22

正在为 Go 中的 MySQL 到 JSON 组合一个快速转储器。但是我发现我从数据库中检索到的所有东西都是一个[]byte数组。因此，我将所有内容编码为字符串，而不是原生 JSON 整数或布尔值。

代码子集：

import (
    "encoding/json"
    "database/sql"
    _ "github.com/go-sql-driver/mysql"
)


func dumpTable(w io.Writer, table) {
    // ...

    rows, err := Query(db, fmt.Sprintf("SELECT * FROM %s", table))
    checkError(err)
    columns, err := rows.Columns()
    checkError(err)

    scanArgs := make([]interface{}, len(columns))
    values   := make([]interface{}, len(columns))

    for i := range values {
        scanArgs[i] = &values[i]
    }

    for rows.Next() {
        err = rows.Scan(scanArgs...)
        checkError(err)

        record := make(map[string]interface{})

        for i, col := range values {
            if col != nil {
                fmt.Printf("\n%s: type= %s\n", columns[i], reflect.TypeOf(col))

                switch t := col.(type) {
                default:
                    fmt.Printf("Unexpected type %T\n", t)
                case bool:
                    fmt.Printf("bool\n")
                    record[columns[i]] = col.(bool)
                case int:
                    fmt.Printf("int\n")
                    record[columns[i]] = col.(int)
                case int64:
                    fmt.Printf("int64\n")
                    record[columns[i]] = col.(int64)
                case float64:
                    fmt.Printf("float64\n")
                    record[columns[i]] = col.(float64)
                case string:
                    fmt.Printf("string\n")
                    record[columns[i]] = col.(string)
                case []byte:   // -- all cases go HERE!
                    fmt.Printf("[]byte\n")
                    record[columns[i]] = string(col.([]byte))
                case time.Time:
                    // record[columns[i]] = col.(string)
                }
            }
        }

        s, _ := json.Marshal(record)
        w.Write(s)
        io.WriteString(w, "\n")
    }
}
4

6 回答 6

43

我还需要将数据库表转储到 json，这就是我的实现方式：（与本主题中的另一个答案不同，一切都不是字符串，感谢这个答案：https ://stackoverflow.com/a/17885636/4124416 ，我可以正确获取整数字段）

func getJSON(sqlString string) (string, error) {
    rows, err := db.Query(sqlString)
    if err != nil {
        return "", err
    }
    defer rows.Close()
    columns, err := rows.Columns()
    if err != nil {
        return "", err
    }
    count := len(columns)
    tableData := make([]map[string]interface{}, 0)
    values := make([]interface{}, count)
    valuePtrs := make([]interface{}, count)
    for rows.Next() {
        for i := 0; i < count; i++ {
          valuePtrs[i] = &values[i]
        }
        rows.Scan(valuePtrs...)
        entry := make(map[string]interface{})
        for i, col := range columns {
            var v interface{}
            val := values[i]
            b, ok := val.([]byte)
            if ok {
                v = string(b)
            } else {
                v = val
            }
            entry[col] = v
        }
        tableData = append(tableData, entry)
    }
    jsonData, err := json.Marshal(tableData)
    if err != nil {
        return "", err
    }
    fmt.Println(string(jsonData))
    return string(jsonData), nil 
}

这是一个示例输出：

[{"ID":0,"Text":"Zero"},{"ID":1,"Text":"One"},{"ID":2,"Text":"Two"}]
于 2015-03-20T10:15:41.350 回答
3

需要使用准备好的语句来获取本机类型。MySQL 有两种协议，一种以文本形式传输所有内容，另一种以“真实”类型传输。并且该二进制协议仅在您使用准备好的语句时使用。见https://github.com/go-sql-driver/mysql/issues/407

下面的函数getJSON是正确的：

func getJSON(sqlString string) (string, error) {
  stmt, err := db.Prepare(sqlString)
  if err != nil {
    return "", err
  }
  defer stmt.Close()

  rows, err := stmt.Query()
  if err != nil {
    return "", err
  }
  defer rows.Close()

  columns, err := rows.Columns()
  if err != nil {
    return "", err
  }

  tableData := make([]map[string]interface{}, 0)

  count := len(columns)
  values := make([]interface{}, count)
  scanArgs := make([]interface{}, count)
  for i := range values {
    scanArgs[i] = &values[i]
  }

  for rows.Next() {
    err := rows.Scan(scanArgs...)
    if err != nil {
      return "", err
    }

    entry := make(map[string]interface{})
    for i, col := range columns {
      v := values[i]

      b, ok := v.([]byte)
      if (ok) {
        entry[col] = string(b)
      } else {
        entry[col] = v
      }
    }

    tableData = append(tableData, entry)
  }

  jsonData, err := json.Marshal(tableData)
  if err != nil {
    return "", err
  }

  return string(jsonData), nil 
}
于 2016-01-19T09:20:51.557 回答
2

您无能为力，因为driver-database/sql交互几乎是单向街道，当数据移交给时，司机无法帮助您database/sql。

你可以试试http://godoc.org/github.com/arnehormann/sqlinternals/mysqlinternals

  • 查询数据库
  • 检索列切片cols, err := mysqlinternals.Columns(rows)
  • 创建一个新的 varvalues := make([]interface{}, len(cols))并迭代cols
  • 获取每列最匹配的 Go 类型refType, err := cols[i].ReflectGoType()
  • 创建类型占位符values[i] = reflect.Zero(refType).Interface()
  • rows.Next()和err = rows.Scan(values...)。不要重新创建values、复制和重复使用它。

我想这仍然会很慢，但是您应该可以使用它。如果您遇到问题，请提出问题 - 我会尽快解决。

于 2014-01-27T16:46:32.397 回答
2

我在 practice_db 数据库中有一个名为 users 的表。我在以下程序中提到了带有数据的表结构，该程序将用户表转换为 JSON 格式。

您还可以在https://gist.github.com/hygull/1725442b0f121a5fc17b28e04796714d查看源代码。

/**
    {
        "created_on": "26 may 2017",
        "todos": [
            "go get github.com/go-sql-driver/mysql",
            "postman(optional)",
            "browser(optional)",    
        ],
        "aim": "Reading fname column into []string(slice of strings)"
    }
*/


/* 
    mysql> select * from users;
    +----+-----------+----------+----------+-------------------------------+--------------+-------------------------------------------------------------------------------------------------+
    | id | fname     | lname    | uname    | email                         | contact      | profile_pic                                                                                     |
    +----+-----------+----------+----------+-------------------------------+--------------+-------------------------------------------------------------------------------------------------+
    |  1 | Rishikesh | Agrawani | hygull   | rishikesh0014051992@gmail.com | 917353787704 | https://cdn4.iconfinder.com/data/icons/rcons-user/32/user_group_users_accounts_contacts-512.png |
    |  2 | Sandeep   | E        | sandeep  | sandeepeswar8@gmail.com       | 919739040038 | https://cdn4.iconfinder.com/data/icons/eldorado-user/40/user-512.png                            |
    |  3 | Darshan   | Sidar    | darshan  | sidardarshan@gmail.com        | 917996917565 | https://cdn4.iconfinder.com/data/icons/rcons-user/32/child_boy-512.png                          |
    |  4 | Surendra  | Prajapat | surendra | surendrakgadwal@gmail.com     | 918385894407 | https://cdn4.iconfinder.com/data/icons/rcons-user/32/account_male-512.png                       |
    |  5 | Mukesh    | Jakhar   | mukesh   | mjakhar.kjakhar@gmail.com     | 919772254140 | https://cdn2.iconfinder.com/data/icons/rcons-user/32/male-circle-512.png                        |
    +----+-----------+----------+----------+-------------------------------+--------------+-------------------------------------------------------------------------------------------------+
    5 rows in set (0.00 sec)

    mysql> 
*/

package main

import "log"
import "net/http"
import "encoding/json"

import (
    _"github.com/go-sql-driver/mysql"   
    "database/sql"
)

func users(w http.ResponseWriter, r *http.Request) {
    // db, err := sql.Open("mysql", "<username>:<password>@tcp(127.0.0.1:<port>)/<dbname>?charset=utf8" )
    db, err := sql.Open("mysql", "hygull:admin@67@tcp(127.0.0.1:3306)/practice_db?charset=utf8")

    w.Header().Set("Content-Type", "application/json")

    if err != nil {
        log.Fatal(err)
    }

    rows, err := db.Query("select id, fname, lname, uname, email, contact, profile_pic from users")

    if err != nil {
        log.Fatal(err)
    }

    type User struct {
        Id int       `json:"id"`
        Fname string `json:"firstname"`
        Lname string `json:"lastname"`
        Uname string `json:"username"`
        Email string `json:"email"`
        Contact int `json:"contact"`
        ProfilePic string `json:"profile_pic"`
    }

    var users []User

    for rows.Next() {
        var id, contact int
        var fname string
        var lname string
        var uname, email, profile_pic string

        rows.Scan(&id ,&fname, &lname, &uname, &email, &contact, &profile_pic)
        users = append(users, User{id, fname, lname, uname, email, contact, &profile_pic })
    }

    usersBytes, _ := json.Marshal(&users)

    w.Write(usersBytes)
    db.Close()
}

func main() {
    http.HandleFunc("/users/", users)
    http.ListenAndServe(":8080", nil)
}

/* REQUSET

   http://127.0.0.1:8080/users/
*/

/* RESPONSE
[
  {
    "id": 1,
    "firstname": "Rishikesh",
    "lastname": "Agrawani",
    "username": "hygull",
    "email": "rishikesh0014051992@gmail.com",
    "contact": 917353787704,
    "profile_pic": "https://cdn4.iconfinder.com/data/icons/rcons-user/32/user_group_users_accounts_contacts-512.png"
  },
  {
    "id": 2,
    "firstname": "Sandeep",
    "lastname": "E",
    "username": "sandeep",
    "email": "sandeepeswar8@gmail.com",
    "contact": 919739040038,
    "profile_pic": "https://cdn4.iconfinder.com/data/icons/eldorado-user/40/user-512.png"
  },
  {
    "id": 3,
    "firstname": "Darshan",
    "lastname": "Sidar",
    "username": "darshan",
    "email": "sidardarshan@gmail.com",
    "contact": 917996917565,
    "profile_pic": "https://cdn4.iconfinder.com/data/icons/rcons-user/32/child_boy-512.png"
  },
  {
    "id": 4,
    "firstname": "Surendra",
    "lastname": "Prajapat",
    "username": "surendra",
    "email": "surendrakgadwal@gmail.com",
    "contact": 918385894407,
    "profile_pic": "https://cdn4.iconfinder.com/data/icons/rcons-user/32/account_male-512.png"
  },
  {
    "id": 5,
    "firstname": "Mukesh",
    "lastname": "Jakhar",
    "username": "mukesh",
    "email": "mjakhar.kjakhar@gmail.com",
    "contact": 919772254140,
    "profile_pic": "https://cdn2.iconfinder.com/data/icons/rcons-user/32/male-circle-512.png"
  }
]
*/
于 2017-05-27T05:26:29.620 回答
0

根据此处的答案，这是我能想到的最有效的代码。请注意，这是将每一行作为单独的 JSON 数组输出以保存键名重复。

// OutputJSONMysqlRowsStream outputs rows as a JSON array stream to save ram & output size due to key name repetition
func OutputJSONMysqlRowsStream(writer http.ResponseWriter, rows *sql.Rows) {

    defer rows.Close()

    columns, err := rows.Columns()

    if err != nil {
        OutputJSONError(writer, "Failed to get column names")
        return
    }

    jsonColumns, err := json.Marshal(columns)

    if err != nil {
        OutputJSONError(writer, "Failed to encode json of column names")
        return
    }

    writer.Header().Set("Content-Type", "application/cal-json-stream; charset=utf-8")

    fmt.Fprintln(writer, "{\"status\": \"done\", \"data\":{ \"json_stream_fields\":"+string(jsonColumns)+"}}")

    columnCount := len(columns)
    rowDataHolder := make([]interface{}, columnCount)
    rowDataHolderPointers := make([]interface{}, columnCount)

    if err != nil {
        log.Println(err)
    }

    for rows.Next() {

        for i := 0; i < columnCount; i++ {
            rowDataHolderPointers[i] = &rowDataHolder[i]
        }

        err := rows.Scan(rowDataHolderPointers...)

        if err != nil {
            log.Println(err)
        } else {

            for i, value := range rowDataHolder {
                tempValue, ok := value.([]byte)

                if ok {
                    rowDataHolder[i] = string(tempValue)
                }
            }

            jsonEncoder := json.NewEncoder(writer)
            err = jsonEncoder.Encode(rowDataHolder)

            if err != nil {
                log.Println(err)
            }
        }
    }
}
于 2019-05-08T07:28:39.790 回答
-1

您可以将表格转储到 json 中就好了，但是一切都将是字符串:(

q := "select * from table"
debug("SQL: %s", q)

rows, err := db.Query(q)
checkError(err)
defer rows.Close()

columns, err := rows.Columns()
checkError(err)

scanArgs := make([]interface{}, len(columns))
values := make([]interface{}, len(columns))

for i := range values {
    scanArgs[i] = &values[i]
}

for rows.Next() {
    err = rows.Scan(scanArgs...)
    checkError(err)

    record := make(map[string]interface{})

    for i, col := range values {
        if col != nil {
            record[columns[i]] = fmt.Sprintf("%s", string(col.([]byte)))
        }
    }

    s, _ := json.Marshal(record)
    fmt.Printf("%s\n", s)
}
于 2014-05-20T18:04:55.650 回答