Created
March 25, 2024 17:51
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Example to handle image upload in go lang (with gorilla mux router). Save image as temp files, remove image, return image / serve image as response
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| /* | |
| Handle image uploaded with multipart/form-data POST Request. | |
| Save image to temp files, | |
| image then removed after some process, | |
| then return / serve the (processed) image as response. | |
| Using gorilla mux router. | |
| */ | |
| package main | |
| import ( | |
| "fmt" | |
| "io" | |
| "net/http" | |
| "path/filepath" | |
| "runtime" | |
| "strings" | |
| ) | |
| type ImageFile struct { | |
| Name string | |
| FullPath string | |
| MimeType string | |
| Bytes []byte | |
| } | |
| var ( | |
| _, b, _, _ = runtime.Caller(0) | |
| RootPath = filepath.Join(filepath.Dir(b), "../") | |
| tempFolderPath = filepath.Join(RootPath, "/temp-files") | |
| ) | |
| func uploadHandler(w http.ResponseWriter, r *http.Request) { | |
| // max total size 20mb | |
| r.ParseMultipartForm(200 << 20) | |
| f, h, err := r.FormFile("image") | |
| if err != nil { | |
| fmt.Printf("Error reading file of 'image' form data. Reason: %s\n", err) | |
| http.Error(w, err.Error(), http.StatusInternalServerError) | |
| return | |
| } | |
| sourceImg, err := saveFile(f, h) | |
| if err != nil { | |
| fmt.Printf("Error saving file. Reason: %s\n", err) | |
| http.Error(w, err.Error(), http.StatusInternalServerError) | |
| return | |
| } | |
| // some processing here | |
| removeFile(sourceImg.FullPath) | |
| w.Header().Set("Content-Type", sourceImg.MimeType) | |
| w.Header().Set("Content-Disposition", `inline; filename="`+removedExt(sourceImg.Name)+`.jpg"`) | |
| w.Write(sourceImg.Bytes) | |
| } | |
| func removedExt(f string) string { | |
| return strings.TrimSuffix(f, filepath.Ext(f)) | |
| } | |
| func saveFile(f multipart.File, h *multipart.FileHeader) (ImageFile, error) { | |
| defer f.Close() | |
| tempFileName := fmt.Sprintf("uploaded-%s-*%s", removedExt(h.Filename), filepath.Ext(h.Filename)) | |
| tempFile, err := os.CreateTemp(tempFolderPath, tempFileName) | |
| if err != nil { | |
| errStr := fmt.Sprintf("Error in creating the file. Reason: %s\n", err) | |
| fmt.Println(errStr) | |
| return ImageFile{}, err | |
| } | |
| defer tempFile.Close() | |
| filebytes, err := io.ReadAll(f) | |
| if err != nil { | |
| errStr := fmt.Sprintf("Error in reading the file buffer. Reason: %s\n", err) | |
| fmt.Println(errStr) | |
| return ImageFile{}, err | |
| } | |
| tempFile.Write(filebytes) | |
| _, tFilename := filepath.Split(tempFile.Name()) | |
| imgFile := ImageFile{ | |
| Name: tFilename, | |
| FullPath: tempFile.Name(), | |
| MimeType: h.Header.Get("Content-Type"), | |
| Bytes: filebytes, | |
| } | |
| return imgFile, nil | |
| } | |
| func removeFile(p string) bool { | |
| err := os.Remove(p) | |
| if err != nil { | |
| fmt.Printf("\nCannot remove file. Reason: %s\n", err) | |
| return false | |
| } | |
| return true | |
| } |
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| /* | |
| Steps | |
| 1. In a new project folder, run `go mod init projectName`. | |
| 2. Add gorilla mux package by running `go get github.com/gorilla/mux`. | |
| 2. Copy 'main.go' and 'uploadHandler.go' to your folder. | |
| 3. Run `go run main.go` or with specified port from terminal `go run main.go --addr :5050` | |
| */ | |
| package main | |
| import ( | |
| "flag" | |
| "fmt" | |
| "log" | |
| "net/http" | |
| "github.com/gorilla/mux" | |
| ) | |
| func main() { | |
| addr := flag.String("addr", ":5000", "server port") | |
| flag.Parse() | |
| r := mux.NewRouter() | |
| r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { | |
| w.Write([]byte("{\"message\": \"hello world\"}")) | |
| }).Methods(http.MethodGet) | |
| r.HandleFunc("/upload", uploadHandler).Methods(http.MethodPost) | |
| fmt.Printf("server run on %s\n", *addr) | |
| log.Fatal(http.ListenAndServe(*addr, r)) | |
| } |
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