自定义回调处理是最常见的接口开发实现，我们往往只需要对接口中的部分实现进行替换修改，以在原有的实现逻辑中注入自定义的逻辑实现。我们来看一个自定义回调处理的示例，我们需要将所有执行的SQL语句记录到monitor表中，以方便于进行SQL审计。

    为简化示例编写，我们这里实现了一个自定义的MySQL驱动，该驱动继承于gdb模块中已经实现的DriverMysql，并按照需要修改覆盖相应的接口方法。由于所有的SQL语句执行必定会通过DoQuery或者DoExec接口，因此我们在自定义的驱动中实现并覆盖这两个接口方法即可。

    1. package driver
    3. import (
    4.     "database/sql"
    5.     "github.com/gogf/gf/database/gdb"
    6.     "github.com/gogf/gf/os/gtime"
    7. )
    9. // MyDriver is a custom database driver, which is used for testing only.
    10. // For simplifying the unit testing case purpose, MyDriver struct inherits the mysql driver
    11. // gdb.DriverMysql and overwrites its functions DoQuery and DoExec.
    12. // So if there's any sql execution, it goes through MyDriver.DoQuery/MyDriver.DoExec firstly
    13. // and then gdb.DriverMysql.DoQuery/gdb.DriverMysql.DoExec.
    14. // You can call it sql "HOOK" or "HiJack" as your will.
    15. type MyDriver struct {
    16.     *gdb.DriverMysql
    17. }
    19. var (
    20.     // customDriverName is my driver name, which is used for registering.
    21.     customDriverName = "MyDriver"
    22. )
    24. func init() {
    25.     // It here registers my custom driver in package initialization function "init".
    26.     // You can later use this type in the database configuration.
    27.     if err := gdb.Register(customDriverName, &MyDriver{}); err != nil {
    28.         panic(err)
    29.     }
    30. }
    32. // New creates and returns a database object for mysql.
    33. // It implements the interface of gdb.Driver for extra database driver installation.
    34. func (d *MyDriver) New(core *gdb.Core, node *gdb.ConfigNode) (gdb.DB, error) {
    35.     return &MyDriver{
    36.         &gdb.DriverMysql{
    37.             Core: core,
    38.         },
    39.     }, nil
    40. }
    42. // DoQuery commits the sql string and its arguments to underlying driver
    43. // through given link object and returns the execution result.
    44. func (d *MyDriver) DoQuery(ctx context.Context, link gdb.Link, sql string, args ...interface{}) (rows *sql.Rows, err error) {
    45.     tsMilli := gtime.TimestampMilli()
    46.     rows, err = d.DriverMysql.DoQuery(ctx, link, sql, args...)
    47.     link.Exec(
    48.         "INSERT INTO `monitor`(`sql`,`cost`,`time`,`error`) VALUES(?,?,?,?)",
    49.         gdb.FormatSqlWithArgs(sql, args),
    50.         gtime.TimestampMilli()-tsMilli,
    51.         gtime.Now(),
    52.         err,
    53.     )
    54.     return
    55. }
    57. // DoExec commits the query string and its arguments to underlying driver
    58. // through given link object and returns the execution result.
    59. func (d *MyDriver) DoExec(ctx context.Context, link gdb.Link, sql string, args ...interface{}) (result sql.Result, err error) {
    60.     tsMilli := gtime.TimestampMilli()
    61.     result, err = d.DriverMysql.DoExec(ctx, link, sql, args...)
    62.     link.Exec(
    63.         "INSERT INTO `monitor`(`sql`,`cost`,`time`,`error`) VALUES(?,?,?,?)",
    64.         gdb.FormatSqlWithArgs(sql, args),
    65.         gtime.TimestampMilli()-tsMilli,
    66.         gtime.Now(),
    67.         err,
    68.     )
    69.     return
    70. }

    我们看到，这里在包初始化方法init中使用了gdb.Register("MyDriver", &MyDriver{})来注册了了一个自定义名称的驱动。我们也可以通过gdb.Register("mysql", &MyDriver{})来覆盖已有的框架mysql驱动为自己的驱动。

    驱动名称mysql为框架默认的DriverMysql驱动的名称。

    由于这里我们使用了一个新的驱动名称MyDriver，因此在gdb配置中的type数据库类型时，需要填写该驱动名称。以下是一个使用配置的示例：

    1. [database]
    2.     type = "MyDriver"
    3.     link = "root:12345678@tcp(127.0.0.1:3306)/test"