go语言功能代码

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一、数据类型转换

package main

import (
    "fmt"
    "strconv"
)

func main() {
    //int到string
    str := strconv.Itoa(int(1))
    fmt.Println("int转string", str)
    //int64到string
    str2 := strconv.FormatInt(int64(1), 10)
    fmt.Println("int64转string", str2)
    //float64转string formatFloat只能接收float64如果想用float32需要强转float64(float32(0.8))
    //下面是参数说明
    // 'b' (-ddddp±ddd，二进制指数)
    // 'e' (-d.dddde±dd，十进制指数)
    // 'E' (-d.ddddE±dd，十进制指数)
    // 'f' (-ddd.dddd，没有指数)
    // 'g' ('e':大指数，'f':其它情况)
    // 'G' ('E':大指数，'f':其它情况)
    str3 := strconv.FormatFloat(float64(0.8), 'f', -1, 32)
    fmt.Println("float32转string", str3)
    //string到int  有异常的都不进行处理这个后面说
    i, _ := strconv.Atoi("10")
    fmt.Println("strin转int", i)
    //string 到int64
    i64, _ := strconv.ParseInt("123", 10, 64)
    fmt.Println("strin转int64", i64)
    //string转float64 如果想转float32 用float32(fl32)强转一下就可以
    fl32, _ := strconv.ParseFloat("3.1415926535", 32/64)
    fmt.Println("strin转float64", fl32)
}

二、时间类型转换

package main

import (
    "fmt"
    "time"
)

func main() {
    //获取当前时间
    now := time.Now()
    //时间转化为string
    //在go语言里将日期格式化并不是yyyy-MM-dd HH:ss:mm 而是用"2006-01-02 15:04:05具体含义如下
    //月份 1,01,Jan,January
    //日　 2,02,_2
    //时　 3,03,15,PM,pm,AM,am
    //分　 4,04
    //秒　 5,05
    //年　 06,2006
    //周几 Mon,Monday
    //时区时差表示 -07,-0700,Z0700,Z07:00,-07:00,MST
    //时区字母缩写 MST
    timeStr := now.Format("2006-01-02 15:04:05")
    fmt.Println("日期类型当前时间: ", now)
    fmt.Println("字符串类型当前时间: ", timeStr)
    //string转化为时间
    date, _ := time.Parse("2006-01-02 15:04:05", "2017-08-29 08:37:18")
    fmt.Println("string转日期:", date)
    //判断两个时间先后
    trueOrFalse := date.After(now)
    if trueOrFalse == true {
        fmt.Println("2017-08-29 08:37:18在", timeStr, "之后")
    } else {
        fmt.Println("2017-08-29 08:37:18在", timeStr, "之前")
    }
    // ParseDuration parses a duration string.
    // A duration string is a possibly signed sequence of decimal numbers,
    // each with optional fraction and a unit suffix,
    // such as "300ms", "-1.5h" or "2h45m".
    //  Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
    // -代表时间之前,不加代表时间之后 m表示分钟,如20分钟前
    m, _ := time.ParseDuration("-20m")
    m1 := now.Add(m)
    fmt.Println("10分钟之前：", m1)
    // h代表小时 一天之前为-24h
    h, _ := time.ParseDuration("-8h")
    h1 := now.Add(h)
    fmt.Println("8小时之前", h1)
    //    // 一天前
    d, _ := time.ParseDuration("-24h")
    d1 := now.Add(d)
    fmt.Println(d1)
    //计算两个时间差几秒
    sec := now.Sub(m1)
    fmt.Println(sec.Seconds(), "秒")
    //计算两个时间差几分钟
    minutes := now.Sub(m1)
    fmt.Println(minutes.Minutes(), "分钟")
    //计算两个时间差几小时
    hours := now.Sub(h1)
    fmt.Println(hours.Hours(), "小时")
    //计算两个时间差几天
    day := now.Sub(d1)
    fmt.Println(day.Hours()/24, "天")
    //注意:splite3数据库中字段如果是datetime类型获取数据时格式转换会有问题
    //如2017-08-29 08:37:18这样的时间从数据库获取后会变成2017-08-29T08:37:18Z
    //进行格式转化之后不能比较，所以需要将T和Z替换为" "
    //不知道其他数据库有没有这样的问题
}

三、配置文件读取

package main

import (
    "flag"
    "sync"

    "github.com/larspensjo/config"
)

var Conf_Main_Topic = "DEFAULT"

var (
    //config.ini为配置文件格式为 key=value
    configFile = flag.String("configfile", "config.ini", "General configuration file")
)
var commonConf = make(map[string]string)
var lock sync.RWMutex

func LoadCommonConfiguration() {
    lock.Lock()
    defer lock.Unlock()
    cfg, err := config.ReadDefault(*configFile)
    if err != nil {
        //....
    }
    commonConf = make(map[string]string)
    if cfg.HasSection(Conf_Main_Topic) {
        section, err := cfg.SectionOptions(Conf_Main_Topic)
        if err != nil {
            //....
        }
        for _, v := range section {
            options, err := cfg.String(Conf_Main_Topic, v)
            if err != nil {
                //....
            }
            commonConf[v] = options
        }
    }
}

//通过GetConf方法将key传入获取value值
func GetConf(key string) string {
    lock.RLock()
    defer lock.RUnlock()
    return commonConf[key]
}

四、Json与Map转换

package main

import (
    "encoding/json"
    "strings"
    //    "github.com/bitly/go-simplejson" // for json get
)

//把两层嵌套结构的json格式的数据组转成map(map中不含interface结构)
func NoInterfaceJsonToMap(input string) (map[string]map[string]interface{}, error) {
    result := make(map[string]map[string]interface{})
    err := json.Unmarshal([]byte(input), &result)
    if err != nil {
        return nil, err
    }
    return result, nil
}
func MapToJson(input map[string]interface{}) (string, error) {
    result, err := json.Marshal(input)
    if err != nil {
        //        panic(err)
        return "", err
    }
    return string(result), nil
}

func MapMapToJson(input map[string]map[string]interface{}) (string, error) {
    result, err := json.Marshal(input)
    if err != nil {
        return "", err
    }
    return string(result), nil
}

func JsonToMap(input string) (map[string]interface{}, error) {
    result := make(map[string]interface{})
    err := json.Unmarshal([]byte(input), &result)
    if err != nil {
        return nil, err
    }
    return result, nil
}

func BoltKeyValueToJson(key, value string, delimeter string) (string, error) {
    keys := []string{key}
    values := []string{value}
    return BoltKeyValuesToJson(keys, values, delimeter)
}
func BoltKeyValuesToJson(keys, values []string, delimeter string) (string, error) {
    mapResult := make(map[string]interface{})
    for i := range keys {
        key := strings.Split(keys[i], delimeter)
        value := values[i]
        cur := mapResult
        for j := range key {
            if j == len(key)-1 {
            } else if j == len(key)-2 {
                if cur[key[j]] == nil {
                    cur[key[j]] = map[string]string{key[len(key)-1]: value}
                } else {
                    cur[key[j]].(map[string]string)[key[len(key)-1]] = value
                }
            } else {
                if cur[key[j]] == nil {
                    cur[key[j]] = make(map[string]interface{})
                }
                cur = cur[key[j]].(map[string]interface{})
            }
        }
    }
    return MapToJson(mapResult)
}

五、通过JSON数据发送Email

package main

import (
    "bytes"
    "errors"
    "fmt"
    "io/ioutil"
    "net/http"
    "strconv"
    "strings"
)

func HttpPostByJSON(accessUrl string, json string, redo int) error {
    fmt.Println(json)
    fmt.Println("post write json bytes:" + strconv.Itoa(len(json)))
    for j := 1; j <= redo; j++ {
        req_new := bytes.NewBuffer([]byte(json))
        request, err := http.NewRequest("POST", accessUrl, req_new)
        if err == nil {
            request.Header.Set("Content-Type", "application/json;charset=UTF-8")
            client := http.Client{}
            response, err1 := client.Do(request)
            if err1 == nil {
                body, err := ioutil.ReadAll(response.Body)
                if err != nil {
                    fmt.Println("Unknown error in sending Email")
                } else {
                    resp := string(body)
                    if strings.Contains(resp, "\"code\":\"200\"") {
                        return nil
                    } else {
                        fmt.Println(string(body))
                    }
                }
            } else {
                fmt.Println(err1)
            }
        } else {
            fmt.Println(err)
        }
    }
    return errors.New("Fail to send email notification")
}

六、文件读写删除操作

package main

import (
    "bufio"
    "fmt"
    "io"
    "os"
    "strings"
)
func FileExist(filename string) bool {
    _, err := os.Stat(filename)
    if os.IsNotExist(err) {
        return false
    }
    fmt.Println(err)
    return err == nil || os.IsExist(err)
}

func ReadFileByLine(filename string) []string {
    if !FileExist(filename) {
        return []string{}
    }
    f, err := os.Open(filename)
    fmt.Println(err)
    defer f.Close()
    rd := bufio.NewReader(f)
    result := []string{}
    for {
        line, err := rd.ReadString('\n')
        if err == nil || io.EOF == err {
            line = strings.TrimSpace(line)
            if len(line) > 0 {
                result = append(result, line)
            }
        }
        if io.EOF == err {
            break
        }
        fmt.Println(err)
    }
    return result
}

func WriteFileByLine(filename string, data []string) {
    f, err := os.Create(filename)
    fmt.Println(err)
    defer f.Close()
    wt := bufio.NewWriter(f)
    for i := range data {
        _, err := wt.WriteString(data[i])
        if io.EOF == err {
            break
        }
        fmt.Println(err)
    }
    wt.Flush()
}

func DeleteFile(filename string) {
    if FileExist(filename) {
        err := os.Remove(filename)
        fmt.Println(err)
    }
}

七、go执行linux和windows命令操作

package main

import (
    "errors"
    "fmt"
    "os/exec"
    "runtime"
    "strings"
)

func runInLinux(cmd string) string {
    fmt.Println("Running Linux Cmd:" + cmd)
    result, err := exec.Command("/bin/sh", "-c", cmd).Output()
    if err != nil {
        fmt.Println(err.Error())
    }
    return strings.TrimSpace(string(result))
}

func runInWindows(cmd string) string {
    fmt.Println("Running Win Cmd:" + cmd)
    result, err := exec.Command("cmd", "/c", cmd).Output()
    if err != nil {
        fmt.Println(err.Error())
    }
    return strings.TrimSpace(string(result))
}

func RunCommand(cmd string) string {
    if runtime.GOOS == "windows" {
        return runInWindows(cmd)
    } else {
        return runInLinux(cmd)
    }
}

func RunLinuxCommand(cmd string) string {
    if runtime.GOOS == "windows" {
        return ""
    } else {
        return runInLinux(cmd)
    }
}

func runInLinuxWithErr(cmd string) (string, error) {
    fmt.Println("Running Linux Cmd:" + cmd)
    result, err := exec.Command("/bin/sh", "-c", cmd).Output()
    if err != nil {
        fmt.Println(err.Error())
    }
    return strings.TrimSpace(string(result)), err
}

func runInWindowsWithErr(cmd string) (string, error) {
    fmt.Println("Running Win Cmd:" + cmd)
    result, err := exec.Command("cmd", "/c", cmd).Output()
    if err != nil {
        fmt.Println(err.Error())
    }
    return strings.TrimSpace(string(result)), err
}

func RunCommandWithErr(cmd string) (string, error) {
    if runtime.GOOS == "windows" {
        return runInWindowsWithErr(cmd)
    } else {
        return runInLinuxWithErr(cmd)
    }
}

func RunLinuxCommandWithErr(cmd string) (string, error) {
    if runtime.GOOS == "windows" {
        return "", errors.New("could not run in windows OS")

    } else {
        return runInLinuxWithErr(cmd)
    }
}

八、异常处理

Golang 有2个内置的函数 panic() 和 recover()，用以报告和捕获运行时发生的程序错误，与 error 不同，panic-recover 一般用在函数内部。一定要注意不要滥用 panic-recover，可能会导致性能问题，我一般只在未知输入和不可靠请求时使用。

golang 的错误处理流程：当一个函数在执行过程中出现了异常或遇到 panic()，正常语句就会立即终止，然后执行 defer 语句，再报告异常信息，最后退出 goroutine。如果在 defer 中使用了 recover() 函数,则会捕获错误信息，使该错误信息终止报告。

package main
import (
 "log"
 "strconv"
)
//捕获因未知输入导致的程序异常
func catch(nums ...int) int {
 defer func() {
  if r := recover(); r != nil {
   log.Println("[E]", r)
  }
 }()
 return nums[1] * nums[2] * nums[3] //index out of range
}
//主动抛出 panic，不推荐使用，可能会导致性能问题
func toFloat64(num string) (float64, error) {
 defer func() {
  if r := recover(); r != nil {
   log.Println("[W]", r)
  }
 }()
 if num == "" {
  panic("param is null") //主动抛出 panic
 }
 return strconv.ParseFloat(num, 10)
}
func main() {
 catch(2, 8)
 toFloat64("")
}

go语言有异常的返回会有两个返回参数包括值跟error，判断error是否为nil进行相应处理就可以最好不要panic

十、数据库操作

package main

import (
    "database/sql"
    "errors"
    "fmt"
    "sync"

    _ "github.com/mattn/go-sqlite3"
)

var db *sql.DB
var dbLock sync.Mutex

func main() {
    //查询调用RunQuery或者RunQueryWithErr
    //?为占位符对应相应参数
    rows := RunQuery("select age from table where id = ? and name = ?", 1, "abc")
    //也可以使用struct构建对象,获取数据库字段时需要用sql.Null...否则取空值会报错
    var age sql.NullInt64
    var ages []Int64

    //如果有多条返回值用for循环遍历,如果确定只有一条可以用if,这里只有一条所以用if,也可以将if改为for
    if rows.Next() {
        err := rows.Scan(&age)
        if err != nil {
            //........
        }
        //sql.NullInt64中有两个方法Int64和Valid,Valid用来判断值是否为空返回值为true、false
        //Int64为实际值,sql.NullInt64对象如果为空Int64值为0
        if age.Valid {
            //对获取到的age做操作
            fmt.Println(age.Int64)
        }
    }
    //sqlite3中使用完rows之后一定要调用close释放锁,否则继续调用数据库语句会报数据库被锁的异常
    rows.Close()
    //sqlite3中查询和增删改不能同时进行,也会报数据库被锁的异常
    //需要在查询之后统一进行增删改操作,增删改调用ExecSQL或ExecSqlWithErr
}

func OpenDB() {
    var err error
    //foo.db为数据库名字
    db, err = sql.Open("sqlite3", "./foo.db?_txlock=exclusive")
    fmt.Println(err)
    _, err = db.Exec("PRAGMA synchronous = OFF;")
    fmt.Println(err)
}

func CloseDB() {
    if db != nil {
        err := db.Close()
        db = nil
        fmt.Println(err)
    }
}

func ExecSQL(query string, args ...interface{}) sql.Result {
    dbLock.Lock()
    defer dbLock.Unlock()
    if db == nil {
        OpenDB()
    }
    if query == "" {
        panic("Empty sql input")
    }
    fmt.Println("Running Exec:")
    fmt.Println(query)
    fmt.Println(args...)
    res, err := db.Exec(query, args...)
    fmt.Println(err)
    return res
}

func RunQuery(query string, args ...interface{}) *sql.Rows {
    dbLock.Lock()
    defer dbLock.Unlock()
    if db == nil {
        OpenDB()
    }
    if query == "" {
        panic("Empty sql input")
    }
    fmt.Println("Running Query:")
    fmt.Println(query)
    fmt.Println(args...)
    res, err := db.Query(query, args...)
    fmt.Println(err)
    return res
}
//多条语句的事物操作
func ExecTransaction(querys []string, args [][]string) {
    dbLock.Lock()
    defer dbLock.Unlock()
    if db == nil {
        OpenDB()
    }
    tx, err := db.Begin()
    fmt.Println(err)
    fmt.Println("Running Trans:")
    for index, query := range querys {
        if query == "" {
            panic("Empty sql input")
        }
        oldArgs := args[index]
        newArgs := make([]interface{}, len(oldArgs))
        for i, v := range oldArgs {
            newArgs[i] = interface{}(v)
        }
        fmt.Println(query)
        fmt.Println(newArgs...)
        _, err := tx.Exec(query, newArgs...)
        fmt.Println(err)
    }
    err = tx.Commit()
    fmt.Println(err)
}

func OpenDBWithErr() error {
    var err error
    db, err = sql.Open("sqlite3", "./pjm.db?_txlock=exclusive")
    if err != nil {
        return err
    }
    _, err = db.Exec("PRAGMA synchronous = OFF;")
    return err
}

func CloseDBWithErr() error {
    if db != nil {
        err := db.Close()
        db = nil
        return err
    }
    return nil
}

func ExecSQLWithErr(query string, args ...interface{}) (sql.Result, error) {
    dbLock.Lock()
    defer dbLock.Unlock()
    if db == nil {
        err := OpenDBWithErr()
        if err != nil {
            return nil, err
        }
    }
    if query == "" {
        return nil, errors.New("Empty sql input")
    }
    fmt.Println("Running Exec With Err:")
    fmt.Println(query)
    fmt.Println(args...)
    return db.Exec(query, args...)
}

func RunQueryWithErr(query string, args ...interface{}) (*sql.Rows, error) {
    dbLock.Lock()
    defer dbLock.Unlock()
    if db == nil {