13.2 Scoped Services

By default, access to service methods is not synchronised, so nothing prevents concurrent execution of those methods. In fact, because the service is a singleton and may be used concurrently, you should be very careful about storing state in a service. Or take the easy (and better) road and never store state in a service.

You can change this behaviour by placing a service in a particular scope. The supported scopes are:

  • prototype - A new service is created every time it is injected into another class

  • request - A new service will be created per request

  • flash - A new service will be created for the current and next request only

  • flow - In web flows the service will exist for the scope of the flow

  • conversation - In web flows the service will exist for the scope of the conversation. ie a root flow and its sub flows

  • session - A service is created for the scope of a user session

  • singleton (default) - Only one instance of the service ever exists

If your service is flash, flow or conversation scoped it must implement java.io.Serializable and can only be used in the context of a Web Flow.

To enable one of the scopes, add a static scope property to your class whose value is one of the above, for example

  1. static scope = "flow"
UpgradingStarting with Grails 2.3, new applications are generated with configuration that defaults the scope of controllers to singleton.If singleton controllers interact with prototype scoped services, the services effectively behave as per-controller singletons.If non-singleton services are required, controller scope should be changed as well.See Controllers and Scopes in the user guide for more information.

Lazy initialization

You can also configure whether the service is lazily initialized. By default, this is set to true, but you can disable this and make initialization eager with the lazyInit property:

  1. static lazyInit = false