前言
泛型思路
baseservice.gobasebaseservice.gointerface代码
- 父结构体及业务逻辑：baseservice.go
package services
import (
"encoding/json"
"github.com/go-redis/redis/v7"
"github.com/jinzhu/gorm"
"math"
"reflect"
"strconv"
"time"
"weichai/app/cache"
"weichai/app/models/entity"
"weichai/pkg/utils"
)
type BaseService struct {
// 要操作的model结构体[必须为指针类型的结构体*slice]
Model interface{} //model必须是指针
CachePrefix string //缓存的前缀
// 不同的业务，有不同的库查询逻辑，所以抽象此方法，让子结构体来实现。默认方法 queryList
QueryList func(wheres interface{}, columns interface{}, orderBy interface{}, page, rows int, total *int) (list interface{}, err error)
}
// model必须是指针
func NewBaseService(model interface{}, cachePrefix string) *BaseService {
bs := &BaseService{}
bs.Model = model
bs.CachePrefix = cachePrefix
// 赋值默认方法
bs.QueryList = bs.queryList
return bs
}
// 根据id返回数据
// 返回值 nil|*struct{} ,当err不为nil|没有找到记录时，返回值=nil
func (service *BaseService) GetById(id int) (interface{}, error) {
db := entity.DB
model := service.GetNewModel()
err := db.Where("id = ?", id).First(model, id).Error
if err != nil && err != gorm.ErrRecordNotFound {
return nil, err
} else if err == gorm.ErrRecordNotFound {
return nil, nil
}
return model, nil
}
// 根据查询条件返回列表数据[会走缓存]
// 返回值 list:nil|*[]*struct{} ,当err不为nil时，list=nil
func (service *BaseService) List(wheres interface{}, columns interface{}, orderBy interface{}, page, rows int, total *int) (list interface{}, err error) {
vb, err := json.Marshal([]interface{}{wheres, columns, orderBy, page, rows})
if err != nil {
return nil, err
}
pkey := utils.GetMd5String(string(vb))
prefix := service.CachePrefix
ckey := prefix + "_list:" + pkey
ckey_total := prefix + "_list_total:" + pkey
_total, err := cache.Get(ckey_total)
if err == nil {
_t, err := strconv.Atoi(_total)
if err == nil {
*total = _t
if math.Ceil(float64(_t/rows)) < float64(page) {
list = service.GetNewModelSlice()
return list, nil
}
}
}
data, err := cache.Get(ckey)
is_cache_data := false
if err == redis.Nil || err != nil {
// 防止缓存穿透，需要加锁 【只有ckey相同时，才会互斥锁】
lock := utils.MultipleMutex.Lock(ckey)
data, err = cache.Get(ckey)
if err == redis.Nil || err != nil {
if service.QueryList == nil {
service.QueryList = service.queryList
}
list, err = service.QueryList(wheres, columns, orderBy, page, rows, total)
if err == nil {
exp := time.Second * 30 //在实际开发中，可以把过期时间放到结构体中，让子结构体赋值
_, _ = cache.Set(ckey, list, exp)
_, _ = cache.Set(ckey_total, total, exp)
//set出错，上报
} else {
utils.MultipleMutex.Unlock(lock)
return nil, err
}
} else {
is_cache_data = true
}
utils.MultipleMutex.Unlock(lock)
} else {
is_cache_data = true
}
if is_cache_data {
list = service.GetNewModelSlice()
err := json.Unmarshal(([]byte)(data), list)
if err != nil {
return nil, err
}
}
return list, err
}
// 根据查询条件返回列表数据[直接查库]
// 返回值 list:nil|*[]*struct{} ,当err不为nil时，list=nil
func (service *BaseService) queryList(wheres interface{}, columns interface{}, orderBy interface{}, page, rows int, total *int) (list interface{}, err error) {
db := entity.DB
list = service.GetNewModelSlice()
db, err = entity.BuildQueryList(db, wheres, columns, orderBy, page, rows)
if err != nil {
return nil, err
}
err = db.Find(list).Error
if err != nil {
return nil, err
}
db = entity.DB
db, err = entity.BuildWhere(db, wheres)
if err != nil {
return nil, err
}
db.Model(service.GetNewModel()).Count(total)
return list, nil
}
// 获取新的struct，返回值 *struct{}
func (service *BaseService) GetNewModel() interface{} {
t := reflect.TypeOf(service.Model)
m := t.Elem()
return reflect.Indirect(reflect.New(m)).Addr().Interface()
}
// 获取新的struct切片，返回值 *[]*struct{}
func (service *BaseService) GetNewModelSlice() interface{} {
t := reflect.TypeOf(service.Model)
// return reflect.Indirect(reflect.New(reflect.SliceOf(t))).Addr().Interface()
list := reflect.New(reflect.SliceOf(t)).Elem()
list.Set(reflect.MakeSlice(list.Type(), 0, 0))
return reflect.Indirect(list).Addr().Interface()
}
代码说明：
BaseServiceQueryListListgormBaseService必须为指针类型的结构体*slice参数entity.DBentity.BuildQueryList说明：baseservice.go只实现了部分公用方法，在实际开发中，公用逻辑远比这多，可以根据自己业务需求来做相应的封装- 子结构体：user.go
package user
import (
"github.com/jinzhu/gorm"
"weichai/app/models/entity"
userModel "weichai/app/models/user"
"weichai/app/services"
)
type userService struct {
*services.BaseService // 组合BaseService结构体，实现继承
}
// 必须是指针 &userModel.User{}
var _bs = services.NewBaseService(&userModel.User{}, "user")
var _us = &userService{BaseService: _bs}
func NewUserService() *userService {
// 给父结构体的QueryList方法赋值，来达到重写需求【由于golang不是OOP，所以'重写'也不能达到重写，父结构体是没有办法直接调用重写的方法的，所以要通过在结构体中定义方法，子结构体给它赋值】
_bs.QueryList = _us.QueryList
return _us
}
/*// 重写(覆盖)父结构体的List方法，来实现特殊需求
func (service *userService) List(wheres interface{}, columns interface{}, orderBy interface{}, page, rows int, total *int) (list interface{}, err error) {
// 调用父的List: service.BaseService.List()
return nil, nil
}*/
// 实现抽象方法，来实现特殊业务，此方法包含了 关联查询的预加载逻辑
func (service *userService) QueryList(wheres interface{}, columns interface{}, orderBy interface{}, page, rows int, total *int) (list interface{}, err error) {
db := entity.DB
var model []*userModel.User
var mod userModel.User
db, err = entity.BuildQueryList(db, wheres, columns, orderBy, page, rows)
if err != nil {
return nil, err
}
err = db.Preload("UserCard", func(db *gorm.DB) *gorm.DB {
return db.Order("created_at asc")
}).Find(&model).Error
db = entity.DB
db, err = entity.BuildWhere(db, wheres)
if err != nil {
return nil, err
}
db.Model(&mod).Count(total)
return &model, nil
}
- 在controller里查询用户列表
func List(ctx *gin.Context) {
total := 0
where := []interface{}{
[]interface{}{"id", "in", []int{1, 2}},
}
//var wg sync.WaitGroup
//wg.Add(2)
//测试多协程查询时加锁
/*go func() {
bll := userService.NewUserService()
list, _ := bll.BaseService.List(where, []string{"*"}, "id desc", 1, 1, &total)
list = list.(*[]*user.User)
wg.Done()
}()
go func() {
bll := userService.NewUserService()
_, _ = bll.BaseService.List(where, []string{"*"}, "id desc", 1, 1, &total)
wg.Done()
}()*/
bll := userService.NewUserService()
res, _ := bll.List(where, []string{"*"}, "id desc", 1, 1, &total)
list := res.(*[]*user.User)
//wg.Wait()
ctx.JSON(http.StatusOK, utils.Result(result.OK, map[string]interface{}{
"list": list, "total": total,
}, ""))
}
其它代码
- utils.MultipleMutex所用到代码文件
逻辑也比较简单，根据相同的key返回sync.Mutex的指针，并存储在map里；在Unlock时，删除map的值
不同的key会返回不同的sync.Mutex，所以在应用时不会锁住资源，达到并发需求
package utils
import (
"sync"
)
var MultipleMutex = &multipleMutex{
keys: map[string]*lock{},
keyMutex: &sync.Mutex{},
}
type multipleMutex struct {
keys map[string]*lock
keyMutex *sync.Mutex
}
type lock struct {
key *string
mutex *sync.Mutex
}
func (mm *multipleMutex) Lock(key string) *lock {
mm.keyMutex.Lock()
mutex, ok := mm.keys[key]
if !ok {
mutex = &lock{
key: &key,
mutex: new(sync.Mutex),
}
mm.keys[key] = mutex
}
mm.keyMutex.Unlock()
mutex.mutex.Lock()
return mutex
}
func (mm *multipleMutex) Unlock(lock *lock) {
key := lock.key
mm.keyMutex.Lock()
mutex, ok := mm.keys[*key]
if ok && mutex == lock {
// 删除map的key，如果有引用lock，是不会触发GC的，所以别的协程执行后面的lock.mutex.Unlock()不会有问题
delete(mm.keys, *key)
}
mm.keyMutex.Unlock()
lock.mutex.Unlock()
}
- cache用到的代码文件
package cache
import (
"encoding/json"
"reflect"
"time"
"weichai/pkg/redis"
)
func Set(key string, val interface{}, expire time.Duration) (ok bool, err error) {
kind := reflect.TypeOf(val).Kind()
var v interface{}
switch kind {
case reflect.Interface, reflect.Map, reflect.Slice, reflect.Struct, reflect.Array, reflect.Ptr:
vb, err := json.Marshal(val)
if err != nil {
return false, err
}
v = string(vb)
default:
v = val
}
res, err := redis.RedisClient.Set(redis.CreateKey(key), v, expire).Result()
return res == "OK", err
}
func Get(key string) (val string, err error) {
return redis.RedisClient.Get(redis.CreateKey(key)).Result()
}
// redis用的是 github.com/go-redis/redis/v7，redis.CreateKey(key)返回一个加了前缀的key。这些代码就不贴了
总结
继承重写抽象方法