J2EE Design Patterns and Web Technologies

This is false. SAX cannot be used to modify XML because it's a read-only, forward-only parser. It doesn't build a tree structure or maintain the document in memory - it just fires events as it reads. To modify XML, you need DOM (which loads the full tree) or use StAX with write capabilities. The claimed answer (B/False) is correct.

The Document Object Model (DOM) parser loads the entire XML document into memory and builds a tree structure for navigation and manipulation. This approach makes it easy to traverse the document, but it requires substantial memory for large files. Alternative parsers, such as SAX, process XML sequentially without loading the entire tree into memory.

StAX (Streaming API for XML) uses a pull-based parsing model where the application controls when to read the next event. Push-based parsers like SAX generate events automatically and the application must handle them. Since StAX is pull-based, not push-based, the statement is False.

When an application uses Container Managed Persistence (CMP), the container handles database operations automatically. Adding a DAO layer on top would be redundant since the container already provides the abstraction and CRUD functionality. The DAO pattern is most useful with Bean Managed Persistence (BMP) where you need manual control.

The Intercepting Filter pattern in Java EE is implemented by implementing the javax.servlet.Filter interface. This interface defines methods like init(), doFilter(), and destroy() that allow pre/post-processing of requests and responses. FilterChain and FilterConfig are supporting interfaces used by filters but are not the primary interface to implement.

Both jsp:include and <%@ include %> (directive) are used for implementing the Composite View pattern, which allows composing complex views from smaller reusable components. The question uses <%include...%> (likely meaning the include directive). Both mechanisms support composite views, making 'All of the above' the correct answer.

The statement is FALSE. The include directive (<%@ include %>) performs better than the include tag (jsp:include) because the directive includes content at translation/compile time (once), while the tag includes at runtime (every request). The tag is slower but more dynamic. The claimed answer (B/False) correctly identifies this.

The Front Controller pattern is implemented by creating a servlet that implements the javax.servlet.Servlet interface (typically by extending HttpServlet). The servlet acts as a centralized entry point for all requests. ServletConfig and ServletContext are interfaces for configuration and context access, not for implementing the controller itself.

The statement is FALSE. The Business Delegate pattern primarily provides a client-side abstraction to reduce complexity and hide business service lookup/communication details. While it does simplify access to business services, its main purpose isn't to simplify the underlying business service interfaces for easier modification - that's more aligned with patterns like Session Facade or Service Locator. The claimed answer (B/False) correctly identifies this.

Session Facade provides coarse-grained access to the business tier by encapsulating fine-grained business components and presenting a simplified, unified interface to clients. Business Delegate provides client-side abstraction, and Transfer Object is for data transfer. Session Facade is specifically designed for coarse-grained business tier access.

The statement is FALSE. Transfer Object pattern is primarily designed for reading and transferring data across tiers (from business tier to client). It's typically used for data retrieval, not for updating data on the business tier. Updates are handled through other patterns like Session Facade or Business Delegate. The claimed answer (B/False) is correct.

DAO (Data Access Object) pattern provides an abstraction layer between business logic and data source. It encapsulates all details of connecting to and interacting with data sources, making the application code independent of the underlying data storage mechanism. The pattern can work with any type of data source - relational databases, LDAP directories, XML files, flat files, or even NoSQL stores.

The Business Delegate design pattern is used to decouple presentation tier code from business tier services. To achieve this, it frequently leverages the Service Locator pattern to hide the underlying complexities of locating, creating, and accessing remote enterprise beans and web services.

Transfer Objects (also called Value Objects) are used to transfer data across tiers. While they often implement Serializable for network transmission in Java EE environments, it's not strictly mandatory. Other serialization mechanisms (XML, JSON, custom protocols) can be used. The interface is a practical requirement for RMI/IIOP but not a theoretical necessity for the pattern itself.

In Struts framework, ActionServlet implements the Front Controller pattern. It receives all HTTP requests and delegates them to appropriate Action classes based on the struts-config.xml configuration. ActionServlet is the single entry point that handles common request processing tasks like navigation, workflow, and security, which is the essence of Front Controller pattern.