Gen Tool

Gen Tool is a single binary without dependencies can be used to generate structs from database

Install

go install gorm.io/gen/tools/gentool@latest

Version and Go compatibility

The tool module (gorm.io/gen/tools/gentool, currently v0.0.3) and the
library module (gorm.io/gen, currently v0.3.29) version independently —
check both when reporting issues.

The tool module and its current dependency set (e.g. golang.org/x/tools
v0.40.0) declare go 1.24.0, so building gentool requires Go 1.24 or newer;
the generated code and the gorm.io/gen library itself only require
Go 1.18+ (-useAny likewise only needs Go 1.18 in the target module). If
you write your own generator program importing gorm.io/gen v0.3.29 under a
recent toolchain and hit build errors inside golang.org/x/tools, bump
golang.org/x/tools in your module to a version compatible with your toolchain
(gen’s minimum pin v0.17.0 predates current compilers).

Usage

gentool -h

Usage of gentool:
 -c string
       is path for gen.yml
 -db string
       input mysql|postgres|sqlite|sqlserver|clickhouse. consult[https://gorm.io/docs/connecting_to_the_database.html] (default "mysql")
 -dsn string
       consult[https://gorm.io/docs/connecting_to_the_database.html]
 -fieldCoverable
       generate with pointer when field has default value
 -fieldNullable
       generate with pointer when field is nullable
 -fieldSignable
       detect integer field's unsigned type, adjust generated data type
 -fieldWithDefaultTag
       generate field with gorm default tag
 -fieldWithIndexTag
       generate field with gorm index tag
 -fieldWithTypeTag
       generate field with gorm column type tag
 -modelPkgName string
       generated model code's package name
 -onlyModel
       only generate models (without query file)
 -outFile string
       query code file name, default: gen.go
 -outPath string
       specify a directory for output (default "./dao/query")
 -tables string
       enter the required data table or leave it blank
 -unitTestTemplate string
       custom unit test template file path for query code
 -useAny
       emit "any" instead of "interface{}" in generated code (requires Go 1.18+)
 -withDefaultQuery
       create default query in generated code
 -withGeneric
       generate code with generic
 -withQueryInterface
       generate code with exported interface object
 -withUnitTest
       generate unit test for query code
 -withoutContext
       generate code without context constrain

c

Path to a YAML configuration file. When -c is set, the configuration file
completely replaces command-line flags — every other flag on the same
invocation is ignored, even if set. Use either flags or a config file, not both.

db

Specify driver dialector, default value “mysql”, refer: https://gorm.io/docs/connecting_to_the_database.html

Supported: mysql, postgres, sqlite, sqlserver, clickhouse. (The tool’s
own error message for an unknown -db omits clickhouse, but it is supported.)

dsn

DSN that used to connect database, refer: https://gorm.io/docs/connecting_to_the_database.html

fieldNullable

Generate with pointer when field is nullable

fieldWithIndexTag

Generate field with gorm index tag

fieldWithTypeTag

Generate field with gorm column type tag

modelPkgName

Generated model code’s package name.

outFile

Generated query code file name, default: gen.go. It names the entry file
(Use/SetDefault/Q) only; every model always gets its own <model>.gen.go
regardless.

outPath

Specify a directory for output (default “./dao/query”)

tables

Specify tables want to be generated from, default all tables. Names are
comma-separated, whitespace-trimmed, empty entries dropped.

eg :

--tables="orders"       # generate from `orders`

--tables="orders,users" # generate from `orders` and `users`

--tables=""             # generate from all tables

Generate some tables code.

withUnitTest

Generate unit test, default value false, options: false / true

fieldSignable

Use signable datatype as field type, default value false, options: false / true

Example

gentool -dsn "user:pwd@tcp(localhost:3306)/database?charset=utf8mb4&parseTime=True&loc=Local" -tables "orders,doctor"

gentool -c "./gen.tool"

version: "0.1"
database:
  # consult[https://gorm.io/docs/connecting_to_the_database.html]"
  dsn : "username:password@tcp(address:port)/db?charset=utf8mb4&parseTime=true&loc=Local"
  # input mysql or postgres or sqlite or sqlserver or clickhouse
  db  : "mysql"
  # enter the required data table as a LIST, or leave it empty for all tables
  # tables:
  #   - orders
  #   - users
  tables:
  # only generate models (without query file)
  onlyModel : false
  # specify a directory for output
  outPath : "./dao/query"
  # query code file name, default: gen.go
  outFile : ""
  # generate unit test for query code
  withUnitTest : false
  # custom unit test template file path for query code
  unitTestTemplate : ""
  # generated model code's package name
  modelPkgName : ""
  # generate with pointer when field is nullable
  fieldNullable : false
  # generate with pointer when field has default value
  fieldCoverable : false
  # generate field with gorm index tag
  fieldWithIndexTag : false
  # generate field with gorm column type tag
  fieldWithTypeTag : false
  # generate field with gorm default tag
  fieldWithDefaultTag : false
  # detect integer field's unsigned type, adjust generated data type
  fieldSignable : false
  # create default query in generated code
  withDefaultQuery : false
  # generate code without context constrain
  withoutContext : false
  # generate code with exported interface object
  withQueryInterface : false
  # generate code with generic
  withGeneric : false
  # emit "any" instead of "interface{}" in generated code (requires Go 1.18+)
  useAny : false

Note that tables must be a list — a scalar string fails YAML decoding with
cannot unmarshal !!str ... into []string.