I've got 3 classes:
class Author {
static hasMany = [books: Book]
static belongsTo = [company: Company]
String name
}
class Book {
static mapping = {
collection "documents"
id generator: 'assigned',index: true, indexAttributes:[background:true, unique:true, dropDups:true]
}
String id
String name
}
class Company {
static mapping = {
collection "documents"
id generator: 'assigned',index: true, indexAttributes:[background:true, unique:true, dropDups:true]
}
String id
String name
}
I want to use
Author author = Author.getByCompanyAndBook(1,1);
but when running this Grails retrieves all the Book objects from the database.
I need those Books only as identifiers for the Author and I am not going to use those objects.
Is there a way for me to force Grails not to fetch the Books and Companies from the database?
I tried to use:
static mapping = {
books lazy: true
}
but still all of the Books and the Company were loaded.
Edit:
I am using mongo db as my database.
That's weird - collections are lazy by default, so getting an author shouldn't retrieve anything in the books collection until you access the books property. But regardless, even if it worked as expected I recommend that you avoid mapped collections. See this talk which shows why collections are unnecessarily expensive and provides workarounds to minimize the costs.
Related
I am new to Grails.
Can I use "hasOne" or "hasMany" without using "belongsTo" to another domain-class?
Thanks in advance.
Yes, you can. See examples in Grails doc: http://grails.org/doc/2.3.8/guide/GORM.html#manyToOneAndOneToOne
hasMany (without belongsTo) example from the doc:
A one-to-many relationship is when one class, example Author, has many
instances of another class, example Book. With Grails you define such
a relationship with the hasMany setting:
class Author {
static hasMany = [books: Book]
String name
}
class Book {
String title
}
In this case we have a unidirectional one-to-many. Grails will, by
default, map this kind of relationship with a join table.
hasOne (without belongsTo) example from the doc:
Example C
class Face {
static hasOne = [nose:Nose]
}
class Nose {
Face face
}
Note that using this property puts the foreign key on the inverse
table to the previous example, so in this case the foreign key column
is stored in the nose table inside a column called face_id. Also,
hasOne only works with bidirectional relationships.
Finally, it's a good idea to add a unique constraint on one side of
the one-to-one relationship:
class Face {
static hasOne = [nose:Nose]
static constraints = {
nose unique: true
}
}
class Nose {
Face face
}
Yes you can, but it behave differently
class Author {
static hasMany = [books: Book]
String name
}
class Book {
String title
}
In this case if you delete Author the books still existing and are independent.
class Author {
static hasMany = [books: Book]
String name
}
class Book {
String title
static belongsTo = [author: Author]
}
In this other case if you delete the Author it will delete all the books pf that author in cascade.
Many-to-one/one-to-one: saves and deletes cascade from the owner to the dependant (the class with the belongsTo).
One-to-many: saves always cascade from the one side to the many side, but if the many side has belongsTo, then deletes also cascade in that direction.
Many-to-many: only saves cascade from the "owner" to the "dependant", not deletes.
http://grails.org/doc/2.3.x/ref/Domain%20Classes/belongsTo.html
yes very easy like a class defintion but only specify hasMany but no need for hasOne
class Student {
String name
User userProfile
static hasMany =[files:File]
}
class User {
String uname
Student student
}
class File {
String path
Student student // specify the belongs to like this no belong to
}
Done!!
i have this issue when i want to save my object
My Customer
String firstName
String lastName
LocalDate dateOfBirth
CountryCode nationality
My CountryCode
#Audited
class CountryCode implements Serializable {
String code
String symbolA2
String symbolA3
String countryName
static constraints = {
code size:3..3, unique: true, matches: '[0-9]+'
symbolA2 size:2..2, nullable: false, unique: true, matches: '[A-Z]+'
symbolA3 size:3..3, nullable: false, unique: true, matches: '[A-Z]+'
countryName size:1..50
}
static mapping = {
id generator: 'assigned', name: 'code'
}
def beforeValidate() {
symbolA2 = symbolA2?.toUpperCase()
symbolA3 = symbolA3?.toUpperCase()
}
#Override
String toString() {
return countryName
}
}
when i try to save my object i recieve this error
Class
org.hibernate.TransientObjectException
Message
object references an unsaved transient instance - save the transient instance before flushing: lookup.iso.CountryCode
Do you have ideas how to fix this?
Thankx
Use Grails relation convention
static hasOne = [nationality:CountryCode]
at Customer class and
static belongsTo = [customer:Customer]
at CountryCode class
Check grails docs about that, especially paragraph stating about cascade saves.
If this doesn't fit your case than you need to call save() on CountryCode instance before assigning it to a Customer instance.
You can also use static embedded if apply to your case.
Another thing if you consider CountryCode as a dictionary entity, then load desired ContryCode instance from repository before assigning it to the Customer instance.
The specific reason for your error is because you haven't saved CountryCode before assigning it to the Customer, so Hibernate (the underlying ORM for Grails) considers it transient. Basically you do not have any GORM relationships (e.g, has*, belongsTo) defined. By defining a GORM relationship, you gain the ability to have cascade save/delete depending on how the relationships are defined.
Before simply adding hasOne or belongsTo to Customer and CountryCode respectively, you may want to consider how you are using CountryCode. Is CountryCode used as:
one-to-many lookup/reference/dictionary entity where many Customers may be mapped to a particular CountryCode
one-to-one unique entity where there's a unique CountryCode per Customer
To implement #1, you should define just a uni-directional relationship using belongsTo in CountryCode WITHOUT a hasOne in Customer like so:
class CountryCode {
static belongsTo = [customer: Customer]
...
}
This will create a foreign key on the Customer table referencing a particular CountryCode - basically a one-to-many.
To implement #2, you should define a bi-directional relationship using belongsTo in CountryCode WITH a hasOne in Customer like so:
class Customer {
static hasOne = [country: CountryCode]
..
}
class CountryCode {
static belongsTo = [customer: Customer]
..
}
This will create a foreign key on the CountryCode table back to a particular Customer - basically a one-to-one mapping.
I have a relationship between two domain class: User and Bank, user has many of bank and bank has many of user, the result table I call it as mm_user_banks that keep both table IDs for MM relationship.
class User {
String name
String password
Date createdAt = new Date()
Date loginAt
static hasMany = [banks:Bank]
static fetchMode = [banks: 'eager']
static constraints = {
}
static mapping = {
banks joinTable: [name: 'mm_user_banks', key: 'mm_user_id']
}
}
and Bank...
class Bank {
Long id
String name
static belongsTo = User
static hasMany = [users:User]
static constraints = {
}
static mapping = {
id generator: 'assigned'
users joinTable: [name: 'mm_user_banks', key: 'mm_bank_id'], lazy: false
}
}
I can save users with banks as well, but the problem is when I try to retrieve bank list from an user instance and it only fetch one row even if there is more than one row for this user in mm_user_banks table.
E.g:
User u = new User(name: 'user', password: 'pwd')
u.addToBanks(Bank.findById(1))
u.addToBanks(Bank.findById(2))
u.addToBanks(Bank.findById(3))
u.save(flush: true)
In database it is OK, fetching 3 rows, but when I get the user and see its bank list:
def user = User.findById(1) //OK
println "Size ${user.banks?.size()}" //only 1??? How?
Thanks in advance!
Just tested it out - "user.banks?.size()" returns "3". Are you sure that data in DB is OK?
Anyway, if you want to use eager fetching for collections then define it in "mapping" of User class (instead of "fetchMode" static field):
static mapping = {
banks joinTable: [name: 'mm_user_banks', key: 'mm_user_id'], fetch: 'join'
}
in Bank class use fetch: 'join' in mapping instead of lazy: false
Thanks so much, Sergei, but didn't worked out.
I fixed it in an ugly way, but this is was my remaining way out.
I created another domain class to mapping the MM table, so I did a mm_user_banks class. I use it to fetch records from bank or user and worked OK. To save banks for a user I actually do it in the old way as well, not changed from that. I guess this mighty not be the best way, but like I said, worked out.
I've tried "fetch: 'join'" and "lazy: false" and "static fetchMode = [banks: 'eager']" without success.
The new domain class is:
class UserBanks {
User user
Bank bank
static constraints = {
}
static mapping = {
table name: 'mm_user_banks'
user column: 'mm_user_id'
bank column: 'mm_bank_id'
}
}
I had the similar problem but in my case I had another relation between my equivalents to User and the Bank. This made the hasMany statement to use the wrong relation to map the many to many relation. In my case it was solved by adding a mappedBy statement to the relation:
class Bank{
...
static mappedBy=[users:'banks']
...
}
and
class User{
...
static mappedBy=[banks:'users']
...
}
or as it was in my case, since it was a uni-directional relation:
class ArticleGroup {
String name
static hasMany = [articles:Article]
static mappedBy = [articles: 'none']
static constraints = {
name(nullable:false, blank:false, unique:true, maxSize:100)
}
static mapping = {
table 'article_group'
sort 'name'
articles joinTable: [name:'article_group_article', key: 'articleGroup_id', column:'article_id'], fetch: 'join'
}
I'm creating a (theoretically) simple hasMany relationship within a domain class. I have two tables with a foreign key relationship between the two. Table 1's domain object is as follows:
Functionality{
String id
static hasMany = [functionalityControllers:FunctionalityController]
static mapping =
{
table 'schema.functionality'
id column:'FUNCTIONALITY_NAME', type:'string', generator:'assigned'
version false
}
}
and domain object 2
FunctionalityController
{
String id
String functionalityName
String controllerName
static mapping =
{
table 'schema.functionality_controller'
id column:'id', type:'string', generator:'assigned'
version:false
}
}
The issue I am having is that when I have the hasMany line inside of the Functionality domain object, the app won't start (both the app and the integration tests). The error is org.springframework.beans.factory.BeanCreationException leading to Invocation of init method failed; nested exception is java.lang.NullPointerException.
Any help would be appreciated.
UPDATE:
*Working Domains*:
class Functionality {
String id
static hasMany = [functionalityConts:FunctionalityCont]
static mapping =
{
table 'schema.functionality'
id column:'FUNCTIONALITY_NAME', type: 'string', generator: 'assigned'
functionalityConts( column:'functionality_name')
version false;
}
}
and
class FunctionalityCont {
String id
String functionalityName
String controllerName
static belongsTo = [functionality: Functionality]
static contraints = {
}
static mapping =
{
table 'schema.functionality_controller'
id column:'id', type: 'string', generator: 'assigned'
functionality(column:'FUNCTIONALITY_NAME')
version false;
}
}
Well 2 things...
1.I'm not sure but I guess that your domain class with the prefix 'Controller' maybe is the responsible, this is because grails is convention over configuration and by convention the controller class ends with Controller prefix and are in the controller folder, in this case is a lil' confusing
2.In GORM and in this case the relationship between objects can be unidirectional or bidirectional, is your decision to choose one, but in both cases there are different implementations, the class Functionality(btw is missing the 'class' word) has the right relationship to FunctionalityController through hasMany, but FunctionalityController doesn't knows about the relationship, so you can implement:
// For unidirectional
static belongsTo = Functionality
// For bidirectional
static belongsTo = [functionality:Functionality]
// Or put an instance of Functionality in your domain class,
// not common, and you manage the relationship
Functionality functionality
So check it out and tell us pls...
Regards
Try adding
static belongsTo = [functionality: Functionality]
to your FunctionalityController class. I suspect there is more to your error than what you've shown, but generally a hasMany needs an owning side to it. Since that is where the foreign key actually lives.
Have been trying to look for an answer for hours, but have so far not managed to come up with an adequate solution, so I'm hoping someone here might have some more experience with Grails, and implementing custom relationships in it.
My problem is that I have two classes:
Company
OrderConfig
OrderConfig contains two references to Company. 1 for a consignee, 1 for a shipper. I implemented the relationship (see below), and everything looks dandy, with my order_config table containing both a consignee_company_id column and a shipper_company_id column.
However, I do not want or need a company_id column at all. I would prefer using the CompanyName as the identifying column. How can I prevent Grails from automatically adding the id column to the company table, and instead use the companyName column as the primary key, thus ensuring my order_config table will be generated containing the companyName and not the company_id?
I tried embedding the company in the orderconfig class, and wrestled with all kinds of other options including the mappings, however I ran into trouble with each and every one of them.
Thanks in advance!
My code so far:
class OrderConfig {
static hasMany = [consignee:Company, shipper:Company]
String toString() {
return "${consignee}"
}
static constraints = {
consignee (blank:false, maxSize:10)
shipper (blank:false, maxSize:10)
}
Company consignee
Company shipper
}
class Company {
String toString() {
return "${companyName}"
}
static constraints = {
companyName(blank:false, maxSize:10)
companyAddress1(blank:false, maxSize:40)
companyAddress2(blank:false, maxSize:40)
companyAddress3(blank:false, maxSize:40)
companyAddress4(blank:false, maxSize:40)
companyZipCode(blank:false, maxSize:36)
companyCountry(blank:false, maxSize:36)
}
String companyName
String companyAddress1
String companyAddress2
String companyAddress3
String companyAddress4
String companyZipCode
String companyCountry
}
You need to look at the advanced GORM config options in the documentation, in section 5.5.2.1
There is an example
class Person {
String firstName
static hasMany = [addresses:Address]
static mapping = {
table 'people'
firstName column:'First_Name'
addresses joinTable:[name:'Person_Addresses', key:'Person_Id', column:'Address_Id']
}
}
there you can see how they are specifying the key and column name on which to do the stuff.
Edit -- I reread your question: if you are asking how to change it so Company has an assigned id, you might be able to do something like this example
static mapping = {
id generator:'assigned', column:'column_name',name:'propertyName'
}
where more options are available here: http://www.grails.org/doc/1.3.x/ref/Database%20Mapping/id.html