NacosValue 注解

NacosValue 定义在 nacos-api 工程中：com.alibaba.nacos.api.config.annotation.NacosValue

注解解析在 nacos-spring-project 工程中：

com.alibaba.nacos.spring.util.NacosBeanUtils#registerNacosValueAnnotationBeanPostProcessor

com.alibaba.nacos.spring.context.annotation.config.NacosValueAnnotationBeanPostProcessor

实现 BeanPostProcessor 接口，可以在创建 bean 的过程中插入自定义逻辑，NacosValueAnnotationBeanPostProcessor 扫描属性和方法上的 NacosValue 注解。

执行顺序：bean 的构造方法，postProcessBeforeInitialization，init，postProcessAfterInitialization

@Override

public Object postProcessBeforeInitialization(Object bean, final String beanName)

    throws BeansException {

    doWithFields(bean, beanName);

    doWithMethods(bean, beanName);

    return super.postProcessBeforeInitialization(bean, beanName);

}

nacos 客户端定时从 nacos server 拉取更新，如果有更新，则通过事件把新值注入到属性中。

com.alibaba.nacos.client.config.impl.ClientWorker.LongPullingRunnable
com.alibaba.nacos.client.config.impl.CacheData#safeNotifyListener
检测到变化

// 配置文件发生变化，把这种变化转化为 spring 事件

private void safeNotifyListener(final String dataId, final String group, final String content,

                                final String md5, final ManagerListenerWrap listenerWrap) {

    final Listener listener = listenerWrap.listener;

    // 把逻辑封装成 job，可异步可同步

    Runnable job = new Runnable() {

        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();

                // 真正发布事件的地方

                listener.receiveConfigInfo(contentTmp);

                listenerWrap.lastCallMd5 = md5;

                LOGGER.info("[{}] [notify-ok] dataId={}, group={}, md5={}, listener={} ", name, dataId, group, md5,

                    listener);

            } catch (NacosException de) {

                LOGGER.error("[{}] [notify-error] dataId={}, group={}, md5={}, listener={} errCode={} errMsg={}", name,

                    dataId, group, md5, listener, de.getErrCode(), de.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);

}

发布事件

com.alibaba.nacos.spring.context.event.config.DelegatingEventPublishingListener#publishEvent

DelegatingEventPublishingListener 类在 nacos-spring-context 工程中

private void publishEvent(String content) {

    NacosConfigReceivedEvent event = new NacosConfigReceivedEvent(configService, dataId, groupId, content);

    applicationEventPublisher.publishEvent(event);

}

消费事件

com.alibaba.nacos.spring.context.annotation.config.NacosValueAnnotationBeanPostProcessor#onApplicationEvent

NacosValueAnnotationBeanPostProcessor 类在 nacos-spring-context 工程中

NacosValueAnnotationBeanPostProcessor 实现了 ApplicationListener<NacosConfigReceivedEvent> 接口，NacosConfigReceivedEvent 继承自 ApplicationEvent。

public void onApplicationEvent(NacosConfigReceivedEvent event) {

    String content = event.getContent();

    if (content != null) {

        Properties configProperties = toProperties(content);

        for (Object key : configProperties.keySet()) {

            String propertyKey = (String)key;

            List<NacosValueTarget> beanPropertyList = placeholderNacosValueTargetMap.get(propertyKey);

            if (beanPropertyList == null) {

                continue;

            }

            String propertyValue = configProperties.getProperty(propertyKey);

            for (NacosValueTarget nacosValueTarget : beanPropertyList) {

                if (nacosValueTarget.method == null) {

                    setField(nacosValueTarget, propertyValue);

                } else {

                    setMethod(nacosValueTarget, propertyValue);

                }

            }

        }

    }

}

巴特西

NacosValue 注解

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