Constraints Usage 约束用法

Constraints provide Grails with a declarative DSL for defining validation rules, schema generation and CRUD generation meta data. An example of a set of constraints applied to a domain class are as follows: 约束为Grails提供了声明式的DSL定义，包括验证规则，schema生成（数据库相关信息的生成--译者注）和CRUD元数据的生成。比如一个领域类的约束集合如下：

class User {
    ...
    static constraints = {
        login(size:5..15, blank:false, unique:true)
        password(size:5..15, blank:false)
        email(email:true, blank:false)
        age(min:18, nullable:false)
    }
}

Refer to the user guide topic on Constraints for more information. 更多信息请参照用户指南约束主题。