# ServiceAbility Lifecycle


You can override lifecycle callbacks (described in the table below) for ServiceAbility based on service requirements.  


 **Table 1** ServiceAbility lifecycle callbacks

| API| Description|
| -------- | -------- |
| onStart(): void | Called to initialize a ServiceAbility when the ServiceAbility is being created. This callback is invoked only once in the entire lifecycle of a ServiceAbility.|
| onCommand(want: Want, startId: number): void | Called every time a ServiceAbility is started on the client. You can collect calling statistics and perform initialization operations in this callback.|
| onConnect(want: Want): rpc.RemoteObject | Called when the ServiceAbility is connected.|
| onDisconnect(want: Want): void | Called when the connection to the ServiceAbility is disconnected.|
| onStop(): void | Called when the ServiceAbility is being destroyed. You should override this callback for your ServiceAbility to clear its resources, such as threads and registered listeners.|