orbital.util
Class Activation

java.lang.Object
  java.lang.Throwable
      orbital.util.Activation

All Implemented Interfaces:

java.io.Serializable

public abstract class Activation
extends java.lang.Throwable

Activation is the base class for conditional exception handling. It adds tracing, delegation and rejection to java's common terminal exception handling capabilities.

Conditional exceptions thrown with Activation semantics can be:

• handled normally in the corresponding try..catch block where it occured in, with handle(Object).
• delivered to descendant conditional exception handlers up the activation chain with super.raise(Object).
• returned to the part that caused it with return Object, possibly after prophylaxis and global fixing changes.

by implementing the raise method.

The creator should be set up as follows:

 // Activation derivative MyActivation
 Activation frame = new MyActivation(myCaller);
 try {
     // something like
     if (some_condition)
         frame.raise(some_exception_info);
 }
 catch (Activation a) {
     if (a != frame)
         throw a; // rethrow foreign conditional exceptions
     Object info = a.info();
     // deal with information somehow
 }
 

Conditional exceptions can be

resumed

after where the exception occured.

retried

when the operation that caused the exception is repeated under the new circumstances.

If their Activation instances are constructed such that they resume or retry the operations. Even ordinary terminal ones can do this, but only when used within their own try..catch blocks (and loops).

Author:

Axel-Tobias Schreiner, Bernd Kühl, André Platzer

See Also:

Throwable, Exception, Serialized Form

Constructor Summary

protected

Activation(Activation caller) Creates a new activation.

Method Summary

protected void	handle(java.lang.Object information) Initiate normal exception handling in the corresponding catch-clause.
java.lang.Object	info() Get this exception's information that is to be handled.
java.lang.Object	raise(java.lang.Object information) Raises this conditional exception with additional information.

Methods inherited from class java.lang.Throwable

fillInStackTrace, getCause, getLocalizedMessage, getMessage, getStackTrace, initCause, printStackTrace, printStackTrace, printStackTrace, setStackTrace, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Activation

protected Activation(Activation caller)

Creates a new activation.

Parameters:

caller - the activation corresponding to the method that called this.

Method Detail

raise

public java.lang.Object raise(java.lang.Object information)
                       throws Activation

Raises this conditional exception with additional information. (Conditionally) sends an object up the activation chain.

This method should be overwritten in a concrete class to define reactional behaviour. It is called by a descendant to try to send an object back the activation chain. This implementation will deliver the conditional exception to the outer caller up the activation chain.

Conditional exceptions thrown with Activation semantics can be:

• handled normally in the corresponding try..catch block where it occured in, with handle(Object).
• delivered to descendant conditional exception handlers up the activation chain with super.raise(Object).
• returned to the part that caused it with return Object, possibly after prophylaxis and global fixing changes.

Parameters:

information - to be sent up the chain.

Returns:

the information sent back to descendant.

Throws:

Activation - to be caught by the creator who should retrieve the object by calling info().

java.lang.NullPointerException - if this is the first activation in a chain.

handle

protected final void handle(java.lang.Object information)
                     throws Activation

Initiate normal exception handling in the corresponding catch-clause. Sends an object back to the creator of this conditional exception in order to initiate normal exception handling in the corresponding try..catch block.

Parameters:

information - any informational data the finite catch-handler needs to know about the exception.

Throws:

Activation

See Also:

info()

info

public final java.lang.Object info()

Get this exception's information that is to be handled.

Returns:

information data to be handled, as stated in the call to handle(Object).

See Also:

handle(java.lang.Object), information