Small refactor of the middleware code + tests

This is a preparation for further middleware improvements.

Author: ant0ine

rest/handler.go

@@ -8,15 +8,6 @@ import (
 	"strings"
 )
 
-// HandlerFunc defines the handler function. It is the go-json-rest equivalent of http.HandlerFunc.
-type HandlerFunc func(ResponseWriter, *Request)
-
-// Middleware defines the interface that objects must implement in order to wrap a HandlerFunc and
-// be used in the middleware stack.
-type Middleware interface {
-	MiddlewareFunc(handler HandlerFunc) HandlerFunc
-}
-
 // ResourceHandler implements the http.Handler interface and acts a router for the defined Routes.
 // The defaults are intended to be developemnt friendly, for production you may want
 // to turn on gzip and disable the JSON indentation for instance.
@@ -140,12 +131,9 @@ func (rh *ResourceHandler) instantiateMiddlewares() {
 		rh.PreRoutingMiddlewares...,
 	)
 
-	handler := rh.app()
-	for i := len(middlewares) - 1; i >= 0; i-- {
-		handler = middlewares[i].MiddlewareFunc(handler)
-	}
-
-	rh.handlerFunc = rh.adapter(handler)
+	rh.handlerFunc = rh.adapter(
+		wrapMiddlewares(middlewares, rh.app()),
+	)
 }
 
 // Middleware that handles the transition between http and rest objects.

rest/middleware.go

@@ -0,0 +1,20 @@
+package rest
+
+// HandlerFunc defines the handler function. It is the go-json-rest equivalent of http.HandlerFunc.
+type HandlerFunc func(ResponseWriter, *Request)
+
+// Middleware defines the interface that objects must implement in order to wrap a HandlerFunc and
+// be used in the middleware stack.
+type Middleware interface {
+	MiddlewareFunc(handler HandlerFunc) HandlerFunc
+}
+
+// wrapMiddlewares calls the MiddlewareFunc in the reverse order and returns an HandlerFunc ready
+// to be executed.
+func wrapMiddlewares(middlewares []Middleware, handler HandlerFunc) HandlerFunc {
+	wrapped := handler
+	for i := len(middlewares) - 1; i >= 0; i-- {
+		wrapped = middlewares[i].MiddlewareFunc(wrapped)
+	}
+	return wrapped
+}

rest/middleware_test.go

@@ -0,0 +1,57 @@
+package rest
+
+import (
+	"testing"
+)
+
+type testMiddleware struct {
+	name string
+}
+
+func (mw *testMiddleware) MiddlewareFunc(handler HandlerFunc) HandlerFunc {
+	return func(w ResponseWriter, r *Request) {
+		if r.Env["BEFORE"] == nil {
+			r.Env["BEFORE"] = mw.name
+		} else {
+			r.Env["BEFORE"] = r.Env["BEFORE"].(string) + mw.name
+		}
+		handler(w, r)
+		if r.Env["AFTER"] == nil {
+			r.Env["AFTER"] = mw.name
+		} else {
+			r.Env["AFTER"] = r.Env["AFTER"].(string) + mw.name
+		}
+	}
+}
+
+func TestWrapMiddlewares(t *testing.T) {
+
+	a := &testMiddleware{"A"}
+	b := &testMiddleware{"B"}
+	c := &testMiddleware{"C"}
+
+	app := func(w ResponseWriter, r *Request) {
+		// do nothing
+	}
+
+	handlerFunc := wrapMiddlewares([]Middleware{a, b, c}, app)
+
+	// fake request
+	r := &Request{
+		nil,
+		nil,
+		map[string]interface{}{},
+	}
+
+	handlerFunc(nil, r)
+
+	before := r.Env["BEFORE"].(string)
+	if before != "ABC" {
+		t.Error("middleware executed in the wrong order, expected ABC")
+	}
+
+	after := r.Env["AFTER"].(string)
+	if after != "CBA" {
+		t.Error("middleware executed in the wrong order, expected CBA")
+	}
+}