org.apache.commons.workflow
Interface Block

All Superinterfaces:

Owner, Step

All Known Subinterfaces:

Iterator

All Known Implementing Classes:

BaseBlock, IfAnyStep, IfNotAnyStep, IfNotStep, IfStep, WhileAnyStep, WhileNotAnyStep, WhileNotStep, WhileStep

public interface Block
extends Owner, Step

A Block is a Step that can include nested Steps. It is used to create Step implementations supporting conditional execution and iteration.

DESIGN NOTES - The execute() method will be called when the Block is first encountered in the normal flow of execution (as with any other Step), and each time the execution of the nested Steps associated with this Block. The Block implementation is responsible for satisfying the following contract requirements:

• Determine whether this is a first-time entry, or a repeated entry after execution of the nested Steps for this Block:
  • Peek at the top item on the BlockState stack maintained for us by the current Context.
  • If the top item exists, and has a block property equal to the current Block, this is a repeated entry after execution of the nested Steps for this Block.
  • If there is no top element, or the top element is for a different Block, this is the initial entry from the preceeding Step in the current Activity (or Block).
• When this is the initial entry into the Block, make a decision about whether the nested Steps should be executed:
  • If the nested Steps SHOULD be executed, create a new BlockState object (associated with this Block) and push it onto the BlockState stack. Then, set the next Step to be the first nested Step for this Block.
  • If the nested Steps SHOULD NOT be executed, simply return. The next Step will have already been set to the next Step of the current Activity (or Block) at the same nesting level.
• When this is a repeated entry into the Block, make a decision about whether the nested Steps should be executed again:
  • If the nested Steps SHOULD be executed again, set the next Step to be the first nested Step for this Block.
  • If the nested Steps SHOULD NOT be executed again, pop our BlockState object off of the stack maintained by our Context. Then, set the next Step to the nextStep property of this Block, which will cause execution to flow past the Block.

Version:

$Revision: 155475 $ $Date: 2005-02-26 13:31:11 +0000 (Sat, 26 Feb 2005) $

Author:

Craig R. McClanahan

Method Summary

Methods inherited from interface org.apache.commons.workflow.Owner

addStep, clearSteps, findStep, getFirstStep, getLastStep, getSteps, setSteps

Methods inherited from interface org.apache.commons.workflow.Step

execute, getId, getNextStep, getOwner, getPreviousStep, setId, setNextStep, setOwner, setPreviousStep