死机简单配置

编写整个框架的目的是为了处理应用程序的配置。我更喜欢一种简单的方法。

如果通过配置我们的意思是“ 部署之间可能有所不同的所有内容 ”，那么我们应该尝试使配置保持简单。在Java中，最简单的选项是不起眼的属性文件。属性文件的缺点是，当您希望应用程序接收更改时必须重新启动它。还是你

这是我在多个项目中使用的一种简单方法：

public class MyAppConfig extends AppConfiguration {private static MyAppConfig instance = new MyAppConfig();public static MyAppConfig instance() {return instance;}private MyAppConfig() {this("myapp.properties");}public String getServiceUrl() {return getRequiredProperty("service.url");}public boolean getShouldStartSlow() {return getFlag("start-slow", false);}public int getHttpPort(int defaultPort) {return getIntProperty("myapp.http.port", defaultPort);}}

AppConfiguration类如下所示：

public abstract class AppConfiguration {private static Logger log = LoggerFactory.getLogger(AppConfiguration.class);private long nextCheckTime = 0;private long lastLoadTime = 0;private Properties properties = new Properties();private final File configFile;protected AppConfiguration(String filename) {this.configFile = new File(filename);}public String getProperty(String propertyName, String defaultValue) {String result = getProperty(propertyName);if (result == null) {log.trace("Missing property {} in {}", propertyName, properties.keySet());return defaultValue;}return result;}public String getRequiredProperty(String propertyName) {String result = getProperty(propertyName);if (result == null) {throw new RuntimeException("Missing property " + propertyName);}return result;}private String getProperty(String propertyName) {if (System.getProperty(propertyName) != null) {log.trace("Reading {} from system properties", propertyName);return System.getProperty(propertyName);}if (System.getenv(propertyName.replace('.', '_')) != null) {log.trace("Reading {} from environment", propertyName);return System.getenv(propertyName.replace('.', '_'));}ensureConfigurationIsFresh();return properties.getProperty(propertyName);}private synchronized void ensureConfigurationIsFresh() {if (System.currentTimeMillis() < nextCheckTime) return;nextCheckTime = System.currentTimeMillis() + 10000;log.trace("Rechecking {}", configFile);if (!configFile.exists()) {log.error("Missing configuration file {}", configFile);}if (lastLoadTime >= configFile.lastModified()) return;lastLoadTime = configFile.lastModified();log.debug("Reloading {}", configFile);try (FileInputStream inputStream = new FileInputStream(configFile)) {properties.clear();properties.load(inputStream);} catch (IOException e) {throw new RuntimeException("Failed to load " + configFile, e);}}
}

这样可以高效地读取配置文件，并根据需要更新设置。它支持默认的环境变量和系统属性。而且它甚至可以很好地记录正在发生的事情。