// mapper returns a valid mapper using the configured NameMapper func.
func mapper() *reflectx.Mapper {
	if mpr == nil {
		mpr = reflectx.NewMapperFunc("db", NameMapper)
	} else if origMapper != reflect.ValueOf(NameMapper) {
		// if NameMapper has changed, create a new mapper
		mpr = reflectx.NewMapperFunc("db", NameMapper)
		origMapper = reflect.ValueOf(NameMapper)
	}
	return mpr
}

// NewDbMap returns a new DbMap using the db connection and dialect.
func NewDbMap(db *sql.DB, dialect Dialect) *DbMap {
	return &DbMap{
		Db:      db,
		Dialect: dialect,
		Dbx:     sqlx.NewDb(db, dialect.DriverName()),
		mapper:  reflectx.NewMapperFunc("db", sqlx.NameMapper),
	}
}

// MapperFunc sets a new mapper for this db using the default sqlx struct tag
// and the provided mapper function.
func (db *DB) MapperFunc(mf func(string) string) {
	db.Mapper = reflectx.NewMapperFunc("db", mf)
}

func TestNamedQuery(t *testing.T) {
	var schema = Schema{
		create: `
			CREATE TABLE person (
				first_name text NULL,
				last_name text NULL,
				email text NULL
			);
			CREATE TABLE jsperson (
				"FIRST" text NULL,
				last_name text NULL,
				"EMAIL" text NULL
			);`,
		drop: `
			drop table person;
			drop table jsperson;
			`,
	}

	RunWithSchema(schema, t, func(db *DB, t *testing.T) {
		type Person struct {
			FirstName sql.NullString `db:"first_name"`
			LastName  sql.NullString `db:"last_name"`
			Email     sql.NullString
		}

		p := Person{
			FirstName: sql.NullString{String: "ben", Valid: true},
			LastName:  sql.NullString{String: "doe", Valid: true},
			Email:     sql.NullString{String: "[email protected]", Valid: true},
		}

		q1 := `INSERT INTO person (first_name, last_name, email) VALUES (:first_name, :last_name, :email)`
		_, err := db.NamedExec(q1, p)
		if err != nil {
			log.Fatal(err)
		}

		p2 := &Person{}
		rows, err := db.NamedQuery("SELECT * FROM person WHERE first_name=:first_name", p)
		if err != nil {
			log.Fatal(err)
		}
		for rows.Next() {
			err = rows.StructScan(p2)
			if err != nil {
				t.Error(err)
			}
			if p2.FirstName.String != "ben" {
				t.Error("Expected first name of `ben`, got " + p2.FirstName.String)
			}
			if p2.LastName.String != "doe" {
				t.Error("Expected first name of `doe`, got " + p2.LastName.String)
			}
		}

		// these are tests for #73;  they verify that named queries work if you've
		// changed the db mapper.  This code checks both NamedQuery "ad-hoc" style
		// queries and NamedStmt queries, which use different code paths internally.
		old := *db.Mapper

		type JSONPerson struct {
			FirstName sql.NullString `json:"FIRST"`
			LastName  sql.NullString `json:"last_name"`
			Email     sql.NullString
		}

		jp := JSONPerson{
			FirstName: sql.NullString{String: "ben", Valid: true},
			LastName:  sql.NullString{String: "smith", Valid: true},
			Email:     sql.NullString{String: "[email protected]", Valid: true},
		}

		db.Mapper = reflectx.NewMapperFunc("json", strings.ToUpper)

		// prepare queries for case sensitivity to test our ToUpper function.
		// postgres and sqlite accept "", but mysql uses ``;  since Go's multi-line
		// strings are `` we use "" by default and swap out for MySQL
		pdb := func(s string, db *DB) string {
			if db.DriverName() == "mysql" {
				return strings.Replace(s, `"`, "`", -1)
			}
			return s
		}

		q1 = `INSERT INTO jsperson ("FIRST", last_name, "EMAIL") VALUES (:FIRST, :last_name, :EMAIL)`
		_, err = db.NamedExec(pdb(q1, db), jp)
		if err != nil {
			t.Fatal(err, db.DriverName())
		}

		// Checks that a person pulled out of the db matches the one we put in
		check := func(t *testing.T, rows *Rows) {
			jp = JSONPerson{}
			for rows.Next() {
				err = rows.StructScan(&jp)
				if err != nil {
					t.Error(err)
				}
				if jp.FirstName.String != "ben" {
//.........这里部分代码省略.........