Workflow Engine

The workflow engine is responsible for creating and maintaining workflows. Unless you need to create your own workflows programmatically, the most important information in this section is the conceptual overview which explains the basic concepts of the workflow engine. The [fleXive] workflow engine is a specialized workflow implementation used by the content engine, it does not offer a generic workflow implementation.

A workflow combines a collection of workflow states and the enumeration of all possible transitions between those states. In [fleXive], the following terminology is used:

Step definition

An abstract definition of a workflow step. It defines a localized label and a unique target.

Unique target

Supports the concept of unique steps for versioned contents. When a workflow step with a unique target is assigned to a content instance version, all other versions of the instance that are in the same workflow step are moved to the unique target step. Since this transition is executed every time a content instance is saved, there can be at most one content instance version in a step with a unique target at any given time.

The canonical example for this is the Edit/Live/Archived workflow for publishing website contents: a content is created in the Edit workflow step. When it is deemed to be ready for publication, the latest version is set to the Live workflow step and is shown on the web page. When an update is necessary, a new version is created in the Edit workflow step which can be modified without altering the Live instance. When the new version is to be published, it is set to the Live workflow step. However, there already exists an old version in the Live step: to resolve this, the Live step has a unique target (e.g. Archived). When the latest version is set to the Live step, the previous Live version is moved to the Archived step.

Workflow

A concrete workflow that consists of steps and routes, including the permission configuration for both.

Step

A concrete assignment of a step definition to a workflow, including an ACL that defines the permissions on objects in this workflow step.

Route

A transition between two steps of a workflow, including the user group for which it should be available.

Although workflows can be edited in the backend administration application, you can also setup new workflows programmatically. The workflow engine is spread across four EJB interfaces, each one handling the create/update/delete operations for its part of the workflow: step definitions, steps, routes, and the workflow objects themselves. We'll show how to create a simple workflow from scratch, for a more elaborate explanation of the methods please refer to the [fleXive] JavaDoc.


Example 6.20. Creating a new workflow with steps and routes

There are EJB interfaces for adding steps and routes to an existing workflow. However, when we create a new workflow we would have to first create an empty workflow, and then create each step and route using EJB calls. To simplify things a bit, the workflow engine can create the steps and routes for a new workflow object using intermediate IDs. An intermediate step or route ID is negative (IDs retrieved from the database are always positive) and can be referenced in routes. Finally we retrieve the created workflow from the environment (workflows are always cached, so there isn't even a method to load workflows directly from the database) and perform some validity checks.

// create a workflow and auto-create steps using intermediate IDs
final Step step1 = new Step(-10, definition1.getId(), ACL.Category.WORKFLOW.getDefaultId());
final Step step2 = new Step(-20, definition2.getId(), ACL.Category.WORKFLOW.getDefaultId());

// create a route between step1 and step2
final Route route = new Route(-1, UserGroup.GROUP_EVERYONE, -10, -20);

// create workflow object and store it in the database
final Workflow workflow = new Workflow(-1, "test wf", "my test workflow",
        Arrays.asList(step1, step2), Arrays.asList(route));
final long workflowId = EJBLookup.getWorkflowEngine().create(workflow);

final Workflow dbWorkflow = CacheAdmin.getEnvironment().getWorkflow(workflowId);
assert dbWorkflow.getRoutes().size() == 1;      // route available?
assert dbWorkflow.getSteps().size() == 2;       // both steps available?

// check from and to steps of our route
assert dbWorkflow.getRoutes().get(0).getFromStepId() == dbWorkflow.getSteps().get(0).getId();
assert dbWorkflow.getRoutes().get(0).getToStepId() == dbWorkflow.getSteps().get(1).getId();