1.4.2. How it works

After logging in, todo.jsp uses the taskInstanceList component to display a table of outstanding todo items for the current user. (Initially there are none.) The page also displays a form to enter a new task item. When the user types the todo item and clicks the Create New Item button, #{todoList.createTodo} is called. This starts the todo process, as defined in todo.jpdl.xml.

When the process instance is created, it transitions immediately to the todo state, where a new task is created. The task description is set based on the user input saved to #{todoList.description}. The task is then assigned to the current user, stored in the seam actor component. In this example, the process has no extra process state — all the state is stored in the task definition. The process and task information is stored in the database at the end of the request.

When todo.jsp is redisplayed, taskInstanceList finds the newly-created task and displays it in an h:dataTable. The internal state of the task is displayed in each column: #{task.description}, #{task.priority}, #{task.dueDate}, etc. These fields can all be edited and saved to the database.

Each todo item also has a Done button, which calls #{todoList.done}. Each button specifies taskInstance="#{task}" (the task for that particular row of the table) so that the todoList component is able to distinctly identify which task is complete. The @StartTask and @EndTask annotations activate and immediately complete the task. The original process then transitions into the done state (according to the process definition) and ends. The state of the task and process are both updated in the database.

When todo.jsp is displayed again, the completed task is no longer shown in the taskInstanceList, since this component displays only incomplete tasks.