Spring Boot：從數據庫檢索配置

Question

任何人都可以爲我提供一些關於實現此目標的最佳方式的指導。

我想擴展Spring Boot Externalized Configuration，這樣我就可以在我的應用程序的任何地方調用一個方法。該方法將使用鍵檢索屬性值。此方法將首先詢問數據庫表，如果未找到指定的鍵，則它將回落到1中所述的PropertySource順序。

所以我也有類似的服務：

@Service 
public class ConfigurationService { 

    private final ConfigurationRepository configurationRepository; 

    @Autowired 
    public ConfigurationService(ConfigurationRepository configurationRepository) { 
     this.configurationRepository = configurationRepository; 
    } 

    public String getValue(String key) { 
     Configuration configuration = configurationRepository.findOne(key); 

     // Add something here to get the property from application.properties if the key does not exist in the db 

     return configuration == null ? null : configuration.getValue(); 
    } 

} 

，我可以使用如下：

foo = configuration.getValue("my.property"); 

有沒有要去這個更好的辦法？我錯過了我可以使用的Spring Boot功能嗎？

編輯：我希望能夠在應用程序運行時更改屬性的值，並獲取這些新值。

Answer 1

我已經使用EnvironmentPostProcessor彈簧功能來做到這一點。

你需要創建一個類是這樣的：

public class ReadDbPropertiesPostProcessor implements EnvironmentPostProcessor { 
    /** 
    * Name of the custom property source added by this post processor class 
    */ 
    private static final String PROPERTY_SOURCE_NAME = "databaseProperties"; 

    /** 
    * Adds Spring Environment custom logic. This custom logic fetch properties from database and setting highest precedence 
    */ 
    @Override 
    public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) { 
     Map<String, Object> propertySource = new HashMap<>(); 

     try { 
      // Build manually datasource to ServiceConfig 
      DataSource ds = DataSourceBuilder 
        .create() 
        .username(USERNAME) // replace with your config 
        .password(PASSWORD) // replace with your config 
        .url(DATASOURCE-URL)// replace with your config 
        .driverClassName(DRIVER) // replace with your config 
        .build(); 

      // Fetch all properties 
      PreparedStatement preparedStatement = ds.getConnection().prepareStatement("SELECT name, value FROM propertyConfig WHERE service = ?"); 
      preparedStatement.setString(1, APP_NAME); 

      ResultSet rs = preparedStatement.executeQuery(); 

      // Populate all properties into the property source 
      while (rs.next()) { 
       String propName = rs.getString("name"); 
       propertySource.put(propName, rs.getString("value")); 
      } 

      // Create a custom property source with the highest precedence and add it to Spring Environment 
      environment.getPropertySources().addFirst(new MapPropertySource(PROPERTY_SOURCE_NAME, propertySource)); 

     } catch (Exception e) { 
      throw new RuntimeException("Error fetching properties from db"); 
     } 
    } 
} 

，因爲你需要在春天的一個非常早期的階段運行這個類，您需要創建該文件spring.factories並註冊您的環境後處理器。這個文件需要在這裏位於：

src/main/META-INF/spring-factories 

在您需要將類設置彈簧屬性的內容：

# Environment Post Processor 
org.springframework.boot.env.EnvironmentPostProcessor=com.your.package.ReadDbPropertiesPostProcessor