1. 优化性能：减少func (session *Session) slice2Bean方法中的strings.ToLower调用次数以及减少map创建和访问次数（见工单 https://gitea.com/xorm/xorm/issues/2243）

2. 新增SetDefaultJSONHandler方法，用于用户自行设置DefaultJSONHandler（见工单 https://gitea.com/xorm/xorm/issues/2129）

rows.go

@@ -129,7 +129,9 @@ func (rows *Rows) Scan(beans ...interface{}) error {
 		return err
 	}
 
-	if err := rows.session.scan(rows.rows, rows.session.statement.RefTable, beanKind, beans, types, fields); err != nil {
+	columnsSchema := ParseColumnsSchema(fields, types, rows.session.statement.RefTable)
+
+	if err := rows.session.scan(rows.rows, rows.session.statement.RefTable, beanKind, beans, columnsSchema, types, fields); err != nil {
 		return err
 	}
 

session.go

@@ -16,8 +16,6 @@ import (
 	"io"
 	"reflect"
 	"strconv"
-	"strings"
-
 	"xorm.io/xorm/contexts"
 	"xorm.io/xorm/convert"
 	"xorm.io/xorm/core"
@@ -395,10 +393,10 @@ func (session *Session) doPrepareTx(sqlStr string) (stmt *core.Stmt, err error)
 	return
 }
 
-func getField(dataStruct *reflect.Value, table *schemas.Table, colName string, idx int) (*schemas.Column, *reflect.Value, error) {
+func getField(dataStruct *reflect.Value, table *schemas.Table, field *QueryedField) (*schemas.Column, *reflect.Value, error) {
-	col := table.GetColumnIdx(colName, idx)
+	col := field.ColumnSchema
 	if col == nil {
-		return nil, nil, ErrFieldIsNotExist{colName, table.Name}
+		return nil, nil, ErrFieldIsNotExist{field.FieldName, table.Name}
 	}
 
 	fieldValue, err := col.ValueOfV(dataStruct)
@@ -406,10 +404,10 @@ func getField(dataStruct *reflect.Value, table *schemas.Table, colName string, i
 		return nil, nil, err
 	}
 	if fieldValue == nil {
-		return nil, nil, ErrFieldIsNotValid{colName, table.Name}
+		return nil, nil, ErrFieldIsNotValid{field.FieldName, table.Name}
 	}
 	if !fieldValue.IsValid() || !fieldValue.CanSet() {
-		return nil, nil, ErrFieldIsNotValid{colName, table.Name}
+		return nil, nil, ErrFieldIsNotValid{field.FieldName, table.Name}
 	}
 
 	return col, fieldValue, nil
@@ -418,7 +416,7 @@ func getField(dataStruct *reflect.Value, table *schemas.Table, colName string, i
 // Cell cell is a result of one column field
 type Cell *interface{}
 
-func (session *Session) rows2Beans(rows *core.Rows, fields []string, types []*sql.ColumnType,
+func (session *Session) rows2Beans(rows *core.Rows, columnsSchema *ColumnsSchema, fields []string, types []*sql.ColumnType,
 	table *schemas.Table, newElemFunc func([]string) reflect.Value,
 	sliceValueSetFunc func(*reflect.Value, schemas.PK) error,
 ) error {
@@ -432,7 +430,7 @@ func (session *Session) rows2Beans(rows *core.Rows, fields []string, types []*sq
 		if err != nil {
 			return err
 		}
-		pk, err := session.slice2Bean(scanResults, fields, bean, &dataStruct, table)
+		pk, err := session.slice2Bean(scanResults, columnsSchema, fields, bean, &dataStruct, table)
 		if err != nil {
 			return err
 		}
@@ -705,28 +703,16 @@ func (session *Session) convertBeanField(col *schemas.Column, fieldValue *reflec
 	return convert.AssignValue(fieldValue.Addr(), scanResult)
 }
 
-func (session *Session) slice2Bean(scanResults []interface{}, fields []string, bean interface{}, dataStruct *reflect.Value, table *schemas.Table) (schemas.PK, error) {
+func (session *Session) slice2Bean(scanResults []interface{}, columnsSchema *ColumnsSchema, fields []string, bean interface{}, dataStruct *reflect.Value, table *schemas.Table) (schemas.PK, error) {
 	defer func() {
 		executeAfterSet(bean, fields, scanResults)
 	}()
 
 	buildAfterProcessors(session, bean)
 
-	tempMap := make(map[string]int)
 	var pk schemas.PK
-	for i, colName := range fields {
+	for i, field := range columnsSchema.Fields {
-		var idx int
+		col, fieldValue, err := getField(dataStruct, table, field)
-		lKey := strings.ToLower(colName)
-		var ok bool
-
-		if idx, ok = tempMap[lKey]; !ok {
-			idx = 0
-		} else {
-			idx++
-		}
-		tempMap[lKey] = idx
-
-		col, fieldValue, err := getField(dataStruct, table, colName, idx)
 		if _, ok := err.(ErrFieldIsNotExist); ok {
 			continue
 		} else if err != nil {
@@ -800,3 +786,7 @@ func (session *Session) NoVersionCheck() *Session {
 	session.statement.CheckVersion = false
 	return session
 }
+
+func SetDefaultJSONHandler(jsonHandler json.Interface) {
+	json.DefaultJSONHandler = jsonHandler
+}

session_find.go

@@ -5,8 +5,10 @@
 package xorm
 
 import (
+	"database/sql"
 	"errors"
 	"reflect"
+	"strings"
 
 	"xorm.io/builder"
 	"xorm.io/xorm/caches"
@@ -161,6 +163,64 @@ func (session *Session) find(rowsSlicePtr interface{}, condiBean ...interface{})
 	return session.noCacheFind(table, sliceValue, sqlStr, args...)
 }
 
+type QueryedField struct {
+	FieldName      string
+	LowerFieldName string
+	ColumnType     *sql.ColumnType
+	TempIndex      int
+	ColumnSchema   *schemas.Column
+}
+
+type ColumnsSchema struct {
+	Fields     []*QueryedField
+	FieldNames []string
+	Types      []*sql.ColumnType
+}
+
+func (columnsSchema *ColumnsSchema) ParseTableSchema(table *schemas.Table) {
+	for _, field := range columnsSchema.Fields {
+		field.ColumnSchema = table.GetColumnIdx(field.FieldName, field.TempIndex)
+	}
+}
+
+func ParseColumnsSchema(fieldNames []string, types []*sql.ColumnType, table *schemas.Table) *ColumnsSchema {
+	var columnsSchema ColumnsSchema
+
+	fields := make([]*QueryedField, 0, len(fieldNames))
+
+	for i, fieldName := range fieldNames {
+		field := &QueryedField{
+			FieldName:      fieldName,
+			LowerFieldName: strings.ToLower(fieldName),
+			ColumnType:     types[i],
+		}
+		fields = append(fields, field)
+	}
+
+	columnsSchema.Fields = fields
+
+	tempMap := make(map[string]int)
+	for _, field := range fields {
+		var idx int
+		var ok bool
+
+		if idx, ok = tempMap[field.LowerFieldName]; !ok {
+			idx = 0
+		} else {
+			idx++
+		}
+
+		tempMap[field.LowerFieldName] = idx
+		field.TempIndex = idx
+	}
+
+	if table != nil {
+		columnsSchema.ParseTableSchema(table)
+	}
+
+	return &columnsSchema
+}
+
 func (session *Session) noCacheFind(table *schemas.Table, containerValue reflect.Value, sqlStr string, args ...interface{}) error {
 	elemType := containerValue.Type().Elem()
 	var isPointer bool
@@ -238,7 +298,10 @@ func (session *Session) noCacheFind(table *schemas.Table, containerValue reflect
 		if err != nil {
 			return err
 		}
-		err = session.rows2Beans(rows, fields, types, tb, newElemFunc, containerValueSetFunc)
+
+		columnsSchema := ParseColumnsSchema(fields, types, tb)
+
+		err = session.rows2Beans(rows, columnsSchema, fields, types, tb, newElemFunc, containerValueSetFunc)
 		rows.Close()
 		if err != nil {
 			return err

session_get.go

@@ -164,7 +164,9 @@ func (session *Session) nocacheGet(beanKind reflect.Kind, table *schemas.Table,
 		return true, err
 	}
 
-	if err := session.scan(rows, table, beanKind, beans, types, fields); err != nil {
+	columnsSchema := ParseColumnsSchema(fields, types, table)
+
+	if err := session.scan(rows, table, beanKind, beans, columnsSchema, types, fields); err != nil {
 		return true, err
 	}
 	rows.Close()
@@ -172,7 +174,7 @@ func (session *Session) nocacheGet(beanKind reflect.Kind, table *schemas.Table,
 	return true, session.executeProcessors()
 }
 
-func (session *Session) scan(rows *core.Rows, table *schemas.Table, firstBeanKind reflect.Kind, beans []interface{}, types []*sql.ColumnType, fields []string) error {
+func (session *Session) scan(rows *core.Rows, table *schemas.Table, firstBeanKind reflect.Kind, beans []interface{}, columnsSchema *ColumnsSchema, types []*sql.ColumnType, fields []string) error {
 	if len(beans) == 1 {
 		bean := beans[0]
 		switch firstBeanKind {
@@ -186,7 +188,7 @@ func (session *Session) scan(rows *core.Rows, table *schemas.Table, firstBeanKin
 			}
 
 			dataStruct := utils.ReflectValue(bean)
-			_, err = session.slice2Bean(scanResults, fields, bean, &dataStruct, table)
+			_, err = session.slice2Bean(scanResults, columnsSchema, fields, bean, &dataStruct, table)
 			return err
 		case reflect.Slice:
 			return session.getSlice(rows, types, fields, bean)