How to use annotations in xorm

When using golang as a development language, it is often necessary to use an ORM library for database operations. xorm As one of the commonly used ORM libraries in golang, it has the characteristics of high flexibility and ease of use. This article mainly introduces how to use annotations in xorm.

Comments are an important way to improve code readability and maintainability in programming. When using xorm, we can also use comments to annotate data tables and fields to facilitate later reference and maintenance work.

Data table and field comments

In xorm, we can implement the comment function by adding the comment tag to the data table and field definitions . The following is an example of a table definition:

type User struct {
  Id       int64  `xorm:"pk autoincr"`
  Name     string `xorm:"varchar(30) notnull comment('姓名')"`
  Age      int    `xorm:"default 0 comment('年龄')"`
  Email    string `xorm:"varchar(22) not null comment('邮箱')"`
  Password string `xorm:"varchar(40) not null comment('密码')"`
}

In this example, we see that each field has a comment tag added, and the comment content is added to the tag. In this way, during later maintenance, you can more intuitively understand the data structure and business meaning by viewing the annotations of the data tables and fields.

Getting data table and field comments

Using the function provided by the xorm package, we can get the comment information of a data table. The following is an example of obtaining the comment information of the data table user:

db := xorm.NewEngine("driverName", "dsn")
db.ShowSQL(true)
db.ShowDebug(true)
db.SetMaxIdleConns(10)
db.SetMaxOpenConns(20)

res, err := db.Prepare("SELECT TABLE_COMMENT FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = ? AND TABLE_NAME = ?")
if err != nil {
    return "", err
}
var tableName = "user"
var tableComment = ""
row := res.QueryRow(db.DatabaseName(), tableName)
err = row.Scan(&tableComment)
if err != nil {
    return "", err
}

In the above example, we first use the db.Prepare() function to create a query statement preparation operations. The formatted SQL statement is then used in the res.QueryRow() function. Finally, execute the row.Scan() function and assign the query result to the tableComment variable we defined. In this way, we can obtain the annotation information of the user data table through this function.

Similarly, we can use the following code to obtain the annotation information of a field in a data table:

fields, err := db.DBMetas()
if err != nil {
    return nil, err
}

for _, field := range fields {
    tableName := field.TableName
    for _, column := range field.Columns {
        columnName := column.Name
        columnComment := column.Comment
        // do something here
    }
}

In this example, we first pass db.DBMetas() The function obtains all data table and field information in a database. Then obtain the annotation information of each field by traversing the table and field information. Here we can handle it accordingly according to our own needs.

Conclusion

Through the introduction of this article, we can use xorm to easily implement the annotation function, which is very helpful for the later maintenance and reading of a project. . At the same time, we also introduced how to obtain annotation information of data tables and fields through the xorm function. In this way, in actual use, we can better understand the data structure and business meaning, so as to better maintain and develop our projects.

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