💼 IT4206 Enterprise Application Development
UCSC BIT 2024 | MCQ Solutions with Theory & Examples
What is Plumbing?
Theory: Plumbing is the underlying infrastructure that allows different software components to communicate and exchange data.
Example: When you click Buy on a shopping site, the request travels from UI → Server → Payment → Database. This communication chain is called plumbing.
What is a God Class?
Theory: A God Class is a class that does too many tasks, violating the Single Responsibility Principle (SRP).
StudentManager - Login() - Register() - Delete() - PrintReport() - SendEmail() - CalculateMarks()
Fix: Split into smaller classes like AuthService, ReportService, EmailService.
What is Business Logic?
Theory: Contains all business rules and calculations of the application.
If customer is Gold Discount = 20% Else Discount = 10%
This calculation belongs to the Business Logic Layer.
What is a Server Helper?
Theory: Works inside the Server JVM and helps execute remote requests.
Flow: Client → Server Helper → Server Object → Database
What is Distributed Garbage Collection?
Theory: DGC automatically removes unused remote objects in Java RMI to save memory.
Example: Client disconnects → Remote object no longer used → Java deletes it automatically.
What is an MDB?
Theory: Processes messages asynchronously. Clients cannot call its methods directly.
Example: Customer places order → Message sent to queue → MDB processes it later.
Java EE Transaction Management
Theory: Java EE servers provide automatic transaction management (also supports manual control).
Example: Bank transfer: Deduct + Add money. If one fails → entire transaction rolls back.
What is an Entity Bean?
Theory: Represents permanent data stored in databases.
Examples: Student table, Employee table, Product table. Each record = one entity.
What does JNDI lookup() do?
Theory: Searches the naming service and returns the requested object.
DataSource ds = (DataSource) ctx.lookup("jdbc/MyDB");
What is @JoinColumn?
Theory: Defines the foreign key between two database tables.
Student (student_id) ↓ foreign key Course (student_id)
Which is NOT an HTTP method?
Theory: Standard HTTP methods: GET, POST, PUT, DELETE, OPTIONS. There is no CREATE method.
Note: POST is used to create new resources (e.g., new user).
What does POST do?
Theory: Sends data to the server to create or update resources.
Examples: User Registration, Login Form, Online Order.
What do 3xx status codes mean?
Theory: 3xx codes mean the requested page has been redirected.
- 301 → Permanent Redirect
- 302 → Temporary Redirect
What does service() do?
Theory: Checks if request is GET or POST and calls the correct method.
GET → doGet() | POST → doPost()
What is web.xml?
Theory: The deployment descriptor for Java web applications. Maps Servlets to URL patterns.
What does <servlet-mapping> do?
Theory: Connects a Servlet with a URL.
/login → LoginServlet
What is ServletRequest?
Theory: Contains all data sent by the client.
request.getParameter("username");
What is a Web Container?
Theory: Manages Servlets, JSPs, sessions, and HTTP requests.
Example: Apache Tomcat's servlet container processes incoming web requests.
What is @OnOpen?
Theory: Executed when a WebSocket connection starts.
Example: User joins a live chat → @OnOpen is called.
What are Control Frames?
Theory: Manage the WebSocket connection.
- Ping – Check connection
- Pong – Reply to Ping
- Close – End connection
What is a Stateless Session Bean?
Theory: Does not remember client information between requests.
Example: Currency Converter – each request is independent.
When does NoSuchObjectException occur?
Theory: When a client tries to access a remote object that no longer exists.
Example: Server deletes object → Client calls it again → Exception thrown.
What is init-method?
Theory: Runs immediately after a Spring Bean is created.
Example: Open database connection, load configuration files.
MDB Use Case
Theory: Processes messages asynchronously from a queue.
Example: Email notification service processes emails after an order is placed.
What is @PostActivate?
Theory: Called after a Stateful Session Bean is reactivated from passive storage.
Example: User session temporarily stored → later restored → @PostActivate executes.
| Q | Ans | Memory Tip |
|---|---|---|
| 1 | C | Plumbing = Communication infrastructure |
| 2 | E | God Class = One class does everything |
| 3 | A | Server Helper = Runs inside server JVM |
| 4 | C | DGC = Deletes unused remote objects |
| 5 | C | Business Logic = Rules & calculations |
| 6 | A | MDB = Asynchronous messaging |
| 7 | B | Java EE = Automatic transactions |
| 8 | E | CREATE is NOT an HTTP method |
| 9 | A | Entity = Database object |
| 10 | B | lookup() = Find object by name |
| 11 | D | Stateless = No client memory |
| 12 | C | Object removed → NoSuchObjectException |
| 13 | B | init-method = Bean initialization |
| 14 | A | @JoinColumn = Foreign key |
| 15 | D | service() calls doGet()/doPost() |
| 16 | B | POST = Send data |
| 17 | C | 3xx = Redirect |
| 18 | E | web.xml = Deployment descriptor |
| 19 | D | servlet-mapping = URL mapping |
| 20 | D | ServletRequest = Client request data |
| 21 | A | @OnOpen = Connection starts |
| 22 | E | Control Frames = Ping/Pong/Close |
| 23 | B | Web Container = Runs Servlets |
| 24 | B | MDB = Queue message processor |
| 25 | A | @PostActivate = Bean reactivated |
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