A ActionEventListener can be used to add some logic when action's instance is created or when exception occurred during processing the action.
Configuration
Right now there can be only one instance of ActionEventListener for the whole Struts2 application. You can configure it via struts.xml by adding bean definition:
<bean type="com.opensymphony.xwork2.ActionEventListener" class="com.demo.MyActionEventListener"/>
Examples
public class MyActionEventListener implements ActionEventListener {
public Object prepare(Object action, ValueStack stack) {
if (action instanceof MyBaseAction) {
((MyBaseAction)action).setUserService(stack.findValue("userService"));
}
}
public String handleException(Throwable t, ValueStack stack) {
if (t instanceof MyBusinessException) {
return stack.findString("defaultBusinesResult");
}
return null;
}
}