throw

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Module

The throw accessor is exported by the urn:org:ten60:netkernel:ext:sys module. Import this module to gain access to the accessor.

Syntax

URI

active: throw

Argument	Rules	Description
operand	Mandatory	a canonical exception document

Example Usage

DPML

<instr>
  <type>throw</type>
  <operand>
    <ex>
      <id>DELIBERATE</id>
      <message>broken!</message>
    </ex>
  </operand>
</instr>

NetKernel Foundation API

The throw accessor is for use within the DPML. Do not use the throw accessor when programming in a language that works directly with the NKF API. Instead, use the native excpetion throwing mechanism of your choosen language.

Purpose

The throw accessor is used to throw an exception. When used, the throw accessor throws a canonical exception document conforming to the follow structure, supplied as the operand parameter.

<ex>
  <id>Anything you like to identify your exception</id>
  <message>A message decscribing the exception</message>
</ex>

Exceptions are caught in a DPML <exception> block where they can be processed just like any other document. A thrown exception is accessed with the this:exception URI.

When an exception is thrown, execution switches to the nearest exception block. If no exception block is found in the current instruction block it flows out to any outer blocks. If the exception is not caught in the current process it is returned as the response document of the process. Any parent calling process is again checked for exception handling blocks.