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// Copyright 2009 The Go Authors. All rights reserved.
// Copyright 2012 The Gorilla Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package rpc
import (
"fmt"
"net/http"
"reflect"
"strings"
)
// ----------------------------------------------------------------------------
// Codec
// ----------------------------------------------------------------------------
// Codec creates a CodecRequest to process each request.
type Codec interface {
NewRequest(*http.Request) CodecRequest
}
// CodecRequest decodes a request and encodes a response using a specific
// serialization scheme.
type CodecRequest interface {
// Reads the request and returns the RPC method name.
Method() (string, error)
// Reads the request filling the RPC method args.
ReadRequest(interface{}) error
// Writes the response using the RPC method reply.
WriteResponse(http.ResponseWriter, interface{})
// Writes an error produced by the server.
WriteError(w http.ResponseWriter, status int, err error)
}
// ----------------------------------------------------------------------------
// Server
// ----------------------------------------------------------------------------
// NewServer returns a new RPC server.
func NewServer() *Server {
return &Server{
codecs: make(map[string]Codec),
services: new(serviceMap),
}
}
// Server serves registered RPC services using registered codecs.
type Server struct {
codecs map[string]Codec
services *serviceMap
}
// RegisterCodec adds a new codec to the server.
//
// Codecs are defined to process a given serialization scheme, e.g., JSON or
// XML. A codec is chosen based on the "Content-Type" header from the request,
// excluding the charset definition.
func (s *Server) RegisterCodec(codec Codec, contentType string) {
s.codecs[strings.ToLower(contentType)] = codec
}
// RegisterService adds a new service to the server.
//
// The name parameter is optional: if empty it will be inferred from
// the receiver type name.
//
// Methods from the receiver will be extracted if these rules are satisfied:
//
// - The receiver is exported (begins with an upper case letter) or local
// (defined in the package registering the service).
// - The method name is exported.
// - The method has three arguments: *http.Request, *args, *reply.
// - All three arguments are pointers.
// - The second and third arguments are exported or local.
// - The method has return type error.
//
// All other methods are ignored.
func (s *Server) RegisterService(receiver interface{}, name string) error {
return s.services.register(receiver, name)
}
// HasMethod returns true if the given method is registered.
//
// The method uses a dotted notation as in "Service.Method".
func (s *Server) HasMethod(method string) bool {
if _, _, err := s.services.get(method); err == nil {
return true
}
return false
}
// ServeHTTP
func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
if r.Method != "POST" {
WriteError(w, 405, "rpc: POST method required, received "+r.Method)
return
}
contentType := r.Header.Get("Content-Type")
idx := strings.Index(contentType, ";")
if idx != -1 {
contentType = contentType[:idx]
}
var codec Codec
if contentType == "" && len(s.codecs) == 1 {
// If Content-Type is not set and only one codec has been registered,
// then default to that codec.
for _, c := range s.codecs {
codec = c
}
} else if codec = s.codecs[strings.ToLower(contentType)]; codec == nil {
WriteError(w, 415, "rpc: unrecognized Content-Type: "+contentType)
return
}
// Create a new codec request.
codecReq := codec.NewRequest(r)
// Get service method to be called.
method, errMethod := codecReq.Method()
if errMethod != nil {
codecReq.WriteError(w, 400, errMethod)
return
}
serviceSpec, methodSpec, errGet := s.services.get(method)
if errGet != nil {
codecReq.WriteError(w, 400, errGet)
return
}
// Decode the args.
args := reflect.New(methodSpec.argsType)
if errRead := codecReq.ReadRequest(args.Interface()); errRead != nil {
codecReq.WriteError(w, 400, errRead)
return
}
// Call the service method.
reply := reflect.New(methodSpec.replyType)
errValue := methodSpec.method.Func.Call([]reflect.Value{
serviceSpec.rcvr,
reflect.ValueOf(r),
args,
reply,
})
// Cast the result to error if needed.
var errResult error
errInter := errValue[0].Interface()
if errInter != nil {
errResult = errInter.(error)
}
// Prevents Internet Explorer from MIME-sniffing a response away
// from the declared content-type
w.Header().Set("x-content-type-options", "nosniff")
// Encode the response.
if errResult == nil {
codecReq.WriteResponse(w, reply.Interface())
} else {
codecReq.WriteError(w, 400, errResult)
}
}
func WriteError(w http.ResponseWriter, status int, msg string) {
w.WriteHeader(status)
w.Header().Set("Content-Type", "text/plain; charset=utf-8")
fmt.Fprint(w, msg)
}