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

1@Override
2public Object postProcessBeforeInitialization(Object bean, final String beanName)
3    throws BeansException {
4
5    doWithFields(bean, beanName);
6
7    doWithMethods(bean, beanName);
8
9    return super.postProcessBeforeInitialization(bean, beanName);
10}

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

1// 配置文件发生变化，把这种变化转化为 spring 事件
2private void safeNotifyListener(final String dataId, final String group, final String content,
3                                final String md5, final ManagerListenerWrap listenerWrap) {
4    final Listener listener = listenerWrap.listener;
5
6    // 把逻辑封装成 job，可异步可同步
7    Runnable job = new Runnable() {
8        public void run() {
9            ClassLoader myClassLoader = Thread.currentThread().getContextClassLoader();
10            ClassLoader appClassLoader = listener.getClass().getClassLoader();
11            try {
12                if (listener instanceof AbstractSharedListener) {
13                    AbstractSharedListener adapter = (AbstractSharedListener) listener;
14                    adapter.fillContext(dataId, group);
15                    LOGGER.info("[{}] [notify-context] dataId={}, group={}, md5={}", name, dataId, group, md5);
16                }
17                // 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）。
18                Thread.currentThread().setContextClassLoader(appClassLoader);
19
20                ConfigResponse cr = new ConfigResponse();
21                cr.setDataId(dataId);
22                cr.setGroup(group);
23                cr.setContent(content);
24                configFilterChainManager.doFilter(null, cr);
25                String contentTmp = cr.getContent();
26                // 真正发布事件的地方
27                listener.receiveConfigInfo(contentTmp);
28                listenerWrap.lastCallMd5 = md5;
29                LOGGER.info("[{}] [notify-ok] dataId={}, group={}, md5={}, listener={} ", name, dataId, group, md5,
30                    listener);
31            } catch (NacosException de) {
32                LOGGER.error("[{}] [notify-error] dataId={}, group={}, md5={}, listener={} errCode={} errMsg={}", name,
33                    dataId, group, md5, listener, de.getErrCode(), de.getErrMsg());
34            } catch (Throwable t) {
35                LOGGER.error("[{}] [notify-error] dataId={}, group={}, md5={}, listener={} tx={}", name, dataId, group,
36                    md5, listener, t.getCause());
37            } finally {
38                Thread.currentThread().setContextClassLoader(myClassLoader);
39            }
40        }
41    };
42
43    final long startNotify = System.currentTimeMillis();
44    try {
45        if (null != listener.getExecutor()) {
46            listener.getExecutor().execute(job);
47        } else {
48            job.run();
49        }
50    } catch (Throwable t) {
51        LOGGER.error("[{}] [notify-error] dataId={}, group={}, md5={}, listener={} throwable={}", name, dataId, group,
52            md5, listener, t.getCause());
53    }
54    final long finishNotify = System.currentTimeMillis();
55    LOGGER.info("[{}] [notify-listener] time cost={}ms in ClientWorker, dataId={}, group={}, md5={}, listener={} ",
56        name, (finishNotify - startNotify), dataId, group, md5, listener);
57}

发布事件

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

DelegatingEventPublishingListener 类在 nacos-spring-context 工程中

1private void publishEvent(String content) {
2    NacosConfigReceivedEvent event = new NacosConfigReceivedEvent(configService, dataId, groupId, content);
3    applicationEventPublisher.publishEvent(event);
4}

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。

1public void onApplicationEvent(NacosConfigReceivedEvent event) {
2    String content = event.getContent();
3    if (content != null) {
4        Properties configProperties = toProperties(content);
5
6        for (Object key : configProperties.keySet()) {
7            String propertyKey = (String)key;
8
9            List<NacosValueTarget> beanPropertyList = placeholderNacosValueTargetMap.get(propertyKey);
10            if (beanPropertyList == null) {
11                continue;
12            }
13
14            String propertyValue = configProperties.getProperty(propertyKey);
15            for (NacosValueTarget nacosValueTarget : beanPropertyList) {
16                if (nacosValueTarget.method == null) {
17                    setField(nacosValueTarget, propertyValue);
18                } else {
19                    setMethod(nacosValueTarget, propertyValue);
20                }
21            }
22        }
23    }
24}