thread.currentThread().setContextClassLoader(myClassLoader);            }        }    };    final long startNotify = System.currentTimeMillis();    try {        if (null != listener.getExecutor()) {            listener.getExecutor().execute(job);        } else {            job.run();        }    } catch (Throwable t) {        LOGGER.error("[{}] [notify-error] dataId={}, group={}, md5={}, listener={} throwable={}", name, dataId,                group, md5, listener, t.getCause());    }    final long finishNotify = System.currentTimeMillis();    LOGGER.info("[{}] [notify-listener] time cost={}ms in ClientWorker, dataId={}, group={}, md5={}, listener={} ",            name, (finishNotify - startNotify), dataId, group, md5, listener);}

调用 CacheData 的 checkListenerMd5()

AbstractSharedListener

public abstract class AbstractSharedListener implements Listener {    private volatile String dataId;    private volatile String group;    public final void fillContext(String dataId, String group) {        this.dataId = dataId;        this.group = group;    }    @Override    public final void receiveConfigInfo(String configInfo) {        innerReceive(dataId, group, configInfo);    }    @Override    public Executor getExecutor() {        return null;    }        public abstract void innerReceive(String dataId, String group, String configInfo);}

调用 AbstractSharedListener 的 receiveConfigInfo()，在 NacosContextRefresher 的 registerNacosListener() 中进行实现

NacosContextRefresher

private void registerNacosListener(final String groupKey, final String dataKey) {    String key = NacosPropertySourceRepository.getMapKey(dataKey, groupKey);    Listener listener = listenerMap.computeIfAbsent(key,            lst -> new AbstractSharedListener() {                @Override                public void innerReceive(String dataId, String group,                        String configInfo) {                    refreshCountIncrement();                    nacosRefreshHistory.addRefreshRecord(dataId, group, configInfo);                    // todo feature: support single refresh for listening                    applicationContext.publishEvent(                            new RefreshEvent(this, null, "Refresh Nacos config"));                    if (log.isDebugEnabled()) {                        log.debug(String.format(                                "Refresh Nacos config group=%s,dataId=%s,configInfo=%s",                                group, dataId, configInfo));                    }                }            });    try {        configService.addListener(dataKey, groupKey, listener);    }    catch (NacosException e) {        log.warn(String.format(                "register fail for nacos listener ,dataId=[%s],group=[%s]", dataKey,                groupKey), e);    }}

最终通过 ApplicationContext 发布事件 RefreshEvent

至此，nacos 逻辑执行完毕。

RefreshEventListener

public class RefreshEventListener implements SmartApplicationListener {    private static Log log = LogFactory.getLog(RefreshEventListener.class);    private ContextRefresher refresh;    private AtomicBoolean ready = new AtomicBoolean(false);    public RefreshEventListener(ContextRefresher refresh) {        this.refresh = refresh;    }    @Override    public boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {        return ApplicationReadyEvent.class.isAssignableFrom(eventType)                || RefreshEvent.class.isAssignableFrom(eventType);    }    @Override    public void onApplicationEvent(ApplicationEvent event) {        if (event instanceof ApplicationReadyEvent) {            handle((ApplicationReadyEvent) event);        }        else if (event instanceof RefreshEvent) {            handle((RefreshEvent) event);        }    }    public void handle(ApplicationReadyEvent event) {        this.ready.compareAndSet(false, true);    }    public void handle(RefreshEvent event) {        if (this.ready.get()) { // don't handle events before app is ready            log.debug("Event received " + event.getEventDesc());            Set<String> keys = this.refresh.refresh();            log.info("Refresh keys changed: " + keys);        }    }}

调用 RefreshEventListener 的 onApplicationEvent()，事件对象为 RefreshEvent。

执行完可以看到打印了日志

Event received Refresh Nacos config

后面调用 ContextRefresher 的 refresh()

ContextRefresher

public synchronized Set<String> refresh() {    Set<String> keys = refreshEnvironment();    this.scope.refreshAll();    return keys;}public synchronized Set<String> refreshEnvironment() {    Map<String, Object> before = extract(            this.context.getEnvironment().getPropertySources());    addConfigFilesToEnvironment();    Set<String> keys = changes(before,            extract(this.context.getEnvironment().getPropertySources())).keySet();    this.context.publishEvent(new EnvironmentChangeEvent(this.context, keys));    return keys;} ConfigurableApplicationContext addConfigFilesToEnvironment() {    ConfigurableApplicationContext capture = null;    try {        StandardEnvironment environment = copyEnvironment(                this.context.getEnvironment());        SpringApplicationBuilder builder = new SpringApplicationBuilder(Empty.class)                .bannerMode(Mode.OFF).web(WebApplicationType.NONE)                .environment(environment);        // Just the listeners that affect the environment (e.g. excluding logging        // listener because it has side effects)        builder.application()                .setListeners(Arrays.asList(new BootstrapApplicationListener(),                        new ConfigFileApplicationListener()));        capture = builder.run();        if (environment.getPropertySources().contains(REFRESH_ARGS_PROPERTY_SOURCE)) {            environment.getPropertySources().remove(REFRESH_ARGS_PROPERTY_SOURCE);        }        MutablePropertySources target = this.context.getEnvironment()                .getPropertySources();        String targetName = null;        for (PropertySource<?> source : environment.getPropertySources()) {            String name = source.getName();            if (target.contains(name)) {                targetName = name;            }            if (!this.standardSources.contains(name)) {                if (target.contains(name)) {                    target.replace(name, source);                }                else {                    if (targetName != null) {                        target.addAfter(targetName, source);                        // update targetName to preserve ordering                        targetName = name;                    }                    else {                        // targetName was null so we are at the start of the list                        target.addFirst(source);                        targetName = name;                    }                }            }        }    }    finally {        ConfigurableApplicationContext closeable = capture;        while (closeable != null) {            try {                closeable.close();            }            catch (Exception e) {                // Ignore;            }            if (closeable.getParent() instanceof ConfigurableApplicationContext) {                closeable = (ConfigurableApplicationContext) closeable.getParent();            }            else {                break;            }        }    }    return capture;}

refreshEnvironment() 中执行如下操作

addConfigFilesToEnvironment() 添加到配置文件到环境中，发布一系列事件 BootstrapApplicationListener、ConfigFileApplicationListener

调用 EventPublishingRunListener 的发布一系列事件进行 jvm 的重启相关操作，其中 EventPublishingRunListener 是默认的监听器，在 spring boot 的 META-INF/spring.factories 中进行了指定

# Run Listeners
org.springframework.boot.SpringApplicationRunListener=\
org.springframework.boot.context.event.EventPublishingRunListener

EventPublishingRunListener

public class EventPublishingRunListener implements SpringApplicationRunListener, Ordered {    private final SpringApplication application;    private final String[] args;    private final SimpleApplicationEventMulticaster initialMulticaster;    public EventPublishingRunListener(SpringApplication application, String[] args) {        this.application = application;        this.args = args;        this.initialMulticaster = new SimpleApplicationEventMulticaster();        for (ApplicationListener<?> listener : application.getListeners()) {            this.initialMulticaster.addApplicationListener(listener);        }    }    @Override    public int getOrder() {        return 0;    }    @Override    public void starting() {        this.initialMulticaster.multicastEvent(new ApplicationStartingEvent(this.application, this.args));    }    @Override    public void environmentPrepared(ConfigurableEnvironment environment) {        this.initialMulticaster                .multicastEvent(new ApplicationEnvironmentPreparedEvent(this.application, this.args, environment));    }    @Override    public void contextPrepared(ConfigurableApplicationContext context) {        this.initialMulticaster                .multicastEvent(new ApplicationContextInitializedEvent(this.application, this.args, context));    }    @Override    public void contextLoaded(ConfigurableApplicationContext context) {        for (ApplicationListener<?> listener : this.application.getListeners()) {            if (listener instanceof ApplicationContextAware) {                ((ApplicationContextAware) listener).setApplicationContext(context);            }            context.addApplicationListener(listener);        }        this.initialMulticaster.multicastEvent(new ApplicationPreparedEvent(this.application, this.args, context));    }    @Override    public void started(ConfigurableApplicationContext context) {        context.publishEvent(new ApplicationStartedEvent(this.application, this.args, context));    }    @Override    public void running(ConfigurableApplicationContext context) {        context.publishEvent(new ApplicationReadyEvent(this.application, this.args, context));    }    @Override    public void failed(ConfigurableApplicationContext context, Throwable exception) {        ApplicationFailedEvent event = new ApplicationFailedEvent(this.application, this.args, context, exception);        if (context != null && context.isActive()) {            // Listeners have been registered to the application context so we should            // use it at this point if we can            context.publishEvent(event);        }        else {            // An inactive context may not have a multicaster so we use our multicaster to            // call all of the context's listeners instead            if (context instanceof AbstractApplicationContext) {                for (ApplicationListener<?> listener : ((AbstractApplicationContext) context)                        .getApplicationListeners()) {                    this.initialMulticaster.addApplicationListener(listener);                }            }            this.initialMulticaster.setErrorHandler(new LoggingErrorHandler());            this.initialMulticaster.multicastEvent(event);        }    }    private static class LoggingErrorHandler implements ErrorHandler {        private static final Log logger = LogFactory.getLog(EventPublishingRunListener.class);        @Override        public void handleError(Throwable throwable) {            logger.warn("Error calling ApplicationEventListener", throwable);        }    }}

调用了 contextLoaded()，在 RestartListener 的 onApplicationEvent() 中进行调用

RestartListener

public class RestartListener implements SmartApplicationListener {    private ConfigurableApplicationContext context;    private ApplicationPreparedEvent event;    @Override    public int getOrder() {        return 0;    }    @Override    public boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {        return ApplicationPreparedEvent.class.isAssignableFrom(eventType)                || ContextRefreshedEvent.class.isAssignableFrom(eventType)                || ContextClosedEvent.class.isAssignableFrom(eventType);    }    @Override    public boolean supportsSourceType(Class<?> sourceType) {        return true;    }    @Override    public void onApplicationEvent(ApplicationEvent input) {        if (input instanceof ApplicationPreparedEvent) {            this.event = (ApplicationPreparedEvent) input;            if (this.context == null) {                this.context = this.event.getApplicationContext();            }        }        else if (input instanceof ContextRefreshedEvent) {            if (this.context != null && input.getSource().equals(this.context)                    && this.event != null) {                this.context.publishEvent(this.event);            }        }        else {            if (this.context != null && input.getSource().equals(this.context)) {                this.context = null;                this.event = null;            }        }    }}

RestartListener 的 onApplicationEvent() 传入 ApplicationPreparedEvent，调用 AbstractApplicationContext 的 refresh()，即进行 ioc 容器重启，此时是第一次

调用 EventPublishingRunListener 的 running()，进行新的配置加载

调用 PropertySourceBootstrapConfiguration 的 initialize()，间接调用 NacosPropertySourceLocator 的 locate() 进行文件加载

调用 RestartListener 的 onApplicationEvent()，参数为 ApplicationPreparedEvent，调用 AbstractApplicationContext 的 refresh() 进行 ioc 容器重启，此时是第二次

调用 RestartListener 的 onApplicationEvent()，参数为 ContextRefreshedEvent

至此，ContextRefresher 的 refreshEnvironment() 逻辑执行完毕

接下来调用 RefreshScope 的 refreshAll()，间接调用父类 GenericScope 的 destroy()，发布事件 RefreshScopeRefreshedEvent 到 ApplicationContext 中

Java连接nacos后会定时心跳连接

通过 NacosWatch 开启 ThreadPoolTaskScheduler 进行定时任务发起，事件为 HeartbeatEvent。

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