The java.rmi.registry package

The Registry Interface

A Registry is used to locate RMI services. The server is responsible for registering remote objects. A client must first locate the exported remote objects. Once a client has retrieved a reference to a remote object, subsequent objects can be accessed through other means, namely return values. The java.rmi.registry.Registry interface provides methods for lookup, binding, rebinding, and listing the contents of a registry. Actually, the methods of java.rmi.Naming class call the methods of a remote object that implements the Registry interface.

Methods

• public void bind(String name, Remote obj) - This method binds the specified "name" to a remote object. It throws an AlreadyBoundException, if the name is already bound to an object. Binding means associating a name for a remote object that can be used to look up that remote object.

• public String[] list() - It returns an array of the Strings bound in the registry. Each String object contains a name that is bound to a remote object. The names are URL-formatted strings.

• public Remote lookup(String name) - The lookup method is used to get a remote object from a registry. It returns a stub for the remote object associated with the specified "name". It takes a string containing the URL to a remote object reference on the server.

• public void rebind(String name, Remote obj) - It rebinds the specified name to a remote object. It replaces an object that is already bound with the registry with the new object specified with obj.

• public void unbind(String name) - It removes an object reference from the registry. It throws a NotBoundException if there was no binding.

The LocateRegistry Class

The LocateRegistry class can be used to find or create a new registry.

Methods

• public static Registry createRegistry(int port) - This method is used to create and export a registry on the local host that accepts requests on the specified port. The port must be available otherwise an exception will be thrown.

• public static Registry getRegistry() - This method returns a reference to the registry on port no. 1099.

• public static Registry getRegistry(int port) - This method attempts to return a reference to the registry on the specified port.

• public static Registry getRegistry(String host) - This method returns a reference to the registry on the specified host on port no. 1099. If host is null, the local host is assumed. If the given host cannot be resolved, an UnknownHostException is thrown.

• public static Registry getRegistry(String host, int port) - This method returns a reference to the registry on the specified host and port. If the given host cannot be resolved, an UnknownHostException is thrown.

• public static Registry getRegistry(String host, int port,RMIClientSocketFactory csf) - This method returns a locally created remote reference to the registry on the specified host and port. Communication with the registry will use the supplied RMIClientSocketFactory csf.

There are two ways to start a registry:

Use the RMI registry application (rmiregistry)
Use java.rmi.registry package to write your own registry service.