HTTP Request Documentation: What is an HTTP Request?

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catalogs

  1. Definition of an HTTP request
    • basic concept
    • Explanation of analogies (example of online purchase order)
  2. Structure of an HTTP request
    • Request line, request header, request body
    • Comparison of common request methods
  3. How HTTP requests work
    • Client-server interaction flow
    • Status Codes and Response Mechanisms
  4. Common types of HTTP requests
    • GET, POST, PUT, DELETE
    • Safety and idempotency statements
  5. Practical applications and debugging tools
    • Browser Developer Tools
    • Postman and cURL Example
  6. Security and Best Practices
  7. Frequently Asked Questions (FAQ)

1. Definition of an HTTP request

basic concept

HTTP Request is a standard communication format for clients (e.g., browsers, apps) to initiate operation commands to the server, following the rules of the HTTP protocol. It is the cornerstone of Web data interaction, determining what resources the client wants to obtain or what operations to perform.

analogy

Suppose you place an order on an e-commerce platform:

  • You (client): submit an order (request to buy an item)
  • Order system (HTTP request): specify product ID, quantity, shipping address (structured parameters)
  • Warehouse (server-side): parses orders and processes them, returns packages (response data)
    An HTTP request is like an order, it tells the server what needs to be done in a standardized format.

2. Structure of HTTP requests

Three major components

http

GET /api/products/123 HTTP/1.1 --> request line
Host: api.example.com --> request header
User-Agent: Mozilla/5.0
Accept: application/json

{ --> request body (only for some methods)
  "name": "New Product"
}

1. Request line

  • Methods: define the type of operation (e.g. GET, POST)
  • Path: resource address (e.g. /api/products)
  • Protocol version: HTTP/1.1 or HTTP/2

2. Request headers

  • Passing Metadata:
    • Content-Type: data format (e.g. application/json)
    • Authorization: Authentication token
    • Cache-Control: Cache Policy

3. Body of requests

  • Only for POST, PUT, etc.
  • Carrying structured data (JSON, XML, etc.)

3. How HTTP requests work

interactive process

  1. Client build request: set method, URL, headers, data
  2. Sending to the server: transmission via TCP/IP protocol
  3. Server-side processing: validating permissions, executing logic, querying the database
  4. Return response: contains status code and result data

Status Code Classification

status codeformtypical example
2xxsuccesses200 OK (request successful)
3xxredirects301 Moved Permanently
4xxclient-side error404 Resource does not exist
5xxserver-side error500 Internal server error

4. Common types of HTTP requests

Comparison of core methods

methodologiesuseidempotence (math.)safetyrequestor support
GETAccess to resourcesbebeclogged
POSTCreating resources or submitting datacloggedcloggedbe
PUTUpdate the entire resourcebecloggedbe
DELETEDelete resourcesbecloggedclogged

sample scenario

  • GET: load product detail page httpGET /products/123 HTTP/1.1
  • POST: Submit user registration form httpPOST /s HTTP/1.1 Content-Type: application/json { "name": "John", "email": "john@example.com" }

5. Practical applications and debugging tools

Developer tools (browser)

  1. Press F12 to open the console → Network tab
  2. View request details (Headers/Response)

cURL Example

bash

Example of a # GET request
curl -X GET "https://api.example.com/products/123"

# POST request example
curl -X POST "https://api.example.com/s" \
  -H "Content-Type: application/json" \
  -d '{"name": "John"}'

6. Security and best practices

Key principles

  • HTTPS: always use encrypted transmission (avoid HTTP plaintext)
  • Request header security:
    • Setting Content-Security-Policy to Defend Against XSS
    • Use Authorization: Bearer to manage permissions.
  • Data validation: the server side needs to verify the legitimacy of the request parameters

RESTful Design Specification

  • URL paths use the noun plural (e.g. /api/products)
  • Corresponding to CRUD operations with HTTP methods

7. Frequently Asked Questions (FAQ)

Q1: What is the difference between GET and POST?

  • GET parameters are in the URL, with a length limit; POST data is in the request body, which is safer and supports big data.

Q2：How to choose between PUT and PATCH?

  • PUT replaces the entire resource, PATCH updates only some of the fields.

Q3：How to prevent duplicate POST requests?

  • Front-end disable duplicate clicks + server-side idempotency design (e.g. generate unique request IDs).

Q4: How to solve the cross domain request (CORS) problem?

  • The server side sets the response header Access-Control-Allow-Origin.
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