Anurag Affection

Posted on May 18

Get API & Fetching Data from MongoDB in Go - 05

First check the Go version by running the command

go version

Create a folder

mkdir <folder_name>

Switch to created folder

cd <folder_name>

Initialize the go project by running the given command. You will get go.mod file.

go mod init <folder_name>

Create a main.go file, use terminal or bash

notepad main.go 
touch main.go

Let's write some basic code in main.go file.

package main 

import (
    "fmt"
)


func main () {
    fmt.Println("Hello From Go")
}

Run the code by following command

go run main.go

You will see this output in console

Hello From Go

Install some packages to connect MongoDB. Here are commands

go get go.mongodb.org/mongo-driver
go get go.mongodb.org/mongo-driver/mongo

Revisit the main.go file to connect MongoDB. Add some code to connect MongoDB. This is how it will look after adding.

package main 

// package importing
import (
    "fmt"

    "log"
    "context"

    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)


// mongodb connections
var collection *mongo.Collection
var ctx = context.TODO()

func init() {
    clientOptions := options.Client().ApplyURI("mongodb://localhost:27017/")
    client, err := mongo.Connect(ctx, clientOptions)
    if err != nil {
        log.Fatal(err)
    }

    // check connection
    err = client.Ping(ctx, nil)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println("Connected to MongoDB!")

    collection = client.Database("testingWithGo").Collection("movies")
}



// entry point 
func main () {
    fmt.Println("Hello From Go")
}

Run the code by following command

go run main.go

You will see this output in console

Connected to MongoDB!
Hello From Go

Till, Our MongoDB is connected. Now let's add some data. We are going to add movie data. So, let's make a movie structure.

// movie model or structure 
type Movie struct {
    ID    string `json:"id"`
    Title string `json:"title"`
}

Now write a function to add movie to database.

// to add movie to db
func addMovie(id, title string) {

    movie := Movie{
        ID:    id,
        Title: title,
    }

    _, err := collection.InsertOne(ctx, movie)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println("Movie added successfully!")
}

Call the addMovie function to main function.

addMovie("1", "Captain America")

This is how our code will look like after completing above steps

package main 

// package importing
import (
    "fmt"

    "log"
    "context"

    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)




// mongodb connections
var collection *mongo.Collection
var ctx = context.TODO()

func init() {
    clientOptions := options.Client().ApplyURI("mongodb://localhost:27017/")
    client, err := mongo.Connect(ctx, clientOptions)
    if err != nil {
        log.Fatal(err)
    }

    // check connection
    err = client.Ping(ctx, nil)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println("Connected to MongoDB!")

    collection = client.Database("testingWithGo").Collection("movies")
}



// movie model or structure 
type Movie struct {
    ID    string `json:"id"`
    Title string `json:"title"`
}


// to add movie to db
func addMovie(id, title string) {

    movie := Movie{
        ID:    id,
        Title: title,
    }

    _, err := collection.InsertOne(ctx, movie)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println("Movie added successfully!")
}




// entry point 
func main () {
    fmt.Println("Hello From Go")

    // callig addMovie 
    addMovie("1", "Captain America")
}

Run the code by following command

go run main.go

You will see this output in console

Connected to MongoDB!
Hello From Go
Movie added successfully!

We have successfully added some data to MongoDB, you can verify in your database, which is your localhost.

mongodb://localhost:27017/

Now import these packages

"encoding/json"
"net/http"
"go.mongodb.org/mongo-driver/bson"

This how our import will look like

// package importing
import (
    "fmt"

    "log"
    "context"

    "encoding/json"
    "net/http"

        "go.mongodb.org/mongo-driver/bson"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)

Now write a function to getAllMovies. Here is the code

// api to get all movies
func getAllMovies(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")

    // Define a slice to store the decoded documents
    var movies []Movie

    // Find all movies in the collection
    cursor, err := collection.Find(ctx, bson.M{})
    if err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }
    defer cursor.Close(ctx)

    // Iterate through the cursor and decode each document
    for cursor.Next(ctx) {
        var movie Movie
        if err := cursor.Decode(&movie); err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }
        movies = append(movies, movie)
    }

    // Check for cursor errors after iterating
    if err := cursor.Err(); err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }

    // Encode the movies slice as JSON and write it to the response
    if err := json.NewEncoder(w).Encode(movies); err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }
}

Call the getAllMovies with route in main, also run the server.

        // api to getAllMovies 
    http.HandleFunc("/movies", getAllMovies)

    // our server on port on 8000
    http.ListenAndServe(":8000", nil)

Let's have a full code, after completing all the above steps

package main 

// package importing
import (
    "fmt"

    "log"
    "context"

    "encoding/json"
    "net/http"

    "go.mongodb.org/mongo-driver/bson"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)




// mongodb connections
var collection *mongo.Collection
var ctx = context.TODO()

func init() {
    clientOptions := options.Client().ApplyURI("mongodb://localhost:27017/")
    client, err := mongo.Connect(ctx, clientOptions)
    if err != nil {
        log.Fatal(err)
    }

    // check connection
    err = client.Ping(ctx, nil)
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println("Connected to MongoDB!")

    collection = client.Database("testingWithGo").Collection("movies")
}



// movie model or structure 
type Movie struct {
    ID    string `json:"id"`
    Title string `json:"title"`
}


// to add movie to db
func addMovie(id, title string) {

    movie := Movie{
        ID:    id,
        Title: title,
    }

    _, err := collection.InsertOne(ctx, movie)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println("Movie added successfully!")
}





// api to get all movies
func getAllMovies(w http.ResponseWriter, r *http.Request) {
    w.Header().Set("Content-Type", "application/json")

    // Define a slice to store the decoded documents
    var movies []Movie

    // Find all movies in the collection
    cursor, err := collection.Find(ctx, bson.M{})
    if err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }
    defer cursor.Close(ctx)

    // Iterate through the cursor and decode each document
    for cursor.Next(ctx) {
        var movie Movie
        if err := cursor.Decode(&movie); err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }
        movies = append(movies, movie)
    }

    // Check for cursor errors after iterating
    if err := cursor.Err(); err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }

    // Encode the movies slice as JSON and write it to the response
    if err := json.NewEncoder(w).Encode(movies); err != nil {
        http.Error(w, err.Error(), http.StatusInternalServerError)
        return
    }
}






// entry point 
func main () {
    fmt.Println("Hello From Go")

    // callig addMovie 
    addMovie("1", "Captain America")

    // api to getAllMovies 
    http.HandleFunc("/movies", getAllMovies)

    // visit this url in browser
    fmt.Println("Your Server is running on http://localhost:8000")

    // our server on port on 8000
    http.ListenAndServe(":8000", nil)
}

Run the code by following command

go run main.go

You will see this output in console

Connected to MongoDB!
Hello From Go
Movie added successfully!
Your Server is running on http://localhost:8000

Visit http://localhost:8000/movies on browser to verify the API. This what you will get.

[
    {
        "id": "1",
        "title": "The Shawshank Redemption"
    },
    {
        "id": "1",
        "title": "The Shawshank Redemption"
    },
    {
        "id": "1",
        "title": "Captain America"
    },
    {
        "id": "1",
        "title": "Captain America"
    },
    {
        "id": "1",
        "title": "Captain America"
    },
    {
        "id": "1",
        "title": "Captain America"
    }
]

That's for this article. Thank You.

DEV Community

Get API & Fetching Data from MongoDB in Go - 05

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