Middleware in GoFr

Middleware allows you intercepting and manipulating HTTP requests and responses flowing through your application's router. Middlewares can perform tasks such as authentication, authorization, caching etc. before or after the request reaches your application's handler.

CORS Middleware in GoFr

GoFr includes built-in CORS (Cross-Origin Resource Sharing) middleware to handle CORS-related headers. This middleware allows you to control access to your API from different origins. It automatically adds the necessary headers to responses, allowing or restricting cross-origin requests. User can also override the default response headers sent by GoFr by providing the suitable CORS configs.

The CORS middleware provides the following overridable configs:

• ACCESS_CONTROL_ALLOW_ORIGIN: Set the allowed origin(s) for cross-origin requests. By default, it allows all origins (*).
• ACCESS_CONTROL_ALLOW_HEADERS: Define the allowed request headers (e.g., Authorization, Content-Type).
• ACCESS_CONTROL_ALLOW_CREDENTIALS: Set to true to allow credentials (cookies, HTTP authentication) in requests.
• ACCESS_CONTROL_EXPOSE_HEADERS: Specify additional headers exposed to the client.
• ACCESS_CONTROL_MAX_AGE: Set the maximum time (in seconds) for preflight request caching.

Note: GoFr automatically interprets the registered route methods and based on that sets the value of ACCESS_CONTROL_ALLOW_METHODS

Adding Custom Middleware in GoFr

By adding custom middleware to your GoFr application, user can easily extend its functionality and implement cross-cutting concerns in a modular and reusable way. User can use the UseMiddleware or UseMiddlewareWithContainer method on your GoFr application instance to register your custom middleware.

Using UseMiddleware method for Custom Middleware

The UseMiddleware method is ideal for simple middleware that doesn't need direct access to the application's container.

Example:

import (
    "net/http"

    gofrHTTP "gofr.dev/pkg/gofr/http"
)

// Define your custom middleware function
func customMiddleware() gofrHTTP.Middleware {
    return func(inner http.Handler) http.Handler {
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            // Your custom logic here
            // For example, logging, authentication, etc.
            
            // Call the next handler in the chain
            inner.ServeHTTP(w, r)
        })
    }
}

func main() {
    // Create a new instance of your GoFr application
    app := gofr.New()

    // Add your custom middleware to the application
    app.UseMiddleware(customMiddleware())

    // Define your application routes and handlers
    // ...

    // Run your GoFr application
    app.Run()
}

Using UseMiddlewareWithContainer for Custom Middleware with Container Access

The UseMiddlewareWithContainer method allows middleware to access the application's container, providing access to services like logging, configuration, and databases. This method is especially useful for middleware that needs access to resources in the container to modify request processing flow.

Example:

import (
    "fmt"
    "net/http"
    
    "gofr.dev/pkg/gofr"
    "gofr.dev/pkg/gofr/container"
)

func main() {
    // Create a new GoFr application instance
    a := gofr.New()

    // Add custom middleware with container access
    a.UseMiddlewareWithContainer(customMiddleware)

    // Define the application's routes
    a.GET("/hello", HelloHandler)

    // Run the application
    a.Run()
}

// Define middleware with container access
func customMiddleware(c *container.Container, handler http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        c.Logger.Log("Hey! Welcome to GoFr")
        
        // Continue with the request processing
        handler.ServeHTTP(w, r)
    })
}

// Sample handler function
func HelloHandler(c *gofr.Context) (interface{}, error) {
    name := c.Param("name")
    if name == "" {
        c.Log("Name came empty")
        name = "World"
    }

    return fmt.Sprintf("Hello %s!", name), nil
}