How do I pass http.ResponseWriter in a parameter?
I'm coming from nodejs and would really like to learn Go.
Here is the main file:
import (
"net/http"
"./libs/database"
)
func bla (w http.ResponseWriter, r *http.Request) {
go database.AddFriend("bob", w)
}
Here is database file:
import (
"net/http"
)
func AddFriend (friendName string, w http.ResponseWriter){
fmt.Println(friendName)
w.Write([]byte("Yoooooooo"))
}
Everything works but the w.Write returns nothing to my ajax post.
I'm keep thinking its like nodejs where I can pass an
object then use it. I know its probably something simple but I just can't seem to figure it out.
Don't call database.AddFriend in a goroutine. This is most likely the cause of your problem. By using a goroutine, your connection is closed and response sent, before the output is written to the HTTP response.
func bla (w http.ResponseWriter, r *http.Request) {
database.AddFriend("bob", w)
}
Related
I'm currently using a basic http.FileServer setup to serve a simple static site. I need to handle 404 errors with a custom not found page. I've been looking into this issue quite a bit, and I cannot determine what the best solution is.
I've seen several responses on GitHub issues along the lines of:
You can implement your own ResponseWriter which writes a custom message after WriteHeader.
It seems like this is the best approach but I'm a bit unsure of how this would actually be implemented. If there are any simple examples of this implementation, it'd be greatly appreciated!
I think this can be solved with your own middleware. You can try to open the file first and if it doesn't exist, call your own 404 handler. Otherwise just dispatch the call to the static file server in the standard library.
Here is how that could look:
package main
import (
"fmt"
"net/http"
"os"
"path"
)
func notFound(w http.ResponseWriter, r *http.Request) {
// Here you can send your custom 404 back.
fmt.Fprintf(w, "404")
}
func customNotFound(fs http.FileSystem) http.Handler {
fileServer := http.FileServer(fs)
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
_, err := fs.Open(path.Clean(r.URL.Path)) // Do not allow path traversals.
if os.IsNotExist(err) {
notFound(w, r)
return
}
fileServer.ServeHTTP(w, r)
})
}
func main() {
http.ListenAndServe(":8080", customNotFound(http.Dir("/path/to/files")))
}
My code looks like this at the moment:
package main
import (
"io"
"net/http"
"fmt"
"net"
)
const (
PORT = ":443"
KEY = "./localhost.key"
CERT = "./localhost.crt"
)
func hello(w http.ResponseWriter, r *http.Request) {
io.WriteString(w, "Hello world! :)")
}
func main() {
http.HandleFunc("/", hello)
http.ListenAndServeTLS(PORT, CERT, KEY, nil)
}
What I would like to be able to do is to use the net.Conn that is created when a client reaches my host. The reason behind this is to use golang.org/x/net/http2 in order to create custom frames and edit the transmission of data at a lower level. And for example http2.NewFramer requires a writer and a reader, which I guess would be the actual net.Conn in both cases.
I am pretty to new to Golang so any advice on how to improve myself is well welcomed. Thank you in advance everyone! :)
I'm new to Golang and trying to get a basic http app running using the httprouter API. I've hit a wall with reading posted form data, despite following the advice given in another StackOverflow question.
Here's my code (minus irrelevancies):
import (
"fmt"
"net/http"
"github.com/julienschmidt/httprouter"
)
func main() {
r := httprouter.New()
r.POST("/sub", func(w http.ResponseWriter, r *http.Request, _ httprouter.Params) {
r.Header.Set("content-type", "text/html")
err := r.ParseForm()
if err != nil {
fmt.Fprintf(w, "<h1>Error: %s</h1>\n", err)
}
fmt.Fprintf(w, "<h1>Submitted message!</h1>\n<p>-%s-</p>\n", r.PostFormValue("msg"))
})
http.ListenAndServe("localhost:3000", r)
}
In the output, where I should see -hello-, I just see --. When I inspect the http request in Firefox, in the Form Data panel, I see msg:"hello", so why is r.PostFormValue("msg") returning a blank string?
Thanks to Volker for pointing out an error. When I commented out the line r.Header.Set("content-type", "text/html"), the problem was resolved. Perhaps that was the issue, or perhaps there was some issue with the IDE (LiteIDE) caching an old version of the code. In any case, I can now read the posted value.
I want to perform a get operation. I am passng name as a resource to the URL.
The URL I am hitting in Postman is : localhost:8080/location/{titan rolex} ( I chose the GET method in the dropdown list)
On the URL hit in Postman, I am executing the GetUser func() with body as:
func GetUser(rw http.ResponseWriter, req *http.Request) {
}
Now I wish to get the resource value i.e 'titan rolex' in the GetUser method.
How can I achieve this in golang?
In main(), I have this :
http.HandleFunc("/location/{titan rolex}", GetUser)
Thanks in advance.
What you are doing is binding the complete path /location/{titan rolex} to be handled by GetUser.
What you really want is to bind /location/<every possible string> to be handled by one handler (e.g. LocationHandler).
You can do that with either the standard library or another router. I will present both ways:
Standard lib:
import (
"fmt"
"net/http"
"log"
)
func locationHandler(w http.ResponseWriter, r *http.Request) {
name := r.URL.Path[len("/location/"):]
fmt.Fprintf(w, "Location: %s\n", name)
}
func main() {
http.HandleFunc("/location/", locationHandler)
log.Fatal(http.ListenAndServe(":8080", nil))
}
Note however, more complex paths (such as /location/<every possible string>/<some int>/<another string>) will be tedious to implement this way.
The other way is to use github.com/julienschmidt/httprouter, especially if you encounter these situations more often (and have more complex paths).
Here's an example for your use case:
import (
"fmt"
"github.com/julienschmidt/httprouter"
"net/http"
"log"
)
func LocationHandler(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
fmt.Fprintf(w, "Location: %s\n", ps.ByName("loc"))
}
func main() {
router := httprouter.New()
router.GET("/location/:loc", LocationHandler)
log.Fatal(http.ListenAndServe(":8080", router))
}
Note that httprouter uses a slightly different signature for handlers. This is because, as you can see, it passes these parameters to the functions as well.
Oh and another note, you can just hit http://localhost:8080/location/titan rolex with your browser (or something else) - if that something else is decent enough, it will URLEncode that to be http://localhost:8080/location/titan%20rolex.
I'm starting to write server-side applications in Go. I'd like to use the Accept-Encoding request header to determine whether to compress the response entity using GZIP. I had hoped to find a way to do this directly using the http.Serve or http.ServeFile methods.
This is quite a general requirement; did I miss something or do I need to roll my own solution?
The New York Times have released their gzip middleware package for Go.
You just pass your http.HandlerFunc through their GzipHandler and you're done. It looks like this:
package main
import (
"io"
"net/http"
"github.com/nytimes/gziphandler"
)
func main() {
withoutGz := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "text/plain")
io.WriteString(w, "Hello, World")
})
withGz := gziphandler.GzipHandler(withoutGz)
http.Handle("/", withGz)
http.ListenAndServe("0.0.0.0:8000", nil)
}
There is no “out of the box” support for gzip-compressed HTTP responses yet. But adding it is pretty trivial. Have a look at
https://gist.github.com/the42/1956518
also
https://groups.google.com/forum/?fromgroups=#!topic/golang-nuts/cgUp8_ATNtc
For the sake of completeness, I eventually answered my own question with a handler that is simple and specialises in solving this issue.
https://pkg.go.dev/github.com/rickb777/servefiles?tab=doc
https://github.com/rickb777/servefiles
This serves static files from a Go http server, including the asked-for performance-enhancing features. It is based on the standard net/http ServeFiles, with gzip/brotli and cache performance enhancements.
There is yet another "out of the box" middleware now, supporting net/http and Gin:
https://github.com/nanmu42/gzip
net/http example:
import github.com/nanmu42/gzip
func main() {
mux := http.NewServeMux()
mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
writeString(w, fmt.Sprintf("This content is compressed: l%sng!", strings.Repeat("o", 1000)))
})
// wrap http.Handler using default settings
log.Println(http.ListenAndServe(fmt.Sprintf(":%d", 3001), gzip.DefaultHandler().WrapHandler(mux)))
}
func writeString(w http.ResponseWriter, payload string) {
w.Header().Set("Content-Type", "text/plain; charset=utf8")
_, _ = io.WriteString(w, payload+"\n")
}
Gin example:
import github.com/nanmu42/gzip
func main() {
g := gin.Default()
// use default settings
g.Use(gzip.DefaultHandler().Gin)
g.GET("/", func(c *gin.Context) {
c.JSON(http.StatusOK, map[string]interface{}{
"code": 0,
"msg": "hello",
"data": fmt.Sprintf("l%sng!", strings.Repeat("o", 1000)),
})
})
log.Println(g.Run(fmt.Sprintf(":%d", 3000)))
}