从零实现ORM框架GeoORM-对象表结构映射-02

package dialect

import "reflect"

//dialectsMap 每种数据库及其对应的方言
var dialectsMap = map[string]Dialect{}

//Dialect 每一种数据库都需要有一个对应的方言实现类进行解释
type Dialect interface {
	//DataTypeOf go语言中某个类型映射到当前数据库中是什么类型
	DataTypeOf(typ reflect.Value) string
	//TableExistSQL 为当前数据库构造一个查询表是否存在的sql
	TableExistSQL(tableName string) (string, []interface{})
}

//RegisterDialect 注册方言
func RegisterDialect(name string, dialect Dialect) {
	dialectsMap[name] = dialect
}

//GetDialect 获取某一个数据库对应的方言
func GetDialect(name string) (dialect Dialect, ok bool) {
	dialect, ok = dialectsMap[name]
	return
}

package dialect

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

//sqlite3 框架默认为sqlite数据库提供的方言
type sqlite3 struct{}

//确保sqlite3实现了Dialect接口,否则此行代码再编译器就会报错
var _ Dialect = (*sqlite3)(nil)

//init 导入包后,会默认注册当前数据库的方言
func init() {
	RegisterDialect("sqlite3", &sqlite3{})
}

//DataTypeOf 将go数据类型转换为sqlite中的数据类型
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:
		//获取反射对象的接口值,尝试转换为Time,如果成功说明是Time类型
		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
}

CREATE TABLE `User` (`Name` text PRIMARY KEY, `Age` integer);

package schema

// Field 每个字段代表表中某一列信息
type Field struct {
	//字段名
	Name string
	//字段类型
	Type string
	//附加信息---主键,非空...
	Tag  string
}


// Schema 代表数据库中某张表
type Schema struct {
	//当前表对应的实体对象
	Model      interface{}
	//表名
	Name       string
	//表的字段信息
	Fields     []*Field
	//表字段名
	FieldNames []string
	//表字段名和对应Field实体映射关系
	fieldMap   map[string]*Field
}

//GetField 通过字段名获取到对应的Field信息
func (schema *Schema) GetField(name string) *Field {
	return schema.fieldMap[name]
}

//Parse 根据对象实体和当前数据库对应的方言,解析得到当前视图映射到的表对象
func Parse(dest interface{}, d dialect.Dialect) *Schema {
	//先获取到值对象指针,然后Indirect拿到真正的值对象,然后获取值对象的类型
	modelType := reflect.Indirect(reflect.ValueOf(dest)).Type()
	//构造表对象
	schema := &Schema{
		//实体对象
		Model: dest,
		//实体名作为表名
		Name: modelType.Name(),
		//初始化字段map
		fieldMap: make(map[string]*Field),
	}
	//遍历实体对象的字段列表
	for i := 0; i < modelType.NumField(); i++ {
		//拿到属性
		p := modelType.Field(i)
		//当前属性不是匿名自动并且当前属性是被导出的
		if !p.Anonymous && ast.IsExported(p.Name) {
			//构造一个字段对象
			field := &Field{
				//字段名为当前属性名
				Name: p.Name,
				//先获取到当前字段类型反射对象,然后通过方言解析得到对象的数据库表的列类型
				//reflect.New初始化一个当前类型的零值对象,返回一个指向该零值对象的指针
				//Indirect拿到那个零值对象
				Type: d.DataTypeOf(reflect.Indirect(reflect.New(p.Type))),
			}
			//解析当前字段上可能存在的标签
			if v, ok := p.Tag.Lookup("geoOrm"); ok {
				//如果存在geoOrm标签,就保存到当前字段对象中
				field.Tag = v
			}
			//保存当前字段信息
			schema.Fields = append(schema.Fields, field)
			schema.FieldNames = append(schema.FieldNames, p.Name)
			schema.fieldMap[p.Name] = field
		}
	}
	//返回解析好的表对象
	return schema
}

package schema

import (
	"GeoORM/dialect"
	"testing"
)

type User struct {
	Name string `geoOrm:"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,
	}
}

package session

import (
	myLog "GeoORM/mylog"
	"GeoORM/schema"
	"reflect"
)

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 {
		myLog.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
}

package cmd

import (
	"GeoORM"
	"testing"
)

type Stu struct {
	Name string `geoOrm:"PRIMARY KEY"`
	Age  int
}

func TestSession_CreateTable(t *testing.T) {
	engine, _ := GeoORM.NewEngine("sqlite3", "geo.db")
	defer engine.Close()
	s := engine.NewSession()
	s.Model(&Stu{})

	_ = s.DropTable()
	_ = s.CreateTable()
	if !s.HasTable() {
		t.Fatal("Failed to create table Stu")
	}
}

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

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