110.借助golang 的template实现类mybatis

package user
import (
 "bytes"
 "fmt"
 "reflect"
 "strconv"
 "strings"
 "text/template"
)
const (
 COLUMNS = `
 id ID,
 code Code
 `
 SEARCH_COUNT = `
 SELECT
 count(0) count
 FROM user 
 WHERE 1=1 
 `
 SEARCH = `
 SELECT
 {{COLUMNS}}
 FROM user 
 LEFT JOIN user
 `
 INSERT = `
 {{$size := (len .) |Sub 1}}
 INSERT INTO sm_user(id,code,name)
 VALUES
 {{range $index, $elem := .}}
 (E_SEQ('sm_user'),'{{.Code}}'){{ if ne $index $size }} ,{{else}};{{end}}
 {{end}}
 `
 UPDATE = `
 UPDATE sm_user set
 {{if ne .Code ""}} code='{{.Code}}', {{end}}
 {{if ne .Name ""}} name='{{.Name}}',{{end}}
 update_time=NOW()
 WHERE id={{.ID}}
 `
 DELETE = ` UPDATE sm_user set deleted_flag='Y' WHERE id={{.ID}} `
 WHERE = `
 {{if ne .Code ""}} and smu.code = '{{.Code}}' , {{end}}
 {{if ne .Name ""}} and smu.name = '{{.Name}}' {{end}}
 `
)
var (
 count *template.Template
 search *template.Template
 insert *template.Template
 update *template.Template
 delete *template.Template
 condition *template.Template
 funcs map[string]interface{}
)
//给template添加自定义的方法
func init(){
 funcs = template.FuncMap{"Add": Add,"Sub":Sub}
}
//根据业务组装相应的SQL
func assembly(model interface{}, mode string) string {
 buffer := bytes.NewBufferString("")
 switch mode {
 case "searchCount":
 if count == nil {
 count = template.New("count")
 count.Parse(SEARCH_COUNT)
 }
 count.Execute(buffer, model)
 buffer.WriteString(where(model, mode))
 break
 case "get":
 if count == nil {
 count = template.New("search")
 count.Parse(SEARCH_COUNT)
 }
 count.Execute(buffer, model)
 buffer.WriteString(" limit 1")
 break
 case "search":
 if search == nil {
 search = template.New("search")
 //此处可以修改为子模板 {{template "COLUMNS" .}}
 search.Parse(strings.Replace(SEARCH, "{{COLUMNS}}", COLUMNS, -1))
 }
 search.Execute(buffer, model)
 buffer.WriteString(where(model, mode))
 break
 case "searchPage":
 if search == nil {
 search = template.New("search")
 search.Parse(strings.Replace(SEARCH, "{{COLUMNS}}", COLUMNS, -1))
 }
 search.Execute(buffer, model)
 buffer.WriteString(where(model, mode))
 buffer.WriteString(limit(model))
 break
 case "insert":
 if insert == nil {
 insert = template.New("insert")
 insert.Parse(INSERT)
 }
 insert.Execute(buffer, model)
 break
 case "batchInsert":
 if insert == nil {
 insert = template.New("insert").Funcs(funcs)
 insert.Parse(INSERT)
 }
 insert.Execute(buffer, model)
 break
 case "update":
 if update == nil {
 update = template.New("update")
 update.Parse(UPDATE)
 }
 update.Execute(buffer, model)
 break
 case "delete":
 if delete == nil {
 delete = template.New("delete")
 update.Parse(DELETE)
 }
 update.Execute(buffer, model)
 break
 }
 fmt.Println(buffer.String())
 return buffer.String()
}
//条件where
func where(model interface{}, mode string) string {
 buffer := bytes.NewBufferString("")
 if condition == nil {
 condition = template.New("where")
 condition.Parse(WHERE)
 }
 condition.Execute(buffer, model)
 return buffer.String()
}
//分页limit
func limit(model interface{}) string {
 invoke := reflect.ValueOf(model).Elem()
 //fmt.Println("%t",invoke.Kind())
 //fmt.Println("%t",invoke.FieldByName("PageNo"))
 pageNo := invoke.FieldByName("PageNo").Int()
 pageSize := invoke.FieldByName("PageSize").Int()
 offset := (pageNo - 1) * pageSize
 return " limit " + strconv.FormatInt(offset, 10) + "," + strconv.FormatInt(pageSize, 10)
}
func Add(left int, right int) int{
 return left+right
}
func Sub(left int, right int) int{
 return right - left
}

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