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See the Singleton Beans page for a full description of the javax.ejb.Singleton api.

The Code

PropertyRegistryBean

Here we see a bean that uses the Bean-Managed Concurrency option as well as the @Startup annotation which causes the bean to be instantiated by the container when the application starts. Singleton beans with @ConcurrencyManagement(BEAN) are responsible for their own thread-safety. The bean shown is a simple properties "registry" and provides a place where options could be set and retrieved by all beans in the application.

{snippet:url=openejb3/examples/simple-singleton/src/main/java/org/superbiz/registry/PropertyRegistryBean.java|lang=java|id=code}

ComponentRegistryBean

Here we see a bean that uses the Container-Managed Concurrency option, the default. With @ConcurrencyManagement(CONTAINER) the container controls whether multi-threaded access should be allowed to the bean (@Lock(READ)) or if single-threaded access should be enforced (@Lock(WRITE)).

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