response.go

package restful

// Copyright 2013 Ernest Micklei. All rights reserved.
// Use of this source code is governed by a license
// that can be found in the LICENSE file.

import (
	"bufio"
	"errors"
	"net"
	"net/http"
)

// DefaultResponseMimeType is DEPRECATED, use DefaultResponseContentType(mime)
var DefaultResponseMimeType string

//PrettyPrintResponses controls the indentation feature of XML and JSON serialization
var PrettyPrintResponses = true

// Response is a wrapper on the actual http ResponseWriter
// It provides several convenience methods to prepare and write response content.
type Response struct {
	http.ResponseWriter
	requestAccept string        // mime-type what the Http Request says it wants to receive
	routeProduces []string      // mime-types what the Route says it can produce
	statusCode    int           // HTTP status code that has been written explicitly (if zero then net/http has written 200)
	contentLength int           // number of bytes written for the response body
	prettyPrint   bool          // controls the indentation feature of XML and JSON serialization. It is initialized using var PrettyPrintResponses.
	err           error         // err property is kept when WriteError is called
	hijacker      http.Hijacker // if underlying ResponseWriter supports it
}

// NewResponse creates a new response based on a http ResponseWriter.
func NewResponse(httpWriter http.ResponseWriter) *Response {
	hijacker, _ := httpWriter.(http.Hijacker)
	return &Response{ResponseWriter: httpWriter, routeProduces: []string{}, statusCode: http.StatusOK, prettyPrint: PrettyPrintResponses, hijacker: hijacker}
}

// DefaultResponseContentType set a default.
// If Accept header matching fails, fall back to this type.
// Valid values are restful.MIME_JSON and restful.MIME_XML
// Example:
// 	restful.DefaultResponseContentType(restful.MIME_JSON)
func DefaultResponseContentType(mime string) {
	DefaultResponseMimeType = mime
}

// InternalServerError writes the StatusInternalServerError header.
// DEPRECATED, use WriteErrorString(http.StatusInternalServerError,reason)
func (r Response) InternalServerError() Response {
	r.WriteHeader(http.StatusInternalServerError)
	return r
}

// Hijack implements the http.Hijacker interface.  This expands
// the Response to fulfill http.Hijacker if the underlying
// http.ResponseWriter supports it.
func (r *Response) Hijack() (net.Conn, *bufio.ReadWriter, error) {
	if r.hijacker == nil {
		return nil, nil, errors.New("http.Hijacker not implemented by underlying http.ResponseWriter")
	}
	return r.hijacker.Hijack()
}

// PrettyPrint changes whether this response must produce pretty (line-by-line, indented) JSON or XML output.
func (r *Response) PrettyPrint(bePretty bool) {
	r.prettyPrint = bePretty
}

// AddHeader is a shortcut for .Header().Add(header,value)
func (r Response) AddHeader(header string, value string) Response {
	r.Header().Add(header, value)
	return r
}

// SetRequestAccepts tells the response what Mime-type(s) the HTTP request said it wants to accept. Exposed for testing.
func (r *Response) SetRequestAccepts(mime string) {
	r.requestAccept = mime
}

// EntityWriter returns the registered EntityWriter that the entity (requested resource)
// can write according to what the request wants (Accept) and what the Route can produce or what the restful defaults say.
// If called before WriteEntity and WriteHeader then a false return value can be used to write a 406: Not Acceptable.
func (r *Response) EntityWriter() (EntityReaderWriter, bool) {
	sorted := sortedMimes(r.requestAccept)
	for _, eachAccept := range sorted {
		for _, eachProduce := range r.routeProduces {
			if eachProduce == eachAccept.media {
				if w, ok := entityAccessRegistry.accessorAt(eachAccept.media); ok {
					return w, true
				}
			}
		}
		if eachAccept.media == "*/*" {
			for _, each := range r.routeProduces {
				if w, ok := entityAccessRegistry.accessorAt(each); ok {
					return w, true
				}
			}
		}
	}
	// if requestAccept is empty
	writer, ok := entityAccessRegistry.accessorAt(r.requestAccept)
	if !ok {
		// if not registered then fallback to the defaults (if set)
		if DefaultResponseMimeType == MIME_JSON {
			return entityAccessRegistry.accessorAt(MIME_JSON)
		}
		if DefaultResponseMimeType == MIME_XML {
			return entityAccessRegistry.accessorAt(MIME_XML)
		}
		// Fallback to whatever the route says it can produce.
		// https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
		for _, each := range r.routeProduces {
			if w, ok := entityAccessRegistry.accessorAt(each); ok {
				return w, true
			}
		}
		if trace {
			traceLogger.Printf("no registered EntityReaderWriter found for %s", r.requestAccept)
		}
	}
	return writer, ok
}

// WriteEntity calls WriteHeaderAndEntity with Http Status OK (200)
func (r *Response) WriteEntity(value interface{}) error {
	return r.WriteHeaderAndEntity(http.StatusOK, value)
}

// WriteHeaderAndEntity marshals the value using the representation denoted by the Accept Header and the registered EntityWriters.
// If no Accept header is specified (or */*) then respond with the Content-Type as specified by the first in the Route.Produces.
// If an Accept header is specified then respond with the Content-Type as specified by the first in the Route.Produces that is matched with the Accept header.
// If the value is nil then no response is send except for the Http status. You may want to call WriteHeader(http.StatusNotFound) instead.
// If there is no writer available that can represent the value in the requested MIME type then Http Status NotAcceptable is written.
// Current implementation ignores any q-parameters in the Accept Header.
// Returns an error if the value could not be written on the response.
func (r *Response) WriteHeaderAndEntity(status int, value interface{}) error {
	writer, ok := r.EntityWriter()
	if !ok {
		r.WriteHeader(http.StatusNotAcceptable)
		return nil
	}
	return writer.Write(r, status, value)
}

// WriteAsXml is a convenience method for writing a value in xml (requires Xml tags on the value)
// It uses the standard encoding/xml package for marshalling the value ; not using a registered EntityReaderWriter.
func (r *Response) WriteAsXml(value interface{}) error {
	return writeXML(r, http.StatusOK, MIME_XML, value)
}

// WriteHeaderAndXml is a convenience method for writing a status and value in xml (requires Xml tags on the value)
// It uses the standard encoding/xml package for marshalling the value ; not using a registered EntityReaderWriter.
func (r *Response) WriteHeaderAndXml(status int, value interface{}) error {
	return writeXML(r, status, MIME_XML, value)
}

// WriteAsJson is a convenience method for writing a value in json.
// It uses the standard encoding/json package for marshalling the value ; not using a registered EntityReaderWriter.
func (r *Response) WriteAsJson(value interface{}) error {
	return writeJSON(r, http.StatusOK, MIME_JSON, value)
}

// WriteJson is a convenience method for writing a value in Json with a given Content-Type.
// It uses the standard encoding/json package for marshalling the value ; not using a registered EntityReaderWriter.
func (r *Response) WriteJson(value interface{}, contentType string) error {
	return writeJSON(r, http.StatusOK, contentType, value)
}

// WriteHeaderAndJson is a convenience method for writing the status and a value in Json with a given Content-Type.
// It uses the standard encoding/json package for marshalling the value ; not using a registered EntityReaderWriter.
func (r *Response) WriteHeaderAndJson(status int, value interface{}, contentType string) error {
	return writeJSON(r, status, contentType, value)
}

// WriteError writes the http status and the error string on the response. err can be nil.
// Return an error if writing was not succesful.
func (r *Response) WriteError(httpStatus int, err error) (writeErr error) {
	r.err = err
	if err == nil {
		writeErr = r.WriteErrorString(httpStatus, "")
	} else {
		writeErr = r.WriteErrorString(httpStatus, err.Error())
	}
	return writeErr
}

// WriteServiceError is a convenience method for a responding with a status and a ServiceError
func (r *Response) WriteServiceError(httpStatus int, err ServiceError) error {
	r.err = err
	return r.WriteHeaderAndEntity(httpStatus, err)
}

// WriteErrorString is a convenience method for an error status with the actual error
func (r *Response) WriteErrorString(httpStatus int, errorReason string) error {
	if r.err == nil {
		// if not called from WriteError
		r.err = errors.New(errorReason)
	}
	r.WriteHeader(httpStatus)
	if _, err := r.Write([]byte(errorReason)); err != nil {
		return err
	}
	return nil
}

// Flush implements http.Flusher interface, which sends any buffered data to the client.
func (r *Response) Flush() {
	if f, ok := r.ResponseWriter.(http.Flusher); ok {
		f.Flush()
	} else if trace {
		traceLogger.Printf("ResponseWriter %v doesn't support Flush", r)
	}
}

// WriteHeader is overridden to remember the Status Code that has been written.
// Changes to the Header of the response have no effect after this.
func (r *Response) WriteHeader(httpStatus int) {
	r.statusCode = httpStatus
	r.ResponseWriter.WriteHeader(httpStatus)
}

// StatusCode returns the code that has been written using WriteHeader.
func (r Response) StatusCode() int {
	if 0 == r.statusCode {
		// no status code has been written yet; assume OK
		return http.StatusOK
	}
	return r.statusCode
}

// Write writes the data to the connection as part of an HTTP reply.
// Write is part of http.ResponseWriter interface.
func (r *Response) Write(bytes []byte) (int, error) {
	written, err := r.ResponseWriter.Write(bytes)
	r.contentLength += written
	return written, err
}

// ContentLength returns the number of bytes written for the response content.
// Note that this value is only correct if all data is written through the Response using its Write* methods.
// Data written directly using the underlying http.ResponseWriter is not accounted for.
func (r Response) ContentLength() int {
	return r.contentLength
}

// CloseNotify is part of http.CloseNotifier interface
func (r Response) CloseNotify() <-chan bool {
	return r.ResponseWriter.(http.CloseNotifier).CloseNotify()
}

// Error returns the err created by WriteError
func (r Response) Error() error {
	return r.err
}