Grails rest-api app to handle multiple params - rest

Question

Using Grails 3.1.3, I created a rest-api so that I am able to capture GET requests that not only query for one parameter, but multiple if needed. I don't know how to code this correctly inside the UrlMappings file. Here are the details.
Domain class:
class ProdDetail {
Integer pid
String title
String category
Integer year
}
And some of these inside the BootStrap:
new ProdDetail(pid:'101', title:'No Highway', author:'Nevil Shute', category:'fiction', year:1948).save(failOnError:true)
new ProdDetail(pid:'214', title:'In the Country of Men', author:'Hisham Matar', category:'misery', year:2007).save(failOnError:true)
Controller:
protected List<ProdDetail> listAllResources(Map params) {
println params
try {
ProdDetail.where {
if (params.category && params.maxYear) {
category == params.category && year <= params.int('maxYear')
} else if (params.category) {
category == params.category
} else if (params.maxYear) {
year <= params.int('maxYear')
} else {
pid > 0
}
}.list()
} catch (Exception e) {
[]
}
}
UrlMappings:
static mappings = {
"/prodDetails"(resources:'prodDetail')
"/prodDetails/category/$category?"(controller:'prodDetail', action:'index')
"/prodDetails/yearUnder/$maxYear?"(controller:'prodDetail', action:'index')
// the line below is not right I think, what's the correct format?
"/prodDetails/combo/$category?&$maxYear?"(controller:'prodDetail', action:'index')
}
Now, where as these two curls would work:
curl localhost:8080/prodDetails/category/misery
curl localhost:8080/prodDetails/yearUnder/2007
This one fails to go into the desired clause in the controller to detect both params:
curl localhost:8080/prodDetails/combo/?category=misery&maxYear=2007
It just detects 'category' but not the 'maxYear' which it considers as 'null'.
How can I cater for such a curl please?

Answer 1

It kind of depends on what you want your URLs to look like, but assuming you want your requests to look like this:
http://localhost:8080/prodDetails/combo/misery?maxYear=2007&title=common
The UrlMappings should look like
static mappings = {
"/prodDetails/combo/$category"(controller:'prodDetail', action:'index')
}
Then the params object in the controller should have both whatever's in the place of $category, in this example misery, and the other parameters after the ? as well.
If you want the parameters to be in the path you can do this:
static mappings = {
"/prodDetails/combo/$category/$title/$maxYear"(controller:'prodDetail', action:'index')
}
And the request would then be:
http://localhost:8080/prodDetails/combo/misery/common/2007
One other option would be to use a command object. So if you had:
static mappings = {
"/prodDetails/combosearch"(controller:'prodDetail', action:'comboSearch')
}
And then created an object beside the controller called ComboSearchCommand.groovy that looked like:
import grails.validation.Validateable
class ComboSearchCommand implements Validetable {
String category
String title
int maxYear
static constraints = {
category blank: false, nullable: true
title blank: false, nullable: true
maxYear blank: false, nullable: true
}
}
(Which you can do validation on just like a domain object)
And then in your controller you have the method take the command object instead of params
protected List<ProdDetail> comboSearch(ComboSearchCommand command) {
println command.category
}
Then your URL would be
http://localhost:8080/prodDetails/combosearch?category=misery&maxYear=2007&title=common
And the parameters will bind to the command object.
I've used that quite a bit, you can share validations or have your command object inherit validations from domain objects, lots of flexibility.
https://grails.github.io/grails-doc/latest/guide/single.html#commandObjects

Answer 2

You don't need to specify the parameters in UrlMappings if those params are not part of the URL:
No need of this:
"/prodDetails/combo/$category&?$maxYear?"(controller:'prodDetail', action:'index')
Yes you need this to match the URL to a controller/action (but remove the ?)
"/prodDetails/yearUnder/$maxYear?"(controller:'prodDetail', action:'index')
Also, you don't need Map params in listAllResources(Map params)
"params" is an injected property of controllers, the println params will work OK with: listAllResources()
What I would do is to define:
listAllResources(String category, int maxYear, ...) where ... are all the params that action can receive, most would be optional, so you will receive a null value if not included in your request.
Remember: UrlMappings are to map URLs to controller/actions, and you have the same controller/action, so I would remove all the mappings and process the optional parameters in the action just checking which are null or not.
Edit (considering comments)
Q: the method is not overloaded to handle params like that
A: methods are dynamic, this is Grails / Groovy, not Java. It will call the action method even if all the params are null. I would recommend you to go through the Grails controller documentation in detail.
Q: found that the listAllResources method was never called
A: remove the protected keyword from the action, only subclasses would be able to invoke that method. Also, you can add an UrlMapping to avoid users to invoke that URL (match the URL and return 404 Not Available or something like that)
Q: I want to handle a GET request like this localhost:8080/prodDetails/combo?category=misery&year=2016&title=commonTitle, how exactly should the i) entry in UrlMappings, and ii) the listAllResources method look like?
A:
static mappings = {
// if "compo" comes in the action portion, map that to the listAllResources method
// as I said, if all parameters comes in the query string, no further actions are needed, if you need parameters to be part of the URL path, then you need to play with the $xxxx in the URL
"/prodDetails/combo"(controller:'prodDetail', action:'listAllResources')
}
def listAllResources()
{
println params
// logic here
render "OK"
}
Check:
https://grails.github.io/grails-doc/latest/ref/Controllers/params.html
https://grails.github.io/grails-doc/latest/ref/Controllers/render.html
How does grails pass arguments to controller methods?