reorganization of _examples and add some new examples such as iris+groupcache+mysql+docker

Former-commit-id: ed635ee95de7160cde11eaabc0c1dcb0e460a620

_examples/database/mongodb/store/movie.go

@@ -0,0 +1,180 @@
+package store
+
+import (
+	"context"
+	"errors"
+
+	"go.mongodb.org/mongo-driver/bson"
+	"go.mongodb.org/mongo-driver/bson/primitive"
+	"go.mongodb.org/mongo-driver/mongo"
+	// up to you:
+	// "go.mongodb.org/mongo-driver/mongo/options"
+)
+
+type Movie struct {
+	ID          primitive.ObjectID `json:"_id" bson:"_id"` /* you need the bson:"_id" to be able to retrieve with ID filled */
+	Name        string             `json:"name"`
+	Cover       string             `json:"cover"`
+	Description string             `json:"description"`
+}
+
+type MovieService interface {
+	GetAll(ctx context.Context) ([]Movie, error)
+	GetByID(ctx context.Context, id string) (Movie, error)
+	Create(ctx context.Context, m *Movie) error
+	Update(ctx context.Context, id string, m Movie) error
+	Delete(ctx context.Context, id string) error
+}
+
+type movieService struct {
+	C *mongo.Collection
+}
+
+var _ MovieService = (*movieService)(nil)
+
+func NewMovieService(collection *mongo.Collection) MovieService {
+	// up to you:
+	// indexOpts := new(options.IndexOptions)
+	// indexOpts.SetName("movieIndex").
+	// 	SetUnique(true).
+	// 	SetBackground(true).
+	// 	SetSparse(true)
+
+	// collection.Indexes().CreateOne(context.Background(), mongo.IndexModel{
+	// 	Keys:    []string{"_id", "name"},
+	// 	Options: indexOpts,
+	// })
+
+	return &movieService{C: collection}
+}
+
+func (s *movieService) GetAll(ctx context.Context) ([]Movie, error) {
+	// Note:
+	// The mongodb's go-driver's docs says that you can pass `nil` to "find all" but this gives NilDocument error,
+	// probably it's a bug or a documentation's mistake, you have to pass `bson.D{}` instead.
+	cur, err := s.C.Find(ctx, bson.D{})
+	if err != nil {
+		return nil, err
+	}
+	defer cur.Close(ctx)
+
+	var results []Movie
+
+	for cur.Next(ctx) {
+		if err = cur.Err(); err != nil {
+			return nil, err
+		}
+
+		//	elem := bson.D{}
+		var elem Movie
+		err = cur.Decode(&elem)
+		if err != nil {
+			return nil, err
+		}
+
+		// results = append(results, Movie{ID: elem[0].Value.(primitive.ObjectID)})
+
+		results = append(results, elem)
+	}
+
+	return results, nil
+}
+
+func matchID(id string) (bson.D, error) {
+	objectID, err := primitive.ObjectIDFromHex(id)
+	if err != nil {
+		return nil, err
+	}
+
+	filter := bson.D{{Key: "_id", Value: objectID}}
+	return filter, nil
+}
+
+var ErrNotFound = errors.New("not found")
+
+func (s *movieService) GetByID(ctx context.Context, id string) (Movie, error) {
+	var movie Movie
+	filter, err := matchID(id)
+	if err != nil {
+		return movie, err
+	}
+
+	err = s.C.FindOne(ctx, filter).Decode(&movie)
+	if err == mongo.ErrNoDocuments {
+		return movie, ErrNotFound
+	}
+	return movie, err
+}
+
+func (s *movieService) Create(ctx context.Context, m *Movie) error {
+	if m.ID.IsZero() {
+		m.ID = primitive.NewObjectID()
+	}
+
+	_, err := s.C.InsertOne(ctx, m)
+	if err != nil {
+		return err
+	}
+
+	// The following doesn't work if you have the `bson:"_id` on Movie.ID field,
+	// therefore we manually generate a new ID (look above).
+	// res, err := ...InsertOne
+	// objectID := res.InsertedID.(primitive.ObjectID)
+	// m.ID = objectID
+	return nil
+}
+
+func (s *movieService) Update(ctx context.Context, id string, m Movie) error {
+	filter, err := matchID(id)
+	if err != nil {
+		return err
+	}
+
+	// update := bson.D{
+	// 	{Key: "$set", Value: m},
+	// }
+	// ^ this will override all fields, you can do that, depending on your design. but let's check each field:
+	elem := bson.D{}
+
+	if m.Name != "" {
+		elem = append(elem, bson.E{Key: "name", Value: m.Name})
+	}
+
+	if m.Description != "" {
+		elem = append(elem, bson.E{Key: "description", Value: m.Description})
+	}
+
+	if m.Cover != "" {
+		elem = append(elem, bson.E{Key: "cover", Value: m.Cover})
+	}
+
+	update := bson.D{
+		{Key: "$set", Value: elem},
+	}
+
+	_, err = s.C.UpdateOne(ctx, filter, update)
+	if err != nil {
+		if err == mongo.ErrNoDocuments {
+			return ErrNotFound
+		}
+		return err
+	}
+
+	return nil
+}
+
+func (s *movieService) Delete(ctx context.Context, id string) error {
+	filter, err := matchID(id)
+	if err != nil {
+		return err
+	}
+	_, err = s.C.DeleteOne(ctx, filter)
+	if err != nil {
+		if err == mongo.ErrNoDocuments {
+			return ErrNotFound
+		}
+		return err
+	}
+
+	return nil
+}