Web Fundamentals, HTTP & REST APIs

What you will be able to do

• Explain what happens between typing a URL and seeing a page
• Read and write HTTP requests and responses: methods, headers, status codes and bodies
• Convert Java objects to and from JSON with Jackson
• Design REST endpoints with correct URLs, methods and status codes
• Test APIs with browser dev tools, curl and Postman
• Call a REST API from Java and build a tiny HTTP server without a framework

What it will cover

1. 14.1How the Web Works

   The path a request takes from your browser to a server and back.

   Show 6 topics
   • Clients and servers
   • IP addresses, ports and DNS
   • URLs: scheme, host, port, path and query
   • TCP and why HTTP sits on top of it
   • HTTPS and TLS in plain words
   • Watching requests in browser dev tools

2. 14.2HTTP Requests & Responses

   The structure of an HTTP message and what each part means.

   Show 6 topics
   • Request line, headers and body
   • GET, POST, PUT, PATCH and DELETE
   • Safe and idempotent methods
   • Status code families: 2xx, 3xx, 4xx and 5xx
   • Important headers: Content-Type, Accept, Authorization, Location
   • Sending requests with curl

3. 14.3State, Cookies & Sessions

   How a stateless protocol remembers who you are.

   Show 5 topics
   • Why HTTP is stateless
   • Cookies: how they are set and sent
   • Server-side sessions
   • Tokens in headers as an alternative
   • Same-origin policy and CORS (the idea)

4. 14.4JSON & Jackson

   Send structured data as JSON and convert it to and from Java objects.

   Show 6 topics
   • JSON syntax: objects, arrays and types
   • Adding Jackson with Maven
   • ObjectMapper: object to JSON and back
   • Lists, nested objects, records and dates
   • Renaming and ignoring fields with annotations
   • Handling unknown or missing fields

5. 14.5REST API Design

   The rules that make an API easy to understand and use.

   Show 7 topics
   • Resources and nouns in URLs
   • Mapping CRUD to methods and status codes
   • Nested resources: /customers/{id}/orders
   • Filtering, sorting and pagination with query parameters
   • Consistent error response format
   • API versioning
   • Designing the ShopLite API on paper

6. 14.6Testing APIs with Tools

   Explore and test any API without writing code.

   Show 5 topics
   • Postman: requests, collections and environments
   • Sending JSON bodies and headers
   • Saving tests in a collection
   • curl recipes for daily use
   • Reading an API's documentation

7. 14.7Calling APIs from Java

   Use Java's built-in HttpClient to talk to real web services.

   Show 5 topics
   • HttpClient, HttpRequest and HttpResponse
   • GET and POST with JSON
   • Timeouts and checking status codes
   • Parsing responses with Jackson
   • Handling network failures

8. 14.8A Tiny HTTP Server Without a Framework

   Build a small JSON API with the JDK's HttpServer to see the work a framework does for you.

   Show 5 topics
   • Starting an HttpServer and adding handlers
   • Routing by method and path by hand
   • Reading request bodies and writing JSON responses
   • Returning the right status codes
   • What Spring Boot will do for you next

9. 14.9Web & REST Practice

   Check your understanding with design exercises and a small API client project.

   Show 4 topics
   • Design REST endpoints for given requirements
   • Spot the mistakes in a badly designed API
   • Build a command-line client for a public API
   • HTTP and REST interview questions