I am currently working on a project written in Go for Google App Engine. I have problem with uploading file/image to blobstore without having to reload the site.
So this is the html form:
<form id="file-form" action="{{.UploadUrl}}" method="POST" enctype="multipart/form-data">
<fieldset style="width: 100%;" data-uk-margin>
<div class="uk-form-row">
<div id="fields"></div>
</div>
<div class="uk-form-row" style="padding-top: 5px; padding-bottom: 5px;">
<textarea id="textArea" cols="" rows="10" name="description" placeholder="Description"></textarea>
</div>
<div class="uk-form-row" style="padding-top: 5px; padding-bottom: 5px;">
<p>Upload File: </p> <input id="file-select" type="file" name="file-select" accept="image/png">
</div>
<div class="uk-form-row" style="opacity: 1.0;">
<div class="uk-flex uk-flex-center" id="buttonDiv">
<button type="submit" id="submitButton" class="uk-button uk-button-primary">Upload</button>
</div>
</div>
</fieldset>
</form>
And javascript code to upload the image:
var form = document.getElementById("file-form");
var fileSelect = document.getElementById("file-select");
var uploadButton = document.getElementById("submitButton");
var description = document.getElementById("textArea");
form.onsubmit = function(event) {
event.preventDefault();
uploadButton.innerHTML = "Uploading...";
if (fileSelect.files.length == 0) {
alert("No images selected");
uploadButton.innerHTML = "Upload";
return;
}
var file = fileSelect.files[0];
console.log(file.name);
var formData = new FormData();
formData.append("file", file);
formData.append("description", description.value);
var xhr = new XMLHttpRequest();
xhr.open('POST', "/api/files/fileUpload", true);
xhr.onload = function() {
if (xhr.status === 200) {
uploadButton.innerHTML = "Upload"
} else {
alert("An error occurred!");
}
}
xhr.send(formData);
}
Go method to receive file:
c := appengine.NewContext(r)
u := user.Current(c)
if u == nil {
url, err := user.LoginURL(c, r.URL.String())
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
w.Header().Set("Location", url)
w.WriteHeader(http.StatusFound)
return
}
logoutUrl, e := user.LogoutURL(c, "/redirect")
if e != nil {
panic(e)
}
email := u.Email
uploadURL, error := blobstore.UploadURL(c, "/api/files/fileUpload", nil)
if error != nil {
panic(error)
}
data := WebpageData{LogoutUrl: logoutUrl, UserName: email, UploadUrl: uploadURL}
template := template.Must(template.New("template").Parse(fileValue("./console/page/newForm.html")))
err := template.Execute(w, data)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
}
And finally the errors that bother me: 1. from js console in browser:
Failed to load resource: the server responded with a status of 500 (Internal Server Error)
from go console/log:
2015/04/13 15:10:15 http: panic serving 127.0.0.1:49543: mime: no media type goroutine 16 [running]: net/http.func·011() /private/var/folders/00/0v42r000h01000cxqpysvccm003chb/T/appengine/go_appengine/goroot/src/net/http/server.go:1130 +0xbb api.check(0xb0db00, 0xc20800a970) api/api.go:40 +0x50 api.fileUploadHandler(0xb136e0, 0xc208045540, 0xc2080f1d40) api/files.go:19 +0x8a net/http.HandlerFunc.ServeHTTP(0x5a2088, 0xb136e0, 0xc208045540, 0xc2080f1d40) /private/var/folders/00/0v42r000h01000cxqpysvccm003chb/T/appengine/go_appengine/goroot/src/net/http/server.go:1265 +0x41 net/http.(*ServeMux).ServeHTTP(0xc20803a690, 0xb136e0, 0xc208045540, 0xc2080f1d40) /private/var/folders/00/0v42r000h01000cxqpysvccm003chb/T/appengine/go_appengine/goroot/src/net/http/server.go:1541 +0x17d appengine_internal.handleFilteredHTTP(0xb136e0, 0xc208045540, 0xc2080f1d40) /private/var/folders/00/0v42r000h01000cxqpysvccm003chb/T/appengine/go_appengine/goroot/src/appengine_internal/api_dev.go:98 +0x413 net/http.HandlerFunc.ServeHTTP(0x5a20f8, 0xb136e0, 0xc208045540, 0xc2080f1d40) /private/var/folders/00/0v42r000h01000cxqpysvccm003chb/T/appengine/go_appengine/goroot/src/net/http/server.go:1265 +0x41 net/http.serverHandler.ServeHTTP(0xc208042120, 0xb136e0, 0xc208045540, 0xc2080f1d40) /private/var/folders/00/0v42r000h01000cxqpysvccm003chb/T/appengine/go_appengine/goroot/src/net/http/server.go:1703 +0x19a net/http.(*conn).serve(0xc2080454a0) /private/var/folders/00/0v42r000h01000cxqpysvccm003chb/T/appengine/go_appengine/goroot/src/net/http/server.go:1204 +0xb57 created by net/http.(*Server).Serve /private/var/folders/00/0v42r000h01000cxqpysvccm003chb/T/appengine/go_appengine/goroot/src/net/http/server.go:1751 +0x35e
Any ideas how to tackle this problem. Thanks in advance :)
Blobstore is deprecated: https://cloud.google.com/appengine/docs/go/blobstore/reference. Here's how you can upload files to GCS:
import (
// these are the appengine imports
"golang.org/x/oauth2"
"golang.org/x/oauth2/google"
"google.golang.org/appengine"
"google.golang.org/appengine/datastore"
"google.golang.org/appengine/file"
"google.golang.org/appengine/urlfetch"
"google.golang.org/cloud"
"google.golang.org/cloud/storage"
)
func serveFilesUpload(res http.ResponseWriter, req *http.Request) {
ctx := appengine.NewContext(req)
// every app engine app comes with a default bucket
bucket, err := file.DefaultBucketName(ctx)
if err != nil {
panic(err)
}
// we can't use the regular http client because we need
// oauth headers added, and also need to use urlfetch
// for app engine
hc := &http.Client{
Transport: &oauth2.Transport{
Source: google.AppEngineTokenSource(ctx, storage.ScopeFullControl),
Base: &urlfetch.Transport{Context: ctx},
},
}
// I'm just giving files random names
id := uuid.NewRandom().String()
// this get's the file out of the multipart form
ff, _, err := req.FormFile("file")
if err != nil {
panic(err)
}
defer ff.Close()
cctx := cloud.NewContext(appengine.AppID(ctx), hc)
wc := storage.NewWriter(cctx, bucket, id)
io.Copy(wc, ff)
// normally you'd just defer the .Close, but in this case
// we care about the error it returns
err = wc.Close()
if err != nil {
panic(err)
}
json.NewEncoder(res).Encode(id)
}
A complete example is available here: https://github.com/calebdoxsey/tutorials/tree/master/appengine/cms.