Reland: Refactor current GAE abstraction library to be free of the SDK*

go/src/infra/gae/epservice/example/service_add.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package example
 
 import (
         "golang.org/x/net/context"
-        "infra/gae/libs/wrapper"
-        "infra/gae/libs/wrapper/gae"
-        "infra/gae/libs/wrapper/gae/commonErrors"
+        "infra/gae/libs/gae"
+        "infra/gae/libs/gae/prod"
 
         "github.com/GoogleCloudPlatform/go-endpoints/endpoints"
 )
 
 // AddReq describes the input parameters to the 'Add' RPC. Name is required,
 // which makes it show up in the REST path, and Delta will be encoded in the
 // request body as JSON.
 type AddReq struct {
         Name string `endpoints:"required"`
 
         Delta int64 `json:",string"`
 }
 
 // AddRsp describes the return value from the 'Add' RPC. Prev is the previous
 // value, and Cur is the post-increment value.
 type AddRsp struct {
         Prev int64 `json:",string"`
         Cur  int64 `json:",string"`
 }
 
 // Add adds a value to the current counter, and returns the old+new values. It
 // may cause a counter to come into existance.
-func (Example) Add(c endpoints.Context, r *AddReq) (rsp *AddRsp, err error) {
+func (Example) Add(c context.Context, r *AddReq) (rsp *AddRsp, err error) {
         rsp = &AddRsp{}
 
-        ds := wrapper.GetDS(gae.Use(context.Background(), c))
-        err = ds.RunInTransaction(func(context.Context) error {
-                ctr := &Counter{ID: r.Name}
-                if err := ds.Get(ctr); err != nil && err != commonErrors.ErrNoSuchEntityDS {
+        c = prod.Use(c)
+        err = gae.GetRDS(c).RunInTransaction(func(c context.Context) error {
+                rds := gae.GetRDS(c)
+                ctr := &Counter{}
+                key := rds.NewKey("Counter", r.Name, 0, nil)
+                if err := rds.Get(key, ctr); err != nil && err != gae.ErrDSNoSuchEntity {
                         return err
                 }
                 rsp.Prev = ctr.Val
                 ctr.Val += r.Delta
                 rsp.Cur = ctr.Val
-                _, err := ds.Put(ctr)
+                _, err := rds.Put(key, ctr)
                 return err
         }, nil)
         return
 }
 
 func init() {
         mi["Add"] = &endpoints.MethodInfo{
                 Path: "counter/{Name}",
                 Desc: "Add an an amount to a particular counter",
         }
 }