org.apache.felix.dm.annotation.api

Annotation Type Init

@Retention(value=CLASS)
@Target(value=METHOD)
public @interface Init

Annotates a method used to configure dynamic dependencies. When this method is invoked, all required dependencies (except the ones declared with a name attribute) are already injected, and optional dependencies on class fields are also already injected (possibly with NullObjects).

The purpose of the @Init method is to either declare more dynamic dependencies using the DM API, or to return a Map used to dynamically configure dependencies that are annotated using a name attribute. After the init method returns, the added or configured dependencies are then tracked, and when all dynamic dependencies are injected, then the start method (annotated with @Start) is then invoked.

Usage Examples

In this sample, the "PersistenceImpl" component dynamically configures the "storage" dependency from the "init" method. The dependency "required" flag and filter string are derived from an xml configuration that is already injected before the init method.

 
 @Component
 public class PersistenceImpl implements Persistence {
     // Injected before init.
     @ServiceDependency
     LogService log;
     
     // Injected before init.
     @ConfigurationDependency
     void updated(Dictionary conf) {
        if (conf != null) {
           _xmlConfiguration = parseXmlConfiguration(conf.get("xmlConfiguration"));
        }
     }
     
     // Parsed xml configuration, where we'll get our storage service filter and required dependency flag.
     XmlConfiguration _xmlConfiguration;
  
     // Injected after init (dependency filter is defined dynamically from our init method).
     @ServiceDependency(name="storage")
     Storage storage;
 
     // Dynamically configure the dependency declared with a "storage" name.
     @Init
     Map init() {
        log.log(LogService.LOG_WARNING, "init: storage type=" + storageType + ", storageRequired=" + storageRequired);
        Map props = new HashMap<>();
        props.put("storage.required", Boolean.toString(_xmlConfiguration.isStorageRequired()))
        props.put("storage.filter", "(type=" + _xmlConfiguration.getStorageType() + ")");
        return props;       
     }
     
     // All dependencies injected, including dynamic dependencies defined from init method.
     @Start
     void start() {
        log.log(LogService.LOG_WARNING, "start");
     }