Using JSON

We’ll use cJSON to work with JSON objects in this example, but you can also use jansson if you prefer. For more information, refer to its official documentation.

Creating JSON

Let’s write our hello world example again, but this time it will send a JSON object instead of a plain text.

src/handlers.h

#ifndef HANDLERS_H
#define HANDLERS_H

#include "ecewo.h"

void hello_world(Req *req, Res *res);

#endif

src/handlers.c

#include "handlers.h"   // To handle the request and send a response
#include "cJSON.h"      // To deal with JSON

void hello_world(Req *req, Res *res)
{
    // Create a JSON object
    cJSON *json = cJSON_CreateObject();

    // Add string to the JSON object we just created
    cJSON_AddStringToObject(json, "hello", "world");

    // Convert the JSON object to a string
    char *json_string = cJSON_PrintUnformatted(json);

    // Send the json response with 200 status code
    send_json(200, json_string);

    // Free the memory that allocated by jansson
    cJSON_Delete(json);
    free(json_string);
}

src/main.c

#include "server.h"
#include "handlers.h"

int main()
{
    init_router();
    get("/", hello_world);
    ecewo(3000);
    reset_router();
    return 0;
}

Now we can recompile and send a request to http://localhost:3000/ again. We’ll receive a JSON:

{"hello":"world"}

Parsing JSON

This time, let’s take a JSON and print it to console.

src/handlers.h

#ifndef HANDLERS_H
#define HANDLERS_H

#include "ecewo.h"

void handle_user(Req *req, Res *res);

#endif

src/handlers.c

#include "handlers.h"
#include "cJSON.h"

void handle_user(Req *req, Res *res)
{
    const char *body = req->body;

    if (body == NULL)
    {
        send_text(400, "Missing request body");
        return;
    }

    cJSON *json = cJSON_Parse(body);

    if (!json)
    {
        send_text(400, "Invalid JSON");
        return;
    }

    const char *name = cJSON_GetObjectItem(json, "name")->valuestring;
    const char *surname = cJSON_GetObjectItem(json, "surname")->valuestring;
    const char *username = cJSON_GetObjectItem(json, "username")->valuestring;

    if (!name || !surname || !username)
    {
        cJSON_Delete(json);
        send_text(400, "Missing fields");
        return;
    }

    printf("Name: %s\n", name);
    printf("Surname: %s\n", surname);
    printf("Username: %s\n", username);

    cJSON_Delete(json);
    send_text(200, "Success!");
}

src/main.c

#include "server.h"
#include "handlers.h"

int main()
{
    init_router();
    post("/user", handle_user);
    ecewo(3000);
    reset_router();
    return 0;
}

Let’s recompile the program and send a POST request to http://localhost:3000/user with this body:

{
    "name": "John",
    "surname": "Doe",
    "username": "johndoe"
}

We’ll see in the console:

Name: John
Surname: Doe
Username: johndoe