Go图书管理API服务
go1.17.7
服务说明：
针对前端或其他客户端调用提供图书restful风格的CRUD（创建、检索、更新与删除）服务；
项目代码：
main.go
store/store.go
store/factory/factory.go
internal/store/memstore.go
server/middleware/middleware.go
server/server.go
makeRun
创建目录
$mkdir bookstore
$cd bookstore
$go mod init bookstore
go: creating new go.mod: module bookstore
项目结构
├── cmd/
│ └── bookstore/ // 放置bookstore main包源码
│ └── main.go
├── go.mod // module bookstore的go.mod
├── go.sum
├── internal/ // 存放项目内部包的目录
│ └── store/
│ └── memstore.go
├── server/ // HTTP服务器模块
│ ├── middleware/
│ │ └── middleware.go
│ └── server.go
└── store/ // 图书数据存储模块
├── factory/
│ └── factory.go
└── store.go
main.go
package main
import (
_ "bookstore/internal/store" //internal/store将自身注册到factory中
"bookstore/server"
"bookstore/store/factory"
"context"
"log"
"os"
"os/signal"
"syscall"
"time"
)
func main() {
s, err := factory.New("mem") // 创建名为"mem"的图书数据存储模块实例
if err != nil {
panic(err)
}
srv := server.NewBookStoreServer(":8080", s) // 创建http服务实例
errChan, err := srv.ListenAndServe() // 运行http服务
if err != nil {
log.Println("web server start failed:", err)
return
}
log.Println("web server start ok")
c := make(chan os.Signal, 1)
signal.Notify(c, syscall.SIGINT, syscall.SIGTERM)
select { // 监视来自errChan以及c的事件
case err = <-errChan:
log.Println("web server run failed:", err)
return
case <-c:
log.Println("bookstore program is exiting...")
ctx, cf := context.WithTimeout(context.Background(), time.Second)
defer cf()
err = srv.Shutdown(ctx) // 优雅关闭http服务实例
}
if err != nil {
log.Println("bookstore program exit error:", err)
return
}
log.Println("bookstore program exit ok")
}
// store/store.go
在内存中创建一个 map，以图书 id 作为 key，来保存图书信息
建立一个对应图书条目的抽象数据类型 Book，以及针对 Book 存取的接口类型Store
package store
import "errors"
var (
ErrNotFound = errors.New("not found")
ErrExist = errors.New("exist")
)G
type Book struct {
Id string `json:"id"` // 图书ISBN ID
Name string `json:"name"` // 图书名称
Authors []string `json:"authors"` // 图书作者
Press string `json:"press"` // 出版社
}
type Store interface {
Create(*Book) error // 创建一个新图书条目
Update(*Book) error // 更新某图书条目
Get(string) (Book, error) // 获取某图书信息
GetAll() ([]Book, error) // 获取所有图书信息
Delete(string) error // 删除某图书条目
}
// store/factory/factory.go
使用Go风格的工厂模式来实现store接口实例实现
factory 包采用了一个 map 类型数据，对工厂可以“生产”的、满足 Store 接口的实例类型进行管理。factory 包还提供了 Register 函数，让各个实现 Store 接口的类型可以把自己“注册”到工厂中来。一旦注册成功，factory 包就可以“生产”出这种满足 Store 接口的类型实例。而依赖 Store 接口的使用方，只需要调用 factory 包的 New 函数，再传入期望使用的图书存储实现的名称，就可以得到对应的类型实例了
igo@igoMacBook bookstore % cat store/factory/factory.go
package factory
import (
"bookstore/store"
"fmt"
"sync"
)
var (
providersMu sync.RWMutex
providers = make(map[string]store.Store)
)
func Register(name string, p store.Store) {
providersMu.Lock()
defer providersMu.Unlock()
if p == nil {
panic("store: Register provider is nil")
}
if _, dup := providers[name]; dup {
panic("store: Register called twice for provider " + name)
}
providers[name] = p
}
func New(providerName string) (store.Store, error) {
providersMu.RLock()
p, ok := providers[providerName]
providersMu.RUnlock()
if !ok {
return nil, fmt.Errorf("store: unknown provider %s", providerName)
}
return p, nil
}
// internal/store/memstore.go
基于内存 map 的 Store 接口的实现并自注册到factory包中
memstore 的代码在包的 init 函数中调用 factory 包提供的 Register 函数，把自己的实例以“mem”的名称注册到 factory 中的。这样依赖 Store 接口进行图书数据管理的一方，只要导入 internal/store 这个包，就可以自动完成注册动作
igo@igoMacBook bookstore % cat internal/store/memstore.go
package store
import (
mystore "bookstore/store"
factory "bookstore/store/factory"
"sync"
)
func init() {
factory.Register("mem", &MemStore{
books: make(map[string]*mystore.Book),
})
}
type MemStore struct {
sync.RWMutex
books map[string]*mystore.Book
}
// Create creates a new Book in the store.
func (ms *MemStore) Create(book *mystore.Book) error {
ms.Lock()
defer ms.Unlock()
if _, ok := ms.books[book.Id]; ok {
return mystore.ErrExist
}
nBook := *book
ms.books[book.Id] = &nBook
return nil
}
// Update updates the existed Book in the store.
func (ms *MemStore) Update(book *mystore.Book) error {
ms.Lock()
defer ms.Unlock()
oldBook, ok := ms.books[book.Id]
if !ok {
return mystore.ErrNotFound
}
nBook := *oldBook
if book.Name != "" {
nBook.Name = book.Name
}
if book.Authors != nil {
nBook.Authors = book.Authors
}
if book.Press != "" {
nBook.Press = book.Press
}
ms.books[book.Id] = &nBook
return nil
}
// Get retrieves a book from the store, by id. If no such id exists. an
// error is returned.
func (ms *MemStore) Get(id string) (mystore.Book, error) {
ms.RLock()
defer ms.RUnlock()
t, ok := ms.books[id]
if ok {
return *t, nil
}
return mystore.Book{}, mystore.ErrNotFound
}
// Delete deletes the book with the given id. If no such id exist. an error
// is returned.
func (ms *MemStore) Delete(id string) error {
ms.Lock()
defer ms.Unlock()
if _, ok := ms.books[id]; !ok {
return mystore.ErrNotFound
}
delete(ms.books, id)
return nil
}
// GetAll returns all the books in the store, in arbitrary order.
func (ms *MemStore) GetAll() ([]mystore.Book, error) {
ms.RLock()
defer ms.RUnlock()
allBooks := make([]mystore.Book, 0, len(ms.books))
for _, book := range ms.books {
allBooks = append(allBooks, *book)
}
return allBooks, nil
}
// server/server.go
函数 NewBookStoreServer 接受两个参数，一个是 HTTP 服务监听的服务地址，另外一个是实现了 store.Store 接口的类型实例。这种函数原型的设计是 Go 语言的一种惯用设计方法，也就是接受一个接口类型参数，返回一个具体类型。返回的具体类型组合了传入的接口类型的能力
createBookHandler和getBookHandler大致逻辑:
先获取 http 请求包体数据，然后通过标准库 json 包将这些数据，解码（decode）为我们需要的 store.Book 结构体实例，再通过 Store 接口对图书数据进行存储操作。如果我们是获取图书数据的请求，那么处理函数将通过 response 函数，把取出的图书数据编码到 http 响应的包体中，并返回给客户端
//ListenAndServe函数把 BookStoreServer 内部的 http.Server 的运行，放置到一个单独的轻量级线程 Goroutine 中。这是因为，http.Server.ListenAndServe 会阻塞代码的继续运行，如果不把它放在单独的 Goroutine 中，后面的代码将无法得到执行
//为了检测到 http.Server.ListenAndServe 的运行状态，我们再通过一个 channel（errChan），在新创建的 Goroutine 与主 Goroutine 之间建立的通信渠道。通过这个渠道，这样我们能及时得到 http server 的运行状态
igo@igoMacBook bookstore % cat server/server.go
package server
import (
"bookstore/server/middleware"
"bookstore/store"
"context"
"encoding/json"
"net/http"
"time"
"github.com/gorilla/mux"
)
type BookStoreServer struct {
s store.Store
srv *http.Server
}
func NewBookStoreServer(addr string, s store.Store) *BookStoreServer {
srv := &BookStoreServer{
s: s,
srv: &http.Server{
Addr: addr,
},
}
router := mux.NewRouter()
router.HandleFunc("/book", srv.createBookHandler).Methods("POST")
router.HandleFunc("/book/{id}", srv.updateBookHandler).Methods("POST")
router.HandleFunc("/book/{id}", srv.getBookHandler).Methods("GET")
router.HandleFunc("/book", srv.getAllBooksHandler).Methods("GET")
router.HandleFunc("/book/{id}", srv.delBookHandler).Methods("DELETE")
srv.srv.Handler = middleware.Logging(middleware.Validating(router))
return srv
}
func (bs *BookStoreServer) ListenAndServe() (<-chan error, error) {
var err error
errChan := make(chan error)
go func() {
err = bs.srv.ListenAndServe()
errChan <- err
}()
select {
case err = <-errChan:
return nil, err
case <-time.After(time.Second):
return errChan, nil
}
}
func (bs *BookStoreServer) Shutdown(ctx context.Context) error {
return bs.srv.Shutdown(ctx)
}
func (bs *BookStoreServer) createBookHandler(w http.ResponseWriter, req *http.Request) {
dec := json.NewDecoder(req.Body)
var book store.Book
if err := dec.Decode(&book); err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
if err := bs.s.Create(&book); err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
}
func (bs *BookStoreServer) updateBookHandler(w http.ResponseWriter, req *http.Request) {
id, ok := mux.Vars(req)["id"]
if !ok {
http.Error(w, "no id found in request", http.StatusBadRequest)
return
}
dec := json.NewDecoder(req.Body)
var book store.Book
if err := dec.Decode(&book); err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
book.Id = id
if err := bs.s.Update(&book); err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
}
func (bs *BookStoreServer) getBookHandler(w http.ResponseWriter, req *http.Request) {
id, ok := mux.Vars(req)["id"]
if !ok {
http.Error(w, "no id found in request", http.StatusBadRequest)
return
}
book, err := bs.s.Get(id)
if err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
response(w, book)
}
func (bs *BookStoreServer) getAllBooksHandler(w http.ResponseWriter, req *http.Request) {
books, err := bs.s.GetAll()
if err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
response(w, books)
}
func (bs *BookStoreServer) delBookHandler(w http.ResponseWriter, req *http.Request) {
id, ok := mux.Vars(req)["id"]
if !ok {
http.Error(w, "no id found in request", http.StatusBadRequest)
return
}
err := bs.s.Delete(id)
if err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
}
func response(w http.ResponseWriter, v interface{}) {
data, err := json.Marshal(v)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
w.Header().Set("Content-Type", "application/json")
w.Write(data)
}
igo@igoMacBook bookstore %
// server/middleware/middleware.go
middleware 就是一些通用的 http 处理函数
Logging 函数主要用来输出每个到达的 HTTP 请求的一些概要信息，而 Validating 则会对每个 http 请求的头部进行检查，检查 Content-Type 头字段所表示的媒体类型是否为 application/json。这些通用的 middleware 函数，会被串联到每个真正的处理函数之前，避免我们在每个处理函数中重复实现这些逻辑
func Logging(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
log.Printf("recv a %s request from %s", req.Method, req.RemoteAddr)
next.ServeHTTP(w, req)
})
}
func Validating(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
contentType := req.Header.Get("Content-Type")
mediatype, _, err := mime.ParseMediaType(contentType)
if err != nil {
http.Error(w, err.Error(), http.StatusBadRequest)
return
}
if mediatype != "application/json" {
http.Error(w, "invalid Content-Type", http.StatusUnsupportedMediaType)
return
}
next.ServeHTTP(w, req)
})
}
makeRun
Make:
igo@igoMacBook golang %go mod tidy
go: finding module for package github.com/gorilla/mux
go: found github.com/gorilla/mux in github.com/gorilla/mux v1.8.0
igo@igoMacBook golang %go build bookstore/cmd/bookstore
igo@igoMacBook golang %./bookstore
2021/10/05 16:08:36 web server start ok
Run1:
$curl -X POST -H "Content-Type:application/json" -d '{"id": "978-7-111-55842-2", "name": "The Go Programming Language", "authors":["Alan A.A.Donovan", "Brian W. Kergnighan"],"press": "Pearson Education"}' localhost:8080/book
serv端：
2021/10/05 16:09:10 recv a POST request from [::1]:58021
Run2:
$curl -X GET -H "Content-Type:application/json" localhost:8080/book/978-7-111-55842-2
{"id":"978-7-111-55842-2","name":"The Go Programming Language","authors":["Alan A.A.Donovan","Brian W. Kergnighan"],"press":"Pearson Education"}