How to use annotations in xorm

When usinggolangas a development language, it is often necessary to use an ORM library for database operations.xormAs one of the commonly used ORM libraries ingolang, it has the characteristics of high flexibility and ease of use. This article mainly introduces how to use annotations inxorm.

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

Data table and field comments

Inxorm, we can implement the comment function by adding thecommenttag 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 acommenttag 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 thexormpackage, we can get the comment information of a data table. The following is an example of obtaining the comment information of the data tableuser:

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 thedb.Prepare()function to create a query statement preparation operations. The formatted SQL statement is then used in theres.QueryRow()function. Finally, execute therow.Scan()function and assign the query result to thetableCommentvariable we defined. In this way, we can obtain the annotation information of theuserdata 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 passdb.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 usexormto 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 thexormfunction. 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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