IBuild — Chapter 1 Notes

🌐

Web Architecture — The Big Picture

Client Browser

→
Request

Server Web Server

→
Response

Client Gets content

→Client — The browser. Sends the HTTP request.

→Server — Receives the request, sends back a response.

// HTTP — HyperText Transfer Protocol

The shared language between client and server. A simple protocol built on top of TCP/IP, based entirely on the Request / Response model.

📄

Content Types & URL Anatomy

Static Pages
Pre-built HTML files, sent as-is. No processing needed.

Dynamic Content
Generated on-the-fly (Just-in-time) based on the request. Needs a helper app like a Servlet.

Key insight

A plain web server can't generate dynamic content alone → needs a Helper App like Servlets.

// URL Breakdown

Protocol

https://

Server Name

ibuild.dev

Port

:80

Path

/app/

Resource

index.html

// MIME Types — in the Response Header

text/html

image/jpeg

application/json

text/css

application/pdf

Port 80 = default HTTP port · MIME tells the browser how to handle incoming content

⚔️

CGI vs Servlet

	CGI	Servlet
Language	Perl (typically)	Java
Per request	Separate Process	Lightweight Thread
Resource use	❌ High (heavy)	✅ Low (efficient)
Scalability	❌ Poor	✅ Excellent

CGI's fatal flaw

Spawns a separate process per request — extremely high resource consumption. Servlets use threads instead, sharing a single JVM instance.

☕

Servlet vs JSP

Servlet
A Java class that handles requests on the server. Pure Java — great for logic, painful for HTML.

JSP
HTML with embedded Java code. Gets converted into a Servlet by the server automatically.

// The problem with Servlets

// Tedious HTML in Servlet — error-prone

out.println("<html>");

out.println("<body>Hello</body>"); // ← painful

out.println("</html>");

// The solution with JSP

<html>
<body><%=new java.util.Date() %></body>
</html>
// Clean, readable, JSP → compiled to Servlet by server

⭐

GET vs POST — Key Comparison

Feature	GET	POST
Purpose	Retrieve data	Send data for processing
Data location	Appended to URL	Inside request body
Data size	❌ Limited	✅ Unlimited
Security	❌ Visible in address bar	✅ Hidden
Bookmarkable	✅ Yes	❌ No
Use cases	Search, fetching pages	Passwords, uploads, forms

// GET parameters format in URL

https://site.com/search?name=value&name2=value2
Everything after ? is the query string — fully visible to anyone.

📨

Anatomy of a Request & Response

HTTP Request contains

1

HTTP Method — GET or POST

2

URL — target resource path

3

Headers — e.g. User-Agent, Accept

4

Body — POST only (form data)

HTTP Response contains

1

Status Code — 200 OK / 404 Not Found

2

Content-Type — MIME type header

3

Headers — cache, cookies, etc.

4

Body — actual HTML / image / data

// Common Status Codes

200 OK · 301 Moved Permanently · 403 Forbidden · 404 Not Found · 500 Internal Server Error

🧠

The Golden Analogy

👤

Client

The customer — walks in, places an order (sends a request)

🤵

Server

The waiter — takes the order, delivers the response

👨‍🍳

Servlet

The chef — prepares the meal fresh, on demand

🥫

Static Page

Pre-packaged meal — ready to go, no preparation needed