1  Web Service Intro

1.1 Basic

A web service is a standardized way for applications to communicate over the internet or a network using HTTP(S) and open protocols like REST, SOAP, or GraphQL. It allows different software systems, often running on different platforms, to exchange data and perform functions remotely.

1.1.1 Key Characteristics of a Web Service:

  1. Interoperability – Different applications can communicate regardless of their programming language (e.g., a Python service can interact with a Java service).
  2. Uses Standard Protocols – Typically uses HTTP(S) as the transport protocol.
  3. Data Exchange Format – Uses JSON, XML, or other standardized formats.
  4. Platform-Independent – Works across different operating systems and architectures.
  5. Machine-to-Machine Communication – Designed for programmatic interaction rather than human interaction.

1.1.2 Types of Web Services:

Type Description Example
RESTful API Uses HTTP methods (GET, POST, PUT, DELETE) and JSON for lightweight communication. GitHub API, Twitter API
SOAP (Simple Object Access Protocol) Uses XML-based messaging with strict specifications for security and reliability. Banking and enterprise services
GraphQL Allows clients to request specific data structures, reducing over-fetching. Facebook API

1.2 RESTful API

You can interact with a RESTful API in the Mac Terminal using curl, a command-line tool for making HTTP requests. Here’s an example using a public API.

1.2.1 Example: Fetching data from a RESTful API

Let’s use the JSONPlaceholder API, which provides fake data for testing.

1.2.1.1 1. GET Request (Retrieve Data)

Run this in your Terminal:

curl -X GET https://jsonplaceholder.typicode.com/posts/1

This sends a GET request to retrieve post ID 1. The response will be in JSON format:

{
  "userId": 1,
  "id": 1,
  "title": "sunt aut facere repellat provident occaecati excepturi optio reprehenderit",
  "body": "quia et suscipit..."
}

1.2.1.2 2. POST Request (Send Data)

To create a new post, use:

curl -X POST https://jsonplaceholder.typicode.com/posts \
     -H "Content-Type: application/json" \
     -d '{"title": "Hello World", "body": "This is my first API request!", "userId": 1}'
  • -X POST → Specifies a POST request.
  • -H "Content-Type: application/json" → Sets the request header to JSON.
  • -d → Sends JSON data.

If successful, you’ll get a response like:

{
  "title": "Hello World",
  "body": "This is my first API request!",
  "userId": 1,
  "id": 101
}

1.2.1.3 3. PUT Request (Update Data)

To update post ID 1, use:

curl -X PUT https://jsonplaceholder.typicode.com/posts/1 \
     -H "Content-Type: application/json" \
     -d '{"title": "Updated Title", "body": "Updated body content", "userId": 1}'

This replaces the existing post with new data.

1.2.1.4 4. DELETE Request (Remove Data)

To delete post ID 1, use:

curl -X DELETE https://jsonplaceholder.typicode.com/posts/1

If successful, the API will return an empty response.

1.2.2 Handling API Responses More Readably

To format the JSON output in your Mac Terminal, install jq (a command-line JSON processor):

brew install jq

Then, modify your curl command:

curl -X GET https://jsonplaceholder.typicode.com/posts/1 | jq

This will pretty-print the JSON response.