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See:
Description
Interface Summary | |
---|---|
Activity | An Activity represents an ordered sequence of Steps that comprise the executable actions necessary to accomplish a business task. |
Block | A Block is a Step that can include nested Steps. |
Context | A Context represents the dynamic computational state of a workflow process that is currently being executed. |
ContextListener | A ContextListener registers its interest in receiving
ContextEvent notifications when the occur on a particular
Context of interest. |
Descriptor | A Descriptor is a description of the mechanism by which an arbitrary Java object (typically a JavaBean) is referenced. |
Descriptors | Implementing Descriptors indicates that the corresponding
object has an associated list of Descriptor objects associated
with it, which can be manipulated through the methods defined in this
interface. |
Iterator | An Iterator is a Block that conditionally
repeats the nested Steps associated with the Block more than once (such as
a Block that implements "while" or "for" functionality). |
Owner | Owner represents the common characteristics of Activities and Blocks (that is, Steps that allow nested Steps, such as those that implementat conditionals and iteration). |
Registry | A Registry is a Singleton that provides registration
and lookup facilities for Activity instances. |
Scope | A Scope is a collection of arbitrary Java objects, keyed by String-valued names. |
ScopeListener | A ScopeListener registers its interest in receiving
ScopeEvent notifications when the occur on a particular
Scope of interest. |
Step | A Step represents a single executable action that can occur during the completion of an Activity. |
Class Summary | |
---|---|
BlockState | BlockState represents the current dynamic execution
state of a Block that is executing nested Steps . |
ContextEvent | A ContextEvent provides notification to a
ContextListener that a specified event has occurred for
the specified context. |
ScopeEvent | A ScopeEvent provides notification to a
ScopeListener that a specified event has occurred for
the specified scope. |
Exception Summary | |
---|---|
StepException | A StepException is used to report problems encountered
during the dynamic execution of a specific Step . |
WorkflowException | A WorkflowException is the base class for exceptions related to the workflow engine framework. |
This package contains the core interfaces and classes that define the major components of the workflow management system. There are divided into several categories, as follows.
The static representation of a set of possible workflows is represented internally as a tree of objects that implement the following interfaces. There is a one-to-many relationship between each component and the one immediately below it.
Activity
. Informally, the set of defined
Steps
can be considered to be the "instruction set" of a
"workflow computer". Several sets of predefined Step
implementations are included, and additional sets can be defined by
workflow implementations layered on top of the basic classes (for example,
the web-layer Steps are valid only within a web application, but such
a workflow implementation can still use all of the core Steps).The components described above are typically represented textually in an XML document whose format is not of interest to the core platform. However, the internal representation of these components is shared among concurrent users of those components, so the corresponding object tree (and the bean properties used to represent the linkages) should be considered read only after it is constructed.
The dynamic state of a computation is represented by the following
components. Each "in progress" computation, whether executed by the same
thread or different threads, must have its own Context
to represent the current state.
Activity
. Each Context
provides an evaluation
stack for in-process computations, plus access to one or more
Scopes
for interacting with the object model of the
surrounding application environment.java.util.Map
that provides a pluggable mechanism to attach the workflow engine to the
object model of a surrounding application. Every Context
provides at least one Scope
(called "local"), and
additional Scopes
can be registered by the application.
For example, a web application implementation of the workflow system
would typically register Scope
implementations that map
to the attributes of servlet requests, HTTP sessions, and the servlet
context. Implementations in other environments can provide
Scope
adapters to their own object storage mechanisms,
without affecting how Step
implementations interact with
beans stored in those Scopes
.
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