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package restful
// Copyright 2015 Ernest Micklei. All rights reserved.
// Use of this source code is governed by a license
// that can be found in the LICENSE file.
import (
"encoding/json"
"encoding/xml"
"strings"
"sync"
)
// EntityReaderWriter can read and write values using an encoding such as JSON,XML.
type EntityReaderWriter interface {
// Read a serialized version of the value from the request.
// The Request may have a decompressing reader. Depends on Content-Encoding.
Read(req *Request, v interface{}) error
// Write a serialized version of the value on the response.
// The Response may have a compressing writer. Depends on Accept-Encoding.
// status should be a valid Http Status code
Write(resp *Response, status int, v interface{}) error
}
// entityAccessRegistry is a singleton
var entityAccessRegistry = &entityReaderWriters{
protection: new(sync.RWMutex),
accessors: map[string]EntityReaderWriter{},
}
// entityReaderWriters associates MIME to an EntityReaderWriter
type entityReaderWriters struct {
protection *sync.RWMutex
accessors map[string]EntityReaderWriter
}
func init() {
RegisterEntityAccessor(MIME_JSON, NewEntityAccessorJSON(MIME_JSON))
RegisterEntityAccessor(MIME_XML, NewEntityAccessorXML(MIME_XML))
}
// RegisterEntityAccessor add/overrides the ReaderWriter for encoding content with this MIME type.
func RegisterEntityAccessor(mime string, erw EntityReaderWriter) {
entityAccessRegistry.protection.Lock()
defer entityAccessRegistry.protection.Unlock()
entityAccessRegistry.accessors[mime] = erw
}
// NewEntityAccessorJSON returns a new EntityReaderWriter for accessing JSON content.
// This package is already initialized with such an accessor using the MIME_JSON contentType.
func NewEntityAccessorJSON(contentType string) EntityReaderWriter {
return entityJSONAccess{ContentType: contentType}
}
// NewEntityAccessorXML returns a new EntityReaderWriter for accessing XML content.
// This package is already initialized with such an accessor using the MIME_XML contentType.
func NewEntityAccessorXML(contentType string) EntityReaderWriter {
return entityXMLAccess{ContentType: contentType}
}
// accessorAt returns the registered ReaderWriter for this MIME type.
func (r *entityReaderWriters) accessorAt(mime string) (EntityReaderWriter, bool) {
r.protection.RLock()
defer r.protection.RUnlock()
er, ok := r.accessors[mime]
if !ok {
// retry with reverse lookup
// more expensive but we are in an exceptional situation anyway
for k, v := range r.accessors {
if strings.Contains(mime, k) {
return v, true
}
}
}
return er, ok
}
// entityXMLAccess is a EntityReaderWriter for XML encoding
type entityXMLAccess struct {
// This is used for setting the Content-Type header when writing
ContentType string
}
// Read unmarshalls the value from XML
func (e entityXMLAccess) Read(req *Request, v interface{}) error {
return xml.NewDecoder(req.Request.Body).Decode(v)
}
// Write marshalls the value to JSON and set the Content-Type Header.
func (e entityXMLAccess) Write(resp *Response, status int, v interface{}) error {
return writeXML(resp, status, e.ContentType, v)
}
// writeXML marshalls the value to JSON and set the Content-Type Header.
func writeXML(resp *Response, status int, contentType string, v interface{}) error {
if v == nil {
resp.WriteHeader(status)
// do not write a nil representation
return nil
}
if resp.prettyPrint {
// pretty output must be created and written explicitly
output, err := xml.MarshalIndent(v, " ", " ")
if err != nil {
return err
}
resp.Header().Set(HEADER_ContentType, contentType)
resp.WriteHeader(status)
_, err = resp.Write([]byte(xml.Header))
if err != nil {
return err
}
_, err = resp.Write(output)
return err
}
// not-so-pretty
resp.Header().Set(HEADER_ContentType, contentType)
resp.WriteHeader(status)
return xml.NewEncoder(resp).Encode(v)
}
// entityJSONAccess is a EntityReaderWriter for JSON encoding
type entityJSONAccess struct {
// This is used for setting the Content-Type header when writing
ContentType string
}
// Read unmarshalls the value from JSON
func (e entityJSONAccess) Read(req *Request, v interface{}) error {
decoder := json.NewDecoder(req.Request.Body)
decoder.UseNumber()
return decoder.Decode(v)
}
// Write marshalls the value to JSON and set the Content-Type Header.
func (e entityJSONAccess) Write(resp *Response, status int, v interface{}) error {
return writeJSON(resp, status, e.ContentType, v)
}
// write marshalls the value to JSON and set the Content-Type Header.
func writeJSON(resp *Response, status int, contentType string, v interface{}) error {
if v == nil {
resp.WriteHeader(status)
// do not write a nil representation
return nil
}
if resp.prettyPrint {
// pretty output must be created and written explicitly
output, err := json.MarshalIndent(v, " ", " ")
if err != nil {
return err
}
resp.Header().Set(HEADER_ContentType, contentType)
resp.WriteHeader(status)
_, err = resp.Write(output)
return err
}
// not-so-pretty
resp.Header().Set(HEADER_ContentType, contentType)
resp.WriteHeader(status)
return json.NewEncoder(resp).Encode(v)
}
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