improve gin support

Use gin.IRouter interface instead of *gin.Engine
Switch custom middleware code to gin middleware

Original changes: deepmap#530

pkg/codegen/templates/gin/gin-register.tmpl

@@ -1,23 +1,28 @@
 // GinServerOptions provides options for the Gin server.
 type GinServerOptions struct {
     BaseURL string
-    Middlewares []MiddlewareFunc
+    Middlewares []gin.HandlerFunc
 }
 
+// keeping for backward compatibility
+type MiddlewareFunc = gin.HandlerFunc
+
 // RegisterHandlers creates http.Handler with routing matching OpenAPI spec.
-func RegisterHandlers(router *gin.Engine, si ServerInterface) *gin.Engine {
+func RegisterHandlers(router gin.IRouter, si ServerInterface) gin.IRouter {
   return RegisterHandlersWithOptions(router, si, GinServerOptions{})
 }
 
 // RegisterHandlersWithOptions creates http.Handler with additional options
-func RegisterHandlersWithOptions(router *gin.Engine, si ServerInterface, options GinServerOptions) *gin.Engine {
+func RegisterHandlersWithOptions(router gin.IRouter, si ServerInterface, options GinServerOptions) gin.IRouter {
 {{if .}}wrapper := ServerInterfaceWrapper{
 Handler: si,
-HandlerMiddlewares: options.Middlewares,
 }
 {{end}}
+
+router = router.Group(options.BaseURL, options.Middlewares...)
+
 {{range .}}
-router.{{.Method }}(options.BaseURL+"{{.Path | swaggerUriToGinUri }}", wrapper.{{.OperationId}})
+router.{{.Method }}("{{.Path | swaggerUriToGinUri }}", wrapper.{{.OperationId}})
 {{end}}
 return router
 }

pkg/codegen/templates/gin/gin-wrappers.tmpl

@@ -1,11 +1,8 @@
 // ServerInterfaceWrapper converts contexts to parameters.
 type ServerInterfaceWrapper struct {
     Handler ServerInterface
-    HandlerMiddlewares []MiddlewareFunc
 }
 
-type MiddlewareFunc func(c *gin.Context)
-
 {{range .}}{{$opid := .OperationId}}
 
 // {{$opid}} operation middleware
@@ -165,10 +162,6 @@ func (siw *ServerInterfaceWrapper) {{$opid}}(c *gin.Context) {
     {{end}}
   {{end}}
 
-  for _, middleware := range siw.HandlerMiddlewares {
-    middleware(c)
-  }
-
   siw.Handler.{{.OperationId}}(c{{genParamNames .PathParams}}{{if .RequiresParamObject}}, params{{end}})
 }
 {{end}}