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133 lines
3.9 KiB
133 lines
3.9 KiB
/*
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Copyright 2016 The Kubernetes Authors All rights reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package httputil
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import (
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"encoding/json"
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"errors"
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"fmt"
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"mime"
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"net/http"
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"reflect"
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"strings"
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"github.com/ghodss/yaml"
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)
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// Encoder takes input and translate it to an expected encoded output.
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//
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// Implementations of encoders may use details of the HTTP request and response
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// to correctly encode an object for return to the client.
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//
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// Encoders are expected to produce output, even if that output is an error
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// message.
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type Encoder interface {
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// Encode encoders a given response
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//
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// When an encoder fails, it logs any necessary data and then responds to
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// the client.
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Encode(http.ResponseWriter, *http.Request, interface{})
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}
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// AcceptEncoder uses the accept headers on a request to determine the response type.
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//
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// It supports the following encodings:
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// - application/json: passed to encoding/json.Marshal
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// - text/yaml: passed to gopkg.in/yaml.v2.Marshal
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// - text/plain: passed to fmt.Sprintf("%V")
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//
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// It treats `application/x-yaml` as `text/yaml`.
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type AcceptEncoder struct {
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DefaultEncoding string
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}
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// Encode encodeds the given interface to the first available type in the Accept header.
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func (e *AcceptEncoder) Encode(w http.ResponseWriter, r *http.Request, out interface{}) {
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a := r.Header.Get("accept")
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fn := encoders[e.DefaultEncoding]
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mt := e.DefaultEncoding
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if a != "" {
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mt, fn = e.parseAccept(a)
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}
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data, err := fn(out)
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if err != nil {
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Fatal(w, r, "Could not marshal data: %s", err)
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return
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}
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w.Header().Add("content-type", mt)
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w.Write(data)
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}
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// parseAccept parses the value of an Accept: header and returns the best match.
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//
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// This returns the matched MIME type and the Marshal function.
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func (e *AcceptEncoder) parseAccept(h string) (string, Marshaler) {
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keys := strings.Split(h, ",")
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for _, k := range keys {
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mt, _, err := mime.ParseMediaType(k)
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if err != nil {
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continue
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}
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if enc, ok := encoders[mt]; ok {
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return mt, enc
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}
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}
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return e.DefaultEncoding, encoders[e.DefaultEncoding]
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}
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// Marshaler marshals an interface{} into a []byte.
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type Marshaler func(interface{}) ([]byte, error)
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var encoders = map[string]Marshaler{
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"application/json": json.Marshal,
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"text/yaml": yaml.Marshal,
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"application/x-yaml": yaml.Marshal,
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"text/plain": textMarshal,
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}
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// ErrUnsupportedKind indicates that the marshal cannot marshal a particular Go Kind (e.g. struct or chan).
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var ErrUnsupportedKind = errors.New("unsupported kind")
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// textMarshal marshals v into a text representation ONLY IN NARROW CASES.
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//
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// An error will have its Error() method called.
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// A fmt.Stringer will have its String() method called.
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// Scalar types will be marshaled with fmt.Sprintf("%v").
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//
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// This will only marshal scalar types for securoty reasons (namely, we don't
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// want the possibility of forcing exposure of non-exported data or ptr
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// addresses, etc.)
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func textMarshal(v interface{}) ([]byte, error) {
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switch s := v.(type) {
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case error:
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return []byte(s.Error()), nil
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case fmt.Stringer:
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return []byte(s.String()), nil
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}
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// Error on kinds we don't support.
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val := reflect.Indirect(reflect.ValueOf(v))
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switch val.Kind() {
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case reflect.Invalid, reflect.Array, reflect.Chan, reflect.Func, reflect.Interface,
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reflect.Map, reflect.Ptr, reflect.Slice, reflect.Struct, reflect.UnsafePointer:
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return []byte{}, ErrUnsupportedKind
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}
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return []byte(fmt.Sprintf("%v", v)), nil
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}
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