Is there a way of telling GORM not to persist a property? I'm planning to define a confirm password property on my User class that I'll use for validation, but shouldn't be persisted.
Using transient key word GORM can be directed not to persist specific property.
Following code snippets shows the use of transient proerties
class Book {
static transients = [ "digitalCopy" ]
static constraints = {
releaseDate(nullable: true)
}
String author
String title
Date releaseDate
File digitalCopy
}
digitalCopy property included in transient declaration notifies GORM not to persist digitalCopy
OK - just managed to answer my own question with some more searching. Should have been more patient.
A static transients property "defines a list of property names that should not be persisted to the database. This is often useful if you have read-only getters that include logic."
http://grails.org/doc/latest/ref/Domain%20Classes/transients.html
Related
For example, I've parent class Cafee:
class Cafee {
String name
static hasMany = [
admin: Person
]
}
and a child class Person:
class Person {
String name
static belongsTo = [cafee: Cafee]
}
I've done some records to Cafee using:
def user = new Person(name: "Andrew")
def a = new Cafee(name: "Tarelka")
.addToAdmin(user)
.save()
Adding child to parent works fine, but when I trying to create Person-instance separately, for example:
def visitor = new Person(username: 'testerUser', password:'password', firstName:'Иван', lastName:'Иванов', email:'ivanov#gmail.com', isAdminCafee: false)
visitor.save(flush:true)
I get an error:
ERROR context.GrailsContextLoaderListener - Error initializing the application: object references an unsaved transient instance - save the transient instance before flushing: restorator.auth.Person; nested exception is org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: restorator.auth.Person
Message: object references an unsaved transient instance - save the transient instance before flushing: restorator.auth.Person; nested exception is org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: restorator.auth.Person
How to fix it?
There are two things going on here that aren't entirely obvious. One is that this form of belongsTo
static belongsTo = [cafee: Cafee]
is bidirectional, as compared to
static belongsTo = [Cafee]
which is undirectional; in both variants a Cafee can access its associated Person instances via its admin collection, but using the second syntax there's no direct way for a Person to know which Cafee it's associated with.
Declaring a hasMany like you did creates a Set of Persons in the class, and its name is the key you used in the hasMany map, in this case admin; it's as if you had added
Set<Person> admin
but you shouldn't because it's redundant - an AST transform adds that property to the bytecode.
Similarly, when declaring
static belongsTo = [cafee: Cafee]
a field of type Cafee with the name cafee is added to the class. It's as if you added
Cafee cafee
but again, please don't manually add either, just be aware that they're there.
So the problem is that persistent properties are not-null by default unless you override with nullable: true, so if you printed out the errors for that Person instance you'd see at least one complaining that the non-nullable cafee property is null. This works with addToAdmin because that method does a lot. If instantiates the set to a new Set interface implementation (probably just a HashSet) if it's null (which should only ever occurr when the domain class instance is new; a persistent set will never be null, just empty or containing items), then adds the Person to the collection, and finally if the relationship is bidirectional, it sets the backreference on the Person to the owning Cafee.
So all you're missing is setting the Cafee manually, either as part of the map constructor
user = new Person(cafee: a, username: 'testerUser', ...)
or later in the workflow (but before validation or saving)
user = new Person(username: 'testerUser', ...)
...
user.cafee = a
...
user.save()
For a project I'm currently working on I need to dynamically add properties to a domain class and persist them later in the database. In general, I need a key/value store attached to a "normal" domain class. Sadly I cannot use a NoSQL database (e.g. Redis).
My approach would be to handle the additional properties on a save() by identifying them within afterInsert or afterUpdate and writing them to another table - I would prefer not to use a map property within the domain class but an additional "Field" table (to better support searches).
I tried to add properties using the metaClass approach:
person.metaClass.middlename = "Biterius"
assert person.middlename == "Biterius" // OK
This works and I can identify the additional properties in the afterInsert/afterUpdate methods but it seems that I cannot change the value thereafter - i.e., the following does not work:
person.middlename = "Tiberius"
assert person.middlename == "Tiberius" // FAIL
Then I tried an Expando approach by extending the Person class by the Expando class (directly ("Person extends Expando") and via an abstract intermediate class ("Person extends AbstractPerson" and "AbstractPerson extends Expando")).
def person = new Person()
assert person in Person // OK
assert person in AbstractPerson // OK
assert person in Expando // OK
Both variants did not work - I could assign values to arbitrary "properties" but the values were not stored!
person.mynewproperty = "Tiberius" // no MissingPropertyException is thrown
println person.mynewproperty // returns null
So how can I add properties to a domain class programmatically during runtime, change them and retrieve them during afterInsert or afterUpdate in order to "manually" store them in a "Fields" table?
Or am I doing something completely wrong? Are there other / simpler ways to do this?
What about turning your DB into a "NoSQL" one?
In one of my projects, I just used a String-property to store a map as JSON-Object.
For Groovy it's not a big problem to convert between a map and a JSON-Object. And since you can access a map just like an object with properties, I found this solution very convenient.
Only drawback: you have to plan the size of your String-property in advance...
Update: sorry, just read that you want to support searches...
what about
class Person {
...
static hasMany = [extProperties:KeyValue]
...
def invokeMethod(String name, args) {
if (name.startsWith('get')) {
//an unknown properties's getter is called
}
//add same for setter
}
}
class KeyValue {
String key
String value
}
I guess such a schema would give you all freedom you need. Even without the hasMany, you can make use of invokeMethod to handle your external tables...
The getter and setter can save your values in a transient string propertie (static transients = ['myTransientProperty']). This property should be available in the afterInsert / `afterUpdate´ events.
Why don't you just create a map of strings on the domain object and store your extra data there manually? Unless you're storing complex data you should be able to cast anything you need to/from a string.
I would like to have unique constraints operate on more than 1 field for several entities. How can I achieve this with db4o?
Thanks,
Walter
Currently db4o doesn't support the UniqueConstrain on multiple fields. You can set unique-constrains only field by field, but not combine them.
#Ladlestein Well the intention is good, but it doesn't work. db4o manageds objects by it referencial identity. When you apply the unique-constrain on the Foo.name, you ensure that the reference is unique. So no other object can have the same reference to a name object. But you're not interested that the reference is unique, but you want to have a unique content of the names.
Sounds like a composite key. Can you create a new class that contains the key-constituting fields, and use a member variable with that type in place of the key-constituting fields in your original class?
i.e. where you had
class Foo {
String given_name;
String family_name;
}
instead use
class Name {
String given_name;
String family_name;
}
class Foo {
Name name;
}
and make Foo.name the unique field?
Using Grails i'm trying a dynamic finder like this one
Policy.findAllByResourceAndUser(resource,user)
But When i call this, grails raise this exception
Caused by: org.springframework.dao.InvalidDataAccessApiUsageException: object references
an unsaved transient instance - save the transient instance before flushing: gmedia.User;
nested exception is org.hibernate.TransientObjectException: object references an unsaved
transient instance - save the transient instance before flushing: gmedia.User
Do we need to save the parameter of the finder?
Where i'm wrong?
http://www.grails.org/DomainClass+Dynamic+Methods#findAllBy*
Policy.findAllByResourceAndUser(resource,user)
capital "B" in "By" is the first thing I see wrong? Is that a type on the question?
def res = new Resource(name:"resource name").save()
def user = new User(name:"My Name").save()
def policy = new Policy( user:user, resource:res, right: "right string").save()
println Policy.findAllByResourceAndUser(res,user)
not elegant, but you get the idea, there must be a problem in the way you are saving your objects
your user object will "never" get saved with that code... you have to specify values for all of you properties or define your constraints appropriately. I think you should review the documentation for Domain Objects in Grails because it appears there are fundamental problems in your approach see http://www.grails.org/GORM+-+Creating+a+domain+class
#Aaron Saunders
these are two domain class
class Resource{
static contraints={}
}
class User extends Resource{
String name
String password
String email
Date creationDate
Date lastModicationDate
}
class Policy{
Resource resource
User user
String right
static mapping={
user cascade:'all-delete-orpahn'
resource cascade:'all-delete-orpahn'
}
Maybe it a consequence of the inheritance between User and Resource
i faced the same issue today..i found the solution...there is a foreign key relation which is getting set as NULL.....so when it tries to save null it throws this exception..so make sure all the values are not null...else u may need to change the cascade definition in ur mapping xml..
Hopefully this will be an easy one to answer. I created a class in Grails called player which has this information:
class Player {
String steamId
String name
String portrait
static hasMany = {playerStatistics:PlayerStatistics}
static hasOne = {playerForumProfile:PlayerForumProfile}
}
For clarification, a Player object can have one PlayerForumProfile object, but the player object is always created BEFORE the PlayerForumProfile object. My issue is with accessing the playerForumProfile object associated with the "hasOne" property within the controller of the PlayerForumProfile class. I had assumed that doing this:
def playerForumProfileInstance = new PlayerForumProfile()
def playerInstance = Player.get(params.id)
playerForumProfileInstance = playerInstance.playerForumProfile
would result in pulling the PlayerForumProfile object associated with the playerInstance object into the playerForumProfileInstance variable, however when I try this, Grails throws an error telling me there is no such property as playerForumProfile. Is it possible to access the hasOne properties' object in such a manner or do I need to do something else?
Edit: I also tried modifying the Player class so it included a variable called playerForumProfile and editing PlayerForumProfile so it had a belongsTo declaration, but this kept resulting in a null pointer exception when running my app.
Edit: A little more info, I created a new grails app from scratch and created the relationship the way it appears in the Grails documentation and it ran with no problem so I'm thinking it may be easier just to start a new app and copy the files over.
There is hasOne feature in GORM: http://grails.org/doc/latest/ref/Domain%20Classes/hasOne.html
This answer is no longer correct for grails 2.X and greater, it was true in 2009 when originally answered.
There isn't a "hasOne" property in GORM, it's either belongsTo:
static belongsTo = [playerForumProfile: PlayerForumProfile]
or just a regular typed definition of the attribute name if there isn't a cascading relationship implied by belongsTo:
PlayerForumProfile playerForumProfile
See the one-to-one GORM documentation for details.