httprequest

package module
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 Go to latest Published: Nov 18, 2015 License: LGPL-3.0 Imports: 17 Imported by: 0

README

httprequest

-- import "github.com/juju/httprequest"

Package httprequest provides functionality for unmarshaling HTTP request parameters into a struct type.

Please note that the API is not considered stable at this point and may be changed in a backwardly incompatible manner at any time.

Usage

var (
	ErrUnmarshal        = errgo.New("httprequest unmarshal error")
	ErrBadUnmarshalType = errgo.New("httprequest bad unmarshal type")
)
func Marshal
func Marshal(baseURL, method string, x interface{}) (*http.Request, error)

Marshal is the counterpart of Unmarshal. It takes information from x, which must be a pointer to a struct, and returns an HTTP request using the given method that holds all of the information

The HTTP request will use the given method. Named fields in the given baseURL will be filled out from "path"-tagged fields in x to form the URL path in the returned request. These are specified as for httprouter.

If a field in baseURL is a suffix of the form "*var" (a trailing wildcard element that holds the rest of the path), the marshaled string must begin with a "/". This matches the httprouter convention that it always returns such fields with a "/" prefix.

If a field is of type string or []string, the value of the field will be used directly; otherwise if implements encoding.TextMarshaler, that will be used to marshal the field, otherwise fmt.Sprint will be used.

For example, this code:

type UserDetails struct {
    Age int
}

type Test struct {
    Username string `httprequest:"user,path"`
    ContextId int64 `httprequest:"context,form"`
    Details UserDetails `httprequest:",body"`
}
req, err := Marshal("GET", "http://example.com/users/:user/details", &Test{
    Username: "bob",
    ContextId: 1234,
    Details: UserDetails{
        Age: 36,
    }
})
if err != nil {
    ...
}

will produce an HTTP request req with a URL of http://example.com/users/bob/details?context=1234 and a JSON-encoded body holding {"Age":36}.

It is an error if there is a field specified in the URL that is not found in x.

func ToHTTP
func ToHTTP(h httprouter.Handle) http.Handler

ToHTTP converts an httprouter.Handle into an http.Handler. It will pass no path variables to h.

func Unmarshal
func Unmarshal(p Params, x interface{}) error

Unmarshal takes values from given parameters and fills out fields in x, which must be a pointer to a struct.

Tags on the struct's fields determine where each field is filled in from. Similar to encoding/json and other encoding packages, the tag holds a comma-separated list. The first item in the list is an alternative name for the field (the field name itself will be used if this is empty). The next item specifies where the field is filled in from. It may be:

"path" - the field is taken from a parameter in p.PathVar
	with a matching field name.

"form" - the field is taken from the given name in p.Form
	(note that this covers both URL query parameters and
	POST form parameters)

"body" - the field is filled in by parsing the request body
	as JSON.

For path and form parameters, the field will be filled out from the field in p.PathVar or p.Form using one of the following methods (in descending order of preference):

  • if the type is string, it will be set from the first value.

  • if the type is []string, it will be filled out using all values for that field

    (allowed only for form)

  • if the type implements encoding.TextUnmarshaler, its UnmarshalText method will be used

  • otherwise fmt.Sscan will be used to set the value.

When the unmarshaling fails, Unmarshal returns an error with an ErrUnmarshal cause. If the type of x is inappropriate, it returns an error with an ErrBadUnmarshalType cause.

func WriteJSON
func WriteJSON(w http.ResponseWriter, code int, val interface{}) error

WriteJSON writes the given value to the ResponseWriter and sets the HTTP status to the given code.

type ErrorHandler
type ErrorHandler func(http.ResponseWriter, Params) error

ErrorHandler is like httprouter.Handle except it returns an error which may be returned as the error body of the response. An ErrorHandler function should not itself write to the ResponseWriter if it returns an error.

type ErrorMapper
type ErrorMapper func(err error) (httpStatus int, errorBody interface{})

ErrorMapper holds a function that can convert a Go error into a form that can be returned as a JSON body from an HTTP request. The httpStatus value reports the desired HTTP status.

func (ErrorMapper) Handle
func (e ErrorMapper) Handle(f interface{}) httprouter.Handle

Handle converts a function into an httprouter.Handle. The argument f must be a function of one of the following three forms, where ArgT must be a struct type acceptable to Unmarshal and ResultT is a type that can be marshaled as JSON:

func(w http.ResponseWriter, p Params, arg *ArgT)
func(w http.ResponseWriter, p Params, arg *ArgT) error
func(header http.Header, p Params, arg *ArgT) (ResultT, error)

When processing a call to the returned handler, the provided parameters are unmarshaled into a new ArgT value using Unmarshal, then f is called with this value. If the unmarshaling fails, f will not be called and the unmarshal error will be written as a JSON response.

If an error is returned from f, it is passed through the error mapper before writing as a JSON response.

In the third form, when no error is returned, the result is written as a JSON response with status http.StatusOK.

Handle will panic if the provided function is not in one of the above forms.

func (ErrorMapper) HandleErrors
func (e ErrorMapper) HandleErrors(handle ErrorHandler) httprouter.Handle

HandleErrors returns a handler that passes any non-nil error returned by handle through the error mapper and writes it as a JSON response.

func (ErrorMapper) HandleJSON
func (e ErrorMapper) HandleJSON(handle JSONHandler) httprouter.Handle

HandleJSON returns a handler that writes the return value of handle as a JSON response. If handle returns an error, it is passed through the error mapper.

func (ErrorMapper) WriteError
func (e ErrorMapper) WriteError(w http.ResponseWriter, err error)

WriteError writes an error to a ResponseWriter and sets the HTTP status code.

type JSONHandler
type JSONHandler func(http.Header, Params) (interface{}, error)

JSONHandler is like httprouter.Handle except that it returns a body (to be converted to JSON) and an error. The Header parameter can be used to set custom headers on the response.

type Params
type Params struct {
	*http.Request
	PathVar httprouter.Params
}

Params holds request parameters that can be unmarshaled into a struct.

Documentation

Overview

Package httprequest provides functionality for unmarshaling HTTP request parameters into a struct type.

Please note that the API is not considered stable at this point and may be changed in a backwardly incompatible manner at any time.

Index

Examples

Constants

This section is empty.

Variables

View Source 
var (
	ErrUnmarshal        = errgo.New("httprequest unmarshal error")
	ErrBadUnmarshalType = errgo.New("httprequest bad unmarshal type")
)
View Source 
var DefaultErrorUnmarshaler = ErrorUnmarshaler(new(RemoteError))

DefaultErrorUnmarshaler is the default error unmarshaler used by Client.

Functions

func ErrorUnmarshaler 

func ErrorUnmarshaler(template error) func(*http.Response) error

ErrorUnmarshaler returns a function which will unmarshal error responses into new values of the same type as template. The argument must be a pointer. A new instance of it is created every time the returned function is called.

func Marshal 

func Marshal(baseURL, method string, x interface{}) (*http.Request, error)

Marshal is the counterpart of Unmarshal. It takes information from x, which must be a pointer to a struct, and returns an HTTP request using the given method that holds all of the information.

The Body field in the returned request will always be of type BytesReaderCloser.

If x implements the HeaderSetter interface, its SetHeader method will be called to add additional headers to the HTTP request after it has been marshaled. If x is pointer to a CustomHeader object then Marshal will use its Body member to create the HTTP request.

The HTTP request will use the given method. Named fields in the given baseURL will be filled out from "path"-tagged fields in x to form the URL path in the returned request. These are specified as for httprouter.

If a field in baseURL is a suffix of the form "*var" (a trailing wildcard element that holds the rest of the path), the marshaled string must begin with a "/". This matches the httprouter convention that it always returns such fields with a "/" prefix.

If a field is of type string or []string, the value of the field will be used directly; otherwise if implements encoding.TextMarshaler, that will be used to marshal the field, otherwise fmt.Sprint will be used.

For example, this code: 

type UserDetails struct {
    Age int
}

type Test struct {
    Username string `httprequest:"user,path"`
    ContextId int64 `httprequest:"context,form"`
    Details UserDetails `httprequest:",body"`
}
req, err := Marshal("GET", "http://example.com/users/:user/details", &Test{
    Username: "bob",
    ContextId: 1234,
    Details: UserDetails{
        Age: 36,
    }
})
if err != nil {
    ...
}

will produce an HTTP request req with a URL of http://example.com/users/bob/details?context=1234 and a JSON-encoded body holding `{"Age":36}`.

It is an error if there is a field specified in the URL that is not found in x.

func ToHTTP 

func ToHTTP(h httprouter.Handle) http.Handler

ToHTTP converts an httprouter.Handle into an http.Handler. It will pass no path variables to h.

func Unmarshal 

func Unmarshal(p Params, x interface{}) error

Unmarshal takes values from given parameters and fills out fields in x, which must be a pointer to a struct.

Tags on the struct's fields determine where each field is filled in from. Similar to encoding/json and other encoding packages, the tag holds a comma-separated list. The first item in the list is an alternative name for the field (the field name itself will be used if this is empty). The next item specifies where the field is filled in from. It may be: 

"path" - the field is taken from a parameter in p.PathVar
	with a matching field name.

"form" - the field is taken from the given name in p.Request.Form
	(note that this covers both URL query parameters and
	POST form parameters).

"header" - the field is taken from the given name in
	p.Request.Header.

"body" - the field is filled in by parsing the request body
	as JSON.

For path and form parameters, the field will be filled out from the field in p.PathVar or p.Form using one of the following methods (in descending order of preference):

- if the type is string, it will be set from the first value.

  • if the type is []string, it will be filled out using all values for that field (allowed only for form)

- if the type implements encoding.TextUnmarshaler, its UnmarshalText method will be used

- otherwise fmt.Sscan will be used to set the value.

When the unmarshaling fails, Unmarshal returns an error with an ErrUnmarshal cause. If the type of x is inappropriate, it returns an error with an ErrBadUnmarshalType cause.

func UnmarshalJSONResponse 

func UnmarshalJSONResponse(resp *http.Response, x interface{}) error

UnmarshalJSONResponse unmarshals the given HTTP response into x, which should be a pointer to the result to be unmarshaled into.

func WriteJSON 

func WriteJSON(w http.ResponseWriter, code int, val interface{}) error

WriteJSON writes the given value to the ResponseWriter and sets the HTTP status to the given code.

If val implements the HeaderSetter interface, the SetHeader method will be called to add additional headers to the HTTP response. It is called after the Content-Type header has been added, so can be used to override the content type if required.

Types

type BytesReaderCloser 

type BytesReaderCloser struct {
	*bytes.Reader
}

BytesReaderCloser is a bytes.Reader which implements io.Closer with a no-op Close method.

func (BytesReaderCloser) Close 

func (BytesReaderCloser) Close() error

Close implements io.Closer.Close.

type Client 

type Client struct {
	// BaseURL holds the base URL to use when making
	// HTTP requests.
	BaseURL string

	// Doer holds a value that will be used to actually
	// make the HTTP request. If it is nil, http.DefaultClient
	// will be used instead. If the request has a non-empty body
	// and Doer implements DoerWithBody, DoWithBody
	// will be used instead.
	Doer Doer

	// If a request returns an HTTP response that signifies an
	// error, UnmarshalError is used to unmarshal the response into
	// an appropriate error. See ErrorUnmarshaler for a convenient
	// way to create an UnmarshalError function for a given type. If
	// this is nil, DefaultErrorUnmarshaler will be used.
	UnmarshalError func(resp *http.Response) error
}

Client represents a client that can invoke httprequest endpoints.

func (*Client) Call 

func (c *Client) Call(params, resp interface{}) error

Call invokes the endpoint implied by the given params, which should be of the form accepted by the ArgT argument to a function passed to Handle, and unmarshals the response into the given response parameter, which should be a pointer to the response value.

If params implements the HeaderSetter interface, its SetHeader method will be called to add additional headers to the HTTP request.

If resp is nil, the response will be ignored if the request was successful.

If resp is of type **http.Response, instead of unmarshaling into it, its element will be set to the returned HTTP response directly and the caller is responsible for closing its Body field.

Any error that c.UnmarshalError or c.Doer returns will not have its cause masked.

func (*Client) CallURL 

func (c *Client) CallURL(url string, params, resp interface{}) error

CallURL is like Call except that the given URL is used instead of c.BaseURL.

func (*Client) Do 

func (c *Client) Do(req *http.Request, body io.ReadSeeker, resp interface{}) error

Do sends the given request and unmarshals its JSON result into resp, which should be a pointer to the response value. If an error status is returned, the error will be unmarshaled as in Client.Call. The req.Body field must be nil - any request body should be provided in the body parameter.

If resp is nil, the response will be ignored if the response was successful.

If resp is of type **http.Response, instead of unmarshaling into it, its element will be set to the returned HTTP response directly and the caller is responsible for closing its Body field.

Any error that c.UnmarshalError or c.Doer returns will not have its cause masked.

If req.URL does not have a host part it will be treated as relative to c.BaseURL. req.URL will be updated to the actual URL used.

func (*Client) Get 

func (c *Client) Get(url string, resp interface{}) error

Get is a convenience method that uses c.Do to issue a GET request to the given URL. If the given URL does not have a host part then it will be treated as relative to c.BaseURL.

type CustomHeader 

type CustomHeader struct {
	// Body holds the JSON-marshaled body of the response.
	Body interface{}

	// SetHeaderFunc holds a function that will be called
	// to set any custom headers on the response.
	SetHeaderFunc func(http.Header)
}

CustomHeader is a type that allows a JSON value to set custom HTTP headers associated with the HTTP response.

func (CustomHeader) MarshalJSON 

func (h CustomHeader) MarshalJSON() ([]byte, error)

MarshalJSON implements json.Marshaler by marshaling h.Body.

func (CustomHeader) SetHeader 

func (h CustomHeader) SetHeader(header http.Header)

SetHeader implements HeaderSetter by calling h.SetHeaderFunc.

type Doer 

type Doer interface {
	Do(req *http.Request) (*http.Response, error)
}

Doer is implemented by HTTP client packages to make an HTTP request. It is notably implemented by http.Client and httpbakery.Client.

When httprequest uses a Doer value for requests with a non-empty body, it will use DoWithBody if the value implements it (see DoerWithBody). This enables httpbakery.Client to be used correctly.

type DoerWithBody 

type DoerWithBody interface {
	DoWithBody(req *http.Request, body io.ReadSeeker) (*http.Response, error)
}

DoerWithBody is implemented by HTTP clients that need to be able to retry HTTP requests with a body. It is notably implemented by httpbakery.Client.

type ErrorHandler 

type ErrorHandler func(Params) error

ErrorHandler is like httprouter.Handle except it returns an error which may be returned as the error body of the response. An ErrorHandler function should not itself write to the ResponseWriter if it returns an error.

type ErrorMapper 

type ErrorMapper func(err error) (httpStatus int, errorBody interface{})

ErrorMapper holds a function that can convert a Go error into a form that can be returned as a JSON body from an HTTP request.

The httpStatus value reports the desired HTTP status.

If the returned errorBody implements HeaderSetter, then that method will be called to add custom headers to the request.

func (ErrorMapper) Handle 

func (e ErrorMapper) Handle(f interface{}) Handler

Handle converts a function into a Handler. The argument f must be a function of one of the following six forms, where ArgT must be a struct type acceptable to Unmarshal and ResultT is a type that can be marshaled as JSON: 

func(p Params, arg *ArgT)
func(p Params, arg *ArgT) error
func(p Params, arg *ArgT) (ResultT, error)

func(arg *ArgT)
func(arg *ArgT) error
func(arg *ArgT) (ResultT, error)

When processing a call to the returned handler, the provided parameters are unmarshaled into a new ArgT value using Unmarshal, then f is called with this value. If the unmarshaling fails, f will not be called and the unmarshal error will be written as a JSON response.

As an additional special case to the rules defined in Unmarshal, the tag on an anonymous field of type Route specifies the method and path to use in the HTTP request. It should hold two space-separated fields; the first specifies the HTTP method, the second the URL path to use for the request. If this is given, the returned handler will hold that method and path, otherwise they will be empty.

If an error is returned from f, it is passed through the error mapper before writing as a JSON response.

In the third form, when no error is returned, the result is written as a JSON response with status http.StatusOK. Also in this case, any calls to Params.Response.Write or Params.Response.WriteHeader will be ignored, as the response code and data should be defined entirely by the returned result and error.

Handle will panic if the provided function is not in one of the above forms.

func (ErrorMapper) HandleErrors 

func (e ErrorMapper) HandleErrors(handle ErrorHandler) httprouter.Handle

HandleErrors returns a handler that passes any non-nil error returned by handle through the error mapper and writes it as a JSON response.

func (ErrorMapper) HandleJSON 

func (e ErrorMapper) HandleJSON(handle JSONHandler) httprouter.Handle

HandleJSON returns a handler that writes the return value of handle as a JSON response. If handle returns an error, it is passed through the error mapper.

func (ErrorMapper) Handlers 

func (e ErrorMapper) Handlers(f interface{}) []Handler

Handlers returns a list of handlers that will be handled by the value returned by the given argument, which must be a function of the form: 

func(httprequest.Params) (T, error)

for some type T. Each exported method defined on T defines a handler, and should be in one of the forms accepted by ErrorMapper.Handle.

Handlers will panic if f is not of the required form, no methods are defined on T or any method defined on T is not suitable for Handle.

When any of the returned handlers is invoked, f will be called and then the appropriate method will be called on the value it returns.

If T implements io.Closer, its Close method will be called after the request is completed.

Example 
package main

import (
	"fmt"
	"io"
	"net/http"
	"net/http/httptest"
	"os"

	"github.com/julienschmidt/httprouter"

	"github.com/juju/httprequest"
)

type arithHandler struct {
}

type number struct {
	N int
}

func (arithHandler) Add(arg *struct {
	httprequest.Route `httprequest:"GET /:A/add/:B"`
	A                 int `httprequest:",path"`
	B                 int `httprequest:",path"`
}) (number, error) {
	return number{
		N: arg.A + arg.B,
	}, nil
}

func main() {
	f := func(p httprequest.Params) (arithHandler, error) {
		fmt.Printf("handle %s %s\n", p.Request.Method, p.Request.URL)
		return arithHandler{}, nil
	}
	router := httprouter.New()
	for _, h := range exampleErrorMapper.Handlers(f) {
		router.Handle(h.Method, h.Path, h.Handle)
	}
	srv := httptest.NewServer(router)
	resp, err := http.Get(srv.URL + "/123/add/11")
	if err != nil {
		panic(err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != 200 {
		panic("status " + resp.Status)
	}
	fmt.Println("result:")
	io.Copy(os.Stdout, resp.Body)
}

type exampleErrorResponse struct {
	Message string
}

var exampleErrorMapper httprequest.ErrorMapper = func(err error) (int, interface{}) {
	return http.StatusInternalServerError, &exampleErrorResponse{
		Message: err.Error(),
	}
}

Output:

handle GET /123/add/11
result:
{"N":134}

func (ErrorMapper) WriteError 

func (e ErrorMapper) WriteError(w http.ResponseWriter, err error)

WriteError writes an error to a ResponseWriter and sets the HTTP status code.

It uses WriteJSON to write the error body returned from the ErrorMapper so it is possible to add custom headers to the HTTP error response by implementing HeaderSetter.

type Handler 

type Handler struct {
	Method string
	Path   string
	Handle httprouter.Handle
}

Handler defines a HTTP handler that will handle the given HTTP method at the given httprouter path

type HeaderSetter 

type HeaderSetter interface {
	SetHeader(http.Header)
}

HeaderSetter is the interface checked for by WriteJSON. If implemented on a value passed to WriteJSON, the SetHeader method will be called to allow it to set custom headers on the response.

type JSONHandler 

type JSONHandler func(Params) (interface{}, error)

JSONHandler is like httprouter.Handle except that it returns a body (to be converted to JSON) and an error. The Header parameter can be used to set custom headers on the response.

type Params 

type Params struct {
	Response http.ResponseWriter
	Request  *http.Request
	PathVar  httprouter.Params
}

Params holds the parameters provided to an HTTP request.

type RemoteError 

type RemoteError struct {
	// Message holds the error message.
	Message string

	// Code may hold a code that classifies the error.
	Code string `json:",omitempty"`

	// Info holds any other information associated with the error.
	Info *json.RawMessage `json:",omitempty"`
}

RemoteError holds the default type of a remote error used by Client when no custom error unmarshaler is set.

func (*RemoteError) Error 

func (e *RemoteError) Error() string

Error implements the error interface.

type Route 

type Route struct{}

Route is the type of a field that specifies a routing path and HTTP method. See Marshal and Unmarshal for details.

Source Files

View all Source files

Directories

Path Synopsis
cmd
httprequest-generate-client

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