组件分享之后端组件——对golang数据库/sql的通用扩展组件sqlx

背景

近期正在探索前端、后端、系统端各类常用组件与工具，对其一些常见的组件进行再次整理一下，形成标准化组件专题，后续该专题将包含各类语言中的一些常用组件。欢迎大家进行持续关注。

组件基本信息

• 组件：sqlx
• 开源协议：MIT License

内容

本节我们分享一个对golang数据库/sql的通用扩展组件sqlx

它在 go 的标准库上提供了一组扩展 database/sql。sql.DB, sql.TX, sql.Stmt, 等的 sqlx 版本。所有这些都保持底层接口不变，因此它们的接口是标准接口的超集。这使得使用 database/sql 与 sqlx 集成现有代码库相对容易。

主要的附加概念是：

• 将行编组为结构（具有嵌入式结构支持）、映射和切片
• 命名参数支持，包括准备好的语句
• Get并Select快速从查询转到结构/切片

除了godoc API 文档之外，还有一些用户文档解释了如何database/sql与 sqlx 一起使用。
安装方式如下：

go get github.com/jmoiron/sqlx

使用案例如下：

package main

import (
    "database/sql"
    "fmt"
    "log"
    
    _ "github.com/lib/pq"
    "github.com/jmoiron/sqlx"
)

var schema = `
CREATE TABLE person (
    first_name text,
    last_name text,
    email text
);

CREATE TABLE place (
    country text,
    city text NULL,
    telcode integer
)`

type Person struct {
    FirstName string `db:"first_name"`
    LastName  string `db:"last_name"`
    Email     string
}

type Place struct {
    Country string
    City    sql.NullString
    TelCode int
}

func main() {
    // ping数据库尝试连接
    // 使用sqlx.Open()实现sql.Open()语义
    db, err := sqlx.Connect("postgres", "user=foo dbname=bar sslmode=disable")
    if err != nil {
        log.Fatalln(err)
    }

    // exec the schema or fail; multi-statement Exec behavior varies between
    // database drivers;  pq will exec them all, sqlite3 won't, ymmv
    db.MustExec(schema)
    
    tx := db.MustBegin()
    tx.MustExec("INSERT INTO person (first_name, last_name, email) VALUES ($1, $2, $3)", "Jason", "Moiron", "jmoiron@jmoiron.net")
    tx.MustExec("INSERT INTO person (first_name, last_name, email) VALUES ($1, $2, $3)", "John", "Doe", "johndoeDNE@gmail.net")
    tx.MustExec("INSERT INTO place (country, city, telcode) VALUES ($1, $2, $3)", "United States", "New York", "1")
    tx.MustExec("INSERT INTO place (country, telcode) VALUES ($1, $2)", "Hong Kong", "852")
    tx.MustExec("INSERT INTO place (country, telcode) VALUES ($1, $2)", "Singapore", "65")
    // Named queries can use structs, so if you have an existing struct (i.e. person := &Person{}) that you have populated, you can pass it in as &person
    tx.NamedExec("INSERT INTO person (first_name, last_name, email) VALUES (:first_name, :last_name, :email)", &Person{"Jane", "Citizen", "jane.citzen@example.com"})
    tx.Commit()

    // Query the database, storing results in a []Person (wrapped in []interface{})
    people := []Person{}
    db.Select(&people, "SELECT * FROM person ORDER BY first_name ASC")
    jason, john := people[0], people[1]

    fmt.Printf("%#v\n%#v", jason, john)
    // Person{FirstName:"Jason", LastName:"Moiron", Email:"jmoiron@jmoiron.net"}
    // Person{FirstName:"John", LastName:"Doe", Email:"johndoeDNE@gmail.net"}

    // You can also get a single result, a la QueryRow
    jason = Person{}
    err = db.Get(&jason, "SELECT * FROM person WHERE first_name=$1", "Jason")
    fmt.Printf("%#v\n", jason)
    // Person{FirstName:"Jason", LastName:"Moiron", Email:"jmoiron@jmoiron.net"}

    // if you have null fields and use SELECT *, you must use sql.Null* in your struct
    places := []Place{}
    err = db.Select(&places, "SELECT * FROM place ORDER BY telcode ASC")
    if err != nil {
        fmt.Println(err)
        return
    }
    usa, singsing, honkers := places[0], places[1], places[2]
    
    fmt.Printf("%#v\n%#v\n%#v\n", usa, singsing, honkers)
    // Place{Country:"United States", City:sql.NullString{String:"New York", Valid:true}, TelCode:1}
    // Place{Country:"Singapore", City:sql.NullString{String:"", Valid:false}, TelCode:65}
    // Place{Country:"Hong Kong", City:sql.NullString{String:"", Valid:false}, TelCode:852}

    // Loop through rows using only one struct
    place := Place{}
    rows, err := db.Queryx("SELECT * FROM place")
    for rows.Next() {
        err := rows.StructScan(&place)
        if err != nil {
            log.Fatalln(err)
        } 
        fmt.Printf("%#v\n", place)
    }
    // Place{Country:"United States", City:sql.NullString{String:"New York", Valid:true}, TelCode:1}
    // Place{Country:"Hong Kong", City:sql.NullString{String:"", Valid:false}, TelCode:852}
    // Place{Country:"Singapore", City:sql.NullString{String:"", Valid:false}, TelCode:65}

    // Named queries, using `:name` as the bindvar.  Automatic bindvar support
    // which takes into account the dbtype based on the driverName on sqlx.Open/Connect
    _, err = db.NamedExec(`INSERT INTO person (first_name,last_name,email) VALUES (:first,:last,:email)`, 
        map[string]interface{}{
            "first": "Bin",
            "last": "Smuth",
            "email": "bensmith@allblacks.nz",
    })

    // Selects Mr. Smith from the database
    rows, err = db.NamedQuery(`SELECT * FROM person WHERE first_name=:fn`, map[string]interface{}{"fn": "Bin"})

    // Named queries can also use structs.  Their bind names follow the same rules
    // as the name -> db mapping, so struct fields are lowercased and the `db` tag
    // is taken into consideration.
    rows, err = db.NamedQuery(`SELECT * FROM person WHERE first_name=:first_name`, jason)
    
    
    // batch insert
    
    // batch insert with structs
    personStructs := []Person{
        {FirstName: "Ardie", LastName: "Savea", Email: "asavea@ab.co.nz"},
        {FirstName: "Sonny Bill", LastName: "Williams", Email: "sbw@ab.co.nz"},
        {FirstName: "Ngani", LastName: "Laumape", Email: "nlaumape@ab.co.nz"},
    }

    _, err = db.NamedExec(`INSERT INTO person (first_name, last_name, email)
        VALUES (:first_name, :last_name, :email)`, personStructs)

    // batch insert with maps
    personMaps := []map[string]interface{}{
        {"first_name": "Ardie", "last_name": "Savea", "email": "asavea@ab.co.nz"},
        {"first_name": "Sonny Bill", "last_name": "Williams", "email": "sbw@ab.co.nz"},
        {"first_name": "Ngani", "last_name": "Laumape", "email": "nlaumape@ab.co.nz"},
    }

    _, err = db.NamedExec(`INSERT INTO person (first_name, last_name, email)
        VALUES (:first_name, :last_name, :email)`, personMaps)
}

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