Middleware

This chapter will introduce how to register route middleware in Go-Sail.

Introduction

Routing middleware sits between pre-processing requests and post-processing, acting as a bridge between the two. Typically, we place common processing measures, such as identity verification, in middleware.
Go-Sail uses Gin as its HTTP service engine without any excessive wrapping, so its usage is exactly the same as Gin's own usage.

In the previous chapter, after a user successfully logs in, we will issue a pass token to the user. In subsequent requests, the user can use this token to make a request to access some resources that require identity verification.

Declaring a route middleware

First, let's write a middleware function according to Gin's specifications. The code is as follows.

tip

We assume the user places their access credentials in the request header, and the field name is "Authorization".

main.go

package main

import (
    "github.com/gin-gonic/gin"
    "github.com/keepchen/go-sail/v3/constants"
    "github.com/keepchen/go-sail/v3/sail"
)

...

// ValidateToken validate user's token
func ValidateToken() gin.HandlerFunc {
    return func(c *gin.Context) {
        token := c.Request.Header.Get("Authorization")
        if token != "this-is-a-valid-token" {
            sail.Response(c).Wrap(constants.ErrAuthorizationTokenInvalid, nil).Send()
            return
        }

        c.Next()
    }
}

...

Use route middleware in routes

After that, we can wrap the routes that require authentication and use the same authentication logic uniformly.

main.go

package main

import (
    "github.com/gin-gonic/gin"
    "github.com/keepchen/go-sail/v3/sail"
)
var (
    ...

    registerRoutes = func(ginEngine *gin.Engine) {
        ginEngine.GET("/hello", func(c *gin.Context){
            sail.Response(c).Data("hello world!")
        })
        ginEngine.POST("/login", func(c *gin.Context){
            var loginRequest LoginRequest
            c.ShouldBind(&loginRequest)
            
            if loginRequest.Username != "go-sail" || loginRequest.Password != "password" {
                sail.Response(c).Failure("login failed, username or password not match!")
                return
            }
            
            token := "this-is-a-valid-token"
            sail.Response(c).Data(token)
        })
        userGroup := ginEngine.Group("/user").Use(ValidateToken())
        {
            userGroup.GET("/balance", ...).
                      GET("/info", ...).
                      GET("/logout", ...)
        }
    }
    ...
)

The highlighted code indicates that authentication is required to access the /user/balance, /user/info, and /user/logout routes.