In grails, I have two domain classes Question and QuestionOption.One question have many options.Each option has a question. I went through 4 different scenario. These scenarios has combination of instantiation-namedQuery , belongsTo-namedQuery , instantiation-hasMany and belongsTo-hasMany.
Scenario 1:
class Question
{
String quesText
static constraints={}
static namedQueries={
getAllQuestionOptions{question->
return QuestionOption.findAllWhere(question:question)
}
}
}
class QuestionOption
{
String optionText
Question question
static constraints={}
}
.
Scenario 2:
class Question
{
String quesText
static constraints={}
static namedQueries={
getAllQuestionOptions{question->
return QuestionOption.findAllWhere(question:question)
}
}
}
class QuestionOption
{
String optionText
static constraints={}
static belongsTo=[question:Question]
}
.
Scenario 3:
class Question
{
String quesText
static constraints={}
static hasMany=[questionOption:QuestionOption]
}
class QuestionOption
{
String optionText
Question question
static constraints={}
}
.
Scenario 4:
class Question
{
String quesText
static constraints={}
static hasMany=[questionOption:QuestionOption]
}
class QuestionOption
{
String optionText
static constraints={}
static belongsTo=[question:Question]
}
I used all these scenarios with mysql and all resulted with same schema
mysql> desc question;
+-------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+--------------+------+-----+---------+----------------+
| id | bigint(20) | NO | PRI | NULL | auto_increment |
| version | bigint(20) | NO | | NULL | |
| ques_text | varchar(255) | NO | | NULL | |
+-------------+--------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
mysql> desc question_option;
+-------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+--------------+------+-----+---------+----------------+
| id | bigint(20) | NO | PRI | NULL | auto_increment |
| version | bigint(20) | NO | | NULL | |
| option_text | varchar(255) | NO | | NULL | |
| question_id | bigint(20) | NO | MUL | NULL | |
+-------------+--------------+------+-----+---------+----------------+
What is difference between using these scenarios in the terms of cascading , unidirectional-bidirectional and aggregation-composition? Bidirectional means when both entity knows about each other.Unidirectional means first entity know about second but reverse is not true. To understand cascading I referred this: http://www.mkyong.com/hibernate/hibernate-cascade-example-save-update-delete-and-delete-orphan/ . Please help
