Blog with Go, Gin, MySQL and Docker - Part 2

Welcome to Part 2 of the Blog Project with Go, Gin, MySQL and Docker. Do make sure you have followed part 1, Here is the link.

Contents :

• Architecture
• Getting Started
  • Designing Models
  • Adding Repository Layer
  • Adding Service Layer
  • Adding Controller Layer
  • Adding Utils
  • Adding Routes
  • Main Router
  • Gluing All Things Together
• Test APIs
• Wrap Up

The respective repository can be found here. Clone the project Check out to branch part-2 by git checkout part-2 .

Architecture

We will be following Clean Architecture for this Blog Project. Clean architecture is art of writing software applications in a layered fashion. Please do read this article for more detailed information as all layers (repository, controller e.t.c ) are explained there. Following is the overview of the project that follows clean architecture and this is what you are going to follow. Isn't it awesome?

├── api 
│   ├── controller
│   │   └── post.go
│   ├── repository
│   │   └── post.go
│   ├── routes
│   │   └── post.go
│   └── service
│       └── post.go
├── docker-compose.yml
├── Dockerfile
├── go.mod
├── go.sum
├── infrastructure
│   ├── db.go
│   ├── env.go
│   └── routes.go
├── main
├── main.go
├── models
│   └── post.go
└── util
    └── response.go

Getting Started :

Designing Models

Create a folder models in project directory. Inside the models folder create a blog.go file and add following code

package models
import "time"

//Post Post Model
type Post struct {
    ID        int64     `gorm:"primary_key;auto_increment" json:"id"`
    Title     string    `gorm:"size:200" json:"title"`
    Body      string    `gorm:"size:3000" json:"body" `
    CreatedAt time.Time `json:"created_at,omitempty"`
    UpdatedAt time.Time `json:"updated_at,omitempty"`
}

// TableName method sets table name for Post model
func (post *Post) TableName() string {
    return "post"
}

//ResponseMap -> response map method of Post
func (post *Post) ResponseMap() map[string]interface{} {
    resp := make(map[string]interface{})
    resp["id"] = post.ID
    resp["title"] = post.Title
    resp["body"] = post.Body
    resp["created_at"] = post.CreatedAt
    resp["updated_at"] = post.UpdatedAt
    return resp
}

We are defining Blog model which later gets converted into database table (gorm does this for us). TableName method sets a blog as a table name in the database for the Blog struct. ResponseMap is used to return response from Succesfull API calls. I assume you are familiar with Struct and methods in go.

Adding Repository Layer

This layer is the one that interacts and performs CRUD operations on the database.
Create a folder api on the project directory. Inside api folder create repository folder. Inside the repository folder create a blog.go file. The structure should look like this api -> repository -> blog.go. You can always refer to architecture section for project structure reference.

package repository
import (
    "blog/infrastructure"
    "blog/models"
)

//PostRepository -> PostRepository
type PostRepository struct {
    db infrastructure.Database
}

// NewPostRepository : fetching database
func NewPostRepository(db infrastructure.Database) PostRepository {
    return PostRepository{
        db: db,
    }
}

//Save -> Method for saving post to database
func (p PostRepository) Save(post models.Post) error {
    return p.db.DB.Create(&post).Error
}

//FindAll -> Method for fetching all posts from database
func (p PostRepository) FindAll(post models.Post, keyword string) (*[]models.Post, int64, error) {
    var posts []models.Post
    var totalRows int64 = 0

    queryBuider := p.db.DB.Order("created_at desc").Model(&models.Post{})

    // Search parameter
    if keyword != "" {
        queryKeyword := "%" + keyword + "%"
        queryBuider = queryBuider.Where(
            p.db.DB.Where("post.title LIKE ? ", queryKeyword))
    }

    err := queryBuider.
        Where(post).
        Find(&posts).
        Count(&totalRows).Error
    return &posts, totalRows, err
}

//Update -> Method for updating Post
func (p PostRepository) Update(post models.Post) error {
    return p.db.DB.Save(&post).Error
}

//Find -> Method for fetching post by id
func (p PostRepository) Find(post models.Post) (models.Post, error) {
    var posts models.Post
    err := p.db.DB.
        Debug().
        Model(&models.Post{}).
        Where(&post).
        Take(&posts).Error
    return posts, err
}

//Delete Deletes Post
func (p PostRepository) Delete(post models.Post) error {
    return p.db.DB.Delete(&post).Error
}

Let's explain above codes:

• PostRepository : PostRepository struct has a db field which is a type of infrastructure.Database; which infact is a gorm database type. Infrastructure's Database part has been covered up in Part 1.
• NewPostRepository : NewPostRepository takes database as argument and returns PostRepository. Database argument is provided while initializing the server on main.go file.
• ** Save/FindAll/Find/Update/Delete ** : Perform CRUD operation to database using gorm ORM.

Adding Service Layer

This layer manages the communication between the inner and outer layers (Repository and Controller layers ). More detail here. Inside api folder create service folder. Inside the service folder create a blog.go file. The structure should look like this api -> service -> blog.go.Refer to architecture section for the structure.

package service

import (
    "blog/api/repository"
    "blog/models"
)

//PostService PostService struct
type PostService struct {
    repository repository.PostRepository
}

//NewPostService : returns the PostService struct instance
func NewPostService(r repository.PostRepository) PostService {
    return PostService{
        repository: r,
    }
}

//Save -> calls post repository save method
func (p PostService) Save(post models.Post) error {
    return p.repository.Save(post)
}

//FindAll -> calls post repo find all method
func (p PostService) FindAll(post models.Post, keyword string) (*[]models.Post, int64, error) {
    return p.repository.FindAll(post, keyword)
}

// Update -> calls postrepo update method
func (p PostService) Update(post models.Post) error {
    return p.repository.Update(post)
}

// Delete -> calls post repo delete method
func (p PostService) Delete(id int64) error {
    var post models.Post
    post.ID = id
    return p.repository.Delete(post)
}

// Find -> calls post repo find method
func (p PostService) Find(post models.Post) (models.Post, error) {
    return p.repository.Find(post)
}

Let's explain above codes:

• PostService : PostService struct has repository field which is a type to PostRepository allowing access to PostRepository methods.
• NewPostService : NewPostService takes PostRepository as argument and returns PostService allowing all PostRepository methods.
• ** Save/FindAll/Find/Update/Delete ** : Calls respective repository methods.

Adding Controller Layer

This layer is used to grab the user input and process them or pass them to other layers. More about controllers here. But before adding code for the controller layer let's add some utilities which are used to return responses on sucessfull API calls.

Adding Utils

Create a util folder on project directory and a file response.go inside it. The structure should look like util -> response.go.

package util

import "github.com/gin-gonic/gin"

// Response struct
type Response struct {
    Success bool        `json:"success"`
    Message string      `json:"message"`
    Data    interface{} `json:"data"`
}

// ErrorJSON : json error response function
func ErrorJSON(c *gin.Context, statusCode int, data interface{}) {
    c.JSON(statusCode, gin.H{"error": data})
}

// SuccessJSON : json error response function
func SuccessJSON(c *gin.Context, statusCode int, data interface{}) {
    c.JSON(statusCode, gin.H{"msg": data})
}

• Response : Response is to return JSON Formatted success message with Struct data, here Blog data as of now.
• ErrorJSON : ErrorJSON is used to return JSON Formatted error response
• SuccessJSON : SuccessJSON is used to return JSON Formatted success message.

Create a controller folder inside api folder and blog.go file inside controller folder. Project structure folder should looks like api -> controller -> blog.go.

package controller

import (
    "blog/api/service"
    "blog/models"
    "blog/util"
    "net/http"
    "strconv"

    "github.com/gin-gonic/gin"
)

//PostController -> PostController
type PostController struct {
    service service.PostService
}

//NewPostController : NewPostController
func NewPostController(s service.PostService) PostController {
    return PostController{
        service: s,
    }
}

// GetPosts : GetPosts controller
func (p PostController) GetPosts(ctx *gin.Context) {
    var posts models.Post

    keyword := ctx.Query("keyword")

    data, total, err := p.service.FindAll(posts, keyword)

    if err != nil {
        util.ErrorJSON(ctx, http.StatusBadRequest, "Failed to find questions")
        return
    }
    respArr := make([]map[string]interface{}, 0, 0)

    for _, n := range *data {
        resp := n.ResponseMap()
        respArr = append(respArr, resp)
    }

    ctx.JSON(http.StatusOK, &util.Response{
        Success: true,
        Message: "Post result set",
        Data: map[string]interface{}{
            "rows":       respArr,
            "total_rows": total,
        }})
}

// AddPost : AddPost controller
func (p *PostController) AddPost(ctx *gin.Context) {
    var post models.Post
    ctx.ShouldBindJSON(&post)

    if post.Title == "" {
        util.ErrorJSON(ctx, http.StatusBadRequest, "Title is required")
        return
    }
    if post.Body == "" {
        util.ErrorJSON(ctx, http.StatusBadRequest, "Body is required")
        return
    }
    err := p.service.Save(post)
    if err != nil {
        util.ErrorJSON(ctx, http.StatusBadRequest, "Failed to create post")
        return
    }
    util.SuccessJSON(ctx, http.StatusCreated, "Successfully Created Post")
}

//GetPost : get post by id
func (p *PostController) GetPost(c *gin.Context) {
    idParam := c.Param("id")
    id, err := strconv.ParseInt(idParam, 10, 64) //type conversion string to int64
    if err != nil {
        util.ErrorJSON(c, http.StatusBadRequest, "id invalid")
        return
    }
    var post models.Post
    post.ID = id
    foundPost, err := p.service.Find(post)
    if err != nil {
        util.ErrorJSON(c, http.StatusBadRequest, "Error Finding Post")
        return
    }
    response := foundPost.ResponseMap()

    c.JSON(http.StatusOK, &util.Response{
        Success: true,
        Message: "Result set of Post",
        Data:    &response})

}

//DeletePost : Deletes Post
func (p *PostController) DeletePost(c *gin.Context) {
    idParam := c.Param("id")
    id, err := strconv.ParseInt(idParam, 10, 64) //type conversion string to uint64
    if err != nil {
        util.ErrorJSON(c, http.StatusBadRequest, "id invalid")
        return
    }
    err = p.service.Delete(id)

    if err != nil {
        util.ErrorJSON(c, http.StatusBadRequest, "Failed to delete Post")
        return
    }
    response := &util.Response{
        Success: true,
        Message: "Deleted Sucessfully"}
    c.JSON(http.StatusOK, response)
}

//UpdatePost : get update by id
func (p PostController) UpdatePost(ctx *gin.Context) {
    idParam := ctx.Param("id")

    id, err := strconv.ParseInt(idParam, 10, 64)

    if err != nil {
        util.ErrorJSON(ctx, http.StatusBadRequest, "id invalid")
        return
    }
    var post models.Post
    post.ID = id

    postRecord, err := p.service.Find(post)

    if err != nil {
        util.ErrorJSON(ctx, http.StatusBadRequest, "Post with given id not found")
        return
    }
    ctx.ShouldBindJSON(&postRecord)

    if postRecord.Title == "" {
        util.ErrorJSON(ctx, http.StatusBadRequest, "Title is required")
        return
    }
    if postRecord.Body == "" {
        util.ErrorJSON(ctx, http.StatusBadRequest, "Body is required")
        return
    }

    if err := p.service.Update(postRecord); err != nil {
        util.ErrorJSON(ctx, http.StatusBadRequest, "Failed to store Post")
        return
    }
    response := postRecord.ResponseMap()

    ctx.JSON(http.StatusOK, &util.Response{
        Success: true,
        Message: "Successfully Updated Post",
        Data:    response,
    })
}

Let's explain above codes:

• PostController : PostController struct has service field which is a type to PostService allowing access to PostService methods.
• NewPostController : NewPostController takes PostService as argument and returns PostController allowing all PostController methods which are leveraged on controller.
• ** GetPosts/AddPost/GetPost/DeletePost/UpdatePost ** : User Input are grabbed/ validated / processed / Service layers are called (which calls Repository methods; performing database operations) / and responses are returned by utility response functions.

Adding Routes

Till now we have created foundational part of the APIs. Let's create endpoints by adding routes.

package routes

import (
    "blog/api/controller"
    "blog/infrastructure"
)

//PostRoute -> Route for question module
type PostRoute struct {
    Controller controller.PostController
    Handler    infrastructure.GinRouter
}

//NewPostRoute -> initializes new choice rouets
func NewPostRoute(
    controller controller.PostController,
    handler infrastructure.GinRouter,

) PostRoute {
    return PostRoute{
        Controller: controller,
        Handler:    handler,
    }
}

//Setup -> setups new choice Routes
func (p PostRoute) Setup() {
    post := p.Handler.Gin.Group("/posts") //Router group
    {
        post.GET("/", p.Controller.GetPosts)
        post.POST("/", p.Controller.AddPost)
        post.GET("/:id", p.Controller.GetPost)
        post.DELETE("/:id", p.Controller.DeletePost)
        post.PUT("/:id", p.Controller.UpdatePost)
    }
}

Let's explain above codes:

• PostRoute : PostRoute struct has Controller and Handler fields. Controller is a type of PostController and Handler is of type Gin Router. Gin Router here is used to create router group which is used later to create endpoint.s
  • NewPostRoute : NewPostRoute takes Controller and Handlre as arguments and returns PostRoute struct allowing access to PostController and Gin Router.
• ** Setup ** : Setup method is used to configure endpoint for post APIs.

Main Router

Let's create a function to create and return Gin Router.
Create a routes.go file inside infrastructure folder. It should look like infrastructure -> routes.go.

package infrastructure

import (
    "net/http"

    "github.com/gin-gonic/gin"
)

//GinRouter -> Gin Router
type GinRouter struct {
    Gin *gin.Engine
}

//NewGinRouter all the routes are defined here
func NewGinRouter() GinRouter {

    httpRouter := gin.Default()

    httpRouter.GET("/", func(c *gin.Context) {
        c.JSON(http.StatusOK, gin.H{"data": "Up and Running..."})
    })
    return GinRouter{
        Gin: httpRouter,
    }

}

The above code configures and returns a Default Gin Router instance.

Gluing All Things Together

The foundational part has been now completed. The only part left is to glue things together. Edit main.go file with following code

package main

import (
    "blog/api/controller"
    "blog/api/repository"
    "blog/api/routes"
    "blog/api/service"
    "blog/infrastructure"
    "blog/models"
)

func init() {
    infrastructure.LoadEnv()
}

func main() {

    router := infrastructure.NewGinRouter() //router has been initialized and configured
    db := infrastructure.NewDatabase() // databse has been initialized and configured
    postRepository := repository.NewPostRepository(db) // repository are being setup
    postService := service.NewPostService(postRepository) // service are being setup
    postController := controller.NewPostController(postService) // controller are being set up
    postRoute := routes.NewPostRoute(postController, router) // post routes are initialized
    postRoute.Setup() // post routes are being setup

    db.DB.AutoMigrate(&models.Post{}) // migrating Post model to datbase table
    router.Gin.Run(":8000") //server started on 8000 port
}

That's all for the main.go.

Test APIs

It's time to spin the server and testing the APIs.
Fire up the server via Docker Compose via following command

docker-compose up --build

Now, Bring up your favorite API Tester application. I will be using Insomnia
Testing Create API endpoint -> /posts/

Testing Get All Post endpoint -> /posts/

Testing Get Post endpoint -> /posts/2

Testing Update Post endpoint -> /posts/2

Testing Delete Post endpoint -> /posts/2

Wrap Up

Link to Part 1 : Blog with Go, Gin, MySQL and Docker

Next Up
Upcoming Part 3 will cover the following

• Adding User Struct & APIs
• Related User Posts
• Middleware Layer and many more..

That's a wrap. Hope you enjoyed the article. Do not hesitate to share your feedback. I am on Linkedin . Let's Connect !

Next Part will be published on next weekend. Please stay tuned.

Thank You for reading !

Comments

[Jacob Xie]

Thanks for the great sharing! BTW, one thing I've noticed is that all the structs under api folder are using non-pointer fields. For example, why wouldn't we write PostRoute like this:

type PostRoute struct {
    Controller *controller.PostController
    Handler    *infrastructure.GinRouter
}

And as a result, we can do main.go like below (using references):

func main() {
    router := infrastructure.NewGinRouter()
    db := infrastructure.NewDatabase()
    postRepository := repository.NewPostRepository(&db)
    postService := service.NewPostService(&postRepository)
    postController := controller.NewPostController(&postService)
    postRoute := routes.NewPostRoute(&postController, &router)

    postRoute.Setup()

    db.DB.AutoMigrate(&models.Post{})

    router.Gin.Run(":8080")
}

Again, thanks for sharing!

[Isaac Contreras]

Hi Umesh,

I'm attempting to go through part 2 here of your tutorial, but I keep running into a certain error and was hoping you could help. I get this when running docker-compose up --build:

web-1 | 2024/12/13 00:35:02 stdout: 2024/12/13 00:35:02 /app/infrastructure/db.go:28
web-1 | 2024/12/13 00:35:02 stdout: [error] failed to initialize database, got error dial tcp 192.168.65.254:3306: connect: connection refused
web-1 | 2024/12/13 00:35:02 stderr: panic: Failed to connect to database!

I'm running on Apple silicon and tried changing DB_HOST in .env to host.docker.internal and also docker.for.mac.localhost but I get the same error, just at different IPs. Hope you can get back to me, the tutorial has been very helpful so far!