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109 lines
2.6 KiB
Markdown
109 lines
2.6 KiB
Markdown
+++
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title = "Middleware"
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description = "Middleware"
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type = "middleware"
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[menu.main]
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name = "Middleware"
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pre = "<i class='fa fa-filter'></i>"
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weight = 2
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identifier = "middleware"
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url = "/middleware"
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+++
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## Overview
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Middleware is a function chained in the HTTP request-response cycle with access
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to `Echo#Context` which it uses to perform a specific action, for example, logging
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every request or limiting the number of requests.
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Handler is processed in the end after all middleware are finished executing.
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## Levels
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### Root Level (Before router)
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`Echo#Pre()` can be used to register a middleware which is executed before router
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processes the request. It is helpful to make any changes to the request properties,
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for example, adding or removing a trailing slash from the path so it matches the
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route.
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The following built-in middleware should be registered at this level:
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- HTTPSRedirect
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- HTTPSWWWRedirect
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- WWWRedirect
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- NonWWWRedirect
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- AddTrailingSlash
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- RemoveTrailingSlash
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- MethodOverride
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> As router has not processed the request, middleware at this level won't
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have access to any path related API from `echo.Context`.
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### Root Level (After router)
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Most of the time you will register a middleware at this level using `Echo#Use()`.
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This middleware is executed after router processes the request and has full access
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to `echo.Context` API.
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The following built-in middleware should be registered at this level:
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- BodyLimit
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- Logger
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- Gzip
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- Recover
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- BasicAuth
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- JWTAuth
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- Secure
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- CORS
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- Static
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### Group Level
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When creating a new group, you can register middleware just for that group. For
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example, you can have an admin group which is secured by registering a BasicAuth
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middleware for it.
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*Usage*
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```go
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e := echo.New()
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admin := e.Group("/admin", middleware.BasicAuth())
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```
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You can also add a middleware after creating a group via `admin.Use()`.
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### Route Level
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When defining a new route, you can optionally register middleware just for it.
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*Usage*
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```go
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e := echo.New()
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e.GET("/", <Handler>, <Middleware...>)
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```
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## Skipping Middleware
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There are cases when you would like to skip a middleware based on some condition,
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for that each middleware has an option to define a function `Skipper func(c echo.Context) bool`.
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*Usage*
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```go
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e := echo.New()
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e.Use(middleware.LoggerWithConfig(middleware.LoggerConfig{
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Skipper: func(c echo.Context) bool {
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if strings.HasPrefix(c.Request().Host(), "localhost") {
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return true
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}
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return false
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},
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}))
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```
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Example above skips Logger middleware when request host starts with localhost.
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## [Writing Custom Middleware]({{< ref "recipes/middleware.md">}})
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