archaius源码分析之配置源

配置源

　　配置源定义和实现了获取配置文件的方式。有两种配置源，一种是主动拉去方式获取配置，一种是被动监听方式获取配置

类图结构：

接口PolledConfigurationSource定义了获取配置的方法

public PollResult poll(boolean initial, Object checkPoint) throws Exception;  

　　initial是否是初次获取，checkPoint上次获取的检查点。

　　JDBCConfigurationSource 从数据库中获取配置信息。从指定的DataSource中读取指定的key和value字段。

public PollResult poll(boolean initial, Object checkPoint) throws Exception {
        Map<String, Object> map = new HashMap<String, Object>();
        ...
            conn = getConnection();
            pstmt = conn.prepareStatement(query.toString());
            rs = pstmt.executeQuery();
            while (rs.next()) {
                String key = (String) rs.getObject(keyColumnName);
                Object value = rs.getObject(valueColumnName);
                map.put(key, value);
            }

        ...
        return PollResult.createFull(map);
}

　　URLConfigurationSource从指定url中获取配置信息。从指定的url中读取配置文件。

public PollResult poll(boolean initial, Object checkPoint)
            throws IOException {
        if (configUrls == null || configUrls.length == 0) {
            return PollResult.createFull(null);
        }
        Map<String, Object> map = new HashMap<String, Object>();
        for (URL url: configUrls) {
            InputStream fin = url.openStream();
            Properties props = ConfigurationUtils.loadPropertiesFromInputStream(fin);
            for (Entry<Object, Object> entry: props.entrySet()) {
                map.put((String) entry.getKey(), entry.getValue());
            }
        }
        return PollResult.createFull(map);
  }

WatchedConfigurationSource定义了监听器，当配置发生变化时，调用这些监听器。

    public void addUpdateListener(WatchedUpdateListener l);
    public void removeUpdateListener(WatchedUpdateListener l);
    public Map<String, Object> getCurrentData() throws Exception;

原文地址：https://www.cnblogs.com/zhangwanhua/p/8365161.html