Exception Handling
The Imixs Workflow API prvides a set of Exception classes to signal unexpected program situations. For the Plugin API there exists the specific Exception type ‘PluginException’. This exception can be used throw an exception in a plugin which can be handled by a workflow application.See the following example:
public class MyPlugin extends AbstractPlugin {
......
@Override
public ItemCollection run(ItemCollection workitem, ItemCollection event) throws PluginException {
// some code going wrong.....
Object[] params={workitem.getItemValueString("_attachments")};
throw new PluginException(
MyPlugin.class.getSimpleName(),
ERROR_ATTACHMENTS_MISSING,
"Please enter a valid file name",params);
.....
}
....
}
In this example a Plugin throws a PluginException. The Exception contains the Plugin name, an Error Code, a Error Message and an optional array of params. The optional params can be used by an application to provide additional information to the user.
Handling PluginExceptions in JSF
This is an example how an application can handle a Plugin Exception and create a JSF Faces Message based on the information of the PluginException:
@Named("workflowController")
@SessionScoped
public class WorkflowController extends
org.imixs.workflow.jee.faces.workitem.WorkflowController implements
Serializable {
.....
/**
* The action method processes the current workItem and handles PluginExceptions.
*/
@Override
public String process() throws AccessDeniedException,
ProcessingErrorException {
// process workItem and catch exceptions
try {
actionResult = super.process();
} catch (PluginException pe) {
String message = pe.getErrorCode();
// try to find the message text in resource bundle...
try {
// try to translage the error message code into a readable message text
ResourceBundle rb = ResourceBundle.getBundle("bundle.app");
message = rb.getString(pe.getErrorCode());
} catch (MissingResourceException mre) {
logger.warning("WorkflowController: " + mre.getMessage());
}
// add global message
FacesContext.getCurrentInstance().addMessage(null,
new FacesMessage(FacesMessage.SEVERITY_INFO, message, null));
}
....
}
This example catches a PluginExcpetion and add a global FacesMessage. The message can be displayed in a jsf page using the messages tag:
<h:messages globalOnly="true" />
The attribute ‘globalOnly’ indicates to display global messages not bound to a specific JSF input element.
