php小编子墨在这里为大家解答一个常见的问题：如果在不同模块中访问数据库，应该如何操作呢？在开发过程中，我们经常需要在不同的功能模块中访问数据库，这涉及到如何管理数据库连接和执行数据库操作的问题。为了解决这个问题，我们可以采用多种方式，例如使用全局变量、单例模式、依赖注入等。具体选择哪种方式取决于项目的需求和开发团队的习惯。接下来，我将对这些方式进行详细介绍，希望能帮助到大家。

问题内容

我尝试使用 jwt 进行 atuhorize，但遇到问题，当我检查来自声明的有价值电子邮件的电子邮件时，我收到错误 500。这个问题是因为数据库尚未准备好。

这是代码

套餐路线

package route

import (
    "go_fiber/controller"
    "go_fiber/middleware"


    "github.com/gofiber/fiber/v2"
)

func routeinit(app *fiber.app, usercontroller controller.usercontroller) {
    app.get("/users", middleware.authmiddleware, usercontroller.findall)
    app.post("/login", usercontroller.login)
}

打包应用

package app

import (
    "database/sql"
    "fmt"
    "go_fiber/helper"
    "os"
    "time"

    _ "github.com/go-sql-driver/mysql"
    "github.com/joho/godotenv"
)

func newdb() *sql.db {

    var (   
        username = envvariable("db_username")
        password = envvariable("db_password")
        host = envvariable("db_host")
        port = envvariable("db_port")
        db_name = envvariable("db_name")
    )

    dns := fmt.sprintf("%s:%s@tcp(%s:%s)/%s?parsetime=true", username, password, host, port, db_name)

    db, err := sql.open("mysql", dns)
    if err != nil {
        panic(err)
    }

    db.setmaxidleconns(10)
    db.setmaxopenconns(100)
    db.setconnmaxidletime(5 * time.minute)
    db.setconnmaxlifetime(60 * time.minute)

    return db
}

包主

package main

import (
    "go_fiber/app"
    "go_fiber/controller"
    "go_fiber/exception"
    "go_fiber/repository"
    "go_fiber/route"
    "go_fiber/service"

    "github.com/go-playground/validator/v10"
    "github.com/gofiber/fiber/v2"
)

func main(){

    var db = app.newdb()
    app := fiber.new()
    app.use(func(c *fiber.ctx) error {
        defer func() {
            if err := recover(); err != nil {
                exception.errorhandler(c, err)
            }
        }()
    
        return c.next()
    })

    validator := validator.new()
    userrepository := repository.newuserrepository()
    userservice := service.newuserservice(userrepository, db, validator)
    usercontroller := controller.newusercontroller(userservice)
    
    route.routeinit(app, usercontroller)

    app.listen(":3000")
}

封装中间件

package middleware

import (
    "database/sql"
    "errors"
    "fmt"
    "go_fiber/exception"
    "log"
    "os"
    "time"

    "github.com/gofiber/fiber/v2"
    "github.com/golang-jwt/jwt/v4"
)

func authmiddleware(c *fiber.ctx) error{
    tokenstring := c.cookies("authorization") 

    log.printf("(middleware) token : %v", tokenstring)

    if tokenstring == "" {
        panic(exception.newuserunauthorized(errors.new("user unauthorized").error()))
    }

    token, err := jwt.parse(tokenstring, func(token *jwt.token) (interface{}, error) {
        if _, ok := token.method.(*jwt.signingmethodhmac); !ok {
            return nil, fmt.errorf("unexpected signing method :%v", token.header["sub"])
        }

        return []byte(os.getenv("secret")), nil
    })

    log.printf("(middleware) token : %v", token)
    log.printf("(middleware) error : %v", err)

    if claims, ok := token.claims.(jwt.mapclaims); ok && token.valid {
        if float64(time.now().unix()) > claims["exp"].(float64) {
            panic(exception.newuserunauthorized(errors.new("user unauthorized").error()))
        }

        log.printf("(middleware) claims : %v", claims)
        log.printf("(middleware) ok : %v", ok)
        
        var db *sql.db

        tx, err := db.begin()
        
        log.printf("(middleware) tx : %v", tx)
        log.printf("(middleware) error : %v", err)
        
        query :=`
            select email from users 
            where email = ? 
            limit 1
        `
        log.printf("(middleware) query : %v", query)

        user, err := tx.querycontext(c.context(), query, claims["sub"])

        log.printf("(middleware) user  : %v", user)
        log.printf("(middleware) error : %v", err)
        

        if err != nil {
            panic(exception.newuserunauthorized(errors.new("user unauthorized").error()))
        }

        c.locals("user", user)
        c.next()
    }else {
        panic(exception.newuserunauthorized(errors.new("user unauthorized").error()))
    }

    return nil
}

这部分是问题代码

var db *sql.db
tx, err := db.begin()   
log.printf("(middleware) tx : %v", tx) // no detect in terminal

这是日志的输出

2023/02/12 10:00:04 (middleware) token : eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE2NzYxNzEzOTIsInN1YiI6IkphZmFyQGdtYWlsLmNvbSJ9.6nn_IaNACHfe7flFMOXfj1ygZS-U_yrnU_Gvjn8xCp8
2023/02/12 10:00:04 (middleware) token : &{eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE2NzYxNzEzOTIsInN1YiI6IkphZmFyQGdtYWlsLmNvbSJ9.6nn_IaNACHfe7flFMOXfj1ygZS-U_yrnU_Gvjn8xCp8 0xc0000a6780 map[alg:HS256 typ:JWT] map[exp:1.676171392e+09 sub:[email protected]] 6nn_IaNACHfe7flFMOXfj1ygZS-U_yrnU_Gvjn8xCp8 true}
2023/02/12 10:00:04 (middleware) error : <nil>
2023/02/12 10:00:04 (middleware) claims : map[exp:1.676171392e+09 sub:[email protected]]
2023/02/12 10:00:04 (middleware) ok : true

那么，如果不同的包如何解决访问数据库的问题？

解决方法

您应该通过路由注册将数据库处理程序向下传递到中间件。

更改您的 authmiddleware，以便它由采用 db *sql.db 作为参数的函数返回：

func newauthmiddleware(db *sql.db) fiber.handler {
    return func(c *fiber.ctx) error {
       // the rest of your function is here and has access to db
    }
}

然后您需要在 routeinit 函数中调用 newauthmiddleware

func routeinit(app *fiber.app, usercontroller controller.usercontroller, db *sql.db) {
    app.get("/users", middleware.newauthmiddleware(db), usercontroller.findall)
    app.post("/login", usercontroller.login)
}

然后在主函数中将数据库传递给 routeinit()

func main() {
    // ... as before

    route.RouteInit(app, userController, db)
}