Middlewares

Middlewares connect one process to another. In the context of Pacis, they let you write transformers for your endpoints.

These transformations operate at the HTTP level, not the page level, meaning you don’t change how a specific page behaves or renders, but rather how HTTP requests to that route are handled.

Shape

Pacis’ server package builds on Go’s standard net/http library and stays close to its conventions. For example, server.New returns an http.Handler, allowing you to use it anywhere the standard handler interface is expected.

Middlewares follow the same principle. The server/middleware package defines a simple Middleware interface:

type Middleware interface {
  Apply(http.Handler) http.Handler
}

The Middleware interface allows you to attach data to a struct and provide an Apply method to turn it into a reusable middleware. Because Apply both accepts and returns an http.Handler, it’s compatible with Go’s conventional middleware pattern, meaning you can also use most third-party middlewares that follow this shape.

Example: Cache Middleware

Let’s create a custom cache middleware that controls how long responses can be cached.

type CacheMiddleware struct {
  Duration time.Duration
}

Now implement the Apply method:

func (m *CacheMiddleware) Apply(next http.Handler) http.Handler {
  return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Cache-Control", fmt.Sprintf("public, max-age=%d", int64(m.Duration.Seconds())))
    next.ServeHTTP(w, r)
  })
}

Note: the middleware wraps the incoming handler, sets the cache header, and then calls the next handler in the chain.

Caching is such a common use case that Pacis provides a built-in cache middleware in the server/middleware package:

// Cache responses for one day
cache := middleware.NewCacheMiddleware(time.Hour * 24)
server.HandlePage("/", Page, Layout, cache)

From logging and locale management to automatic color scheme handling and authentication, Pacis provides a variety of built-in middlewares.

See the API Reference for a complete list.