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WorkflowDispatcher.javaAPI DocExample4078Sat Nov 22 19:35:12 GMT 2003s2wexample.controller

WorkflowDispatcher

public class WorkflowDispatcher extends Object implements Dispatcher
An implementation of the dispatcher interface for processing workflows. A workflow is a linear path through a set of states, with actions to determine each state transition.

Fields Summary
private static final String
WORKFLOW_TAG
tags used in the XML definition of workflows and states
private static final String
STATE_TAG
private static final String
NAME_ATTR
attributes shared with JSP pages
private static final String
ACTION_ATTR
private static final String
VIEW_ATTR
private static final String
ACTION_PREFIX
where action classes can be found
private ServletContext
context
the servlet context
private State[]
states
the states this dispatcher uses as data
private int
currentState
the current state of this dispatcher
Constructors Summary
Methods Summary
public java.lang.StringgetNextPage(javax.servlet.http.HttpServletRequest req)
Get the next page to forward the user to

        State s = states[currentState];
        
        // increment the state only if the action suceeds
        if ((s.action == null) || s.action.performAction(req, context)) {
            if (currentState < states.length - 1) {
                s = states[++currentState];
            } else {
                currentState = 0;
                s = states[currentState];
            }
        }
        
        // return the uri of the current state
        return s.viewUri;
private s2wexample.controller.WorkflowDispatcher$State[]parseXML(java.io.InputStream is)
Parse the states XML file

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        
        Document doc = builder.parse(is);
       
        // find the workflow element
        NodeList workflows = doc.getElementsByTagName(WORKFLOW_TAG);
        Element workflow = (Element)workflows.item(0);
        
        // find all the states
        NodeList states = doc.getElementsByTagName(STATE_TAG);
        State[] stateList = new State[states.getLength()];
        
        // read state information
        for(int i = 0; i < states.getLength(); i++) {
            stateList[i] = new State();
            
            Element curState = (Element)states.item(i);
            stateList[i].name = curState.getAttribute(NAME_ATTR);
            stateList[i].viewUri = curState.getAttribute(VIEW_ATTR);
            
            // convert action names into class instances
            String action = curState.getAttribute(ACTION_ATTR);
            if (action != null && action.length() > 0) {
                Class c = Class.forName(ACTION_PREFIX + action);
                stateList[i].action = (Action)c.newInstance();
            }
        }
        
        return stateList;
public voidsetContext(javax.servlet.ServletContext context)
Called by the container to set the servlet context when this dispatcher is initialized.

    
                       
          
        // store the context
        this.context = context;
        
        // load the workflow from this file & parse it
        InputStream is = context.getResourceAsStream("/LanguageWorkflow.xml");
        try {
            states = parseXML(is);
        } catch(Exception ex) {
            throw new IOException(ex.getMessage());
        }
        
        // initialize the current state
        currentState = 0;