Apollo源码解析——客户端API配置（三）之ConfigFile

老艿艿&＃xff1a;本系列假定胖友已经阅读过 《Apollo 官方 wiki 文档》 &＃xff0c;特别是 《Java 客户端使用指南》 。

本文接 《Apollo 源码解析 —— 客户端 API 配置&＃xff08;二&＃xff09;之一览》 一文&＃xff0c;分享 ConfigFile 接口&＃xff0c;及其子类&＃xff0c;如下图&＃xff1a;

从实现上&＃xff0c;ConfigFile 和 Config 超级类似&＃xff0c;所以本文会写的比较简洁。

• Config 基于 KV 数据结构。
• ConfigFile 基于 String 数据结构。

在 《Apollo 源码解析 —— 客户端 API 配置&＃xff08;一&＃xff09;之一览》 的 「3.2 ConfigFile」 中&＃xff0c;有详细分享。

com.ctrip.framework.apollo.internals.AbstractConfigFile &＃xff0c;实现 ConfigFile、RepositoryChangeListener 接口&＃xff0c;ConfigFile 抽象类&＃xff0c;实现了 1&＃xff09;异步通知监听器、2&＃xff09;计算属性变化等等特性&＃xff0c;是 AbstractConfig &＃43; DefaultConfig 的功能子集。

3.1 构造方法

private static final Logger logger &＃61; LoggerFactory.getLogger(AbstractConfigFile.class);/*** ExecutorService 对象&＃xff0c;用于配置变化时&＃xff0c;异步通知 ConfigChangeListener 监听器们** 静态属性&＃xff0c;所有 Config 共享该线程池。*/
private static ExecutorService m_executorService;/*** Namespace 的名字*/
protected String m_namespace;
/*** ConfigChangeListener 集合*/
private List m_listeners &＃61; Lists.newCopyOnWriteArrayList();protected ConfigRepository m_configRepository;
/*** 配置 Properties 的缓存引用*/
protected AtomicReference m_configProperties;static {m_executorService &＃61; Executors.newCachedThreadPool(ApolloThreadFactory.create("ConfigFile", true));
}public AbstractConfigFile(String namespace, ConfigRepository configRepository) {m_configRepository &＃61; configRepository;m_namespace &＃61; namespace;m_configProperties &＃61; new AtomicReference<>();// 初始化initialize();
}private void initialize() {try {// 初始化 m_configPropertiesm_configProperties.set(m_configRepository.getConfig());} catch (Throwable ex) {Tracer.logError(ex);logger.warn("Init Apollo Config File failed - namespace: {}, reason: {}.", m_namespace, ExceptionUtil.getDetailMessage(ex));} finally {//register the change listener no matter config repository is working or not//so that whenever config repository is recovered, config could get changed// 注册到 ConfigRepository 中&＃xff0c;从而实现每次配置发生变更时&＃xff0c;更新配置缓存 &＃96;m_configProperties&＃96; 。m_configRepository.addChangeListener(this);}
}

3.2 获得内容

交给子类自己实现。

3.3 获得 Namespace 名字

&＃64;Override
public String getNamespace() {return m_namespace;
}

3.4 添加配置变更监听器 

&＃64;Override
public void addChangeListener(ConfigFileChangeListener listener) {if (!m_listeners.contains(listener)) {m_listeners.add(listener);}
}

3.5 触发配置变更监听器们 

private void fireConfigChange(final ConfigFileChangeEvent changeEvent) {// 缓存 ConfigChangeListener 数组for (final ConfigFileChangeListener listener : m_listeners) {m_executorService.submit(new Runnable() {&＃64;Overridepublic void run() {String listenerName &＃61; listener.getClass().getName();Transaction transaction &＃61; Tracer.newTransaction("Apollo.ConfigFileChangeListener", listenerName);try {// 通知监听器listener.onChange(changeEvent);transaction.setStatus(Transaction.SUCCESS);} catch (Throwable ex) {transaction.setStatus(ex);Tracer.logError(ex);logger.error("Failed to invoke config file change listener {}", listenerName, ex);} finally {transaction.complete();}}});}
}

3.6 onRepositoryChange

#onRepositoryChange(namespace, newProperties) 方法&＃xff0c;当 ConfigRepository 读取到配置发生变更时&＃xff0c;计算配置变更集合&＃xff0c;并通知监听器们。代码如下&＃xff1a;

&＃64;Override
public synchronized void onRepositoryChange(String namespace, Properties newProperties) {// 忽略&＃xff0c;若未变更if (newProperties.equals(m_configProperties.get())) {return;}// 读取新的 Properties 对象Properties newConfigProperties &＃61; new Properties();newConfigProperties.putAll(newProperties);// 获得【旧】值String oldValue &＃61; getContent();// 更新为【新】值update(newProperties);// 获得新值String newValue &＃61; getContent();// 计算变化类型PropertyChangeType changeType &＃61; PropertyChangeType.MODIFIED;if (oldValue &＃61;&＃61; null) {changeType &＃61; PropertyChangeType.ADDED;} else if (newValue &＃61;&＃61; null) {changeType &＃61; PropertyChangeType.DELETED;}// 通知监听器们this.fireConfigChange(new ConfigFileChangeEvent(m_namespace, oldValue, newValue, changeType));Tracer.logEvent("Apollo.Client.ConfigChanges", m_namespace);
}

• 调用 #update(newProperties) 抽象方法&＃xff0c;更新为【新】值。该方法需要子类自己去实现。抽象方法如下&＃xff1a; 

protected abstract void update(Properties newProperties);

4. PropertiesConfigFile

com.ctrip.framework.apollo.internals.PropertiesConfigFile &＃xff0c;实现 AbstractConfigFile 抽象类&＃xff0c;类型为 .properties 的 ConfigFile 实现类。

4.1 构造方法

private static final Logger logger &＃61; LoggerFactory.getLogger(PropertiesConfigFile.class);/*** 配置字符串缓存*/
protected AtomicReference m_contentCache;public PropertiesConfigFile(String namespace, ConfigRepository configRepository) {super(namespace, configRepository);m_contentCache &＃61; new AtomicReference<>();
}

• 因为 Properties 是 KV 数据结构&＃xff0c;需要将多条 KV 拼接成一个字符串&＃xff0c;进行缓存到 m_contentCache 中。

4.2 更新内容

&＃64;Override
protected void update(Properties newProperties) {// 设置【新】Propertiesm_configProperties.set(newProperties);// 清空缓存m_contentCache.set(null);
}

4.3 获得内容 

&＃64;Override
public String getContent() {// 更新到缓存if (m_contentCache.get() &＃61;&＃61; null) {m_contentCache.set(doGetContent());}// 从缓存中&＃xff0c;获得配置字符串return m_contentCache.get();
}String doGetContent() {if (!this.hasContent()) {return null;}try {return PropertiesUtil.toString(m_configProperties.get()); // 拼接 KV 属性&＃xff0c;成字符串} catch (Throwable ex) {ApolloConfigException exception &＃61; new ApolloConfigException(String.format("Parse properties file content failed for namespace: %s, cause: %s", m_namespace, ExceptionUtil.getDetailMessage(ex)));Tracer.logError(exception);throw exception;}
}&＃64;Override
public boolean hasContent() {return m_configProperties.get() !&＃61; null && !m_configProperties.get().isEmpty();
}

• 调用 PropertiesUtil#toString(Properties) 方法&＃xff0c;将 Properties 拼接成字符串。代码如下&＃xff1a; 

/*** Transform the properties to string format** &＃64;param properties the properties object* &＃64;return the string containing the properties* &＃64;throws IOException*/
public static String toString(Properties properties) throws IOException {StringWriter writer &＃61; new StringWriter();properties.store(writer, null);StringBuffer stringBuffer &＃61; writer.getBuffer();// 去除头部自动添加的注释filterPropertiesComment(stringBuffer);return stringBuffer.toString();
}/*** filter out the first comment line** &＃64;param stringBuffer the string buffer* &＃64;return true if filtered successfully, false otherwise*/
static boolean filterPropertiesComment(StringBuffer stringBuffer) {//check whether has comment in the first lineif (stringBuffer.charAt(0) !&＃61; &＃39;#&＃39;) {return false;}int commentLineIndex &＃61; stringBuffer.indexOf("\n");if (commentLineIndex &＃61;&＃61; -1) {return false;}stringBuffer.delete(0, commentLineIndex &＃43; 1);return true;
}

• 因为 Properties#store(writer, null) 方法&＃xff0c;会自动在首行&＃xff0c;添加注释时间。代码如下&＃xff1a; 

private void store0(BufferedWriter bw, String comments, boolean escUnicode)throws IOException
{if (comments !&＃61; null) {writeComments(bw, comments);}bw.write("#" &＃43; new Date().toString()); // 自动在**首行**&＃xff0c;添加**注释时间**。bw.newLine();synchronized (this) {for (Enumeration e &＃61; keys(); e.hasMoreElements();) {String key &＃61; (String)e.nextElement();String val &＃61; (String)get(key);key &＃61; saveConvert(key, true, escUnicode);/* No need to escape embedded and trailing spaces for value, hence* pass false to flag.*/val &＃61; saveConvert(val, false, escUnicode);bw.write(key &＃43; "&＃61;" &＃43; val);bw.newLine();}}bw.flush();
}

• 从实现代码&＃xff0c;我们可以看出&＃xff0c;拼接的字符串&＃xff0c;每一行一个 KV 属性。例子如下&＃xff1a; 

key2&＃61;value2
key1&＃61;value1


 4.4 获得 Namespace 名字

&＃64;Override
public ConfigFileFormat getConfigFileFormat() {return ConfigFileFormat.Properties;
}
5. PlainTextConfigFile

com.ctrip.framework.apollo.internals.PlainTextConfigFile &＃xff0c;实现 AbstractConfigFile 抽象类&＃xff0c;纯文本 ConfigFile 抽象类&＃xff0c;例如 xml yaml 等等。

更新内容

&＃64;Override
protected void update(Properties newProperties) {m_configProperties.set(newProperties);
}

获得内容 

&＃64;Override
public String getContent() {if (!this.hasContent()) {return null;}return m_configProperties.get().getProperty(ConfigConsts.CONFIG_FILE_CONTENT_KEY);
}&＃64;Override
public boolean hasContent() {if (m_configProperties.get() &＃61;&＃61; null) {return false;}return m_configProperties.get().containsKey(ConfigConsts.CONFIG_FILE_CONTENT_KEY);
}

• 直接从 "content" 配置项&＃xff0c;获得配置文本。这也是为什么类名以 PlainText 开头的原因。

&＃x1f642; PlainTextConfigFile 的子类&＃xff0c;代码基本一致&＃xff0c;差别在于 #getConfigFileFormat() 实现方法&＃xff0c;返回不同的 ConfigFileFormat 。

5.1 XmlConfigFile

com.ctrip.framework.apollo.internals.XmlConfigFile &＃xff0c;实现 PlainTextConfigFile 抽象类&＃xff0c;类型为 .xml 的 ConfigFile 实现类。代码如下&＃xff1a;

public class XmlConfigFile extends PlainTextConfigFile {public XmlConfigFile(String namespace, ConfigRepository configRepository) {super(namespace, configRepository);}&＃64;Overridepublic ConfigFileFormat getConfigFileFormat() {return ConfigFileFormat.XML;}}

5.2 JsonConfigFile

com.ctrip.framework.apollo.internals.JsonConfigFile &＃xff0c;实现 PlainTextConfigFile 抽象类&＃xff0c;类型为 .json 的 ConfigFile 实现类。代码如下&＃xff1a;

public class JsonConfigFile extends PlainTextConfigFile {public JsonConfigFile(String namespace,ConfigRepository configRepository) {super(namespace, configRepository);}&＃64;Overridepublic ConfigFileFormat getConfigFileFormat() {return ConfigFileFormat.JSON;}}

5.3 YamlConfigFile

com.ctrip.framework.apollo.internals.YamlConfigFile &＃xff0c;实现 PlainTextConfigFile 抽象类&＃xff0c;类型为 .yaml 的 ConfigFile 实现类。代码如下&＃xff1a;

public class YamlConfigFile extends PlainTextConfigFile {public YamlConfigFile(String namespace, ConfigRepository configRepository) {super(namespace, configRepository);}&＃64;Overridepublic ConfigFileFormat getConfigFileFormat() {return ConfigFileFormat.YAML;}}

5.4 YmlConfigFile

com.ctrip.framework.apollo.internals.YmlConfigFile &＃xff0c;实现 PlainTextConfigFile 抽象类&＃xff0c;类型为 .yaml 的 ConfigFile 实现类。代码如下&＃xff1a;

public class YmlConfigFile extends PlainTextConfigFile {public YmlConfigFile(String namespace, ConfigRepository configRepository) {super(namespace, configRepository);}&＃64;Overridepublic ConfigFileFormat getConfigFileFormat() {return ConfigFileFormat.YML;}}