Eduardo Henrique da Silva Freitas
17 Jun 2019
•
4 min read
After years relying on Community drivers like mgo and globalsign/mgo, last year MongoDB announced they were building it’s own solution. Last March they released the version 1.0.0, so let’s see how to make some normal operations using the Official driver.
First of all, you need to download the driver using go get.
go.mongodb.org/mongo-driver/mongo
Assuming your MongoDB installation is using the default setting, your method should be like this:
package main
import (
"context"
"log"
"go.mongodb.org/mongo-driver/mongo"
"go.mongodb.org/mongo-driver/mongo/options"
"go.mongodb.org/mongo-driver/mongo/readpref"
)
func GetClient() *mongo.Client {
clientOptions := options.Client().ApplyURI("mongodb://localhost:27017")
client, err := mongo.NewClient(clientOptions)
if err != nil {
log.Fatal(err)
}
err = client.Connect(context.Background())
if err != nil {
log.Fatal(err)
}
return client
}
To test the connection to the mongo, we can call a function called Ping, and check if return any error. Otherwise, out connection was successful.
func main() {
c := GetClient()
err := c.Ping(context.Background(), readpref.Primary())
if err != nil {
log.Fatal("Couldn't connect to the database", err)
} else {
log.Println("Connected!")
}
}
Now for the next examples I created a database called civilact
and a collection heroes
and add the followings documents:
{
"_id" : ObjectId("5d0574824d9f7ff15e989171"),
"name" : "Tony Stark",
"alias" : "Iron Man",
"signed" : true
}
{
"_id" : ObjectId("5d0574d74d9f7ff15e989172"),
"name" : "Steve Rodgers",
"alias" : "Captain America",
"signed" : false
}
{
"_id" : ObjectId("5d0574e94d9f7ff15e989173"),
"name" : "Vision",
"alias" : "Vision",
"signed" : true
}
{
"_id" : ObjectId("5d0575344d9f7ff15e989174"),
"name" : "Clint Barton",
"alias" : "Hawkeye",
"signed" : false
}
To work with these documents, would be better if we create a struct that represents all the Fields and their json names.
type Hero struct {
Name string `json:"name"`
Alias string `json:"alias"`
Signed bool `json:"signed"`
}
Now let's create a Method that will return all Heroes expecting 2 parameters: MongoDB Client and a bson.M that represents a filter. Is this filter is empty, the method will return all documents.
import (
"context"
"log"
"go.mongodb.org/mongo-driver/bson"
"go.mongodb.org/mongo-driver/mongo"
"go.mongodb.org/mongo-driver/mongo/options"
"go.mongodb.org/mongo-driver/mongo/readpref"
)
func ReturnAllHeroes(client *mongo.Client, filter bson.M) []*Hero {
var heroes []*Hero
collection := client.Database("civilact").Collection("heroes")
cur, err := collection.Find(context.TODO(), filter)
if err != nil {
log.Fatal("Error on Finding all the documents", err)
}
for cur.Next(context.TODO()) {
var hero Hero
err = cur.Decode(&hero)
if err != nil {
log.Fatal("Error on Decoding the document", err)
}
heroes = append(heroes, &hero)
}
return heroes
}
The breakdown is:
collection
that represents the collection in the database;collection
to return a cursor of with the elements based oh the filter (in this case the filter is empty, so will return all elements);heroes
array.If we run inside the main function, our return will be:
heroes := ReturnAllHeroes(c, bson.M{})
for _, hero := range heroes {
log.Println(hero.Name, hero.Alias, hero.Signed)
}
2019/06/15 21:07:00 Tony Stark Iron Man true
2019/06/15 21:07:00 Steve Rodgers Captain America false
2019/06/15 21:07:00 Vision Vision true
2019/06/15 21:07:00 Clint Barton Hawkeye false
To retrieve just the Heroes whom signed the Sokovia Accords, we just need to change the filter.
heroes := ReturnAllHeroes(c, bson.M{"signed": true})
2019/06/15 21:18:04 Tony Stark Iron Man true
2019/06/15 21:18:04 Vision Vision true
To retrieve just one Hero, our new method will be like this:
func ReturnOneHero(client *mongo.Client, filter bson.M) Hero {
var hero Hero
collection := client.Database("civilact").Collection("heroes")
documentReturned := collection.FindOne(context.TODO(), filter)
documentReturned.Decode(&hero)
return hero
}
The call will be:
hero := ReturnOneHero(c, bson.M{"name": "Vision"})
log.Println(hero.Name, hero.Alias, hero.Signed)
2019/06/15 22:55:44 Vision Vision true
Now, to increase our collection of Heroes and insert, for example Doctor Strange: The new method will be like this:
func InsertNewHero(client *mongo.Client, hero Hero) interface{} {
collection := client.Database("civilact").Collection("heroes")
insertResult, err := collection.InsertOne(context.TODO(), hero)
if err != nil {
log.Fatalln("Error on inserting new Hero", err)
}
return insertResult.InsertedID
}
That's how we method will be used and checked by our previous method ReturnOneHero
:
hero = Hero{Name: "Stephen Strange", Alias: "Doctor Strange", Signed: true}
insertedID := InsertNewHero(c, hero)
log.Println(insertedID)
hero = ReturnOneHero(c, bson.M{"alias": "Doctor Strange"})
log.Println(hero.Name, hero.Alias, hero.Signed)
Great! We added a Sorcerer Supreme in our Heroes collection, but what if he didn't like and asked us to remove him from it? Well, that's why we need a RemoveOneHero
method.
func RemoveOneHero(client *mongo.Client, filter bson.M) int64 {
collection := client.Database("civilact").Collection("heroes")
deleteResult, err := collection.DeleteOne(context.TODO(), filter)
if err != nil {
log.Fatal("Error on deleting one Hero", err)
}
return deleteResult.DeletedCount
}
And that's how we check:
heroesRemoved := RemoveOneHero(c, bson.M{"alias": "Doctor Strange"})
log.Println("Heroes removed count:", heroesRemove
hero = ReturnOneHero(c, bson.M{"alias": "Doctor Strange"})
log.Println("Is Hero empty?", hero == Hero{ })
For last, let's imagine that Hawkeye changed his mind and now wants to sign the Accords. So let's make de UpdateHero
method.
func UpdateHero(client *mongo.Client, updatedData bson.M, filter bson.M) int64 {
collection := client.Database("civilact").Collection("heroes")
atualizacao := bson.D{ {Key: "$set", Value: updatedData} }
updatedResult, err := collection.UpdateOne(context.TODO(), filter, atualizacao)
if err != nil {
log.Fatal("Error on updating one Hero", err)
}
return updatedResult.ModifiedCount
}
That's it! The regular CRUD Operation was covered and our Heroes can decide their fate. All the code for these examples is available here and this tutorial was also posted at my blog. Here is the Driver's oficial repo and oficial docs
Feel free to get in touch for any question, suggestion or mistake that i made.
Eduardo Henrique da Silva Freitas
See other articles by Eduardo
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