Name space federation

Federating name spaces involves binding contexts from one name space into another name space.

For example, assume that a name space, Name Space 1, contains a context under the name a/b. Also assume that a second name space, Name Space 2, contains a context under the name x/y. (See the following illustration.) If context x/y in Name Space 2 is bound into context a/b in Name Space 1 under the name f2, the two name spaces are federated. Binding f2 is a federated binding because the context associated with that binding comes from another name space. From Name Space 1, a lookup of the name a/b/f2 returns the context bound under the name x/y in Name Space 2. Furthermore, if context x/y contains an enterprise bean (EJB) home bound under the name ejb1, the EJB home can be looked up from Name Space 1 with the lookup name a/b/f2/ejb1. Notice that the name crosses name spaces. This fact is transparent to the naming client.

In a WebSphere Application Server name space, you can create federated bindings with the following restrictions:

• Federation is limited to CosNaming name servers. A WebSphere Application Server name server is a Common Object Request Broker Architecture (CORBA) CosNaming implementation. You can create federated bindings to other CosNaming contexts. You cannot, for example, bind contexts from an LDAP name server implementation.

• If you use JNDI to federate the name space, use a WebSphere Application Server initial context factory to obtain the reference to the federated context. If you use some other initial context factory implementation, you might not be able to create the binding or the level of transparency might be reduced.

• A federated binding to a non-WebSphere Application Server naming context has the following functional limitations:

  • JNDI operations are restricted to the use of CORBA objects. For example, you can look up EJB homes, but you cannot look up non-CORBA objects such as data sources.

  • JNDI caching is not supported for non-WebSphere Application Server name spaces. This restriction affects the performance of lookup operations only.

  • If security is enabled, WebSphere Application Server does not support federated bindings to non-WebSphereApplication Server name spaces.

• Do not federate two WebSphere Application Server stand-alone server name spaces. Incorrect behavior might result. If you want to federate WebSphere Application Server name spaces, use servers running under the Network Deployment package of WebSphere Application Server.

• When federating the name spaces of two cells running a Network Deployment package of WebSphere Application Server, the names of the cells must be different. Otherwise, incorrect behavior can result.

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