Gin Middleware

Middleware format

gin.HandlerFunc, Satisfy this function

//gin.HandlerFunc
type HandlerFunc func(*Context)

Use

adopt engine.Use(gin.HandlerFunc) register

package main

import (
	"fmt"
	"github.com/gin-gonic/gin"
	"net/http"
	"time"
)

func log() gin.HandlerFunc {
    
	return func(c *gin.Context) {
    
		now := time.Now()
       // Execute next Middleware  
		c.Next()
		end := time.Since(now)
		fmt.Printf(" The request takes time  %s", end)
	}
}

func main() {
    
	r := gin.New()
	r.Use(log())
	r.GET("/ping", func(c *gin.Context) {
    
		c.JSON(http.StatusOK, gin.H{
    
			"message": "pong",
		})
	})
	r.Run(":8080")
}

Terminate Middleware

Generally, there are two modes for the implementation of middleware ：
1. Middleware based on responsibility chain , In the middleware return Will not execute the next middleware
2. be based on AOP Faceted middleware ,return It is not necessary that the next middleware will not be executed

gin The middleware of is based on AOP To build the . among return The next middleware will be executed , If you don't want to execute , Need to call gin.Context.Abort() Method

package main

import (
	"fmt"
	"github.com/gin-gonic/gin"
	"net/http"
	"time"
)

func log() gin.HandlerFunc {
    
	return func(c *gin.Context) {
    
		now := time.Now()
		// Want to terminate the execution of middleware ,return  It's invalid 
		c.Abort()
		end := time.Since(now)
		fmt.Printf(" The request takes time  %s", end)
	}
}

func main() {
    
	r := gin.New()
	r.Use(log())
	r.GET("/ping", func(c *gin.Context) {
    
		c.JSON(http.StatusOK, gin.H{
    
			"message": "pong",
		})
	})
	r.Run(":8080")
}

return The reason why it cannot be terminated

// see Next() Method source code 
func (c *Context) Next() {
    
	c.index++
	for c.index < int8(len(c.handlers)) {
    
		c.handlers[c.index](c)
		c.index++
	}
}

c.handlers Is the execution function of middleware ,c.index Decide which middleware should be implemented .
Suppose now c.haandlers There is A,B,C,D Four Middleware . In the beginning gin Would call Next(),
Execution order A,B,C,D. among A Termination will not hinder B,C,D Implementation . If not used in middleware
Next(), At this time, they are parallel . When A Called in Next(),A Nested in B,C,D Execution of middleware .Abort() take c.index Adjust to a far greater than len(c.handlers) Value , To prevent the execution of subsequent middleware .