As in the case of Ice objects, a Dynamic Ice application may represent user exceptions in a native format that is not directly compatible with the Ice API. If the application needs to raise such a user exception to the Ice run time, the exception must be wrapped in a subclass of Ice.UserException. The Dynamic Ice API provides a class to simplify this process:

{zcode:java}
package Ice;

public abstract class UserExceptionWriter extends UserException {

    public UserExceptionWriter(Communicator communicator);

    public abstract void write(Ice.OutputStream os);
    public abstract boolean usesClasses();

    // ...
}
{zcode}

A subclass of UserExceptionWriter is responsible for supplying a communicator to the constructor, and for implementing the following methods:

• void write(OutputStream os)
  This method is invoked when the Ice run time is ready to marshal the exception. The subclass must marshal the exception using the encoding rules for exceptions.

• boolean usesClasses()
  Return true if the exception, or any base exception, contains a data member that is an object by value.

See Also

• Intercepting Object Insertion and Extraction in Java
• Data Encoding for Exceptions