I am working with Grails 3.2.8. I would like to allow both options when generating an id. Is there a way to use assigned and falling back to sequence if unassigned? I tried getting the next id within a constructor and setting id there but running into issues. Any help/guidance would be most appreciated.
class Foo {
static mapping = {
id generator:'assigned'
}
}
vs
class Foo {
static mapping = {
id generator:'sequence'
}
}
Ive tried using mapping set to assigned and setting the id within the domain constructor of beforeValidate function. Neither are working for me. Examples below.
class Foo{
Foo(){
def id = Foo.find("from Foo order by id desc")
id = id ? id : 0
this.id = id
}
static mapping = {
id generator:'assigned'
}
}
class Foo{
def beforeValidate() {
def id = Foo.find("from Foo order by id desc")
id = id ? id : 0
this.id = id
}
static mapping = {
id generator:'assigned'
}
}
Thanks in advance for your help.
Is there a way to use assigned and falling back to sequence if
unassigned?
No, not directly anyway. You could use assigned and when you wanted to fall back on the sequence you could send a query to the database to retrieve the next sequence value and then assign it yourself. I think that is probably as close as you can probably get.
First of all, you need to understand HQL; in your examples you are returning Foo not id, so it's clearly wrong.
Second, you shouldn't depend on the table for next value of id, because it's not guaranteed to be correct -- you might face id is not unique kinda errors.
Third, you aren't incrementing the id, this way you will end up getting the same, most likely 0, every time.
Here is what you can do, use database sequence -- depends on the database.
"select id_seq.nextval from dual" // for Oracle
Finally, it's a very bad idea -- unless you are having a very good reason for it.
Related
I am currently trying to unwind a list of objects that I want to merge to the database using the Neo4J Client. What I would like to do is unwind the list and create the nodes with a label generated based on a property from the items themselves instead of hardcoding a label name. From what I can find I have to use the APOC merge method to do so. However, I am unable to translate this to the Neo4J client. In the neo4J explanation they yield a node after the apoc.merge.node call and then return the node. However, I cannot simply return the node nor can I set the node (I got to the point of just messing about, and at one point I got the labels to work but it overwrote all properties with the last item in the list).
I seem to miss something fundamental but i'm not quite sure what. Does anyone here know how to do this with neo4J client (and if possible, give a bit of an explanation what is going on)? I am very new to the development world and I feel I am just missing a crucial piece of understanding when it comes to this..
The code that I tried that turned all properties into the last node's properties but at least created the labels as I expected:
public async void CreateBatchItems(List<TToDataBase> itemList)
{
await Client.Cypher
.Unwind(itemList, "row")
.Merge("(n)")
.With("row, n")
.Call("apoc.merge.node([n.Name], n)").Yield("node")
.Set("n += node")
.ExecuteWithoutResultsAsync();
}
Thank you in advance!
Edit:
Some clarification about the input:
The objects are actually very basic, as (at least for now), they merely contain a name and an objectID (and these object ID's are later used to create relations). So its a very basic class with two properties:
public class Neo4JBaseClass
{
public Neo4JBaseClass() { }
public Neo4JBaseClass(string name, string objectId)
{
Name = name;
ObjectId = objectId;
}
[JsonProperty(PropertyName = "ObjectId")]
public string ObjectId { get; set; }
[JsonProperty(PropertyName = "Name")]
public string Name { get; set; }
}
I have also tried a slight variation where this class also has the added property
[JsonProperty(PropertyName = "PropertyMap")]
public IProperty PropertyMap { get; set; }
where PropertyMap is another basic object holding the name and objectId. This seemed like a good idea for future proofing anyway, so the propertylist can be easily expanded without having to change the base object.
[EDITED]
The main issue is that Merge("(n)") matches any arbitrary node that already exists.
You have not shown the data structure for each element of itemList, so this answer will assume it looks like this:
{Name: 'SomeLabel', id: 123, Props: {foo: 'xyz', bar: true}}
With above data structure, this should work:
public async void CreateBatchItems(List<TToDataBase> itemList)
{
await Client.Cypher
.Unwind(itemList, "row")
.Call("apoc.merge.node([row.ObjectId], row.id)").Yield("node")
.Set("node += row.Props")
.ExecuteWithoutResultsAsync();
}
[UPDATE]
The data structure you added to your question is very different than what I had imagined. Since neither of the properties in a row is a map, .Set("node += row.Props") would generate an error.
Using your data structure for each row, this might work:
public async void CreateBatchItems(List<TToDataBase> itemList)
{
await Client.Cypher
.Unwind(itemList, "row")
.Merge("(n:Foo {id: row.ObjectId})")
.Set("n += row.Name")
.ExecuteWithoutResultsAsync();
}
This code assigns the node label Foo to all the generated nodes. A node should always have a label, which improves clarity and also tends to improve efficiency -- especially if you also create indexes. For example, an index on :Foo(id) would make the above query more efficient.
This code also assumes that the id property is supposed to contain a unique Foo node identifier.
I'm not a programming savvy person, so please bear with me.
I've read blog entries and docs about command object. I've never used it and was wondering if I should. (I probably should...)
My project requires parsing, sorting, calculating, and saving results into database when users upload files.
So according to one of the blog entries I read and its corresponding github code,
1) SERVICE should receive file uploads, parse uploaded files (mainly docs and pdfs), sort parsed data using RegEx, and calculate data,
2) COMMAND OBJECT should call SERVICE, collect results and send results back to controller, and save results into the database,
3) CONTROLLER should receive request from VIEW, get results from COMMAND OBJECT, and send results back to VIEW.
Did I understand correctly?
Thanks.
I found this to be the best setup. Here is an example that I use on production:
Command Object (to carry data and ensure their validity):
#grails.validation.Validateable
class SearchCommand implements Serializable {
// search query
String s
// page
Integer page
static constraints = {
s nullable: true
page nullable: true
}
}
Controller (directs a request to a Service and then gets a response back from the Service and directs this response to a view):
class SomeController {
//inject service
def someService
def search(SearchCommand cmd) {
def result = someService.search(cmd)
// can access result in .gsp as ${result} or in other forms
render(view: "someView", model: [result: result])
}
}
Service (handles business logic and grabs data from Domain(s)):
class SomeService {
def search(SearchCommand cmd) {
if(cmd.hasErrors()) {
// errors found in cmd.errors
return
}
// do some logic for example calc offset from cmd.page
def result = Stuff.searchAll(cmd.s, offset, max)
return result
}
}
Domain (all database queries are handled here):
class Stuff {
String name
static constraints = {
name nullable: false, blank: false, size: 1..30
}
static searchAll(String searchQuery, int offset, int max) {
return Stuff.executeQuery("select s.name from Stuff s where s.name = :searchQuery ", [searchQuery: searchQuery, offset: offset, max:max])
}
}
Yes, you understood it correctly except the one thing: command object shouldn't save the data to DB - let service to do that. The other advantage of command object is data binding and validation of data from the client. Read more about command objects here grails command object docs
You can also find helpful information regarding your question in this article
grails best practices
I guess not. Its not really related to whether the save is done in a service it should always attempt to carry out complex stuff and specifically db stuff in a service. so that is regardless. I tend to not use command object but have got hooked on helper classes aka beans that sit in src/main/groovy and do all of the validation and formatting. I just did a form and in it has feedback and reason.
Initially I thought I would get away with
def someAction(String feedback, String reason) {
someService.doSomething(feedback,reason)
}
But then I looked closed and my form was firstly a textarea then the selection objects were bytes so above was not working and to simply fix it without adding the complexity to my controller/service I did this:
packe some.package
import grails.validation.Validateable
class SomeBean implements Validateable {
User user
byte reason
String feedback
static constraints = {
user(nullable: true)
reason(nullable:true, inList:UsersRemoved.REASONS)
feedback(nullable:true)
}
void setReason(String t) {
reason=t as byte
}
void setFeedback(String t) {
feedback=t?.trim()
}
}
Now my controller
class SomeController {
def userService
def someService
def doSomething(SomeBean bean){
bean.user = userService.currentUser
if (!bean.validate()) {
flash.message=bean.errors.allErrors.collect{g.message([error : it])}
render view: '/someTemplate', model: [instance: bean,template:'/some/template']
return
}
someService.doSomeThing(bean)
}
}
Now my service
Class SomeService {
def doSomeThing(SomeBean bean) {
if (bean.user=='A') {
.....
}
}
All of that validation would have still had to have been done somewhere, you say no validation but in a good model you should do validation and set things to be stored in proper structures to reduce overloading your db over time. difficult to explain but in short i am talking about your domain class objects and ensuring you are not setting up String something string somethingelse and then not even defining their lenghts etc. be strict and validate
if you have a text area this will be stored in the back end - so you will need to trim it like above - you will need to ensure the input does not exceed the max character of the actual db structure which if not defined will probably be 255
and by doing
static constraints = {
user(nullable: true)
reason(min:1, max:255, nullable:true, inList:UsersRemoved.REASONS)
Has already invalidated it through the bean.validate() in the controller if the user exceeded somehow my front end checks and put in more than 255.
This stuff takes time be patient
Edited to finally add in that example byte - is one to be careful of -
When adding any String or what ever I have started to define the specific like this and in the case of byte if it is a boolean true false - fine if not then define it as a tinyint
static mapping = {
//since there is more than 1 type in this case
reason(sqlType:'tinyint(1)')
feedback(sqlType:'varchar(1000)')
// name(sqlType:'varchar(70)')
}
If you then look at your tables created in the db you should find they have been created as per definition rather than standard 255 varchar which I think is the default for a declared String.
Can someone help me with my situation. I have the following code.
class Employee {
Integer empId
String firstName
String lastName
static constraints = {
empId()
firstName()
lastName()
}
static mapping = {
id generator:'assigned', name:'empId'
version false
}
}
The code allows me to save employee through 'create' but gives the following error message
"Employee not found with id null" and also in the list, all the employees are listed but clicking on any Emp Id gives the same error. Please help. This is driving me nuts.
Rocky
Thanks for your reply. Like I mentioned I am able to save the empId in the database but get that message nonetheless and see the list with assigned ids (empId). The link points to employee/show with no number at end. However employee/show/22(empId) works fine. employee/edit/22 works too but update does not work.
I am not using any assigned sequence. Just some random integer. Maybe a better example would be to use SSN instead of empId.
Thank you once again.
You are a great help buddy. Appreciate your time and patience. I am not writing any special update or save (I am too new to dig too deep). Just using grails to generate-all. However, I did find a workaround. I changed the domain class to add variable id (Long) and added empId setter method to allocate the empId value to id. That did it. Here is my code.
class Employee {
Long id
Long empId
String firstName
String lastName
static constraints = {
empId()
firstName()
lastName()
}
static mapping = {
id generator:'assigned', name:'empId', column: 'emp_id'
version false
}
public void setEmpId(Long empId){
this.empId = empId
this.id = empId
}
}
Please feel free to suggest if you have a better way of doing that.
Regards
Rocky
If you are using the "assigned" sequence, then you have to assign the objects ids yourself before saving them. Otherwise your objects will be saved with a null or 'default 0' id. If you want GORM to assign an id for you, you need to use another type of generator, like "sequence" generator. It would be like:
id name: 'customId', generator: 'sequence', params: [sequence:'some_sequence']
More info on id generators here.
I tried to change the standard 'id' in grails:
calls Book {
String id
String title
static mapping {
id generator:'assigned'
}
}
unfortunately, I soon noticed that this breaks my bootstrap. Instead of
new Book (id:'some ISBN', title:'great book').save(flush:true, failOnError:true)
I had to use
def b = new Book(title:'great book')
b.id = 'some ISBN'
b.save(flush:true, failOnError:true)
otherwise I get an 'ids for this class must be manually assigned before calling save()' error.
but that's ok so far.
I then encountered the same problem in the save action of my bookController. But this time, the workaround didn't do the trick.
Any suggestions?
I known, I can rename the id, but then I will have to change all scaffolded views...
That's a feature of databinding. You don't want submitted data to be able to change managed fields like id and version, so the Map constructor that you're using binds all available properties except those two (it also ignores any value for class, metaClass, and a few others).
So there's a bit of a mismatch here since the value isn't managed by Hibernate/GORM but by you. As you saw the workaround is that you need to create the object in two steps instead of just one.
I can't replicate this problem (used Grails 2.0.RC1). I think it might be as simple as a missing equal sign on your static mapping = { (you just have static mapping {)
Here's the code for a domain object:
class Book {
String id
String name
static mapping = {
id generator:'assigned'
}
}
And inside BootStrap.groovy:
def init = { servletContext ->
new Book(name:"test",id:"123abc").save(failOnError:true)
}
And it works fine for me. I see the id as 123abc.
You need to set the bindable constraint to true for your id prop, e.g.
class Employee {
Long id
String name
static constraints = {
id bindable: true
}
}
Is it possible to explicitly set the id of a domain object in Grails' Bootstrap.groovy (or anywhere, for that matter)?
I've tried the following:
new Foo(id: 1234, name: "My Foo").save()
and:
def foo = new Foo()
foo.id = 1234
foo.name = "My Foo"
foo.save()
But in both cases, when I print out the results of Foo.list() at runtime, I see that my object has been given an id of 1, or whatever the next id in the sequence is.
Edit:
This is in Grails 1.0.3, and when I'm running my application in 'dev' with the built-in HSQL database.
Edit:
chanwit has provided one good solution below. However, I was actually looking for a way to set the id without changing my domain's id generation method. This is primarily for testing: I'd like to be able to set certain things to known id values either in my test bootstrap or setUp(), but still be able to use auto_increment or a sequence in production.
Yes, with manually GORM mapping:
class Foo {
String name
static mapping = {
id generator:'assigned'
}
}
and your second snippet (not the first one) will do the job (Id won't be assigned when passing it through constructor).
What I ended up using as a workaround was to not try and retrieve objects by their id. So for the example given in the question, I changed my domain object:
class Foo {
short code /* new field */
String name
static constraints = {
code(unique: true)
name()
}
}
I then used an enum to hold all of the possible values for code (which are static), and would retrieve Foo objects by doing a Foo.findByCode() with the appropriate enum value (instead of using Foo.get() with the id like I wanted to do previously).
It's not the most elegant solution, but it worked for me.
As an alternative, assuming that you're importing data or migrating data from an existing app, for test purposes you could use local maps within the Bootstrap file. Think of it like an import.sql with benefits ;-)
Using this approach:
you wouldn't need to change your domain constraints just for
testing,
you'll have a tested migration path from existing data, and
you'll have a good data slice (or full slice) for future integration tests
Cheers!
def init = { servletContext ->
addFoos()
addBars()
}
def foosByImportId = [:]
private addFoos(){
def pattern = ~/.*\{FooID=(.*), FooCode=(.*), FooName=(.*)}/
new File("import/Foos.txt").eachLine {
def matcher = pattern.matcher(it)
if (!matcher.matches()){
return;
}
String fooId = StringUtils.trimToNull(matcher.group(1))
String fooCode = StringUtils.trimToNull(matcher.group(2))
String fooName = StringUtils.trimToNull(matcher.group(3))
def foo = Foo.findByFooName(fooName) ?: new Foo(fooCode:fooCode,fooName:fooName).save(faileOnError:true)
foosByImportId.putAt(Long.valueOf(fooId), foo) // ids could differ
}
}
private addBars(){
...
String fooId = StringUtils.trimToNull(matcher.group(5))
def foo = foosByImportId[Long.valueOf(fooId)]
...
}