GO——echo中间件原理

原理

参考：https://blog.csdn.net/liyunlong41/article/details/104043047

func IAMMiddleware1(next echo.HandlerFunc) echo.HandlerFunc {return func(ctx echo.Context) error {fmt.Println("IAMMiddleware1")return next(ctx)}
}

echo中间件struct定义：传入一个func，返回一个func
- 使用一个func包裹另一个func

func applyMiddleware(h HandlerFunc, middleware ...MiddlewareFunc) HandlerFunc {for i := len(middleware) - 1; i >= 0; i-- {h = middleware[i](h)}return h
}

先用最后面的中间件包裹处理函数，然后用前面的，这样第一个中间件就在最外层
这样就能从头开始执行了

原理demo

package mainimport ("fmt""github.com/labstack/echo/v4"
)func main() {e := &MyEcho{}e.Use(IAMMiddleware1, IAMMiddleware2)e.GET("/", IAMGetRequest)ctx := echo.New().NewContext(nil, nil)_ = e.Run(ctx)
}func IAMMiddleware1(next echo.HandlerFunc) echo.HandlerFunc {return func(ctx echo.Context) error {fmt.Println("I am middleware1")return next(ctx)}
}func IAMMiddleware2(next echo.HandlerFunc) echo.HandlerFunc {return func(ctx echo.Context) error {fmt.Println("I am middleware2")defer func() {fmt.Println("I am middleware2 defer")}()return next(ctx)}
}func IAMGetRequest(ctx echo.Context) error {fmt.Println("I am get request")return nil
}type MyEcho struct {myMiddleware []echo.MiddlewareFunchandler      echo.HandlerFunc
}func (e *MyEcho) Use(middleware ...echo.MiddlewareFunc) {e.myMiddleware = append(e.myMiddleware, middleware...)
}func (e *MyEcho) GET(path string, h echo.HandlerFunc, middleware ...echo.MiddlewareFunc) {e.myMiddleware = append(e.myMiddleware, middleware...)//使用中间件将最终的handler包裹起来了，最外层是第一个中间件e.handler = applyMiddleware(h, e.myMiddleware...)
}func applyMiddleware(h echo.HandlerFunc, middleware ...echo.MiddlewareFunc) echo.HandlerFunc {for i := len(middleware) - 1; i >= 0; i-- {h = middleware[i](h)}return h
}func (e *MyEcho) Run(ctx echo.Context) error {return e.handler(ctx)
}

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