Parameter Passing

When you implement an EJB, or write the client code that calls EJB methods, you have to be aware of the parameter-passing conventions used with EJBs.

A parameter that you pass to a bean method, or a return value from a bean method, can be any Java type that is serializable. Java primitive types (int, double) are serializable. Any non-remote object that implements the java.io.Serializable interface can also be passed.

A non-remote object passed as a parameter to a bean, or returned from a bean, is passed by copy, not by reference. So, for example, if you call a bean method as follows:

public class theNumber {
  int x;
}
...
bean.method1(theNumber);

then method1() in the bean gets a copy of theNumber. If the bean changes the value of theNumber object on the server, this change is not reflected back to the client, because of the pass-by-copy semantics.

If the non-remote object is complex, for example a class containing several fields, only the non-static and non-transient fields are copied.

When passing a remote object as a parameter, the stub for the remote object is passed. A remote object passed as a parameter must extend remote interfaces.

The next section demonstrates parameter passing to a bean and remote objects as return values.

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