动手写ORM框架 - GeeORM第二天 对象表结构映射

package dialect

import "reflect"

var dialectsMap = map[string]Dialect{}

type Dialect interface {
	DataTypeOf(typ reflect.Value) string
	TableExistSQL(tableName string) (string, []interface{})
}

func RegisterDialect(name string, dialect Dialect) {
	dialectsMap[name] = dialect
}

func GetDialect(name string) (dialect Dialect, ok bool) {
	dialect, ok = dialectsMap[name]
	return
}

package dialect

import (
	"fmt"
	"reflect"
	"time"
)

type sqlite3 struct{}

var _ Dialect = (*sqlite3)(nil)

func init() {
	RegisterDialect("sqlite3", &sqlite3{})
}

func (s *sqlite3) DataTypeOf(typ reflect.Value) string {
	switch typ.Kind() {
	case reflect.Bool:
		return "bool"
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32,
		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uintptr:
		return "integer"
	case reflect.Int64, reflect.Uint64:
		return "bigint"
	case reflect.Float32, reflect.Float64:
		return "real"
	case reflect.String:
		return "text"
	case reflect.Array, reflect.Slice:
		return "blob"
	case reflect.Struct:
		if _, ok := typ.Interface().(time.Time); ok {
			return "datetime"
		}
	}
	panic(fmt.Sprintf("invalid sql type %s (%s)", typ.Type().Name(), typ.Kind()))
}

func (s *sqlite3) TableExistSQL(tableName string) (string, []interface{}) {
	args := []interface{}{tableName}
	return "SELECT name FROM sqlite_master WHERE type='table' and name = ?", args
}

type User struct {
    Name string `geeorm:"PRIMARY KEY"`
    Age  int
}

package schema

import (
	"geeorm/dialect"
	"go/ast"
	"reflect"
)

// Field represents a column of database
type Field struct {
	Name string
	Type string
	Tag  string
}

// Schema represents a table of database
type Schema struct {
	Model      interface{}
	Name       string
	Fields     []*Field
	FieldNames []string
	fieldMap   map[string]*Field
}

func (schema *Schema) GetField(name string) *Field {
	return schema.fieldMap[name]
}

func Parse(dest interface{}, d dialect.Dialect) *Schema {
	modelType := reflect.Indirect(reflect.ValueOf(dest)).Type()
	schema := &Schema{
		Model:    dest,
		Name:     modelType.Name(),
		fieldMap: make(map[string]*Field),
	}

	for i := 0; i < modelType.NumField(); i++ {
		p := modelType.Field(i)
		if !p.Anonymous && ast.IsExported(p.Name) {
			field := &Field{
				Name: p.Name,
				Type: d.DataTypeOf(reflect.Indirect(reflect.New(p.Type))),
			}
			if v, ok := p.Tag.Lookup("geeorm"); ok {
				field.Tag = v
			}
			schema.Fields = append(schema.Fields, field)
			schema.FieldNames = append(schema.FieldNames, p.Name)
			schema.fieldMap[p.Name] = field
		}
	}
	return schema
}

// schema_test.go
type User struct {
	Name string `geeorm:"PRIMARY KEY"`
	Age  int
}

var TestDial, _ = dialect.GetDialect("sqlite3")

func TestParse(t *testing.T) {
	schema := Parse(&User{}, TestDial)
	if schema.Name != "User" || len(schema.Fields) != 2 {
		t.Fatal("failed to parse User struct")
	}
	if schema.GetField("Name").Tag != "PRIMARY KEY" {
		t.Fatal("failed to parse primary key")
	}
}

type Session struct {
	db       *sql.DB
	dialect  dialect.Dialect
	refTable *schema.Schema
	sql      strings.Builder
	sqlVars  []interface{}
}

func New(db *sql.DB, dialect dialect.Dialect) *Session {
	return &Session{
		db:      db,
		dialect: dialect,
	}
}

func (s *Session) Model(value interface{}) *Session {
	// nil or different model, update refTable
	if s.refTable == nil || reflect.TypeOf(value) != reflect.TypeOf(s.refTable.Model) {
		s.refTable = schema.Parse(value, s.dialect)
	}
	return s
}

func (s *Session) RefTable() *schema.Schema {
	if s.refTable == nil {
		log.Error("Model is not set")
	}
	return s.refTable
}

func (s *Session) CreateTable() error {
	table := s.RefTable()
	var columns []string
	for _, field := range table.Fields {
		columns = append(columns, fmt.Sprintf("%s %s %s", field.Name, field.Type, field.Tag))
	}
	desc := strings.Join(columns, ",")
	_, err := s.Raw(fmt.Sprintf("CREATE TABLE %s (%s);", table.Name, desc)).Exec()
	return err
}

func (s *Session) DropTable() error {
	_, err := s.Raw(fmt.Sprintf("DROP TABLE IF EXISTS %s", s.RefTable().Name)).Exec()
	return err
}

func (s *Session) HasTable() bool {
	sql, values := s.dialect.TableExistSQL(s.RefTable().Name)
	row := s.Raw(sql, values...).QueryRow()
	var tmp string
	_ = row.Scan(&tmp)
	return tmp == s.RefTable().Name
}

type User struct {
	Name string `geeorm:"PRIMARY KEY"`
	Age  int
}

func TestSession_CreateTable(t *testing.T) {
	s := NewSession().Model(&User{})
	_ = s.DropTable()
	_ = s.CreateTable()
	if !s.HasTable() {
		t.Fatal("Failed to create table User")
	}
}

type Engine struct {
	db      *sql.DB
	dialect dialect.Dialect
}

func NewEngine(driver, source string) (e *Engine, err error) {
	db, err := sql.Open(driver, source)
	if err != nil {
		log.Error(err)
		return
	}
	// Send a ping to make sure the database connection is alive.
	if err = db.Ping(); err != nil {
		log.Error(err)
		return
	}
	// make sure the specific dialect exists
	dial, ok := dialect.GetDialect(driver)
	if !ok {
		log.Errorf("dialect %s Not Found", driver)
		return
	}
	e = &Engine{db: db, dialect: dial}
	log.Info("Connect database success")
	return
}

func (engine *Engine) NewSession() *session.Session {
	return session.New(engine.db, engine.dialect)
}