JFetch

A lightweight, header-only library for fetching and parsing JSON responses with libcurl in C++.

Overview

JFetch simplifies HTTP requests and JSON handling by providing an intuitive abstraction over libcurl and nlohmann::json. It allows you to fetch JSON data from APIs in C++ without having to deal with C-style curl functions.

Features

• Single-Header Only: No build required, simply #include "jfetch.hpp"
• Encapsulated HTTP Handling: Eliminates the need of manually dealing with libcurl
• Simple JSON Parsing: Converts API response into usable JSON (via nlohmann::json)
• Extensible: Easily derive classes for different API endpoints

Installation

Since JFetch is header-only, you can simply copy jfetch.hpp into your project and then:

#include "jfetch.hpp"

It just works!

Dependencies

This project depends on:

• libcurl - Website Repo
• nlohmann::json - Website Repo

Example

Here’s an example of a fetcher that retrieves product details from an API and processes the JSON response into a custom struct called Product.

#include "jfetch.hpp"
#include <iostream>
#include <vector>

struct Product {
  int id;
  std::string title;
  double price;
};

class ProductFetcher : public jfetch::JFetch<Product> {
public:
  ProductFetcher() {
    endpoint_lookup = {
      {"/products/1", {jfetch::RequestMethod::GET, [](const nlohmann::json& json_data) {
        return Product{
          json_data["id"].get<int>(),
          json_data["title"].get<std::string>(),
          json_data["price"].get<double>()
        };
      }}},
    };
  }

protected:
  std::string get_base() const override {
    return "https://dummyjson.com";
  }
};

int main() {
  try {
    ProductFetcher fetcher;

    Product product = fetcher.fetch(
      "/products/1",  // Endpoint
      {{"currency", "USD"}},  // Query parameters
      {"Authorization: Bearer my_api_token"}  // Custom headers
    );

    std::cout << "Product ID: " << product.id << std::endl;
    std::cout << "Product Title: " << product.title << std::endl;
    std::cout << "Product Price: $" << product.price << std::endl;
  } catch (const jfetch::JFetchParsingException& e) {
    std::cerr << "Parsing Error: " << e.what() << std::endl;
  } catch (const jfetch::JFetchException& e) {
    std::cerr << "JFetch Error: " << e.what() << std::endl;
  } catch (const std::exception& e) {
    std::cerr << "Unexpected Error: " << e.what() << std::endl;
  }

  return 0;
}

For actual working examples, see examples/ directory of this project.

Motive Behind This Project

This project originally started out as my personal utility library. Some time later, I was given the idea "Why not make it a library for everyone to use?", and here we are!