Grails 中的对象关系映射答案

【问题标题】：Object relational mapping in GrailsGrails 中的对象关系映射
【发布时间】：2016-12-08 09:07:00
【问题描述】：

我有 2 个名为“employees”和“dataentry”的表。我需要将employees表中的employee_id列设置为主键，并将dataentry中的employee_id列设置为employees.employee_id的外键。我怎样才能在 groovy 域类中做到这一点。

here is my employees.groovy model class

package com.standout.utilityapplication

import java.util.Date;
import com.standout.utilityapplication.Dataentry

class Employees {

static mapping = {
	    table 'employees'
		version false
   }

        static hasMany = [employee_id:Dataentry]
		String employee_id
		String employee_name
		String team
		Long contact_no
		String designation

		
		
		static constraints = {
			
			employee_id(nullable: false,maxSize:10)
			employee_name(nullable: false,maxSize:100)
			team(nullable: true,maxSize:40)
			contact_no(nullable: true,maxSize:10)
			designation(nullable: true,maxSize:40)
			
		}

}

and here is my dataentry.groovy model class

package com.standout.utilityapplication
import com.standout.utilityapplication.Employees

class Dataentry {

	static mapping = {
		table 'dataentry'
		version false
   }
	    static belongsTo = [employee_id:Employees]
		String employee_id
		String team
		Date receipt_dt
		String restaurant_name
		int number_of_persons
		float amount
		Date bill_submitted_dt
		String reimbursed
		char presented_bank_fl
		Date presented_bank_dt
		String create_id
		Date create_dt
		String mod_id
		Date mod_dt
		
		
		static constraints = {
			reimbursed(nullable: true)
			presented_bank_fl(nullable: true)
			presented_bank_dt(nullable: true)
			mod_id(nullable: true)
			mod_dt(nullable: true)
		}

}

请告诉我如何使用级联进行映射

【问题讨论】：

标签： grails grails-orm

【解决方案1】：

类似的东西应该让实体加入。约定是以单数命名实体，而不是复数（Employee，不是Employees）：

class Employee {
    static hasMany = [dataentries:Dataentry]
    static mapping = {
        id name:'employee_id'
    }
}

class Dataentry {
    static belongsTo = [employee:Employee]
}

让系统处理细节。

【讨论】：