2.6 Parameter Passing in Remote Method Invocation

An argument to, or a return value from, a remote object can be any Java type that is serializable. This includes Java primitive types, remote Java objects, and nonremote Java objects that implement the java.io.Serializable interface. For more details on how to make classes serializable, see the Java "Object Serialization Specification." For applets, if the class of an argument or return value is not available locally, it is loaded dynamically via the AppletClassLoader. For applications, these classes are loaded by the class loader that loaded the application; this is either the default class loader (which uses the local class path) or the RMIClassLoader (which uses the server's codebase).

Some classes may disallow their being passed (by not being serializable), for example for security reasons. In this case the remote method invocation will fail with an exception.

2.6.1 Passing Nonremote Objects

A nonremote object, that is passed as a parameter of a remote method invocation or returned as a result of a remote method invocation, is passed by copy.

That is, when a nonremote object appears in a remote method invocation, the content of the nonremote object is copied before invoking the call on the remote object. By default, only the nonstatic and nontransient fields are copied.

Similarly, when a nonremote object is returned from a remote method invocation, a new object is created in the calling virtual machine.

2.6.2 Passing Remote Objects

When passing a remote object as a parameter, the stub for the remote object is passed. A remote object passed as a parameter can only implement remote interfaces.