Comment.groovy

package jp.grails

import javax.persistence.*
import org.datanucleus.jpa.annotations.Extension
//import org.hibernate.annotations.*

@Entity
class Comment implements Serializable {
  static belongsTo = [todo:Todo]
  
  @Id
  //@GeneratedValue(generator="system-uuid")
  //@GenericGenerator(name="system-uuid",strategy = "uuid")
  @GeneratedValue(strategy=GenerationType.IDENTITY)
  @Extension (vendorName = "datanucleus",key = "gae.encoded-pk", value = "true")
  String id
  
  @Column
  String message

  @Column
  String user
  
  @Column
  Date dateCreated = new Date()
  
  @ManyToOne
  Todo todo

  static constraints = {
    todo()
    dateCreated display:false
    message()
    user()
    dateCreated()
  }
  String toString(){
     "$message by $user ${dateCreated.format('yyyy/MM/dd HH:mm:ss')}"
  }
  
}

Todo.groovy

package jp.grails

import javax.persistence.*
import org.datanucleus.jpa.annotations.Extension
//import org.hibernate.annotations.*

@Entity
class Todo implements Serializable{
  static hasMany = [comments:Comment]
  
  @Id
  //@GeneratedValue(generator="system-uuid")
  //@GenericGenerator(name="system-uuid",strategy = "uuid")
  @GeneratedValue(strategy=GenerationType.IDENTITY)
  @Extension (vendorName = "datanucleus",key = "gae.encoded-pk", value = "true")
  String id

  @Column
  String content

  @Column
  String user
  
  @Column
  Date due
  
  @OneToMany(mappedBy="todo")
  List<Comment> comments
  
  static constraints = {
    content()
    user()
    due()
  }
  String toString(){
     content
  }
  
}