For instance, suppose I wanted to let that column be set to whatever the database defaults it to, without redefining that default in the domain class?
I can't find much through Google. There are hints that if I were working with Hibernate directly, I could set that particular column/property to private, and this might accomplish what I seek.
I can of course leave that column undefined, and GORM ignores it. But I need the values out of it whenever the Grails app does a select.
You can use the GORM property insertable as in doc or can read the value with a beforeInsert event:
class Book {
String title
String isbn
static mapping = {
isbn nullable: false
}
def beforeInsert {
title = queryFromDatabase...
}
}
I think you have to go the beforeInsert / Hibernate interceptor route since your requirement is to read default values from an existing database.
You can read the database default values for columns with JDBC's DatabaseMetaData.getColumns .
To find out the database table and column names, you can use something like this (this code is not tested)
import org.codehaus.groovy.grails.orm.hibernate.cfg.GrailsDomainBinder
import org.codehaus.groovy.grails.orm.hibernate.cfg.Mapping
import org.codehaus.groovy.grails.commons.DomainClassArtefactHandler
def gdc=grailsApplication.getArtefact(DomainClassArtefactHandler.TYPE, someInstance.class.name)
Mapping mapping=GrailsDomainBinder.getMapping(gdc)
def tableName=mapping.tableName
def columnName=mapping.getPropertyConfig('someColumn').column
This is not a complete answer, but I hope this helps.
Related
I'm trying to learn Grails but am still pretty much on beginner level.
I made a tiny application, where you can basically add events, and people can write reviews about them and rate them.
So I have an eventController and reviewController. The rating is just an Integer in a review. But now I want to show an overall rating for an event. So the events rating should be the average value of the corresponding ratings value.
This is my event domain code where the rating is initially set, I left out the constraints and toString:
class Event {
Double dRating = 2
static hasMany = [ratings:Rating]
}
The controller is simply:
class EventController {
def scaffold = Event
}
The rating domain file:
class Rating {
String comment
java.util.Date date = new java.util.Date()
Integer rating
Event event
}
and the Rating Controller is:
class RatingController {
def scaffold = Rating
}
Hope I didn't make mistakes, I had to translate variable names so they're understandable.
I'm guessing that where dRating is set, I could somehow add some calculation, but I don't even know how to access the values of the rating, and everything I try ends in lots of errors and having to restart the app again and again. I tried adding calculations in the controller, but there I don't know how to get the value into the database. So where do I actually put the logic, and how do I access the values?
If any other file is important, please tell me.
Hoping to get some hints on how to start doing this, I didn't think it would be this hard.
At first I would recommend start reading grails doc. Later from your question it is not much clear what you are asking a there could be several places or possibilities of setting up the value in domain field and persist it to database. I'm telling all of these which are known to me:
If it is generalised calculation that needs to be applied to your dRating field, then create a setter with standard bean naming convention and do this there. For example, you want to find percentage from say 1000 and then add it to dRating
class Event {
static hasMany = [ratings:Rating]
Double dRating
void setDRating(Double value){
this.dRating = value * 100/1000 // alternatively value /10
}
}
Do it in commandObject: If you don't want to put certain calculations and validation in domain then put these in command objects. See this. You can at any point of time assign values from command object to domain object by .properties binding mechanism. For example,
yourDomainObject.properties = yourcommandObjectObject.properties
Remember properties having same name would be binded.
Do it in service: You can do your calculations in service method, inject that service into your controller and call that method to perform calculations and even to persist to db as well. Remember services are by default transactional.
Hope it helps!
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'm feeling a little slow today. I'm trying to do something that I think is very simple. I have a Domain class with a property called 'name'. I want 'name' to have an index, and I want the index to require that the 'name' is unique. I've set the unique constraint and tried creating an index. I can't make sense out of the Gorm docs as to how I add the unique attribute to the index. Here's some code:
class Project {
String name
static hasMany = [things:Things]
static mapping = {
name index:'name_idx'
}
static constraints = {
name(unique:true)
}
}
All is well with the above, except when do "show indexes from project" in mysql it shows my name key as not unique. I know the problem is that I am not specifying unique in the mapping, but quite frankly the docs for gorm are making my head hurt. I see all kinds of stuff about columns, but I can't find a single example anywhere on the web that shows what I want to do. I don't need complex mappings or compound keys, I just want to know the syntax to add the unique attribute to the mapping declaration above. Any advice welcome.
I also did a grails export-schema and see the following:
create index name_idx on project (name);
Nothing in that to indicate this index requires unique values
A related followup question would be once I succeed in making that index unique, what type of error should I expect when I go to save a Project instance and the name is not unique? Is there a specific exception thrown? I realize that even if I check that a given 'name' is unique there's still a possibility that by the time I save it there may be a row with that name.
I'm quite sure the syntax to do what I want is simple but I just can't find a simple example to educate myself with. I've been to this page but it doesn't explain HOW the uniqueness is enforced. I'd like to enforce it at the name index level.
The indexColumn allows additional options to be configured. This may be what you're looking for.
static mapping = {
name indexColumn:[name:'name_idx', unique:true]
}
Grails Documentation for indexColumn
If you put only the unique constraint the GORM send DDL to create an unique index on database.
static constraints = {
name nullable: false, unique: true
}
I know this is simple question but taking more time
How to find first record from table in grails .
I need to get only the first record with out knowing the id number .
Is there any method like find :first in grails ?
thanks in advance .
Updating to Grails 2.1.1 or later adds two new methods (first and last) for GORM to address this needed feature.
From the docs:
class Person {
String firstName
String lastName
Integer age
}
// retrieve the first person ordered by the identifier
def p = Person.first()
// retrieve the first person ordered by the lastName property
p = Person.first(sort: 'lastName')
// retrieve the first person ordered by the lastName property
p = Person.first('lastName')
Well, you have to define by what measure this record is supposed to be the "first".
Assuming that you mean the record with the earliest creation timestamp, the easiest and most robust approach would be to add a dateCreated property to your domain class and then querying for the entity with the lowest such date. In fact you don't even have to set the creation date manually, because Grails does this for you (as long as you name the property dateCreated) - see Automatic timestamping in the Grails Documentation.
The HQL query would be something like:
def firstObject = YourClass.find("FROM YourClass ORDER BY dateCreated")
Check out hibernate criteria and projections, e.g:
def location = Location.createCriteria()
def firstRecord = location.list{
maxResults(1)
order("id","asc")//assuming auto increment just to make sure
}[0]
http://grails.org/doc/1.0.3/ref/Domain%20Classes/createCriteria.html
If timestamp doesn't matter, you could try if Daniel's answer without ORDER BY works, i.e.
def firstObject = YourClass.find("FROM YourClass")
You can use the grails findBy methods to return the first result of a query.
-> From the 1.3.7 docs
findBy*
Purpose
Dynamic method that uses the properties of the domain class to allow
the creation of Grails query method expressions that return the first
result of the query
-> from the latest docs
findBy* Purpose
Dynamic method that uses the properties of the domain class to execute
a query returning the first matching result.
I have a domain class which has two dates in it and I want one of them populated with the current time when a record is created for the object, like a create timestamp...
class Contact {
Date initiatedDate
Date acceptedDate
}
Is it sufficient just to new a Date object on one of them and make the other nullable until such a time as I need to fill it, sort of like this...
class Contact {
static constraints =
{
acceptedDate(nullable:true)
}
Date initiatedDate = new Date()
Date acceptedDate
}
I'm experimenting, but I would like to know whether this is the right way to go about it or whether there is something more Grailsy or GORMy I should do in, say, an init function or by tweaking the domain object definition to have one by default, like it does an id and version.
Thanks
What you've written should work but you can use the GORM auto-timestamping feature by simply adding a field:
class Contact {
Date dateCreated
}
If you want to keep your own names for the fields the same grails docs also show you how to use GORM events to set fields on save or update.
HTH