💼 IT4206 Enterprise Application Development (2023)
UCSC BIT | MCQ Solutions with Simple Theory & Examples
Java Persistence API (JPA)
Theory: JPA helps Java programs communicate with relational databases (MySQL, Oracle) using Java objects instead of raw SQL.
Example: entityManager.find(Student.class, 1); automatically fetches the student.
Memory Trick: JPA = Java ↔ Database
Where do discount calculations go?
Theory: Business rules (like calculating VIP discounts or taxes) belong in the Business Logic Tier.
Example: If customer is VIP → 20% discount. This calculation happens here.
Distributing Standalone Java Apps
Theory: A JAR (Java Archive) file packages Java programs into one executable file.
Example: Run using java -jar MyApp.jar. Easy to share!
Handling SOAP & REST
Theory: The Web Tier receives requests from browsers/apps and handles HTTP, REST APIs, and SOAP Web Services.
Flow: Mobile App → REST Request → Web Server → Business Logic → Database.
Java EE Deployment
Theory: Java EE applications run inside an Application Server (like Tomcat or WildFly), which manages security, sessions, and transactions.
Example: Online Banking runs on a server (Java EE), while a Desktop Calculator runs directly on your PC (Java SE).
WebSocket Imports
Theory: You only need to import packages for annotations actually used in the code. If the code uses @ServerEndpoint and @OnMessage, only those two are required.
Memory Trick: Import only what you use.
WebSocket Communication
Theory: WebSocket creates a lightweight, bi-directional connection. The server can push data anytime without reconnecting.
Example: WhatsApp live chat. Both users can send messages anytime.
Memory Trick: WebSocket = Live Chat
Requesting Information
Theory: The GET method is used to request/read data from a web server.
Example: Opening www.amazon.com sends a GET request to fetch the webpage.
Memory Trick: GET = Get Data
HTTP Redirection
Theory: HTTP status codes in the 300 range indicate redirection (e.g., 301 Moved Permanently).
Memory Trick: 300 = Move Somewhere Else
Java Inside HTML
Theory: JSP (JavaServer Pages) allows Java code to be written inside HTML to generate dynamic web pages.
Example: Welcome <%= "Nimal" %> outputs "Welcome Nimal".
Memory Trick: JSP = Java Inside HTML
RequestDispatcher.forward()
Theory: Transfers the same request and response from one servlet to another. The browser URL does NOT change.
Example: LoginServlet forwards to Dashboard.jsp.
Memory Trick: forward() = Go to another page
Marking Old Methods
Theory: @Deprecated warns developers that a method is outdated and should not be used in new programs.
Memory Trick: Deprecated = Old Method
Hiding Compiler Warnings
Theory: Tells Java to ignore unnecessary compiler warnings (e.g., @SuppressWarnings("unchecked")).
Memory Trick: Suppress = Hide
JSP Elements
Theory: The 4 main JSP elements are:
- Declaration:
<%! int x=10; %>(Variables) - Scriptlet:
<% out.println("Hi"); %>(Java code) - Expression:
<%= name %>(Output) - Directive:
<%@ page ... %>(Instructions)
Memory Trick: DSED
Servlet Initialization Parameters
Theory: Defines configuration values for a servlet during initialization instead of hardcoding them.
Memory Trick: Init = Initial Settings
ServletContextListener
Theory: Listens to the web app lifecycle. contextInitialized() runs on start, contextDestroyed() runs when the app stops.
Memory Trick: Destroyed = Application Closed
Executing Java Code in JSP
Theory: The Scriptlet tag <% ... %> is used to execute Java code on the server.
Memory Trick: Scriptlet = Java Code
Correct JSON Syntax
Theory: JSON stores data as "Key":"Value". It strictly requires double quotes for keys and string values.
Memory Trick: JSON uses DOUBLE QUOTES
Destroying a Session
Theory: When a user logs out, session.invalidate(); destroys their session completely.
Memory Trick: Logout = invalidate()
Handling HTTP Requests
Theory: In the Servlet lifecycle, service() handles every client request and decides whether to call doGet() or doPost().
Memory Trick: service() = Handle Requests
Quick Revision (All 25 Questions)
| Q | Answer | Memory Trick |
|---|---|---|
| 1 | JPA | Java ↔ Database |
| 2 | Business Tier | Business Rules |
| 3 | JAR | Java Package |
| 4 | Web Tier | REST & SOAP |
| 5 | App Server | Java EE |
| 6 | a,b,c | Apache = Server |
| 7 | Session Bean | One Client |
| 8 | @PrePassivate | Before Passivation |
| 9 | Passive | Sleeping State |
| 10 | @ServerEndpoint | WebSocket |
| 11 | Only a,b | Import Used Packages |
| 12 | a,b,d | Live Communication |
| 13 | GET | Read Data |
| 14 | 300 | Redirection |
| 15 | JSP | Java in HTML |
| 16 | forward() | Transfer Request |
| 17 | @Deprecated | Old Method |
| 18 | @SuppressWarnings | Hide Warnings |
| 19 | DSED | JSP Elements |
| 20 | @WebInitParam | Initial Settings |
| 21 | contextDestroyed() | Application Stops |
| 22 | <% ... %> | Scriptlet = Java Code |
| 23 | "Key":"Value" | Double Quotes |
| 24 | invalidate() | Logout |
| 25 | service() | Handles Requests |
🎯 Exam Tips
- JPA → Connects Java applications to relational databases.
- Business Logic Tier → Contains business rules like discounts and tax calculations.
- Web Tier → Handles HTTP, REST, and SOAP communication.
- WebSocket → Enables two-way (bi-directional) communication.
- Servlet Lifecycle → init() → service() → destroy().
- Session → invalidate() logs the user out.
- JSON → Uses "key":"value" format with double quotes.
❓ Frequently Asked Questions (FAQ)
session.invalidate() method, which is typically used during user logout.
<%! %>), Scriptlets (<% %>), Expressions (<%= %>), and Directives (<%@ %>).
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