Responses ​

When the application finishes processing the request, it generates a response object and sends it to the user. The response object contains data such as the HTTP status code, HTTP headers, and the response body. The ultimate goal of developing a Web application is to create response objects for various requests.

In most cases, you will be dealing with the response application component, which is a http1response_t structure.

Status code ​

The first thing you do when building a response is determine if the request was successfully processed. This is done by setting the status_code property to a value that can be one of the valid HTTP status codes. For example, to indicate that a request was successfully processed, you can set the status code value to 200:

void get(http1request_t* request, http1response_t* response) {
    response->statusCode = 200;
    response->data(response, "Ok");
}

However, in most cases an explicit setting is not required, since the default value of status_code is 200. If you need to indicate that a request has failed, you can return a standard response:

void get(http1request_t* request, http1response_t* response) {
    int error = 1;
    if (error) {
        response->def(response, 500);
        return;
    }

    response->data(response, "Ok");
}

Full list of HTTP codes

HTTP headers ​

You can send HTTP headers by working with the headers collection of the response component:

void get(http1request_t* request, http1response_t* response) {
    // add a Content-Type header. Content-Type headers already present will NOT be overwritten.
    response->header_add(response, 'Content-Type', 'text/plain');

    response->data(response, "Ok");
}

Response body ​

Most responses should have a body containing what you want to show users.

If you already have a formatted string for the body, you can pass it to the data method of the response component

void get(http1request_t* request, http1response_t* response) {
    response->data(response, "Hello world!");
}

If your data needs to be formatted before being sent to end users, you should set the Content-type header.

void get(http1request_t* request, http1response_t* response) {
    response->header_add(response, 'Content-Type', 'application/json');

    response->data(response, "{\"message\": \"This is json\"}");
}

Browser redirect ​

The browser redirect is based on sending the Location HTTP header.

You can redirect the user's browser to a URL by calling the redirect method. This method uses the specified URL as the value of the Location header and returns a response.

void get(http1request_t* request, http1response_t* response) {
    response->redirect(response, "/new-page", 301);
}

In code outside of action methods, you must manually set the Location header and call the data method immediately after it. So you can be sure that the answer will be correctly formed.

Sending files ​

Like browser redirection, file upload is another feature based on specific HTTP headers. Cpdy provides a file method for handling file upload tasks. The file method sends an existing file stream to the client as a file.

void get(http1request_t* request, http1response_t* response) {
    response->file(response, "/path/image.jpg");
}

To make sure that no unwanted content is added to the response, you do not need to call the data method when calling the file method.

Sending a response ​

The content of the response is not sent to the user until the data or file methods are called. To send a response, you must call one of these methods at the end of the handler, otherwise the client will never wait for a response.