150 lines
5.8 KiB
Markdown
150 lines
5.8 KiB
Markdown
# go-autorest
|
|
|
|
[](https://godoc.org/github.com/Azure/go-autorest/autorest)
|
|
[](https://travis-ci.org/Azure/go-autorest)
|
|
[](https://goreportcard.com/report/Azure/go-autorest)
|
|
|
|
Package go-autorest provides an HTTP request client for use with [Autorest](https://github.com/Azure/autorest.go)-generated API client packages.
|
|
|
|
An authentication client tested with Azure Active Directory (AAD) is also
|
|
provided in this repo in the package
|
|
`github.com/Azure/go-autorest/autorest/adal`. Despite its name, this package
|
|
is maintained only as part of the Azure Go SDK and is not related to other
|
|
"ADAL" libraries in [github.com/AzureAD](https://github.com/AzureAD).
|
|
|
|
## Overview
|
|
|
|
Package go-autorest implements an HTTP request pipeline suitable for use across
|
|
multiple goroutines and provides the shared routines used by packages generated
|
|
by [Autorest](https://github.com/Azure/autorest.go).
|
|
|
|
The package breaks sending and responding to HTTP requests into three phases: Preparing, Sending,
|
|
and Responding. A typical pattern is:
|
|
|
|
```go
|
|
req, err := Prepare(&http.Request{},
|
|
token.WithAuthorization())
|
|
|
|
resp, err := Send(req,
|
|
WithLogging(logger),
|
|
DoErrorIfStatusCode(http.StatusInternalServerError),
|
|
DoCloseIfError(),
|
|
DoRetryForAttempts(5, time.Second))
|
|
|
|
err = Respond(resp,
|
|
ByDiscardingBody(),
|
|
ByClosing())
|
|
```
|
|
|
|
Each phase relies on decorators to modify and / or manage processing. Decorators may first modify
|
|
and then pass the data along, pass the data first and then modify the result, or wrap themselves
|
|
around passing the data (such as a logger might do). Decorators run in the order provided. For
|
|
example, the following:
|
|
|
|
```go
|
|
req, err := Prepare(&http.Request{},
|
|
WithBaseURL("https://microsoft.com/"),
|
|
WithPath("a"),
|
|
WithPath("b"),
|
|
WithPath("c"))
|
|
```
|
|
|
|
will set the URL to:
|
|
|
|
```
|
|
https://microsoft.com/a/b/c
|
|
```
|
|
|
|
Preparers and Responders may be shared and re-used (assuming the underlying decorators support
|
|
sharing and re-use). Performant use is obtained by creating one or more Preparers and Responders
|
|
shared among multiple go-routines, and a single Sender shared among multiple sending go-routines,
|
|
all bound together by means of input / output channels.
|
|
|
|
Decorators hold their passed state within a closure (such as the path components in the example
|
|
above). Be careful to share Preparers and Responders only in a context where such held state
|
|
applies. For example, it may not make sense to share a Preparer that applies a query string from a
|
|
fixed set of values. Similarly, sharing a Responder that reads the response body into a passed
|
|
struct (e.g., `ByUnmarshallingJson`) is likely incorrect.
|
|
|
|
Errors raised by autorest objects and methods will conform to the `autorest.Error` interface.
|
|
|
|
See the included examples for more detail. For details on the suggested use of this package by
|
|
generated clients, see the Client described below.
|
|
|
|
## Helpers
|
|
|
|
### Handling Swagger Dates
|
|
|
|
The Swagger specification (https://swagger.io) that drives AutoRest
|
|
(https://github.com/Azure/autorest/) precisely defines two date forms: date and date-time. The
|
|
github.com/Azure/go-autorest/autorest/date package provides time.Time derivations to ensure correct
|
|
parsing and formatting.
|
|
|
|
### Handling Empty Values
|
|
|
|
In JSON, missing values have different semantics than empty values. This is especially true for
|
|
services using the HTTP PATCH verb. The JSON submitted with a PATCH request generally contains
|
|
only those values to modify. Missing values are to be left unchanged. Developers, then, require a
|
|
means to both specify an empty value and to leave the value out of the submitted JSON.
|
|
|
|
The Go JSON package (`encoding/json`) supports the `omitempty` tag. When specified, it omits
|
|
empty values from the rendered JSON. Since Go defines default values for all base types (such as ""
|
|
for string and 0 for int) and provides no means to mark a value as actually empty, the JSON package
|
|
treats default values as meaning empty, omitting them from the rendered JSON. This means that, using
|
|
the Go base types encoded through the default JSON package, it is not possible to create JSON to
|
|
clear a value at the server.
|
|
|
|
The workaround within the Go community is to use pointers to base types in lieu of base types within
|
|
structures that map to JSON. For example, instead of a value of type `string`, the workaround uses
|
|
`*string`. While this enables distinguishing empty values from those to be unchanged, creating
|
|
pointers to a base type (notably constant, in-line values) requires additional variables. This, for
|
|
example,
|
|
|
|
```go
|
|
s := struct {
|
|
S *string
|
|
}{ S: &"foo" }
|
|
```
|
|
fails, while, this
|
|
|
|
```go
|
|
v := "foo"
|
|
s := struct {
|
|
S *string
|
|
}{ S: &v }
|
|
```
|
|
succeeds.
|
|
|
|
To ease using pointers, the subpackage `to` contains helpers that convert to and from pointers for
|
|
Go base types which have Swagger analogs. It also provides a helper that converts between
|
|
`map[string]string` and `map[string]*string`, enabling the JSON to specify that the value
|
|
associated with a key should be cleared. With the helpers, the previous example becomes
|
|
|
|
```go
|
|
s := struct {
|
|
S *string
|
|
}{ S: to.StringPtr("foo") }
|
|
```
|
|
|
|
## Install
|
|
|
|
```bash
|
|
go get github.com/Azure/go-autorest/autorest
|
|
go get github.com/Azure/go-autorest/autorest/azure
|
|
go get github.com/Azure/go-autorest/autorest/date
|
|
go get github.com/Azure/go-autorest/autorest/to
|
|
```
|
|
|
|
## License
|
|
|
|
See LICENSE file.
|
|
|
|
-----
|
|
|
|
This project has adopted the [Microsoft Open Source Code of
|
|
Conduct](https://opensource.microsoft.com/codeofconduct/). For more information
|
|
see the [Code of Conduct
|
|
FAQ](https://opensource.microsoft.com/codeofconduct/faq/) or contact
|
|
[opencode@microsoft.com](mailto:opencode@microsoft.com) with any additional
|
|
questions or comments.
|