//Middleware returns a context aware wrapper that converts a GET on a stock symbol
//to a SOAP request to the quote service
func Middleware(ctxHandler cc.ContextHandler) cc.ContextHandler {
return cc.ContextHandlerFunc(func(ctx context.Context, w http.ResponseWriter, r *http.Request) {
const timerName = "message and protocol transformation"
timing.StartTimer(ctx, timerName)
//Grab the symbol to quote from the uri
resourceID, err := extractResource(r.RequestURI)
if err != nil {
w.WriteHeader(http.StatusNotFound)
w.Write([]byte(err.Error()))
return
}
println("quote for", resourceID)
//Convert the method to POST for SOAP, and set the soap service
//endpoint for the destination server
r.Method = "POST"
r.URL.Path = "/services/quote/getquote"
//Form the SOAP payload
payload := getQuoteRequestForSymbol(resourceID)
payloadBytes, err := xml.Marshal(&payload)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
//Post the payload, and record the response
r.Body = ioutil.NopCloser(bytes.NewReader(payloadBytes))
rec := httptest.NewRecorder()
ctxHandler.ServeHTTPContext(ctx, rec, r)
//Parse the recorded response to allow the quote price to be extracted
var response responseEnvelope
err = xml.Unmarshal(rec.Body.Bytes(), &response)
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
timing.EndTimer(ctx, timerName, err)
return
}
//Return just the price to the caller
w.Write([]byte(response.Body.GetLastTradePriceResponse.Price + "\n"))
timing.EndTimer(ctx, timerName, nil)
})
}
//NewQuoteHandler creates a quote handler with the given SOAP service endpoint
func NewQuoteHandler(hostAndPort string) func(ctx context.Context, rw http.ResponseWriter, req *http.Request) {
return func(ctx context.Context, rw http.ResponseWriter, req *http.Request) {
const timerName = "backend service call"
timing.StartTimer(ctx, timerName)
req.URL.Scheme = "http"
req.URL.Host = hostAndPort
req.Host = hostAndPort
resp, err := transport.RoundTrip(req)
if err != nil {
println(err.Error())
http.Error(rw, err.Error(), http.StatusInternalServerError)
timing.EndTimer(ctx, timerName, err)
return
}
io.Copy(rw, resp.Body)
resp.Body.Close()
timing.EndTimer(ctx, timerName, nil)
}
}