Imixs Workflow ...the open source workflow technology for business applications

Core API

The Imixs Workflow Manager

The WorkflowManager is the central element of a Workflow implementation. This interface provides all basic functions and can be implemented in various ways. The WorkflowManager acts as a business delegate and provides the actual business functions of a workflow system.

[/images/org.imixs.workflow.WorkflowManager]Figure 1

The WorkflowManager serves as the central interface between a software system and the actual WorkflowKernel. For this purpose, the WorkflowManager provides methods for generating of and searching for WorkItems, makes a WorkflowModel available, and registers concrete plug-ins for processing with the WorkflowKernel. The WorkflowManager works as a controller that loads and stores the WorkItems to be processed, and registers the functions required for process handling as plug-ins with the WorkflowKernel. The WorkflowManager is not responsible for process control (WorkflowKernel) or processing (plug-ins). The WorkflowManager just provides the infrastructure that allows a user or a software system to process WorkItems within a business process.

This concept facilitates the implementation of a concrete WorkflowManager in a defined software environment.

Registering of Plug-Ins

An essential task of the WorkflowManager is to register the plug-ins required for processing with a WorkflowKernel. This requires the WorkflowManager to instantiate an instance of class org.imixs.workflow.WorkflowKernel, and to subsequently register the plug-ins required for process handling. A typical program section is structured as follows:

....
  // init WorkflowKernel 
  WorkflowKernel workflowKernel =new org.imixs.workflow.WorkflowKernel(this);
  // register Plugins.....
  workflowKernel.registerPlugin("org.imixs.workflow.plugins.AccessPlugin");
  workflowKernel.registerPlugin("org.imixs.workflow.plugins.HistoryPlugin");
  
....

The WorkflowManager forwards a so-called WorkflowContext to the WorkflowKernel. The WorkflowContext is an abstract interface that describes the environment of a workflow system. For instance, a surrounding EJB container of an application server. The WorkflowContext is used to establish a connection between the WorkflowManager and the plug-ins called by the WorkflowKernel.

In most cases, the WorkflowContext is implemented by the WorkflowManager itself. As the WorkflowManager has best knowledge of the actual program function and thus of the environment (e.g., a servlet environment or an EJB container), this is not a big problem in most cases.

Process Handling

The WorkflowManager provides several methods for actual process handling of a WorkItem. The most important one is the process method().

 public void processWorkItem(ItemCollection workitem) throws Exception;

The method processWorkItem() processes the forwarded WorkItem (ItemCollection). For this purpose, the WorkItem is forwarded to the WorkflowKernel. The WorkflowManager finds the WorkItem and implements the persistence strategy. All processing is performed by the WorkflowKernel.

    public void processWorkItem(ItemCollection aWorkItem,int aActivityInstanceID)throws Exception {
     // Finding ItemCollection
    .... getItemCollection(.....);...
    workflowKernel.process(itemCol);
    // Store ItemCollection to a database
    .... saveItemCollection(....);
    ....
    }

Also the WorkflowManager implementation have to verifiy if the items $processID and $ActivityID by the workitem are defining a valid model entry. If not the method should throw an ProcessingErrorException.

For more informations about the interfaces see also the JavaDocs.