Java Web Frameworks - JSF and Struts 2

The f:view tag has minimal performance overhead. It's required for JSF pages to establish the JSF context and component tree. The overhead is negligible and necessary - avoiding or reducing f:view scope would break JSF functionality, not improve performance.

This code is invalid. While the taglib declarations and f:view wrapper are correct, h:commandButton must be inside a form element (h:form) to function. Command buttons require form context to handle action events and submission - this code lacks the required h:form wrapper.

The updateActionListener is designed for command components like h:commandButton and h:commandLink. SelectBooleanCheckbox is an input component for boolean selection, not an action trigger - it doesn't support action listeners. Use valueChangeListeners or converters instead.

The globalOnly property on h:messages filters messages to display only global messages (those not associated with a specific component via for attribute). When set to true, component-specific messages are hidden and only application-wide messages appear.

The processDecodesWithoutValidation method in JSF does exactly what its name suggests: it executes the Apply Request Values phase and decodes parameters without running validation. This is useful for scenarios where you want to process submitted data but skip validation logic. The method will handle RuntimeExceptions appropriately, but its key characteristic is bypassing the validation phase for immediate components.

In Struts 2, the first entry point in the request processing lifecycle is a Servlet Filter (FilterDispatcher or StrutsPrepareAndExecuteFilter). This filter intercepts all requests and dispatches them to the appropriate action. This is different from Struts 1 which used a central ActionServlet.

In Struts 2, HTML form parameters are automatically passed directly to Action classes via parameter interception. The Action class properties match form field names, and Struts 2 populates them automatically. ActionForm (used in Struts 1) is not required in Struts 2.

The Struts 2 exception handling mechanism primarily handles unchecked exceptions (RuntimeException and its subclasses). Checked exceptions need to be caught and handled by the application code or wrapped in runtime exceptions. The exception mapping in struts.xml works with unchecked exceptions.

To receive the HttpServletRequest instance in a Struts 2 Action class, you implement the ServletRequestAware interface. This interface's setServletRequest(HttpServletRequest) method is called by Struts 2 before the action executes, injecting the request object. ServletResponseAware is for responses, ActionSupport is a convenience base class.

Action classes in Struts 2 do NOT have to extend ActionSupport. They only need to implement the Action interface (which has one method: execute()). ActionSupport is a convenient base class that provides default implementations and utility methods, but it's optional. You can even use plain POJOs as actions.

Declarative validation in Struts 2 works through XML validation files that are named based on the Action class, not whether the class extends ActionSupport. Any class can have declarative validation as long as the validation XML follows the naming convention (ClassName-validation.xml). The ActionSupport extension is not required.

In Struts 2, validation XML files are named after the Action class, not the action name specified in struts.xml. For an action with class SampleClass, the validation file must be named SampleClass-validation.xml. The framework looks for validation files based on the fully qualified class name.

In Struts 2, the configuration file name 'struts.xml' cannot be changed. The framework hardcodes this name and looks for it in the classpath. This is different from Struts 1, where you could specify a different config file name in web.xml. Struts 2 requires struts.xml to be in a specific location with that exact name.

Action classes in Struts 2 are instantiated on a per-request basis by default. Each request creates a new instance of the action class, which makes actions thread-safe and stateless. This is a key difference from some frameworks where actions might be singletons. The Struts 2 interceptor stack and valueStack work with this per-request instance model.

In Java web frameworks like Struts, the default interceptor stack includes validation, workflow, and other interceptors. This stack is fully customizable - developers can remove interceptors, add new ones, or create entirely custom stacks to suit application needs.

In JSF, only components that extend UIInput can have their submitted values validated during the Process Validations phase. UIOutput components are for display only and don't receive user input, UICommand is for action events like button clicks, and UIOutputLink renders navigation links without accepting user input.

JSF validators are designed to validate individual component values, not multiple fields simultaneously. Cross-field validation requires workarounds like using phase listeners, custom validators that access other components via UIComponent.findComponent(), or Bean Validation (JSR 303/380) annotations with class-level constraints.

JSF includes standard message bundles with predefined error messages for conversion and validation failures. These messages are automatically associated with components and displayed using <h:message> or <h:messages> tags when errors occur during the Process Validations or Update Model Values phases.

When a converter throws an exception or sets a conversion error, JSF marks the component as invalid. The isValid() method returns false for that component, and the component's value is not updated in the model. This prevents invalid data from propagating through the application.

The section in Web.config defines authorization rules that specify which users or roles can access specific resources. The section defines the authentication mode (Forms, Windows, Passport, None), but authorization rules controlling user access are separate.