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《Golang如何用gorm实现分页的功能》:本文主要介绍Golang如何用gorm实现分页的功能方式,具有很好的参考价值,希望对大家有所帮助,如有错误或未考虑完全的地方,望不吝赐教...
背景
在提供列表接口时一般要用到分页,对于存储在某些数据库中的数据进行分页起来非常的方便,下文给出一个通过gorm进行分页并通过http返回数据的例子。
go库下载
gorm官方文档地址:https://gorm.io/zh_CN/docs/,库下载如下:
go get -u gorm.io/gorm
本文使用的数据库是mysql,因此要下载mysql驱动:
go get -u gorm.io/driver/mysql
这里使用gin框架来提供查询列表的接口想,库下载如下:
go get -u github.com/gin-gonic/gin
初始化数据
【1】建表
建一个用来测试分页的表,sql如下:
CREATE TABLE test_page ( id INT AUTO_INCREMENT PRIMARY KEY, number INT NOT NULL, create_time DATETIME DEFAULT CURRENT_TIMESTAMP, update_time DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP ) ENGINE = InnoDB DEFAULT CHARSET = utf8mb4 COMMENT '测试分页表';
【2】插入数据
插入30条number和create_time字段不同的数据,sql如下:
INSERT INTO test_page (number, create_time)
VALUES (1, NOW() + INTERVAL 0 SECOND),
(2, NOW() + INTERVAL 1 SECOND),
(3, NOW() + INTERVAL 2 SECOND),
(4, NOW() + INTERVAL 3 SECOND),
(5, NOW() + INTERVAL 4 SECOND),
(6, NOW() + INTERVAL 5 SECOND),
(7, NOW() + INTERVAL 6 SECOND),
(8, NOW() + INTERVAL 7 SECOND),
(9, NOW() + INTERVAL 8 SECOND),
(10, NOW() + INTERVAL 9 SECOND),
(11, NOW() + INTERVAL 10 SECOND),
(12, NOW() + INTERVAL 11 SECOND),
(13, www.chinasem.cnNOW() + INTERVAL 12 SECOND),
(14, NOW() + INTERVAL 13 SECOND),
(15, NOW() + INTERVAL 14 SECOND),
(16, NOW() + INTERVAL 15 SECOND),
(17, NOW() + INTERVAL 16 SECOND),
(18, NOW() + INTERVAL 17 SECOND),
(19, NOW() + INTERVAL 18 SECOND),
(20, NOW() + INTERVAL 19 SECOND),
(21, NOW() + INTERVAL 20 SECOND),
(22, NOW() + INTERVAL 21 SECOND),
(23, NOW() + INTERVAL 22 SECOND),
(24, NOW() + INTERVAL 23 SECOND),
(25, NOW() + INTERVAL 24 SECOND),
(26, NOW() + INTERVAL 25 SECOND),
(27, NOW() + INTERVAL 26 SECOND),
(28, NOW() + INTERVAL 27 SECOND),
(29, NOW() + INTERVAL 28 SECOND),
(30, NOW() + INTERVAL 29 SECOND);
【3】查看数据
查看创建出来的30条数据:
mysql [xxx]> select * from test_page; +----+--------+---------------------+---------------------+ | id | number | create_time | update_time | +----+--------+---------------------+---------------------+ | 1 | 1 | 2024-10-21 07:11:19 | 2024-10-21 07:11:19 | | 2 | 2 | 2024-10-21 07:11:20 | 2024-10-21 07:11:19 | | 3 | 3 | 2024-10-21 07:11:21 | 2024-10-21 07:11:19 | | 4 | 4 | 2024-10-21 07:11:22 | 2024-10-21 07:11:19 | | 5 | 5 | 2024-10-21 07:11:23 | 2024-10-21 07:11:19 | | 6 | 6 | 2024-10-21 07:11:24 | 2024-10-21 07:11:19 | | 7 | 7 | 2024-10-21 07:11:25 | 2024-10-21 07:11:19 | | 8 | 8 | 2024-10-21 07:11:26 | 2024-10-21 07:11:19 | | 9 | 9 | 2024-10-21 07:11:27 | 2024-10-21 07:11:19 | | 10 | 10 | 2024-10-21 07:11:28 | 2024-10-21 07:11:19 | | 11 | 11 | 2024-10-21 07:11:29 | 2024-10-21 07:11:19 | | 12js | 12 | 2024-10-21 07:11:30 | 2024-10-21 07:11:19 | | 13 | 13 | 2024-10-21 07:11:31 | 2024-10-21 07:11:19 | | 14 | 14 | 2024-10-21 07:11:32 | 2024-10-21 07:11:19 | | 15 | 15 | 2024-10-21 07:11:33 | 2024-10-21 07:11:19 | | 16 | 16 | 2024-10-21 07:11:34 | 2024-10-21 07:11:19 | | 17 | 17 | 2024-10-21 07:11:35 | 2024-10-21 07:11:19 | | 18 | 18 | 2024-10-21 07:11:36 | 2024-10-21 07:11:19 | | 19 | 19 | 2024-10-21 07:11:37 | 2024-10-21 07:11:19 | | 20 | 20 | 2024-10-21 07:11:38 | 2024-10-21 07:11:19 | | 21 | 21 | 2024-10-21 07:11:39 | 2024-10-21 07:11:19 | | 22 | 22 | 2024-10-21 07:11:40 | 2024-10-21 07:11:19 | | 23 | 23 | 2024-10-21 07:11:41 | 2024-10-21 07:11:19 | | 24 | 24 | 2024-10-21 07:11:42 | 2024-10-21 07:11:19 | | 25 | 25 | 2024-10-21 07:11:43 | 2024-10-21 07:11:19 | | 26 | 26 | 2024-10-21 07:11:44 | 2024-10-21 07:11:19 | | 27 | 27 | 2024-10-21 07:11:45 | 2024-10-21 07:11:19 | | 28 | 28 | 2024-10-21 07:11:46 | 2024-10-21 07:11:19 | | 29 | 29 | 2024-10-21 07:11:47 | 2024-10-21 07:11:19 | | 30 | 30 | 2024-10-21 07:11:48 | 2024-10-21 07:11:19 | +----+--------+---------------------+---------------------+
4、代码示例
【1】gorm结构体定义
可以根据在线sql转go结构体来实现,转换之后如下:
package models import ( "time" ) type TestPage struct { Id int `gorm:"column:id;type:int(11);AUTO_INCREMENT;primary_key" json:"id"` Number int `gorm:"column:number;type:int(11);NOT NULL" json:"number"` CreateTime time.Time `gorm:"column:create_time;type:datetime;default:CURjsRENT_TIMESTAMP" json:"create_time"` UpdateTime time.Time `gorm:"column:update_time;type:datetime;default:CURRENT_TIMESTAMP" json:"update_time"` } func (m *TestPage) TableName() string { return "test_page" }
【2】分页结构体定义
package types import "GoTest/gorm_demo/models" type PageReq struct { Page int `form:"page,default=1"` PageSize int `form:"page_size,default=4"` } type PageResult struct { TotalPage int `json:"total_page"` //总页数 TotalCount int `json:"total_count"` //总条数 Page int `json:"page"` //当前页 PageSize int `json:"page_size"` //当前页数据量 PrevPage bool `json:"prev_page"` //是否存在上页 NextPage bool `json:"next_page"` //是否存在下页 } //要测试的分页结构 type TestPageResp struct { PageResult List []models.TestPage `json:"list"` }
【3】封装分页方法
package page import ( "math" "GoTest/gorm_demo/types" ) // GetOffsetAndLimit // // @Description: 获取查数据库的偏移量和限制数 // @param page 当前页 // @param pageSize 业数据量 // @return offset 数据库偏移 // @return limit 数据库限制量 func GetOffsetAndLimit(page, pageSize int) (offset, limit int) { limit = pageSize if limit <= 0 { limit = 4 } if page > 1 { offset = (page - 1) * limit } return } // GetPageResult // // @Description: 获取分页结果 // @param pg 当前页 // @param pageSize 页数据量 // @param totalCount 根据此数量进行分页 // @return types.PageResult 分页结构 func GetPageResult(pg, pageSize, totalCount int) types.PageResult { res := types.PageResult{} res.TotalCount = totalCount res.PageSize = pageSize res.Page = pg if pageSize > 0 && totalCount > 0 { res.TotalPage = int(math.Ceil(float64(totalCount) / float64(pageSize))) } if res.Page < res.TotalPage { res.NextPage = true } if res.Page > 1 { res.PrevPage = true } return res }
【4】封装获取数据库连接方法
使用gorm连接mysql:
package conn import ( "fmt" "runtime" "sync" "time" "GoTest/comm/logger" "go.uber.org/zap" "gorm.io/driver/mysql" "gorm.io/gorm" gormLog "gorm.io/gorm/logger" ) type MysqlDb string const ( Xxx MysqlDb = "xxx" ) var ( mysqlConn = map[MysqlDb]*gorm.DB{} mysqlLock = sync.RWMutex{} ) func GetXxxDbConn() *gorm.DB { return getDbPool(Xxx) } func getDbPool(dbKey MysqlDb) *gorm.DB { mysqlLock.RLock() if conn, ok := mysqlConn[dbKey]; ok { mysqlLock.RUnlock() return conn } mysqlLock.RUnlock() mysqlLock.Lock() defer mysqlLock.Unlock() var dsn string switch dbKey { case Xxx: dsn = fmt.Sprintf("%s:%s@tcp(%s)/%s?charset=utf8mb4&parseTime=True&loc=Local&timeout=5s", "xxx", "xxx", "127.0.0.1:3306", "xxx") default: logger.Error("unknown db", zap.String("db", string(dbKey))) return nil } conn := newConnect(dsn) mysqlConn[dbKey] = conn return conn } func newConnect(dsn string) *gorm.DB { conn, err := gorm.Open(mysql.Open(dsn), &gorm.Config{ Logger: gormLog.Default.LogMode(gormLog.Info), }) if err != nil { logger.Error("connect mysql error", zap.String("dsn", dsn), zap.Error(err)) return nil } dbPool, err := conn.DB() if err != nil { logger.Error("get mysql db error", zap.String("dsn", dsn), zap.Error(err)) return nil } logger.Info("conn mysql success") //连接池中中最大空闲时间 dbPool.SetConnMaxIdleTime(time.Hour) //连接池中空闲连接的最大数量 dbPool.SetMaxIdleConns(runtime.NumCPU() * 5) //数据库连接的最大数量 dbPool.SetMaxOpenConns(runtime.NumCPU() * 10) //连接可复用最大时间 dbPool.SetConnMaxLifetime(time.Hour * 24) return conn }
使用时只需要调用GetXxxDbConn函数获取连接即可。
【5】查询列表接口
使用gChina编程in框架启动一个http服务,并注册一条路由用于查询列表接口:
r := gin.New() r.GET("/page/list", GetPageListHandler) if err := r.Run(":8888"); err != nil { panic(err) }
查询列表接口回调函数实现如下:
func GetPageListHandler(c *gin.Context) { var req types.PageReq if err := c.ShouldBind(&req); err != nil { logger.Error("invalid req", zap.Error(err)) c.String(500, "invalid req") return } logger.Info("get page list req", zap.Any("req", req)) db := conn.GetXxxDbConn() resp := types.TestPageResp{} resp.List = make([]models.TestPage, 0) //获取所有数量 var count int64 if err := db.Model(&models.TestPage{}).Count(&count).Error; err != nil { logger.Error("get count error", zap.Error(err)) c.String(500, "get count error") return } //计算分页数据 resp.PageResult = page.GetPageResult(req.Page, req.PageSize, int(count)) //计算偏移量 offset, limit := page.GetOffsetAndLimit(req.Page, req.PageSize) //数据库查询 if err := db.Model(&models.TestPage{}).Order("create_time DESC").Offset(offset).Limit(limit).Find(&resp.List).Error; err != nil { logger.Error("get list error", zap.Error(err)) c.String(500, "get list error") return } //返回数据 c.JSON(http.StatusOK, resp) }
【6】启动http服务
控制台输出如下:
[GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production. - using env: export GIN_MODE=release - using code: gin.SetMode(gin.ReleaseMode) [GIN-debug] GET /page/list --> main.GetPageListHandler (1 handlers) [GIN-debug] [WARNING] You trusted all proxies, this is NOT safe. We recommend you to set a value. Please check https://pkg.go.dev/github.com/gin-gonic/gin#readme-don-t-trust-all-proxies for details. [GIN-debug] Listening and serving HTTP on :8888
这里使用的是gin框架的debug模式,生产环境中不要用gin框架的debug模式,会影响程序的qps。
【7】调用获取列表接口
使用curl命令来调用,获取第2页,页数据量为6条的数据,控制台输出如下:
[xxx@xxx ~]# curl -v -X GET --location "http://127.0.0.1:8888/page/list?page=2&page_size=6" * About to connect() to 127.0.0.1 port 8888 (#0) * Trying 127.0.0.1... * Connected to 127.0.0.1 (127.0.0.1) port 8888 (#0) > GET /page/list?page=2&page_size=6 HTTP/1.1 > User-Agent: curl/7.29.0 > Host: 127.0.0.1:8888 > Accept: */* > < HTTP/1.1 200 OK < Content-Type: application/json; charset=utf-8 < Date: Mon, 21 Oct 2024 09:23:13 GMT < Content-Length: 735 < * Connection #0 to host 127.0.0.1 left intact { "total_page": 5, //总共有5页 "total_count": 30, //根据30条数据进行分页 "page": 2, //当前页为第2页 "page_size": 6, //每一页的大小为6 "prev_page": true, //上一页存在 "next_page": true, //下一页存在 "list": [ //根据创建时间倒序的列表 { "id": 24, "number": 24, "create_time": "2024-10-21T07:11:42+08:00", "update_time": "2024-10-21T07:11:19+08:00" }, { "id": 23, "number": 23, "create_time": "2024-10-21T07:11:41+08:00", "update_time": "2024-10-21T07:11:19+08:00" javascript }, { "id": 22, "number": 22, "create_time": "2024-10-21T07:11:40+08:00", "update_time": "2024-10-21T07:11:19+08:00" }, { "id": 21, "number": 21, "create_time": "2024-10-21T07:11:39+08:00", "update_time": "2024-10-21T07:11:19+08:00" }, { "id": 20, "number": 20, "create_time": "2024-10-21T07:11:38+08:00", "update_time": "2024-10-21T07:11:19+08:00" }, { "id": 19, "number": 19, "create_time": "2024-10-21T07:11:37+08:00", "update_time": "2024-10-21T07:11:19+08:00" } ] }
此时gin程序控制台输出:
[GIN-debug] [WARNING] Running in "debug" mode. Switch to "release" mode in production. - using env: export GIN_MODE=release - using code: gin.SetMode(gin.ReleaseMode) [GIN-debug] GET /page/list --> main.GetPageListHandler (1 handlers) [GIN-debug] [WARNING] You trusted all proxies, this is NOT safe. We recommend you to set a value. Please check https://pkg.go.dev/github.com/gin-gonic/gin#readme-don-t-trust-all-proxies for details. [GIN-debug] Listening and serving HTTP on :8888 [2024-10-21 17:23:13.435] | INFO | Goroutine:34 | [gorm_demo/main.go:131] | get page list req | {"req": {"Page":2,"PageSize":6}} //分页请求数据 [2024-10-21 17:23:13.437] | INFO | Goroutine:34 | [conn/mysql.go:74] | conn mysql success 2024/10/21 17:23:13 D:/GoTest/gorm_demo/main.go:139 [0.640ms] [rows:1] SELECT count(*) FROM `test_page` //查询所有数量的sql 2024/10/21 17:23:13 D:/GoTest/gorm_demo/main.go:152 [0.325ms] [rows:6] SELECT * FROM `test_page` ORDER BY create_time DESC LIMIT 6 OFFSET 6 //根据分页请求计算出的偏移位置和限制量sql
上面打印了gorm库中的日志信息,可以通过自定义zap对象来实现gorm的logger对象来自定义gorm输出日志。
总结
分页的方法有很多,上面只是给出了其中一种,根据自己项目的业务场景选择一种最喜欢的方法就行。
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