远程PropertySource

Question

是否有人成功地构建了一个使用远程源(例如数据库)来检索属性值的PropertySource。其想法是构建一个PropertySource (需要一些连接信息，比如主机/端口)并将其插入到PropertySourcePlaceholderConfigurer中。

问题似乎是鸡和蛋的问题。如何才能将连接信息下载到PropertySource？我可以先用配置实例化PropertySourcePlaceholderConfigurer，然后用远程主机和端口属性加载属性文件，然后实例化PropertySource并将其注入配置程序。但是，我似乎想不出一种方法来确保实例化的第一个bean (并迅速注入到配置程序中)是我的属性源。我需要这样做，因为当然，我的所有其他bean都依赖于远程属性。

Answer 1

公域配置支持通过公域配置将各种源(包括JDBC )的属性加载到org.apache.commons.configuration.Configuration对象中。

使用org.apache.commons.configuration.ConfiguratorConverter，您可以将配置对象转换为可以传递给PropertySourcesPlaceholderConfigurer的java.util.Properties对象。

至于如何配置ConfigurationBuilder的鸡和蛋问题，我建议使用org.springframework.core.env.Environment查询系统属性、命令行属性或JNDI属性。

在这个例子中：

@Configuration
public class RemotePropertyConfig {

   @Bean
   public static PropertySourcesPlaceholderConfigurer propertyPlaceholderConfigurer(Environment environment)
    throws Exception {
    final PropertySourcesPlaceholderConfigurer props = new PropertySourcesPlaceholderConfigurer();
    final ConfigurationBuilder configurationBuilder = new DefaultConfigurationBuilder(environment.getProperty("configuration.definition.file"));
    props.setProperties(ConfigurationConverter.getProperties(configurationBuilder.getConfiguration()));
    return props;
}

您需要指定环境属性configuration.definition.file，它指向配置共用配置所需的文件：

Answer 2

类似于上面Recardo的回答，我使用的是Spring的PropertiesLoaderUtils，而不是Apache的，但这等同于相同的东西。不太理想..。硬编码依赖注入，但嘿，它工作！

/**
 * This method must remain static as it's part of spring's initialization effort.
 * @return
 **/
@Bean
public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
  PropertySourcesPlaceholderConfigurer configurer = new PropertySourcesPlaceholderConfigurer();

  String dbHost = null;
  Integer dbPort = null;

  // check system / environment properties first
  Environment environment = new StandardEnvironment();
  if (environment.containsProperty(DB_HOST_KEY)) {
    dbHost = environment.getProperty(DB_HOST_KEY);
  }
  if (environment.containsProperty(DB_PORT_KEY)) {
    dbPort = Integer.valueOf(environment.getProperty(DB_PORT_KEY));
  }

  if (dbHost == null || dbPort == null) {
    // ok one or (probably) both properties null, let's go find the database.properties file
    Properties dbProperties;
    try {
      dbProperties = PropertiesLoaderUtils.loadProperties(new EncodedResource(new ClassPathResource("database.properties"), "UTF-8"));
    }
    catch (IOException e) {
      throw new RuntimeException("Could not load database.properties.  Please confirm the file is in the classpath");
    }

    if (dbHost == null) {
      dbHost = dbProperties.getProperty(DB_HOST_KEY);
    }
    if (dbPort == null) {
      dbPort = Integer.valueOf(dbProperties.getProperty(DB_PORT_KEY));
    }
  }

  PropertySourceService propertySourceService = new DBPropertySourceService(dbHost, dbPort);
  PropertySource<PropertySourceService> propertySource = new DBPropertySource(propertySourceService);
  MutablePropertySources propertySources = new MutablePropertySources();
  propertySources.addFirst(propertySource);
  configurer.setPropertySources(propertySources);

  return configurer;
}

对于每个请求，这里是远程属性源的源。这取决于一个“服务”类。好吧..。任何事..。远程访问套接字上的属性，与数据库对话，什么都可以。

/**
 * Property source for use with spring's PropertySourcesPlaceholderConfigurer where the source is a service
 * that connects to remote server for property values.
 **/
public class RemotePropertySource extends PropertySource<PropertySourceService> {

  private final Environment environment;
  /**
   * Constructor...
   * @param name
   * @param source
   **/
  public RemotePropertySource(PropertySourceService source) {
    super("RemotePropertySource", source);
    environment = new StandardEnvironment();
  }

  /* (non-Javadoc)
   * @see org.springframework.core.env.PropertySource#getProperty(java.lang.String)
   */
  @Override
  public Object getProperty(String name) {

    // check system / environment properties first
    String value;
    if (environment.containsProperty(name)) {
      value = environment.getProperty(name);
    }
    else {
      value = source.getProperty(name);
    }
    return value;
  }
}