(Quick Reference) # 13.2 Scoped Services Version: 3.2.8 ## 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
    static scope = "flow"
| Upgrading Starting 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.
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