Go web Process

Process

Request

http.Request

// 重要字段
type Request struct {
	Method string
	URL *url.URL
    Header Header
	Body io.ReadCloser

    Form url.Values
	PostForm url.Values
	MultipartForm *multipart.Form
}

URL

type URL struct {
	Scheme      string
	Opaque      string    // encoded opaque data
	User        *Userinfo // username and password information
	Host        string    // host or host:port (see Hostname and Port methods)
	Path        string    // path (relative paths may omit leading slash)
	RawPath     string    // encoded path hint (see EscapedPath method)
	OmitHost    bool      // do not emit empty host (authority)
	ForceQuery  bool      // append a query ('?') even if RawQuery is empty
	RawQuery    string    // encoded query values, without '?'
	Fragment    string    // fragment for references, without '#'
	RawFragment string    // encoded fragment hint (see EscapedFragment method)
}

Header

type Header map[string][]string

Body

type ReadCloser interface {
	Reader
	Closer
}

type Reader interface {
	Read(p []byte) (n int, err error)
}

type Closer interface {
	Close() error
}

Form

• Form
  • 如果表单和URL中有相同字段, 都会获得, 表单在前, URL在后
  • ParseForm解析Request;
  • 访问Form字段
• PostForm
  • 只会有表单数据
  • ParseForm解析Request;
  • 访问PostForm字段
• MultipartForm
  • 只包含表单数据
  • ParseMutilpartForm解析Request;
  • 访问MultipartForm字段

    // Form和PostForm只支持application/x-www-form-urlencoded
    Form url.Values
    PostForm url.Values
    type Values map[string][]string
    
    // MultipartForm支持multipart/form-data
    MultipartForm *multipart.Form
    type Form struct {
        Value map[string][]string
        File  map[string][]*FileHeader
    }
    

上传文件

// simple process uploaded file func
func process(w http.ResponseWriter, r *http.Request){
	// 假设大小为1024Bytes
	r.ParseMultipartForm(1024)
	// <input type="file" name="uploaded"> 前端表单, name对应File中的key
	// 支持上传多个文件, 通过index取第一个文件
	fileHeader := r.MultipartForm.File["uploaded"][0]
	file, err := fileHeader.Open()
    // 等价于上面三行代码, 自动Parse, 获取第一个文件
    // file, fileHeader, err:=r.FormFile("uploaded")
	if err == nil{
		data, err := io.ReadAll(file)
		if err == nil{
			fmt.Fprintln(w, string(data))
		}
	}
}

JSON

tags映射

type Entity struct{
    // `json:""` 方式映射, json指明类型, ""中为json字段中的key
    ID int `json:"id"`
    // ...
}

类型映射

• Go bool -> JSON boolean
• Go float64 -> JSON 数值
• Go string -> JSON strings
• Go nil -> JSON null
• 对于未知结构的JSON, 使用map[string]interface{}, 存储任意JSON对象
  • []interface{}, 存储任意的JSON数组

读取与写入JSON

1. decode encode
   • 针对Stream, io.Writer/io.Reader

        func delJSON(w http.ResponseWriter, r *http.Request){
            entity:=Entity{}
            // 读取JSON
            dec:=json.NewDecoder(r.Body)
            err:=dec.Decode(&entity)
            if err!=nil{
                // process error
                return
            }
            // 写入JSON
            enc:=json.NewEncoder(w)
            err = enc.Encode(entity)
            if err!=nil{
                // process error
                return
            }
        }
     

2. Marshal Unmarshal
   • 针对string or bytes

       func delJSON() {
           entity := Entity{}
           jsonStr := `{}`
           // 解码jsonStr到entity中
           _ = json.Unmarshal([]byte(jsonStr), &entity)
           // 写入json
           bytes, _ := json.Marshal(entity)
           // 写入json, 带缩进
           bytesIndent, _ := json.MarshalIndent(entity, "", " ")
     
           fmt.Println(string(bytes))
           fmt.Println(string(bytesIndent))
       }
     

Response

ResponseWriter

• 底层是操作非导出的response

    type ResponseWriter interface {
        Header() Header
        Write([]byte) (int, error)
        // 调用WriteHeader后, 无法修改Header
        WriteHeader(statusCode int)
    }
  

• response是实现了ResponseWriter接口的struct

    type response struct {}
    func (w *response) Header() Header {}
    func (w *response) Write(data []byte) (n int, err error) {}
    func (w *response) WriteHeader(code int) {}
  

内置Response

• NotFound
  • func NotFound(w ResponseWriter, r *Request)
• ServeFile
  • 从文件系统提供文件, 返回给请求者
  • func ServeFile(w ResponseWriter, r *Request, name string)
• ServeContent
  • 把实现了io.ReadSeeker接口的东西的内容返回, 支持只请求资源的一部分内容
  • func ServeContent(w ResponseWriter, req *Request, name string, modtime time.Time, content io.ReadSeeker)
• Redirect
  • func Redirect(w ResponseWriter, r *Request, url string, code int)