go-错误处理_go代理不支持go list -m json all-优快云博客

本文链接：https://blog.youkuaiyun.com/VVVinegar/article/details/103058494

本文介绍了一个使用Go语言实现的文件读取服务，该服务通过HTTP接口提供文件内容。文章详细展示了如何利用defer、panic和recover进行错误处理，确保服务的稳定运行。同时，通过type assertion实现了自定义错误类型的定义和转换。

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摘要：

实现一个读取文件内容的服务。

通过defer+panic+recover及type assertion实现错误处理。

handler.go(实现读取)：

package filelisting

import (
	"io/ioutil"
	"net/http"
	"os"
	"strings"
)

const prefix = "/list/"

type userError string

func (e userError) Error() string {
	return e.Message()
}

func (e userError) Message() string {
	return string(e)
}

func HandleFileList(writer http.ResponseWriter, request *http.Request) error {
	if strings.Index(request.URL.Path, prefix) != 0 {
		return userError("path must start with " + prefix)
	}

	path := request.URL.Path[len("/list/"):]
	file, err := os.Open(path)
	if err != nil {
		return err
	}
	defer file.Close()

	all, err := ioutil.ReadAll(file)
	if err != nil {
		return err
	}

	writer.Write(all)
	return nil
}

web.go(实现服务及错误处理)：

import (
	"learngo/errhandling/filelistingserver/filelisting"
	"log"
	"net/http"
	"os"
)

type appHandler func(writer http.ResponseWriter, request *http.Request) error

func errWrapper(handler appHandler) func(http.ResponseWriter, *http.Request) {
	return func(writer http.ResponseWriter, request *http.Request) {

		defer func() {
			if r := recover(); r != nil {
				log.Printf("panic: %v", r)
				http.Error(writer, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
			}
		}()

		err := handler(writer,   request)
		if err != nil {
			log.Printf("%s", err.Error())

			if userErr, ok := err.(userError); ok {
				http.Error(writer, userErr.Message(), http.StatusBadRequest)
				return
			}

			code := http.StatusOK
			switch {
			case os.IsNotExist(err):
				code = http.StatusNotFound
			case os.IsPermission(err):
				code = http.StatusForbidden
			default:
				code = http.StatusInternalServerError
			}
			http.Error(writer, http.StatusText(code), code)
		}
	}
}

type userError interface {
	error
	Message() string
}

func main() {
	http.HandleFunc("/", errWrapper(filelisting.HandleFileList));
	err := http.ListenAndServe(":8888", nil)
	if err != nil {
		panic(err)
	}
}