Grails not setting database up as expected - grails

Question

Hi this have been going on for several months now and I have lost all hope.
I have 3 domains in question.
Product which is made up of Components, each Component can have alternative products.
Here are my models:
Product:
class Product {
String name
String comments
static hasMany = [components:Components]
}
Component:
class Components {
Product product
static hasMany = [alternatives:Alternatives]
}
Alternatives:
class Alternatives {
Product product
}
To populate this I am parsing an excel Spreadsheet here is the code that does it:
Product st = new Product(
name: row.getCell(0).getStringCellValue().toUpperCase(),
comments: "test"
)
row.getCell(10).getStringCellValue().split("[|]").each {
Product pro = Product.findByName(it.toUpperCase())
if(pro) {
Components c = new Components(product: pro).save(flush:true)
s.add(c)
// Does not work
//st.addToComponents(c)
}
}
st.save(flush:true,failOnError:true)
This does not create a table in the database called product_components. this is what I would expect.
When I try and use addTo the component has a product instance associated with it, the product instance is then changed to the st product instance which I am trying to save it to.
I hope that makes sense.
I have found out that it is mapping the product in the Components domain as the component in the Product domain.
I am now assuming that using mapped by in the Product table may fix it
static MappedBy = [components : //do something here ]
Found the answer see bellow:
I had to add the following in my Product domain.
static mappedBy = {components joinTable: [name:'product_components',
column:'COMPONENTS_ID',
key: 'PRODUCT_ID']}
and change the name of product to part_of in my Components domain.

Answer 1

The way you have it set up now, your Components class only allows one product. So you have a one-to-many relationship from Product to Components, this is the reason the join table product_components is not being created.
You are also trying to assign a Components instance to multiple products:
// To the 'pro' Product
new Components(product: pro)
// To the 'st' Product
st.addToComponents(c)
But your Components domain class only allows for one Product, which is why the referenced Product is being overwritten.
If you want your Components class to have more than one product (which is what the code you've written is trying to accomplish), you'll have to add the Product class to your static hasMany block on Components:
class Components {
static hasMany = [alternatives: Alternatives, products: Product]
}
Then you can perform the following:
def c = new Components().save(flush: true)
pro.addToComponents(c)
st.addToComponents(c)
On an unrelated note, I would recommend making your domain class names singular, i.e. Alternative and Component to follow Grails' conventions and to make more sense.