I'm writing a Grails application and I need to retrieve a persistent value for the collection of my domain class objects. Let's consider we have got the following domain object:
class UserGroup {
SortedSet<User> users
static hasMany = [ users: User ]
// ...
def beforeUpdate() {
println "BEFORE UPDATE: " + this.getPersistentValue('users');
}
}
class User implements Comparable<User> {
String name
}
And the controller which has the following action:
class UserGroupController {
def addUser() {
UserGroup group = UserGroup.get(params.long('gid'))
User user = User.get(params.long('uid'))
group.addToUsers(user)
group.save(failOnError:true, flush:true)
}
}
The problem is that when beforeUpdate() is called, the users collection already contains the recently added user. So, seems that addTo() method doesn't trigger the beforeUpdate() event.
The same problem occurs when we're talking about isDirty() method. As the changes are applied before the beforeUpdate() is called, the collection is not recognized as dirty field.
Does anyone know how to change this? I'm writing a feature which tracks the history of changes for lots of different object, so I need to have access to the previous value in order to understand whether its value was changed or not.
I have had a similar issue, where things are being updated when I wasn't expecting them when I used the .get() on domain classes. I like to use .read() now because it wont update the database when I'm not expecting it to. Grails does a lot of sneaky things behind the sense which are helpful I think but can be a bit confusing.
Related
I need to use a complex query on my Grails application. Instead of using a complex criteriaBuilder(), I instead performed the following:
Created View on the database, say ParentChildView.
Mapped it into a domain class.
Use this ParentChildView domain class to perform a .list() operation.
I'm wondering if I can configure this domain class to something like "select-only mode" or "no-insert-allowed mode"?— you know, just to make sure an Exception will be thrown if some developer accidentally tries to insert to this domain.
As per my understanding of your question, you don't want insertion to happen or for sure updates as well.
Your action could be one from these.
User meta-programming and make save method throw an exception for domain. e.g.
User.metaClass.static.save = {
throw new IllegalStateException("Object is not in a state to be save.")
}
You could use hooks if not sure about meta-programming as below.
def beforeInsert() {
throw new IllegalStateException("Object is not in a state to be save.")
}
def beforeUpdate() {
throw new IllegalStateException("Object is not in a state to be updated.")
}
def beforeDelete() {
throw new IllegalStateException("Object is not in a state to be deleted.")
}
Haven't tried mapWith for inserts / updates as it actually don't allow creation of a table but everything like a domain is available.
static mapWith = "none"
Last but not least we could also use transactions but these won't be of that much help. Like in service you could use #Transactional(readOnly=true). But this will just help in services.
Also, you could disable versioning and want cache just only for reads.
static mapping = {
cache usage: 'read-only'
version false
}
I found this topic about read-only domain very helpful and worth.
I'm not sure about third bullet but you could try this as well.
Hope It would help!
Say we have something like the standard Book domain object and bookCategory object. In my controller I want to return a subset of list of books to the view. That subset is not achievable using a find query. When I try to filer the return object, it deletes relationships from the database!
I tried this:
class BookCategory{
String name
static hasMany = [books:Book]
}
class Book{
String title
}
def myController() {
def categories
categories = BookCategory.list()
def user = getCurrentUser()
categories.each { category ->
category.books.removeAll { book ->
!isBookBannedForThisUser(book.title, user)
}
[bookCategories: categories]
}
}
The problem is that it permanently removes these books from the categories for all users from the database!!!
I tried putting the method in a service and using a readonly transaction, but this did not help.
I assume that even if I copy all the categories and books into new list, they will still update the DB as they will still have the book IDs (which I need)
Saving to the database when you dont say save() is very dangerous. is there a way to disable this feature completely?
There is a fundamental flaw in your approach. Do not modify your domain instances if you don't intend to have the changes persisted. Doing so is going to cause you headaches.
Your domain model is suppose to be your system of record. Any changes to it are suppose to be persisted.
If you need to gather up data and manipulate it without having it reflected in your domain model then use a DTO (data transfer object) or similar pattern.
Simply calling .discard() will discard the changes you have made from being persisted when the session automatically flushes.
Instead of working against the framework, and disabling behavior, change your approach to be correct.
I'm making a web app that stores reports of various types as domain objects, so I have a domain object HeadOfHousehold which contains name data, and references to other domain objects such as the reports, addresses, and any dependants. I am trying to build a list of recently viewed/created HeadOfHousehold objects. After multiple Google searches, and scouring the manual, it appeared that a service would be an appropriate solution. So I created ClientListService:
#Transactional
class ClientListService {
static scope = "session"
String message // right now I'll be happy to just see the same message across
// pages I can add a list and manipulate it later.
}
I thought I could then reference it in my various controllers, and it would persist Something like this:
def clientListService
def index(){
hasSearched = false
clientListService = new ClientListService(message: "Hello")
[errorMessage: params.errorMessage, clients:clientListService]
}
Which should be available in a later controller:
class HeadOfHouseHoldController {
def clientListService
def index() {
[customer: HeadOfHousehold.get(params.id), clients: clientListService]
}//...
However when I try to get the message, it appears as if the object is null.
From my index.gsp:
***************${clients?.message}********************
So I don't know if I am not defining session properly (I'm not doing anything special to do so), if I'm misunderstanding how the session scope works, or something else. I do see the proper message on the original page which has defined the object, however I don't see it on any subsequent pages.
Also, I'm not sure if this is the proper way to go about this; right now all I really need is the list of HeadOfHouseholds that I would need (so I can add to the list from other pages), however I can see possibly adding other logic and items into such a class.
I think you understood the session scope correctly. Each Spring bean with a session scope is bound to the HTTP session.
But your first controller listing does it all wrong. You are not supposed to instantiate the service class yourself. This is what Spring (Grails) does.
class FooController {
def clientListService // gets autowired by Grails/Spring
def index(){
hasSearched = false
clientListService.message = 'Hello' // only assign a String value to the service
[errorMessage: params.errorMessage, clients:clientListService]
}
}
This means you cannot not do something like
clientListService = new ClientListService(message: "Hello")
and expect your code to work. Hope this helps.
I'm still new to Grails and GORM and I got stumped on this and wasn't able to figure out what I am doing wrong. The intent is to automatically relate the record to the logged in user through the Shiro plugin for Grails.
Class User { static hasMany = [stuff: Stuff] }
Class Stuff { static belongsTo = [user:User] }
Class StuffController {
def create = {
params.put('user', User.createCriteria().get{eq('username',SecurityUtils.subject.principal)}.id)
def stuffInstance = new Stuff(params)
stuffInstance.save()
}
}
I saw in the generate-views version of the create scaffold that the relevant field was referred to as name="user.id", but neither it nor variants (such as user_id) seems to work. The query to the Users domain returns the record id necessary, and params.put in this context seems to correctly append the params object with the new value when I render to a test page (so I'm guessing it's not immutable), but this is what I get from the save():
Property [user] of class [class org.stuffing.Stuff] cannot be null
I've even tried flipping it around and going the other way, with the same result:
User.createCriteria().get{eq('username',SecurityUtils.subject.principal)}
.addToStuff(new Stuff(params))`
.save()
Anyone able to enlighten me on what I'm missing here?
Thanks!
EDIT:
Apparently I was being braindead; I was overriding the "create" method, but the default action is "save" in the _form.gsp template, so it wasn't executing that branch.
On the plus side, I did learn about dynamic finders via Burt below, so it wasn't a total wash.
Thanks for your time, guys!
Your code can be a lot cleaner - there's no reason to use createCriteria here. If you're searching by username, use a dynamic finder:
def stuffInstance = new Stuff(params)
def user = User.findByUsername(SecurityUtils.subject.principal)
stuffInstance.user = user
if (!stuffInstance.save()) {
// inspect stuffInstance.errors
}
I have two domain objects:
Customer
CustomerConfig
Customer has a 1-1 association with CustomerConfig. There is a default CustomerConfig with default settings for Customers who do not have an explicitly saved CustomerConfig e.g.
def getConfig() {
if (!config) {
return new CustomerConfig() //the default settings
} else {
return config
}
}
The problem I am having is that when I return the default setting GORM saves the CustomerConfig instance to the database as it appears to GORM that it has changed.
In fact I do not want to save it to the database as I want to be able to control the default settings for customer and make updates for customers until they have an explicitly saved config.
I also am trying avoid using conditional logic as follows:
def config = customer.config?:new CustomerConfig()
And encapsulate it in the Customer domain object. It seems like there's a different pattern I should be following. Would welcome any advice.
Thanks,
cowper
IMHO, it's never a good idea to change behavior of default getter/setter as those are managed by GORM.
You can do something like this
class Customer {
static transients = ['setting']
public CustomerConfig getSetting(){
return getConfig()?:new CustomerConfig()
}