Services¶

Services are singleton components that are started when your Fathom application starts and stopped when your Fathom application stops.

Many of the available Fathom modules include services such as:

• Fathom-JCache
• Fathom-Mailer
• Fathom-Metrics
• Fathom-Quartz
• Fathom-REST
• Fathom-Security

Configuration¶

You must define your Service…

@Singleton
class EmployeeService implements Service {

  Logger log = LoggerFactory.getLogger(EmployeeService.class);

  @Override
  public int getPreferredStartOrder() {
    return 100;
  }

  @Override
  public void start() {
    log.info("Employee Service started!");
  }

  @Override
  public void stop() {
    log.info("Employee Service stopped!");
  }

}

… and you must register your Service as a bound component in order for Fathom to be able to properly inject, start, & stop it.

public class Components extends Module {

  @Override
  protected void setup() {

    bind(EmployeeService.class);
    bind(EmployeeDao.class);

  }

}

Preferred Start Order¶

Services are ordered according to their preferred start order (lower numbers first) and then started serially. Services are stopped in the reverse of the start order.

For reference, here are the start orders of several Fathom modules. This may be helpful in deciding how to order your modules. In general, you should probably order your Services after all dependent services and components have been started.

Service	Preferred Start Order
Fathom-JCache	10
Fathom-Metrics	50
Fathom-Security	50
Fathom-Quartz	50
Fathom-Mailer	50
Fathom-REST	100

Requiring Settings¶

Your service may need one or more settings to function and you may specify them as annotated requirements.

Each required setting must be present in the runtime profile configuration and must have a non-empty value otherwise the service will not be registered.

@RequireSetting("employeeService.url")
@RequireSetting("employeeService.username")
@RequireSetting("employeeService.password")
@Singleton
class EmployeeService implements Service {

  Logger log = LoggerFactory.getLogger(EmployeeService.class);

  @Override
  public int getPreferredStartOrder() {
    return 100;
  }

  @Override
  public void start() {
    log.info("Employee Service started!");
  }

  @Override
  public void stop() {
    log.info("Employee Service stopped!");
  }

}

Requiring Modes¶

You might only want to load your service in a particular runtime mode. This is easily accomplished by using one or more of the mode-specific annotations: @DEV, @TEST, and @PROD.

@DEV @TEST
@Singleton
class DebugService implements Service {

  Logger log = LoggerFactory.getLogger(DebugService.class);

  @Override
  public int getPreferredStartOrder() {
    return 100;
  }

  @Override
  public void start() {
    log.info("Debug Service started!");
  }

  @Override
  public void stop() {
    log.info("Debug Service stopped!");
  }

}

Usage¶

Inject your Service where you need it.

@Singleton
public void EmployeeDao {

  @Inject
  EmployeeService employeeService;
}